Tag Archives: Silwood Park

Not all aphids get eaten – “bottom-up” wins this time

In the lecture that I introduce aphids to our entomology MSc students I show them two quotes that illustrate the prodigious reproductive potential of these fantastic animals.

“In a season the potential descendants of one female aphid contain more substance than 500 million stout men “– Thomas Henry Huxley (1858) and “In a year aphids could form a layer 149 km deep over the surface of the earth.  Thank God for limited resources and natural enemies” – Richard Harrington (1994).

I was a little discomfited whilst researching this article to find that both Huxley and I had been short-changed, although the original quote does hint at the mortality factors that an aphid clone faces during its life.

The original words and the morphed ‘quote’

 

Both these quotes acknowledge the contribution that both bottom-up and top-down factors have on aphid populations.  For those not familiar with the ecological jargon, ecologists have at times over the last 40 years or so, got quite territorial* about whether herbivorous insect populations are regulated by top-down e.g. predators or bottom-up e.g. host plant quality, factors (e.g. Hunter & Price, 1992).  Who is in charge of an aphid clone’s destiny, natural enemies or the food plant?

Aphids are the favourite food of several insect species; ladybirds (but not all species), lacewing larvae, hoverfly larvae, and also the larvae of some Cecidomyiid flies (Aphidoletes spp.), and Chamaemyiid flies (e.g. Leucopis glyphinivora).  They are also attacked by other Hemipteran species, such as Anthocoris nemorum.   Those insects that make a living almost solely from aphids, are termed aphidophagous and every three years you can, if you feel like it, attend an international conference devoted to the subject 🙂

As well as these specialist predators, aphids are also preyed upon by more generalist predators, such as carabid and staphylinid beetles, harvestmen and spiders. Aphids also provide a nutritious snack for birds and bats.  Faced with all these hungry and voracious predators you might wonder why it is that aphids ever get numerous enough to become pests.  There are two answers, their fantastic reproductive rates and second, aphids, despite appearing soft and squishy, do have anti-predator defence mechanisms.  These range from kicking predators in the face, dropping off the plant, gumming up the jaws of predators by smearing them with wax from their siphunculi, and even jumping out of the way of the predator (Dixon, 1958).  On top of all that,  many are extremely unpalatable and even poisonous.

Some population modelling work from the 1970s explains why aphids can often become pests, as well as introducing us to the concept of population dynamics geography; the endemic and epidemic ridges, and my favourite, the natural enemy ravine (Southwood & Comins, 1976).

The geography of population dynamics from Southwood & Comins (1976)

 

They suggested that if enough predators are already present in the habitat or arrive shortly after the aphids, then the aphid population either goes extinct or only reaches the “endemic ridge”.  The phenomenal rate at which aphids can reproduce under favourable conditions, usually gets them past the “natural enemy ravine” and up into “epidemic ridge” with only a slight slowdown in population growth.   Evidence for the “natural enemy ravine” is not very convincing and I feel that the suggestion that the dip in population growth at the start of the season is due to intermittent immigration by winged aphids and not the action of polyphagous predators (Carter & Dixon, 1981) is pretty convincing.   That said, later modelling work suggested that the subsequent growth of aphid populations could be slowed down by the action of natural enemies Carter et al., 1982).

Aphids, despite their ability to produce baby aphids extremely quickly, are not equally abundant all year round. Those of us who want to collect aphids know that the best time of year is early in the season, spring and early summer.  This is the time when the plant sap is flowing quickly and is rich in nutrients, especially nitrogen, which aphids need in large quantities.    A characteristic of aphid populations is the way they suddenly disappear during July, a phenomenon known as the “mid-summer or mid-season crash”.  This is not just a phenomenon confined to aphids living on ephemeral herbaceous hosts, it happens to tree-dwelling aphids too e.g. the sycamore aphid, Drepanoisphum platanoidis.  At Silwood Park, where I monitored sycamore aphid populations on fifty-two trees for twenty years**, I saw the same pattern of a rapid build-up followed by an equally rapid collapse every year.  The pattern was the same in both high population and low population years and happened at pretty much the same time every year.  Herbivorous insects are, as you might expect, strongly

High and low population years of sycamore aphid, Drepanosiphum platanoidis at Silwood Park

affected by the quality of their host plant, the availability of nitrogen in the leaves being of most importance (Awmack & Leather, 2002).  Aphids are no exception, and their whole-life cycle is adapted to the ever-changing, but predictable availability of soluble nitrogen and water in their host plants (Dixon, 1977).  Plants become less suitable for aphids as their tissues mature and they lock their nitrogen away in the leaves and other structures, rather than transporting it around in the phloem as they do in spring and autumn (Dixon, 1976).

Aphids respond in two ways to a decline in the nutritional quality of their host plant, they reduce the number of offspring they produce (e.g. Watt, 1979) and those offspring they produce are winged (e.g. Parry, 1977), or if already winged, more likely to take flight and seek new better quality host plants (e.g. Dixon, 1969; Jarosik & Dixon, 1999).  In some aphids there is also an increase in intrinsic mortality (e.g. Kift et al., 1998).

The mid-season crash is not confined to abundant and common aphids, rare aphids show exactly the same changes in their populations, and this is similarly attributed to changes in the nutritional quality of the aphid host plant leading to increased dispersal (e.g. Kean, 2002).

Population crash of the rare aphid Paradoxaphis plagianthi in New Zealand (data from Kean, 2002).

Although some authors, notably Alison Karley and colleagues have suggested that it is the action of natural enemies and not host nutrition that drives the mid-season crash (Karley et al., 2003, 2004), the overwhelming evidence points to the production of winged (alate) morphs and their dispersal, being the major factor in causing the mid-season crash as the graphs below illustrate.

Cereal aphids on wheat showing increased alate production coinciding and subsequent population crash on cereal crops. Data from Wratten, 1975).

Green spruce aphid, Elatobium abietinum on Norway spruce at Silwood Park, showing the population crash and associated increase in the number of winged aphids. Data from Leather & Owuor (1996).

Green spruce aphid in Ireland, population crash associated with marked decline in fecundity and production of winged forms. Data from Day (1984)

Data presented by Way & Banks (1968) might lend some support to the idea that natural enemies cause the mid-season crash.  A close examination of the data however, which might at first glance suggest that keeping natural enemies away, allows aphid populations to prosper, reveals that the process of excluding natural enemies also prevents the dispersal of the winged aphids, which have no choice but to stay on the host plant and reproduce there.

Aphis fabae populations on Spindle bushes from Way & Banks (1968). Top line shows the population kept free of predators until August 2nd, bottom line, exposed to predators.

Moreover, as the authors themselves state “the rise to peak density in each year, coincided with an enormous increase in the proportion of individuals destined to become alatae” (Way & Banks, 1968).   I do not dispute that natural enemies have an effect on aphid populations, but in my opinion, the evidence does not support the hypothesis that they are the driving force behind the mid-season crash.  Rather, the major factor is the reduction in host quality, caused by a decline in the nutritional status of the plant and overcrowding of the aphids, leading to reduced fecundity and an increase in winged dispersers.

I don’t deny that the natural enemies do a very good mopping-up job of those aphids that are left behind, but they are not the force majeure by any stretch of the imagination. Most aphids do not get eaten 🙂

 

References

Awmack, C.S. & Leather, S.R. (2002) Host plant quality and fecundity in herbivorous insects. Annual Review of Entomology, 47, 817-844.

Carter, N. & Dixon, A.F.G. (1981) The natural enemy ravine in cereal aphid population dynamics: a consequence of predator activity or aphid biology? Journal of Animal Ecology, 50, 605-611.

Carter, N., Gardner, S.M., Fraser, A.M., & Adams, T.H.L. (1982) The role of natural enemies in cereal aphid population dynamics. Annals of Applied Biology, 101, 190-195.

Day, K.R. (1984) The growth and decline of a population of the spruce aphid Elatobium abietinum during a three  study, and the changing pattern of fecundity, recruitment and alary polymorphism in a Northern Ireland Forest. Oecologia, 64, 118-124.

Dixon, A.F.G. (1958) The escape responses shown by certain aphids to the presence of the coccinellid Adalia decempunctata (L.). Transactions of the Royal Entomological Society London, 110, 319-334.

Dixon, A.F.G. (1969) Population dynamics of the sycamore aphid Drepanosiphum platanoides (Schr) (Hemiptera: Aphididae); migratory and trivial flight activity. Journal of Animal Ecology, 38, 585-606.

Dixon, A.F.G. (1976) Factors determining the distribution of sycamore aphids on sycamore leaves during summer. Ecological Entomology, 1, 275-278.

Dixon, A.F.G. (1977) Aphid Ecology: Life cycles, polymorphism, and population regulation. Annual Review of Ecology & Systematics, 8, 329-353.

Harrington, R. (1994) Aphid layer. Antenna, 18, 50-51.

Hunter, M.D. & Price, P.W. (1992) Playing chutes and ladders – heterogeneity and the relative roles of bottom-up and top-down forces in natural communities. Ecology, 73, 724-732.

Huxley, T.H. (1858) On the agmaic reproduction and morphology of Aphis – Part I. Transactions of the Linnean Society London, 22, 193-219.

Jarosik, V. & Dixon, A.F.G. (1999) Population dynamics of a tree-dwelling aphid: regulation and density-independent processes. Journal of Animal Ecology, 68, 726-732.

Karley, A.J., Parker, W.E., Pitchford, J.W., & Douglas, A.E. (2004) The mid-season crash in aphid populations: why and how does it occur? Ecological Entomology, 29, 383-388.

Karley, A.J., Pitchford, J.W., Douglas, A.E., Parker, W.E., & Howard, J.J. (2003) The causes and processes of the mid-summer population crash of the potato aphids Macrosiphum euphorbiae and Myzus persicae (Hemiptera: Aphididae). Bulletin of Entomological Research, 93, 425-437.

Kean, J.M. (2002) Population patterns of Paradoxaphis plagianthi, a rare New Zealand aphid. New Zealand Journal of Ecology, 26, 171-176.

Kift, N.B., Dewar, A.M. & Dixon, A.F.G. (1998) Onset of a decline in the quality of sugar beet as a host for the aphid Myzus persicaeEntomologia experimentalis et applicata, 88, 155-161.

Leather, S.R. & Owuor, A. (1996) The influence of natural enemies and migration on spring populations of the green spruce aphid, Elatobium abietinum Walker (Hom., Aphididae). Journal of Applied Entomology, 120, 529-536.

Parry, W.H. (1977) The effects of nutrition and density on the production of alate Elatobium abietinum on Sitka spruce. Oecologia, 30, 637-675.

Southwood, T.R.E. & Comins, H.N. (1976) A synoptic population model.  Journal of Animal Ecology, 45, 949-965.

Watt, A.D. (1979) The effect of cereal growth stages on the reproductive activity of Sitobion avenae and Metopolphium dirhodum. Annals of Applied Biology, 91, 147-157.

Way, M.J. & Banks, C.J. (1968) Population studies on the active stages of the black bean aphid, Aphis fabae Scop., on its winter host Euonymus europaeus L. Annals of Applied Biology, 62, 177-197.

Wratten, S.D. (1975) The nature of the effects of the aphids Sitobion avenae and Metopolophium dirhodum on the growth of wheat. Annals of Applied Biology, 79, 27-34.

 

Post script

For those interested this is how Huxley arrived at his number of potential descendants, and here I quote from his paper,  “In his Lectures, Prof. Owen adopts the calculations taken from Morren (as acknowledged by him) from Tougard that a single impregnated ovum  of Aphis may give rise, without fecundation, to a quintillion of Aphides.” I have not, so far, been able to track down Tougard.

Morren, C.F.A. (1836) sur le Puceron du Pecher, Annales des Sciences Naturelle series 2. vi.

You may not know what a grain is, so to help you visualise it, 7000 grains equals a pound so 2 000 000 grains gives you 286 pounds, or 20 stone or approximately 130 Kg depending on where you come from J

 

*and generated some magnificent paper titles and quite acrimonious responses J Hassell, M.P., Crawley, M.J., Godfray, H.C.J., & Lawton, J.H. (1998) Top-down versus bottom-up and the Ruritanian bean bug. Proceedings of the National Academy of Sciences USA, 95, 10661-10664.

**A true labour of love as I also counted maple aphids, orange ladybirds, winter moth larvae and any of their predators and parasites that I came across J

 

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Data I am never going to publish – A tale of sixty trees

In 1981 I spent a lot of time trudging through snow, cross-country skiing and snow-shoeing my way across the snowy wastes of Finland to snip twigs off bird cherry trees.  This was part of my post-doc which was to develop a forecasting system for the bird cherry-oat aphid, Rhopalosiphum padi.  On returning to the lab I then spent many a happy hour counting how many aphid eggs were nestled in between the buds and the stem on each twig.  It was while doing this that I noticed that some of the twigs were infested with the overwintering larval shields of the bird cherry ermine moth, Yponomeuta evonymellus.  Of course I then started counting them as well 🙂  I noticed that trees with lots of aphid eggs didn’t have very many larval shields and I wondered why. Some later observations from marked trees in Scotland appeared to provide evidence that the aphids and the moths tended to either prefer different trees or perhaps excluded each other.

Negative correlation between moths and aphids – more moths equals fewer aphids and vice versa

Based on these data I hypothesised that the two insects were indirectly competing for resources by altering plant chemistry and/or architecture thus making the trees less or more suitable for egg laying in the autumn (Leather, 1988).  I tested this experimentally when I was working for the Forestry Commission in Scotland using potted bird cherry trees that I defoliated to a lesser or greater extent to see if I could induce changes in foliar quality and tree growth rates that might influence subsequent colonisation by the aphids and moths. As predicted, those trees that had been defoliated, albeit by me and not by moth larvae, were less attractive to aphids in the autumn (Leather, 1993).  These effects were still apparent five years after the beginning of the experiment (Leather, 1995) when I had to desert my trees as I moved to a new position at Imperial College’s Silwood Park campus.

Given that apart from the location, the SE of England, this was my idea of a dream job for life (colleagues at the time included John Lawton, Mike Hassell, Bob May, Stuart McNeill, Mike Way, Brad Hawkins, Shahid Naeem, Mike Hochberg, Chris Thomas to name but a few), I decided to start up two long-term projects to see me through the next 30 years, one observational (my 52 sycamore tree project), the other experimental, a follow up to my bird cherry defoliation experiment.

I went for a simplified design of my earlier experiments, just two defoliation regimes, one to mimic aphid infestation (50%), the other to mimic bird cherry ermine moth defoliation (100%) and of course a non-defoliated control.  I also planted the trees in the ground to better simulate reality.  Using potted plants is always a little suspect and I figured that I would need to do rather a lot of re-potting over the next 30 years 🙂

The grand plan!

I sourced my trees from a Forestry Commission nursery thinking that as the national organisation responsible for tree planting in the UK I could trust the provenance of the trees.  Things didn’t go well from the start.  Having planted my trees in autumn 1992 and established the treatments in the spring of 1993 I discovered that my bird cherry, rather than being from a native provenance (seed origin) were originally from Serbia! Hmm 🙂  It was too late to start again, so I decided to carry on.  After all, bird cherry although widely planted in the SE, has a native distribution somewhat further north and west, which meant I was already operating close to the edge of ‘real life’, so what did an extra 1600 kilometres matter?

The mainly ‘natural’ distribution of bird cherry (left, Leather, 1996) and the current distribution including ‘introduced’ trees https://www.brc.ac.uk/plantatlas/index.php?q=plant/prunus-padus

Next, I discovered that my fence was neither rabbit nor deer proof.  I almost gave up at this point, but having invested a lot of time and energy in setting up the plot I once again decided to carry on. On the plus side, the trees most heavily defoliated and bitten back were mainly from the 100% defoliation treatment, but did give me some negative growth rates in that year.

My original plan was to record height (annually), bird cherry egg numbers (every December), bird cherry ermine moth larval shields (annually), bud burst and leaf expansion once a week, leaf-fall (annually), and once a month, defoliation rates in two ways, number of damaged leaves and an overall estimation of percentage defoliation.  This was a personal project, so no grant funding and no funding for field assistants.  It soon became clear, especially when my teaching load grew, as Imperial started replacing whole organism biologists with theoretical and molecular biologists, and I was drafted in to take on more and more of the whole organism lecturing, that I would not be able to keep both of my long term projects going with the same intensity.  Given the ‘problems’, associated with the bird cherry project, I decided  that I would ditch some of my sampling, bud burst was scored on 21st March every year and defoliation only measured once, in late summer and egg sampling and height recording came to a halt once the trees grew above me (2005)!  This allowed me to carry on the sycamore project as originally intended*.

I kept an eye on the trees until I left Silwood Park in 2012, but by 2006 I was only monitoring bud burst and leaf fall feeling that this might be useful for showing changes in phenology in our ever-warming world.  One regret as I wandered between the then sizeable trees in the autumn of 2012 was that I had not taken a before and after photograph of the plots.  All I have are two poor quality photos, one from 2006, the other from 2012.

The Sixty Tree site April 2006.

The Sixty Tree site April 2010 with a very obvious browse line

 

So, after all the investment in time, and I guess to a certain extent money (the trees and the failed fencing, which both came out of my meagre start-up funding**), did anything worthwhile come out of the study?

The mean number of Rhopalosiphum padi eggs per 100 buds in relation to defoliation treatment

As a long-time fan of aphid overwintering it was pleasing to see that there was a significant difference not only between years (F= 8.9, d.f. = 9/29, P <0.001), but also between treatments with the trees in the control treatment having significantly more eggs laid on them than the 100% defoliation treatment (F= 9.9, d.f. = 2/ 29, P <0.001 with overall means of 1.62, 1.22 and 0.65 eggs/100 buds).  This also fitted in with the hypothesis that trees that are defoliated by chewing herbivores become less suitable for aphids (Leather, 1988).  I must admit that this was a huge surprise to me as I had thought that as all the trees were attacked by deer the year after the experimental treatments they would all respond similarly, which is why I almost gave up the experiment back in 1994.

Bud burst stage of Prunus padus at Silwood Park on March 21st 1996-2012; by treatment and combined

When it came to budburst there was no treatment effect, but there was a significant trend to earlier budburst as the trees became older which was strongly correlated with warmer springs, although as far as spring temperatures were concerned there was no significant increase with year.

Mean spring temperature (Silwood Park) 1993-2012 and relationship between mean spring temperature and bud bust stage on 21st March.

Mean date of final leaf fall of Prunus padus at Silwood Park 1995-2012; by treatment and combined

At the other end of the year, there was a significant difference between date of final leaf fall between years but no significant difference between treatments.  In retrospect I should have adopted another criterion.  My date for final leaf fall was when the last leaf fell from the tree.  Those of you who have watched leaves falling from trees will know that there are always a few who are reluctant to make that drop to the ground to become part of the recycling process.  Even though they are very obviously dead, they hang there until finally dislodged by the wind.   I should really have used a measure such as last leaf with any pigment remaining.  I am sure that if I could be bothered to hunt down the wind speed data I would find that some sort of correlation.

Mean height (cm) of Prunus padus trees at Silwood Park 1993-2005 and Diameter at Breast Height (DBH) (cm) at the end of 2012

Except for the year after the deer attack, the trees, as expected, grew taller year by year.  There was however, no significant difference between heights reached by 2005 or in DBH at the end of 2012 despite what looked like a widening gap between treatments.

Defoliation scores of Prunus padus at Silwood Park 1993-2004; % leaves damaged and overall defoliation estimates

My original hypothesis that trees that were heavily defoliated at the start of their life would be more susceptible to chewing insects in later life, was not supported.  There was no significant difference between treatments, although, not surprisingly, there was a significant difference between years.  Average defoliation as has been reported for other locations was about 10% (Kozlov et al., 2015; Lim et al., 2015).

Number of Prunus padus trees with severe deer damage

That said, when I looked at the severity of deer attack, there was no effect of year but there was a significant effect of treatment, those trees that had been 100% defoliated in 1993 being most attractive to deer.   In addition, 20% of those trees were dead by 2012 whereas no tree deaths occurred for the control and less severely defoliated treatments.

I confess to being somewhat surprised to find as many significant results as I did from this simple analysis and was momentarily tempted to do a more formal analysis and submit it to a journal.  Given, however, the number of confounding factors, I am pretty certain that I would be looking at an amateur natural history journal with very limited visibility.  Publishing it on my blog will almost certainly get it seen by many more people, and who knows may inspire someone to do something similar but better.

The other reason that I can’t be bothered to do a more formal analysis is that my earlier work on which this experiment was based has not really hit the big time, the four papers in question only accruing 30 cites between them.  Hardly earth shattering despite me thinking that it was a pretty cool idea;  insects from different feeding guilds competing by changing the architecture and or chemsitry of their host plant.  Oh well.  Did anything come out of my confounded experiment or was it a total waste of time?  The only thing published from the Sixty Trees was a result of a totally fortuitous encounter with Marco Archetti and his fascination with autumn colours (Archetti & Leather, 2005), the story of which I have related in a previous post, and which has, in marked contrast to the other papers, had much greater success in the citation stakes 🙂

And finally, if anyone does want to play with the data, I am very happy to give you access to the files.

References

Archetti, M. & Leather, S.R. (2005) A test of the coevolution theory of autumn colours: colour preference of Rhopalosiphum padi on Prunus padus. Oikos, 110, 339-343. 50 cites

Kozlov, M.V., Lanta, V., Zverev, V., & Zvereva, E.L. (2015) Global patterns in background losses of woody plant foliage to insects. Global Ecology & Biogeography, 24, 1126-1135.

Leather, S.R. (1985) Does the bird cherry have its ‘fair share’ of insect pests ? An appraisal of the species-area relationships of the phytophagous insects associated with British Prunus species. Ecological Entomology, 10, 43-56.  14 cites

Leather, S.R. (1988) Consumers and plant fitness: coevolution or competition ? Oikos, 53, 285-288. 10 cites

Leather, S.R. (1993) Early season defoliation of bird cherry influences autumn colonization by the bird cherry aphid, Rhopalosiphum padi. Oikos, 66, 43-47. 11 cites

Leather, S.R. (1995) Medium term effects of early season defoliation on the colonisation of bird cherry (Prunus padus L.). European Journal of Entomology, 92, 623-631. 4 cites

Leather, S.R. (1996) Biological flora of the British Isles Prunus padus L. Journal of Ecology, 84, 125-132.  14 cites

Lim, J.Y., Fine, P.V.A., & Mittelbach, G.G. (2015) Assessing the latitudinal gradient in herbivory. Global Ecology & Biogeography, 24, 1106-1112.

 

 

*which you will be pleased to know, is being analysed as part of Vicki Senior’s PhD project, based at the University of Sheffield.

**£10 000 which even in 1992 was not overly-generous.

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Ideas I had and never followed up

“When I was younger, so much younger than before” I never needed any help to come up with ideas for research topics or papers.   When I was doing my PhD and later as a post-doc, I used to keep a note pad next to my bed so that when I woke up in the middle of night with an idea (which I often did) I could scribble it down and go back to sleep.  (These days sadly, it is my bladder and not ideas that wake me up in the wee small hours 🙂*)

On waking up properly, these ideas, if they still seemed sensible, would  move onto Stage 2, the literature search.  In those days, this was much more difficult than it is now, no Google Scholar or Web of Science then, instead you had to wade though the many hard-copy Abstract series and then get hard copies of the papers of interest.  Once in my hands, either via Inter-library loans or direct from the author, or even photocopied from the journal issue (we did have photocopiers in those days), the papers would be shoved into a handy see-through plastic folder (Stage 3).  Depending on how enthusiastic I was about the idea, I would then either mock-up a paper title page or put the folder in the ‘to deal with later’ pile (Stage 4).   Many of these eventually led on to Stage 5, experiments and published papers.  Others have languished in their folders for twenty or thirty years.

As part of my phased run up to retirement (2021), I have started farming out my long-term publishable (hopefully) data-sets to younger, more statistically astute colleagues and ‘publishing’ less robust, but possibly useful data on my blog site.  I have also, somewhat halfheartedly since the task is monumental, started to go through my old field and lab books that

monumental-data

A monumental collection of data.  The top right picture is my 20-year sycamore data set.  I estimate that there are about 7 million data points in it; of which to date only 1.6 million, give or take a million, are computerised.  I also have a ten-year bird cherry aphid data set from Scotland, waiting to go on the computer, any volunteers?

are not yet computerised.  Whilst doing this I came across some Stage 3 folders, which as you can see from the colour of the paper have languished for some time.

the-forgotten-nine

The Forgotten Nine

 

There were nine forgotten/dismissed proto-papers, the oldest of which, judging by the browning of the paper and my corresponding address, dates from the early 1980s, and is simply titled “What are the costs of reproduction?”.  This appears to have been inspired by a talk given by Graham Bell at a British Ecological Society, Mathematical Ecology Group meeting in 1983.  In case you are wondering, this was one of those meetings supposed to bring theorists and empiricists together.   It didn’t work, neither group felt able to talk to each other 🙂  The idea, inevitably based on aphid data, didn’t bear any fruit, although I do have this graph as a souvenir.  If anyone wants

graph

In those days we used graph paper 🙂

 the data, do let me know.

Slightly later, we find the grandly titled, “Size and phylogeny – factors affecting covariation in the life history traits of aphids”.  This had apparently been worked up from an earlier version of a paper, less grandly, but no less ponderously, titled, “Size and weight: factors affecting the level of reproductive investment in aphids”.  This is based on some basic dissection data from eight aphid species and presents the relationships, or lack of, between adult weight (or surrogate measure), ovariole number, potential fecundity and the number of pigmented embryos.  As far as I can remember these are data that Paul Wellings** and I collected as a follow-up to work we had published from a side project when we were doing our PhDs at the University of East Anglia (Wellings et al., 1980).  The second title was inspired by a paper by Stephen Stearns (Stearns, 1984), who was something of a hero of mine at the time, and was, I guess, an attempt to publish pretty simple data somewhere classier than it deserved 🙂  So this one seems to be a Stage 4, almost Stage 5 idea, and may, if I have time or someone volunteers, actually get published, although I suspect it may only make it to a very minor journal under its original title.

Then we have a real oddity, “Aphids, elephants and oaks: life history strategies re-examined”.  This one as far as I remember, is based on an idea that I had about r- and k-selection being looked at from a human point of view and not the organism’s point of view.  My thesis was that an oak tree was actually r-selected as over its life-time it was more fecund than an aphid 🙂  I suspect this was going to be aimed at the Forum section of Oikos.

The next one, dates from the late-1980s, “Protandry versus protogyny: patterns of occurrence within the Lepidoptera”, and reflects the fact that females of the pine beauty moth, Panolis flammea, on which I was then working, emerge before the males (Leather & Barbour, 1983; Leather, 1984), something not often reported in Lepidoptera.  I wondered what advantage (if any) this gave P. flammea.  I planned this one as a review or forum type paper but never got beyond the title and collecting two references (Robertson, 1987; Zonneveld & Metz, 1991).  I still think this is an interesting idea, but do feel free to have a go yourselves, as again, I suspect that I won’t actually get round to it.

Finishing off my time in Scotland, is a paper simply entitled, “Egg hatch in the bird cherry aphid, Rhopalosiphum padi.” I have ten years of egg hatch data from eight trees waiting to be analysed.  This is almost certainly not worth more than a short note unless I (or a willing volunteer) tie it in with the ten years data on spring and autumn populations on the same trees 🙂 Aphid egg data although not very abundant, is probably not in great demand.  My first published paper (Leather, 1980) was about egg mortality in the bird cherry aphid and 36 years later has only managed to accrue 32 citations, so I guess not an area where one is likely to become famous 🙂

I then have four papers dating from my time as an Associate Member of the NERC Centre for Population Biology at Silwood Park.   The first is titled, “The suitability of British Prunus species as insect host plants” and was definitely inspired by my foray into counting host plant dots as exemplified by the late great Richard Southwood (Leather, 1985, 1986).  I think I was going to look at palatability measures of some sort.

The next is called ‘Realising their full potential: is it important and how many insects achieve it?”  I’m guessing that this was a sort of follow-up to my second most-cited paper ever (Leather, 1988), the story of which you can read here, if at all interested.  Most insects, even those that are pests, die before achieving anywhere near their full reproductive potential, but then so do we humans, and our population continues to grow.  So in answer to the question, I guess not and no it doesn’t matter 🙂

Also linked to insect reproduction is the next paper, which I have followed up with the help of a PhD student, and do hope to submit in the near future, “Queue positions, do they matter”.  As this one may actually see the light of day, I won’t say anything further about it.

And finally, another one about aphid eggs, “Bud burst and egg hatch synchrony in aphids”.  This one was going to be based on my then ten-year sycamore aphid data but is now based on my twenty-year data set and is now in the very capable hands of a PhD student and hopefully will see the light of day next year.

There are also a number of other folders with no titles that are just full of collections of reprints.  I can only guess at what these ideas were so won’t burden you with them.

I mentioned at the beginning of this piece that I don’t wake up in the middle of the night with ideas any more.  As we get older I think there is a tendency to worry that we might run out of ideas, especially when, as we do in the UK, suffer from ludicrously underfunded research councils with very high rejection rates that don’t allow you to resubmit failed grant applications.  It was thus reassuring to see this recent paper that suggests that all is not lost after you hit the grand old age of 30.  That said, I do believe that as you move away from the bench or field, the opportunity to be struck by what you see, does inevitably reduce.  As a PhD student and post-doc you are busy doing whatever it is you do, in my case as an ecological entomologist, counting things, and inevitably you see other things going on within and around your study system, that spark off other ideas.  It was the fear of losing these opportunities as I moved up the academic ladder, which inevitably means, less field and bench time and more time writing grant applications and sitting on committees, that I specifically set aside Monday mornings (very early mornings) to my bird cherry plots and even earlier Thursday mornings to survey my sycamore trees.   Without those sacrosanct mornings I am pretty certain I would have totally lost sight of what is humanly possible to do as a PhD student or post-doc.  This, thankfully for my research group, means that I had, and have, realistic expectations of what their output should be, thus reducing stress levels all round.   As a side benefit I got to go out in the fresh air at least twice a week and do some exercise and at the same time see the wonderful things that were going on around and about my study areas and as a bonus had the chance to get some new ideas.

 

References

Leather, S.R. (1984) Factors affecting pupal survival and eclosion in the pine beauty moth, Panolis flammea (D&S). Oecologia, 63, 75-79.

Leather, S.R. (1985) Does the bird cherry have its ‘fair share’ of insect pests ? An appraisal of the species-area relationships of the phytophagous insects associated with British Prunus species. Ecological Entomology, 10, 43-56.

Leather, S.R. (1986) Insect species richness of the British Rosaceae: the importance of host range, plant architecture, age of establishment, taxonomic isolation and species-area relationships. Journal of Animal Ecology, 55, 841-860.

Leather, S.R. (1988) Size, reproductive potential and fecundity in insects: Things aren’t as simple as they seem. Oikos, 51, 386-389.

Leather, S.R. & Barbour, D.A. (1983) The effect of temperature on the emergence of pine beauty moth, Panolis flammea Schiff. Zeitschrift fur Angewandte Entomologie, 96, 445-448.

Robertson, H.G. (1987) Oviposition and site selection in Cactoblastis cactorum (Lepidoptera): constraints and compromises. Oecologia, 73, 601-608.

Stearns, S.C. (1984) The effects of size and phylogeny on patterns of covariation inthe life history traits of lizards and snakes. American Naturalist, 123, 56-72.

Wellings, P.W., Leather , S.R., & Dixon, A.F.G. (1980) Seasonal variation in reproductive potential: a programmed feature of aphid life cycles. Journal of Animal Ecology, 49, 975-985.

Zonneveld, C. & Metz, J.A.J. (1991) Models on butterfly protandry – virgin females are at risk to die. Theoretical  Population Biology, 40, 308-321.

 

*I hasten to add that I do still have new ideas, they just don’t seem to wake me up any more 🙂

**Now Vice-Chancellor of the University of Wollongong

 

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Red, green or gold? Autumn colours and aphid host choice

“The falling leaves
Drift by my window
The falling leaves
Of red and gold”

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Red, green and gold, all on one tree

When Frank Sinatra sang Autumn Leaves he was almost certainly not thinking of aphids and I am pretty certain that the English lyricist, Johnny Mercer, who translated the words from the original French by Jacques Prévert wasn’t either 🙂

The colours we see in autumn are mainly due to two classes of pigment, the carotenoids (yellow-orange; think carrot) and the anthocyanins (red-purple).  Carotenoids are present in the leaves all year round but are masked by the green chlorophyll.  Chlorophyll breaks down in autumn, leaving the yellow carotenes visible.  The anthocyanins on the other hand are not formed until autumn (Sanger, 1971; Lee & Gould, 2002) and this mixture of pigments give us the colours that have inspired so many artists.

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Autumn Leaves Georgia O’Keeffe (1924) Tate Modern

To many, autumn starts with the appearance of the first turning leaves, to me it is the arrival of gynoparae* of the bird cherry-oat aphid (Rhopalosiphum padi) on my bird cherry (Prunus padus) trees.

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Bird cherry, Prunus padus, leaves on the turn.

Little did I know when I started my PhD in 1977 that almost thirty years later I would be part of a raging debate about the function of autumn colouration in woody plants. At the time I was interested in the colonisation patterns (or as I pretentiously termed it in my thesis ‘remigration’) of bird cherry aphids from their secondary grass and cereal host plants to their primary host bird cherry.  My study system was 30 bird cherry saplings divided between two cold frames in the Biology Compound at the University of East Anglia (Norwich).  Every day from the middle of August until leaf fall I checked every leaf of each tree, for gynoparae, males and oviparae, carefully noting the position of each leaf, its phenological stage and giving it a unique number. I repeated this in the autumns of 1978 and 1979.  The phenological stage was based on the leaf colour: green, mature; yellow, mature to senescent; red, senescent.  What I reported was that more gynoparae landed on green and yellow leaves than on red and that the gynoparae on green and yellow leaves survived for longer and produced more offspring (oviparae), than those on red leaves (Leather, 1981).   The gynoparae of the bird cherry aphid are quite special in that although as adults they do not feed (Leather, 1982), they do not land on bird cherry trees at random (Leather & Lehti, 1982), but choose trees that not only do their offspring (the oviparae) do better on, but that also favour those aphids hatching from eggs in the spring (Leather, 1986).  It should not have come as a surprise then, that when I analysed some of the data I had collected all those years ago, their preference for green and yellow leaves over red ones, is linked to how long those

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Figure 1. Length of time leaves remained on tree after first colonisation by gynoparae of Rhopalosiphum padi (F = 30.1 df 2/77, P <0.001)

leaves have left to live (Figure 1). The timing of events at this time of year, has, of necessity, got to be very precise. The egg-laying females (oviparae) are unable to develop on mature bird cherry leaves (Leather & Dixon, 1981), but it seems that the bird cherry aphid has this under control, making its decisions about the timing of the production of autumn forms (morphs) sometime in August (Ward et al., 1984).  All very sensible as far as I was concerned and that was as far as I took things.  Subsequent work by Furuta (1986) supported this in that he showed that maple aphids settled on and reproduced on green-yellow and yellow-orange leaves but avoided red leaves which had shorter life spans.

Jump forward fifteen years or so, and in a paper, that at the time, had somehow passed me by, the late great Bill Hamilton and Sam Brown (Hamilton & Brown, 2001) hypothesised that trees with an intense autumn display, similarly to those brightly coloured animals that signal their distastefulness with yellows, blacks and reds, were signalling their unsuitability as a host plant to aphids.  Like the costs imposed on insects that sequester plant toxins to protect themselves against predators, the production of anthocyanins responsible for the red autumn colouration is expensive, especially when you consider that the leaves have only a short time left to live (Hoch et al., 2001).  In autumn, trees and woody shrubs are normally mobilising resources in the leaves and moving them back into themselves ready to be used again the following spring (Dixon, 1963). Ecologists and evolutionary biologists were thus keen to explain the phenomenon in terms of trade-offs, for example, fruit flags that advertise the position of fruits for those trees that rely on seed dispersal by vertebrates (Stiles, 1982) or as ultra-violet screens to prevent tissue damage (Merzlyak & Gittelson, 1995).  Hamilton & Brown felt that these hypotheses were either, in the case of the fruit flag, only applicable to trees with fruit present and, in the latter, untenable. Instead they advocated the ‘signalling hypothesis’ which was based on the premise that trees that suffer from a lot of aphids (attacked by more than one species rather than by large numbers of a single species), invest in greater levels of defence and in autumn advertise this using bright warning colours.   The premise being, that although it is metabolically expensive for the plants to produce these colours, it is worth the investment if they result in a reduction in aphid attack.

This hypothesis was not without its detractors. Others suggested, that far from avoiding red colours, aphids were attracted to yellow or green as an indicator of host nutrition (Wilkinson et al., (2002).  Holopainen & Peltonen (2002) also suggested that birch aphids use the onset of autumn colours to pick out those trees where nutrient retranslocation was happening, and thus with higher levels of soluble nitrogen in the leaves.  This was of course, what I was trying to confirm back when I was doing my PhD.  Conversely, supporters of the signalling hypothesis, argued that trees (birch again) that could ‘afford’ to produce bright autumn colours were fitter, so more resistant in general and that they were warning potential herbivores of this by a bright autumn display (Hagen et al 2004).

Round about this time (2002), I was approached by a young Swiss researcher, Marco Archetti, who knew that I had a plot of sixty bird cherry trees that I had planted up when I arrived at Silwood in 1992, originally designed to follow-up some work that I had begun whilst at the Forestry Commission looking at the effects of early season defoliation on subsequent tree growth (Leather, 1993, 1995).  Marco convinced me that I had the ideal set-up to test the ‘signalling hypothesis’ and what was to be a very fruitful collaboration began.

We counted arriving gynoparae and their offspring (oviparae) throughout October (Marco making trips over from Oxford where he was then based**) noting leaf colour before and after each count.  As with my PhD work we found that the greener trees were preferentially colonised by the gynoparae and that more oviparae were produced on those trees and that given what I had found earlier that bird cherry aphid gynoparae chose trees that are good hosts in spring (Leather, 1986), Marco felt that we were able to support the honest signalling hypothesis (Archetti & Leather, 2005).  I was slightly less comfortable about this, as there are only two species of aphid that attack bird cherry and one of those is very rare and the original signalling hypothesis was based on the premise that it was trees that were attacked by a lot of aphid species that used the red colouration as a keep clear signal.  Anyway, it was published 🙂

That said, others agreed with us, for example, Schaefer & Rolshausen (2006) who called it the defence indication hypothesis, arguing that bright colours advertise high levels of plant defence and that the herbivores would do well to stay away from those plants displaying them. On the other hand, Sinkkonen (2006) suggested that reproductively active plants produce autumn colours early to deter insects from feeding on them and thus reduce their seed set.

Chittka & Döring (2007) on the other hand, suggested that there is no need to look further than yellow carotenoids acting as integral components of photosynthesis and protection against light damage and red anthocyanins preventing photo-inhibition (Hoch et al., 2001) as to why trees turn colourful in autumn.  In other words, nothing to do with the insects at all.  A couple of years later however, Thomas Döring and Marco got together with another former colleague of mine from Silwood Park, Jim Hardie, and changed their minds slightly.  This time, whilst conceding that red leaves are not attractive to aphids but noting that yellow leaves are even more attractive than green ones, suggested that the red colour could be being used to mask yellow (Döring et al., 2009).

Others have their own pet theories.  In recent years, veteran Australian entomologist Tom White has become interested in the concept of insect species that specifically feed on senescent plant tissue (White, 2002, 2015) and added to the debate by suggesting that aphids in general are senescence feeders and thus choose green and yellow as they have longest time to live and that the red leaves are also nitrogen depleted (White, 2009) which is supported by my PhD data (Figure 1).  This resulted in a spirited response by Lev-Yadun & Holopainen (2011) who claimed that he had misunderstood the scenario in thinking that leaves go sequentially from green to yellow to red, which they suggest is rare (I question this) and that actually in trees that go from green to red, the leaves still contain significant amounts of nitrogen, so a deterrent signal is still required.

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Maple, green to yellow in this case

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Spindle, Euonymus europaeus, green to red

What about those trees and other plants that have red or purple leaves in the spring or all year round and not just in autumn?

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Some trees have red foliage all year

Trees like some of the ornamental cherries or copper beech? I haven’t been able to find any papers that suggest that red or purple-leaved varieties of beech and cherries are less susceptible to aphid attack.  My own observations, probably imperfectly recalled, are that copper beech is regularly infested by the beech woolly aphid, Phyllaphis fagi , and just as heavily, if not more so than the normal green-leaved  beech trees.  That of course may just be a reflection that the white waxy wool covering the aphid stands out more against the red leaves.  Perhaps someone out here might like to check this out?  Some work that my friend and former colleague, Allan Watt, (sadly unpublished) did many years ago in Scotland looking at the effect of beech species and cultivar on infestation levels by the beech leaf mining weevil, Rhynchaenus fagi, did not indicate any differences between copper and green cultivars.  It does seem however, that in cabbages, leaf colour can tell the specialist cabbage aphid, Brevicoryne brassciae, if plants are well defended or not, the bluer the cabbage, the nastier it is (Green et al, 2015).

To summarise:

  1. Red leaves are produced by the trees in autumn to reduce ultraviolet damage and protect metabolic processes in the leaf.
  2. Red leaves are deliberately produced by the tree to warn aphids that their leaves are well defended – honest signalling.
  3. Red leaves are produced by the tree to ‘fool’ the herbivores that the leaves are likely to drop soon and warn them to keep away so as to safeguard their fruit – dishonest signalling.
  4. The tree is blissfully unaware of the aphids and the aphids are exploiting the intensity of the autumn colours produced by the trees to select which are the best trees to colonise in terms of nutrition and length of time left on the tree.

As I write, the debate still goes on and we seem no nearer to arriving at a definitive answer to the riddle of why trees produce bright leaves in autumn.  If nothing else however, the debate has generated a lot of interest and enabled people to sneak some amusing titles into the scientific literature.  Do make the effort to read the titles of some of the references below.

References

Archetti, M. (2009) Phylogenetic analysis reveals a scattered distribution of autumn colours. Annals of Botany, 103, 703-713.

Archetti, M. & Leather, S.R. (2005) A test of the coevolution theory of autumn colours: colour preference of Rhopalosiphum padi on Prunus padus.  Oikos, 110, 339-343.

Chittka, L. & Döring, T.F. (2007) Are autumn foliage colors red signals to aphids? PLoS Biology , 5(8): e187. Doi:10.1371/journal.pbio.0050187.

Dixon, A.F.G. (1963) Reproductive activity of the sycamore aphid, Drepanosiphum platanoides (Schr) (Hemiptera, Aphididae). Journal of Animal Ecology, 32, 33-48.

Döring, T.F., Archetti, M. & Hardie, J. (2009) Autumn leaves seen through herbivore eyes.  Proceedings of the Royal Society London B., 276, 121-127.

Furuta, K. (1986) Host preferences and population dynamics in an autumnal population of the maple aphid, Periphyllus californiensis Shinji (Homoptera: Aphididae). Zeitschrift fur Angewandte Entomologie, 102, 93-100.

Green, J.P., Foster, R., Wilkins, L., Osorio, D. & Hartley, S.E. (2015) Leaf colour as a signal of chemical defence to insect herbivores in wild cabbage (Brassica oleracea).  PLoS ONE, 10(9): e0136884.doi:10.1371/journal.pone.0136884.

Hagen, S.B. (2004) Autumn coloration as a signal of tree condition. Proceedings of the Royal Society London B, 271, S184-S185.

Hamilton, W.D. & Brown, S.P. (2001) Autumn tree colours as handicap signal. Proceedings of the Royal Society London B, 268, 1489-1493.

Hoch , W.A.,  Zeldin, E.L. & McCown, B.H. (2001) Physiological significance of anthocyanins during autumnal leaf senescence. Tree Physiology, 21, 1-8.

Holopainen, J.K. & Peltonen, P. (2002) Bright colours of deciduous trees attract aphids: nutrient retranslocation hypothesis.  Oikos, 99, 184-188.

Leather, S.R. (1981) Reproduction and survival: a field study of the gynoparae of the bird cherry-oat aphid, Rhopalosiphum padi (L.). Annales Entomologici Fennici, 47, 131-135.

Leather, S.R. (1982) Do gynoparae and males need to feed? An attempt to allocate resources in the bird cherry-oat aphid Rhopalosiphum padiEntomologia experimentalis et applicata, 31, 386-390.

Leather, S.R. (1986) Host monitoring by aphid migrants: do gynoparae maximise offspring fitness? Oecologia, 68, 367-369.

Leather, S.R. (1993) Early season defoliation of bird cherry influences autumn colonization by the bird cherry aphid, Rhopalosiphum padi. Oikos, 66, 43-47.

Leather, S.R. (1995) Medium term effects of early season defoliation on the colonisation of bird cherry (Prunus padus L.). European Journal of Entomology, 92, 623-631.

Leather, S.R. & Dixon, A.F.G. (1981) Growth, survival and reproduction of the bird-cherry aphid, Rhopalosiphum padi, on its primary host. Annals of Applied Biology, 99, 115-118.

Leather, S.R. & Lehti, J.P. (1982) Field studies on the factors affecting the population dynamics of the bird cherry-oat aphid, Rhopalosiphum padi (L.) in Finland. Annales Agriculturae Fenniae, 21, 20-31.

Lee, D.W. & Gould, K.S. (2002) Anthocyanins in leaves and other vegetative organs: An introduction. Advances in Botanical Research, 37, 1-16.

Lev-Yadun, S. & Holopainen, J.K. (2011) How red is the red autumn leaf herring and did it lose its red color? Plant Signalling & Behavior, 6, 1879-1880.

Merzlyak, W.N. & Gittelson, A. (1995) Why and what for the leaves are yellow in autumn? On the interpretation of optical spectra of senescing leaves (Acer platanoides L.). Journal of Plant Physiology, 145, 315-320.

Sanger, J.E. (1971) Quantitative investigations of leaf pigments from their Inception in buds through autumn coloration to decomposition in falling leaves.  Ecology, 52, 1075-1089.

Schaefer, H.M. & Rolshausen, G. (2006) Plants on red alert – do insects pay attentionBioEssays, 28, 65-71.

Sinkkonen, A. (2006) Do autumn leaf colours serve as reproductive insurance against sucking herbivores?  Oikos, 113, 557-562.

Stiles, E.W. (1982) Fruit flags: two hypotheses. American Naturalist, 120, 500-509.

Ward, S.A., Leather, S.R., & Dixon, A.F.G. (1984) Temperature prediction and the timing of sex in aphids. Oecologia, 62, 230-233.

White, T.C.R. (2003) Nutrient translocation hypothesis: a subsect of the flush-feeding/senescence-feeding hypothesis. Oikos, 103, 217.

White, T.C.R. (2009) Catching a red herring: autumn colours and aphids. Oikos, 118, 1610-1612.

White, T.C.R. (2015) Senescence-feesders: a new trophic subguild of insect herbivore. Journal of Applied Entomology, 139, 11-22.

Wilkinson, D.M., Sherratt, T.N., Phillip, D.M., Wratten, S.D., Dixon, A.F.G. & Young, A.J. (2002) The adaptive significance of autumn colours.  Oikos, 99, 402-407.

 

 *for a detailed account of the wonderful terminology associated with aphid life cycles read here

**coincidentally he is now a Lecturer at the University of East Anglia in the same Department where I did my PhD

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The Seven Ages of an Entomologist – Happy 60th Birthday to Me

Today I turned 60 – an event which has come as a bit of a surprise to me as inside I still feel about 17 😉 I thought, given the occasion and the fine example set by Jeff Ollerton‘s recent birthday blog post  that it seems a good time to reflect on my career in particular and academic careers in general. Despite there already being at least two other excellent articles about the “Seven Ages”, Jerry Coyne’s, The Seven Ages of the Scientist and Athene Donald’s The Seven Ages of an Academic Scientist, I felt no qualms in adding my own modest contribution to the genre 😉

Given my own career trajectory it turns out that I need more than seven ages, so as an entomologist I feel justified in adding five larval or nymphal instars to the traditional progression.

 

The Larval Stages

The Infant (first instar)

According to Shakespeare “mewling and puking in the nurse’s arms”, which spending the early part of my childhood in colonial Ghana is actually very apt,

Simon babe in arms

although the photograph below shows a very contented baby indeed.

Simon - baby

I have no entomological memories from this time, although given that then it was normal practice to leave babies outside in their prams, I am sure that I was exposed to the whole range of flying Ghanaian insects. There is some evidence of an early interest in nature and entomology in the picture below where I seem to be investigating a small white butterfly whilst indulging in some early forestry work.

Simon Ghana

My first real biological memory, is however, non-entomological, the blue whale skeleton in the Natural History Museum London in 1958 when my parents were on home leave.

 

The Schoolboy (second instar)

 In 1960 my father was moved to Jamaica to work in the Department of Agriculture as a Plant Pathologist and this is where I started my formal education. Shakespeare describes the schoolboy as “whining schoolboy with his satchel, and shining morning face, creeping like a snail unwillingly to school”.

Simon, Mark & Spences

I certainly had a satchel and it is from this period of my life that I have my first definite entomological memories. We lived in a suburb of Kingston, 32 Gardenia Avenue in Mona Heights. My father kept bees and I spent a lot of time playing with ants, conducting behavioural experiments with crab spiders and having close encounters with wasps and apparently in this picture from 1961, helping with my father’s very luxuriant garden; he grew a great variety of ornamental plants as well as fruit and

Simon 1961      Simon & Pussy cat

 

vegetables, including grapes, bananas, passion fruit, papayas, peanuts and breadfruit as well as coffee and more traditional vegetables. My final school report from my time in Jamaica shows a prescient comment from my biology teacher;

School report

School report bit

 

Secondary school (third instar)

My father’s next posting was to Hong Kong to work for the Ministry of Agriculture; his office was in the New Territories but we lived in Kowloon (Wylie Gardens) where I attended King George V School. Biology was again my favourite subject but apart from cockroaches and ants my entomological experiences were very limited.

Simon - schoolboy           Before braces – 1966

Simon braces

Keeping my mouth shut to hide my orthodontic appliances 1968.

 

Boarding school (fourth instar)

In 1968 my father returned briefly to the UK before his next posting to Fiji and I was sent to a state school, Ripon Grammar School, which had a boarding section. I was to spend five relatively happy years there and despite the competing interests of girls and sports, further developed my interest in invertebrate zoology, due in the main part to my zoology teacher ‘Brian’ Ford. I have many happy memories of pond dipping, searching for Cepea nemoralis and generally fossicking around in hedgerows.

Simon Fiji 1970

When on school holidays in Fiji I found time to investigate the local insect and amphibian fauna; our house seemed to attract toads in huge numbers which my brothers and I used to competitively collect in buckets for later release.

 

Sixth form (final instar)

In my two final years at school sport and girls continued to play a larger part in my life than entomology although I see from the fly-leaf of my books from that time that I owned and had read both volumes of Ralph Bucshbaum’s Life of the Invertebrates and also Darwin’s Origins.

Second fifteen

Ripon Grammar School 2nd XV – I am third from the left on the front row.

 Careers advice when I was at school was not very sophisticated and if you did Biology ‘A’ Level and were a school prefect, it was automatically taken that you were either destined to be a Doctor, a Vet or a Dentist.

School House Prefects1973

I was no different and despite my misgivings, duly applied for and was accepted at Birmingham University to read Medicine. As luck would have it, things did not work out as planned and after a less than happy year at Aston University in Birmingham, in 1974 I left Birmingham and moulted into a proto-entomologist at the University of Leeds.

 

The Undergraduate

The discovery that learning can be fun and that there might actually be a career in doing something that you enjoy.

I did a now extinct degree (although I have plans to exhume it), Agricultural Zoology, essentially a year of vertebrate zoology, with two years of invertebrate zoology, essentially applied entomology, parasitology and nematology. I loved it and thrived on it and grew my hair even longer.

Simon - undergraduate

I decided to become an entomologist in my second year and discovered the wonders of aphids at the same time. It was also round about this time that I decided I was going to become a university academic and started to work a lot harder; the logical end point of someone with a mother who was a secondary school biology teacher and a father who was a research scientist.

 

The Postgraduate

Discovering that being on “the road to find out” (Cat Stevens) is exhilarating

Simon - PhD student

I did my PhD at the University of East Anglia in Norwich – Aspects of the Ecology of the Ecology of the Bird Cherry Aphid, under the supervision of Professor Tony Dixon. A totally fantastic time, despite the ‘second year blues’ which all PhD students seem to go through when they think that they don’t have enough data. I was lucky enough to be in a large research group, at one stage there were thirteen of us in the lab, so there was always plenty of help and advice available. In addition we had the excitement of conferences and the first unsteady steps towards learning to lecture, mainly demonstrating in undergraduate practicals; I spent a lot of time pithing frogs for physiology classes (don’t ask) and also tutoring first year students in mathematics. We also played a lot of squash and enjoyed our social life; for those of you who know Norwich, The Mitre pub on Earlham Road, was our regular haunt.

 

The post-doc

Discovering how to run a research lab

I did two brief post-docs, the first in Finland, under the auspices of the Royal Society and the

Simon Finland 1981

second back at the University of East Anglia funded by the Agriculture and Food Research Council, both working on cereal aphids. At this stage of my career I started to learn how to supervise postgraduate students; the first port of call in a busy lab after the senior PhD student has failed to supply an answer is always the post-doc as the lab head is inevitably very busy. I also got my first real opportunity to lecture undergraduates, which turned out to be a lot harder than I had thought it would be even when talking about my own research.

 

Interlude or host alternation

 The Research Scientist

 Discovering that directed research on its own is not enough

Copy of Simon SSO

In a normal academic career, the next stage after post-doc is an appointment as a University Lecturer. In the early 1980s university lectureships were in short supply and many of us who would normally have gone into an academic career found ourselves either having to go abroad as lecturers at Commonwealth universities (I was offered but turned down a lectureship at Kano University in Nigeria) or joining research institutes. In 1982 I joined the UK Forestry Commission’s Northern Research Station where I spent ten years as a forest entomologist, answering enquiries, conducting directed research and giving the occasional guest lecture. I was however, lucky enough to be able to gain some PhD supervisory experience and after ten years, the last five which were increasingly frustrating, was lucky enough in 1992 to be appointed to a Lectureship at the Silwood Park campus of Imperial College.  In retrospect this was the last time I was able to spend about 90% of my time at the bench and in the field doing ‘hands on’ research, but I have never regretted moving into academia – the opportunity of being able to pass on what you have discovered and hopefully enthuse and motivate a new generation more than makes up for the loss.
Back to the primary host

 

The Lecturer

When I discover that I love teaching

Simon - Lecturer

You may have noticed that I have had a haircut; it was a source of some amusement to me that on joining the university sector I was expected to get my hair cut.

I was appointed as a Lecturer in Pest Management to teach on the world-renowned MSc Entomology course at Silwood Park, and as I was replacing a specific person (Geoff Norton), although not in exactly the same subject area, my ‘grace’ period was shorter that it might have been. Normally at research intensive institutions like Imperial College, new appointments are given two to three years to apply for grants and get their research groups started before being given teaching and departmental jobs. I had a year, but as I discovered that I very much enjoyed teaching (something that many of my colleagues then and later found very strange) I was not dismayed. Unlike some of my colleagues I had read the dictionary definition of the word lecturer: noun. One who delivers lectures, especially professionally.   I have never really understood the mentality of those who aspire to university positions and yet find the idea of having to teach students not only a distraction but in some cases abhorrent and to be avoided at all costs and strive to obtain funding to buy them out of teaching as soon as possible. Some of my senior colleagues at Imperial College (and elsewhere) had and have almost no experience of teaching at all and so have no idea of what is involved in delivering a decent course, a state of affairs that explains some of the very strange decisions that are made at some of the research intensive universities in the UK.   I often felt that they would be much happier in a research institute.

I also discovered that if you take teaching seriously then your ‘bench time’ is much reduced and you begin your career as a research manager, appointing PhD students and post-docs to carry your research ideas forward. I made a decision early on that I would attempt to keep some of my skills extant and set up a long-term field project looking at the insect communities living on sycamores at Silwood Park, especially the aphids. This meant that I had to set a day a week aside to collect data. By doing this it meant that I had a reality check on what was actually possible. I have seen too many colleagues who because of the time they had spent away from the bench or the field, had totally unrealistic expectations of what was actually possible to be achieved by their students and research assistants.

 

The Senior Lecturer

When the Department discovers that I love teaching

In 1996 I was promoted to Senior Lecturer (I think that it is a real shame that some UK universities have decided to adopt North American terminology and introduce the title of Associate Professor, apparently to avoid confusing the rest of the World. At Imperial College promotion to Senior Lecturer was to reward teaching excellence and was usually the kiss of death for any further promotion.

Simon - Lecturera

Senior Lecturer in Applied Ecology

 I was as well as teaching on the MSc Entomology course doing an increasing amount of undergraduate teaching including a final year course in Applied Ecology of which I was very proud, hence the decision to retitle myself. I was also very busy with external activities, being on the Editorial Board of the Bulletin of Entomological Research and just been appointed as Editor-in-Chief of Ecological Entomology, just finished a term on the council of the Royal Entomological Society and been appointed to a slew of Departmental and University committees. My research group was really starting to take off, I was supervising 8 PhD students at the time; given the poor return rate on major grant applications in the UK, I decided early on that going for PhDs was a better use of my limited time and this is a strategy that I have mainly followed to the present day.

Research group

This does not include MSc or BSc students – they would add about 10 to each yearly figure from 1995 onwards

The Reader

 When I discover that it is possible to get even busier

In 2002 I was promoted to Reader one of the definitions of which according to Chambers’s Twentieth Century Dictionary is defined as follows; Old English rǣdere ‘interpreter of dreams, reader’. In the UK university system, it is the rank below full Professor and comes with an endowed title, in my case I chose to become Reader in Applied Ecology to reflect the

Simon - Reader

myriad teaching roles I had accumulated and also to encompass the fact that my research group no longer dealt solely with arthropods, vertebrates had somehow sneaked their way in. Looking at Athene Donald’s list I see that I was pretty much doing a professorial role, serving on external committees, validating degrees for other universities and acting as an external examiner. I was also appointed as Editor-in-Chief of Insect Conservation and Diversity, a new journal for the Royal Entomological Society. My administrative duties had also continued to increase.  It was no wonder that my beard was getting greyer! I was however still preparing my own talks, although I will confess that a lot of my data analysis was being passed on to members of the group, duly acknowledged of course. I am extremely grateful that I have always had a loyal and very supportive research group, without their help life would have been impossible.  My thanks to you all (if any of you are reading this).

 

The Professor

Discovering the joys of being pretty much able to do what I want (with certain restrictions)

It became increasingly obvious that things could not carry on as they were, my teaching and administrative loads were becoming ridiculous; our Director of Teaching calculated that I was actually doing more teaching than anyone else in the Department including the Teaching Fellows. I was seriously considering early retirement although I was reluctant to do this as I was sure that with my retirement the last entomology degree in the UK would quickly disappear. Luckily in 2012 my team and I were miraculously offered the chance to move to a new more supportive location, Harper Adams University in Shropshire.

Simon 2015

So now I have become a Senior Professor, with a new entomology building, with less undergraduate teaching, which I miss, and a role that requires me to sit on more external and internal committees, to meet the great and the good and to make solemn pronouncements.  At the same time however, it does allow me to plough my own furrow and to influence university policy. Most importantly I no longer feel that I am beating my head against a brick wall and that the future of entomology as a degree course in the UK is much safer than it was five years ago.  I think I am at Stage 4 in Jerry Coyne’s list as I now find that I am much more interested in synthesizing and disseminating what I have learnt rather than doing original research – I can feel a book coming on 😉

My hope is that in five years time when I become a retired Professor and my hair and beard colour are the same, that entomology will be taught at more than one university in the UK and not just at postgraduate level.

A small point of personal satisfaction, is that, despite my elevation, I still do not own a suit 😉

 

For reference

Jerry A. Coyne’s summary, reproduced from his blog

  1. As student, listens to advisor give talk on student’s own work
  2. As postdoc, gives talks about his/her own work
  3. As professor, gives talks about his/her students’ work
  4. Talks and writes about “the state of the field”
  5. Talks and writes about “the state of the field” eccentrically and incorrectly—always in a self-aggrandizing way.
  6. Gives after-dinner speeches and writes about society and the history of the field
  7. Writes articles about science and religion

 

And the famous original from which the title is borrowed and adapted.

 

Seven Ages Of Man

(from As You Like It by William Shakespeare)

All the world’s a stage,

And all the men and women merely players,

They have their exits and entrances,

And one man in his time plays many parts,

His acts being seven ages. At first the infant,

Mewling and puking in the nurse’s arms.

Then, the whining schoolboy with his satchel

And shining morning face, creeping like snail

Unwillingly to school. And then the lover,

Sighing like furnace, with a woeful ballad

Made to his mistress’ eyebrow. Then a soldier,

Full of strange oaths, and bearded like the pard,

Jealous in honour, sudden, and quick in quarrel,

Seeking the bubble reputation

Even in the cannon’s mouth. And then the justice

In fair round belly, with good capon lin’d,

With eyes severe, and beard of formal cut,

Full of wise saws, and modern instances,

And so he plays his part. The sixth age shifts

Into the lean and slipper’d pantaloon,

With spectacles on nose, and pouch on side,

His youthful hose well sav’d, a world too wide,

For his shrunk shank, and his big manly voice,

Turning again towards childish treble, pipes

And whistles in his sound. Last scene of all,

That ends this strange eventful history,

Is second childishness and mere oblivion,

Sans teeth, sans eyes, sans taste, sans everything.

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The Dead Entomologists Society

The late and the great: who are the most influential dead entomologists?

In the run-up to the Christmas holidays an ex-student of mine, Andy Salisbury, now at RHS Wisley, and I were discussing who were the most influential dead entomologists ever.  We had begun our discussion discussing Harold Maxwell-LeFroy, http://en.wikipedia.org/wiki/Harold_Maxwell-Lefroy, who among other claims to fame, was the first editor of Annals of Applied Biology http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744-7348 , the founder of Rentokil and former Professor of Entomology at Imperial College.  He was also famous for having killed himself accidentally whilst trying out a pesticide.

Lefroy conversation

Dead entomologists

Up until the early part of this century he was commemorated in the Biology Department at Imperial College’s Silwood Park Campus with a laboratory named after him; sadly with the move into the new Hamilton Building this no longer exists.

We agreed that the great Alfred Russel Wallace was the most influential entomologist of all time; we felt that claiming Darwin as an entomologist, although famous for his beetle collecting, and despite being a Fellow of the Royal Entomological Society, might be a step too far.  So after Wallace, who was the most influential dead entomologist?

I think that this depends on how you define influential – for entomologists of my generation and the one before us, i.e. those born between 1930 and 1960; Imms and Wigglesworth are probably the two who most influenced us mainly because they were our recommended undergraduate texts  (those were the days when you could do entomology  in the UK as an undergraduate);

Wigglesowrth & Imms compresed

today I guess these have been replaced by Chapman’s The Insects: Structure and Function and Gullan & Cranston’s Outline of Entomology.  But of course outside the field of entomology who remembers Imms and Wigglesworth?  So we should, I think, be looking for entomologists whose influence has extended more widely;  a slightly tongue in cheek contender would be Thomas Moufet,  http://en.wikipedia.org/wiki/Thomas_Muffet who is possibly apocryphally, remembered for the nursery rhyme about his daughter Little Miss Muffett and more substantiated, for his compilation of the Theatre of Insects, but he was mainly a man of

Moufet book

medicine and more interested in spiders than insects in general.  A contender widely known outside the entomological world would be H W Bates, http://en.wikipedia.org/wiki/Henry_Walter_Bates#Taxonomy who is today remembered in the term Batesian

Henry Walter Bates

mimicry  http://en.wikipedia.org/wiki/Mimicry#Batesian ; as a former President of the Royal Entomological Society (1868-1869) I think that we can safely claim him as an entomologist.

Other entomologists that have had an influence  on the rest of the non-entomological world, albeit not widely known outside the biological or medical sciences are Fabre and his Lives of  various insects http://en.wikipedia.org/wiki/Jean-Henri_Fabre , Karl von Frisch http://en.wikipedia.org/wiki/Karl_von_Frisch for his work on honeybees, especially in deciphering the waggle-dance,  E B Ford for his work on ecological genetics and for inspiring Kettlewell’s work on Biston betularia,  http://en.wikipedia.org/wiki/E._B._Ford  and more recently Richard Southwood  http://en.wikipedia.org/wiki/Richard_Southwood   (Methods in Ecology) but initially a Hemipteran specialist and Miriam Rothschild  http://en.wikipedia.org/wiki/Miriam_Rothschild for her work on a range of entomological subjects but very famously for her work on fleas.

The acid test of course, is how many living entomologists the man or woman in the pub can bring to mind when asked, let alone those that have joined the Dead Entomologist’s Society. Perhaps it is the fate of entomologists to be largely overlooked, much like the small but highly important organisms we work on 😉

I would dearly love to hear your thoughts on which the most influential dead entomologists are.  I am well aware, that my list is very Euro- and UK-centric.  So let’s see some nominations from the rest of the world, suitably justified of course!

Post script

Getting my vote as a contender for an American entomologist of great influence, albeit British-born, would be Charles Riley, sometimes known as the Father of Biological Control http://en.wikipedia.org/wiki/Charles_Valentine_Riley , but then again, who outside the world of entomology has heard of him?

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