Monthly Archives: October 2016

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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An aphid is… a flea, a louse, and even a marine mammal!

Earlier this year I wrote about the debate that rages about the correct way to talk about thrips during which I got distracted and ended up writing about their names in different languages. It turns out that I am not alone in being curious about international insect naming. I have just finished reading Matthew Gandy’s excellent book Moth, where he waxes lyrical about the different names used to describe butterflies and moths around the world.  This, of course, made me wonder what aphid would turn up, so armed with dictionaries and Google Translate, I traveled the world to see what I could discover.

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The bronze-brown dandelion aphid, Uroleucon taraxaci – Photo by Jasper Hubert

There are a lot of languages so I am only going to highlight a few versions of aphid that I found interesting or surprising.  According to The Oxford English Dictionary, Linneaus coined the word Aphides, which may (or not) have been inspired by the Ancient Greek  ἀφειδής‎ (apheidḗs) meaning unsparing, perhaps in relation to their rapid reproduction and feeding habits.  The modern spelling of aphid seems to have come into being after the Second World War, although you could still find aphides being used in the late 1940s (e.g. Broadbent et al., 1948; Kassanis, 1949), and it can still be found in more recent scientific literature where the journal is hosted in a non-English speaking country.

Many aphid names are very obviously based on the modern Latin word coined by Linneaus, although in some countries more than one name can be used, as in the UK where aphid is the technical term but blackfly and green-fly are also commonly used.

 

Aphide derived names

Albanian              afideja

English                  aphid

French                  aphide

Hindu                    एफिड ephid

Portuguese         afídio

Spanish                áfido

 

More common are those names that relate to the vague resemblance that aphids have to lice and to their plant feeding habit. The term plant lice to describe aphids was commonly used in the scientific literature up and into the early 1930s (e.g. Mordvilko, 1928; Marcovitch, 1935).

 

Names linked to the putative resemblance to lice and their plant feeding habit

Bosnian                lisna uš                 uš is louse, lisna derived from leaf

Bulgarian             listna vŭshka     vŭshka louse, listna plant leaf

Danish                  bladlaus               blad is leaf, laus louse

Dutch                    bladluis                blad is leaf, luis is louse

Estonian               lehetäi                  leht is leaf, tai is louse

German                Blattlaus               blatt is leaf, laus is louse

Greek                   pseíra ton fytón louse on plant

Hungarian           levéltetű               leve is leaf, tetű is louse

Icelandic              lús or blaðlús     lús is louse, blað is plant

Latvian                  laputs                   lapa is, uts is louse

Norwegian          bladlus                 blad is plant, lus is louse

Swedish               bladlus                 as for Norwegian

 

If you draw siphunculi on to a louse and add a cauda to the rear end you can just about see the resemblance.

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Louse with added siphunculi and cauda

 

Names based on the premise that aphids resemble fleas

French  puceron                  puce is flea

Spanish pulgón                   pulga is flea

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Flea with cauda and siphunclus, but still only a poor imitation of the real thing.  Even with added aphid features I don’t see the resemblance 🙂

 

In Turkish, aphid is yaprak biti which roughly translates to leaf biter.  There are then a few languages where there appears to be no connection with their appearance or feeding habit.

 

Other names for aphid

Basque                 zorri

Chinese                蚜

Filipino                 dapulak

Finnish                  kirva

Lithuanian           Mszyca

Tamil                     அசுவினி Acuviṉi

Welsh                   llyslau

Xhosa                    zomthi

 

In Lithuanian, where aphid is Mszyca, which looks like it might be derived from Myzus, an important aphid genus, aphid also translates to amaras which means blight.  In the case of a heavy aphid infestation, this is probably an apt description.  I was also amused to find that whilst the Welsh have a name for aphid, Scottish Gaelic does not.

My all-time favourite, and one for which I can find no explanation at all, is dolphin.  According to Curtis (1845), aphids on cereals in some counties of England were known as wheat dolphins.  I was also able to trace the use of this name back to the previous century (Marsham, 1798), but again with no explanation why this name should have arisen.

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The wheat dolphin 🙂

References

Broadbent, L., Doncaster, J.P., Hull, R. & Watson, M.A. (1948) Equipment used for trapping and identifying alate aphides.  Proceedings of the Royal Entomological Society of London (A), 23, 57-58.

Curtis, J. (1845) Observations on the natural history and economy of various insects etc., affecting the corn-crops, including the parasitic enemies of the wheat midge, the thrips, wheat louse, wheat bug and also the little worm called Vibrio. Journal of the Royal Agricultural Society, 6, 493-518.

Gandy, M. (2016) Moth, Reaktion Books, London

Kassanis, B. (1949) The transmission of sugar-beet yellows virus by mechanical inoculation. Annals of Applied Biology, 36, 270-272.

Marcovitch, S. (1935) Experimental evidence on the value of strip farming as a method for the natural control of injurious insects with special reference to plant lice. Journal of Economic Entomology, 28, 62-70.

Marsham, T. (1798) XIX. Further observations on the wheat insect, in a letter to the Rev. Samuel Goodenough, L.L.D. F.R.S. Tr.L.S.  Transactions of the Linnaean Society of London, 4, 224-229.

Mordvilko, A. (1928) LXX.—The evolution of cycles and the origin of Heteroecy (migrations) in plant-lice , Annals and Magazine of Natural History: Series 10, 2, 570-582.

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It isn’t easy being an applied ecologist – working on crops limits publication venues

“This is Simon Leather, he’s an ecologist, albeit an applied one” Thus was I introduced to a group of visiting ecologists by my then head of department at the Silwood Park campus of Imperial College. As you can imagine I was somewhat taken aback at this public display of the bias that ‘pure’ scientists have against those that they regard as ‘applied’.  I was (and still am), used to this attitude, as even as an undergraduate doing Agricultural Zoology when we shared modules with the ‘pure’ zoologists, we were regarded as a slightly lower life form J  Working in Finland as a post-doc in the early 1980s it was also obvious that there was a certain degree of friction between the pure and applied entomologists, so it was not a phenomenon confined entirely to the UK.  To this day, convincing ecology undergraduates that integrated pest management is a suitable career for them is almost impossible.

I was an ecologically minded entomologist from early childhood, pinning and collecting did not interest me anywhere near as much as insect behaviour and ecology, but I knew that I wanted to do something “useful” when I grew up. Having seen my father in action as a plant pathologist and crop protection officer, it seemed to me that combining entomology with agriculture would be an ideal way to achieve this ambition.  A degree in Agricultural Zoology at Leeds and a PhD in cereal aphid ecology at the University of East Anglia (Norwich) was the ideal foundation for my chosen career as an applied ecologist/entomologist.

I started my professional life as agricultural entomologist working both in the laboratory and in the field (cereal fields to be exact), which were easily accessible, generally flat, weed free and easy to manipulate and sample.  In the UK even the largest fields tend to be visible from end to end and side to side when you stand in the middle or edge (even more so now than when I started as wheat varieties are now so much shorter, less than half the height they were in 1977).

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Having fun as a PhD student – aphid ‘sampling’ in Norfolk 1978

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I haven’t grown since I did my PhD so wheat must have shrunk 🙂

See the post script to see what wheat used to look like.

Laboratory experiments, even when working on mature plants were totally do-able in walk-in growth rooms, and at a push you could even fit whole earing wheat plants into a growth cabinet.

I then spent ten years working as a forest entomologist, where field sites were the exact opposite, and extreme measures were sometimes required to reach my study animals, including going on an official Forestry Commission tree climbing course.

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Pole pruners – (of only limited use) and tree climbing (great fun but laborious)

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Scaffold towers for really high work, but expensive (and scary on sloping hillsides).

And as for lab work, not a chance of using mature plants or even plants more than two to three years old.  Excised branches and/or foliage (rightly or wrongly) were the norm*.

Doing field work was, despite the sometimes very physically challenging aspects, a lot of fun, and in my case, some very scenic locations.  My two main field sites were The Spey Valley and

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Sutherland and Caithness, both of which provided magnificent views and of course, a plethora of whisky distilleries

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where I discovered what is now my favourite single malt 🙂

The real fun came when it was time to submit papers.  Journal choice was (and is) very important.  As Stephen Heard points out, journals have a ‘culture’ and it is very important to pick a journal that has the right editorial board and ethos. The laboratory work never seemed to be a huge problem, referees (perhaps wrongly) very rarely criticised the use of young plants or excised foliage. I was able to publish the output from what was a very applied project, in a range of journals from the very specialised to the more ecological. This selection for example, from 1985-1987 (Leather, 1985, 1986; Leather & Burnand, 1987; Leather et al., 1985), appeared in Ecological Entomology, Oecologia, Functional Ecology and Bulletin of Entomological Research respectively.

Papers reporting field-based work were a little bit harder to place in journals outside the mainstream forestry ones, particularly when it came to experimental work.  One of the problems was that ecological referees unused to working in forests tended not to have a grasp of what was involved in setting up and servicing an experiment in a forest plantation or stand.  A farmer has no great objection to an entomologist removing 100 wheat tillers a week from his 2 ha field (at 90 stems per metre2, even a 16 week field season would only remove a tiny fraction of his crop).  A forest manager on the other hand with a stocking density of 3000 stems per hectare would look askance at a proposal to remove even 100 trees a month from a hectare plot, especially if this was repeated for seven years.  Sample size was thus a problem, even when using partial sampling of trees, e.g. by removing say only one branch.  When it came to field scale replication, to compare for example, three treatments and a control on two different soil types, where each treatment plot is a hectare, things get a bit difficult. The most that we could service, even with help (since we did not have huge financial resources), was three replicates of each treatment.  In agricultural terms this seems incredibly low, where 10m2 plots or even smaller, are very often used (e.g. Staley et al., 2009; Garratt et al., 2011).

We thus ended up with our experimental papers in the really specialised forestry journals (e.g.  Leather, 1993; Hicks et al., 2007).  On the other hand, those papers based on observational, long-term data were easier to place in more general ecological journals (e.g. Watt et al., 1989), although that was not always enough to guarantee success (e.g. Walsh et al., 1993; Watt et al., 1991).  Another bias that I came across (perhaps unconscious) was that referees appeared, and still do, think that work from production forests is not as valid as that coming from ‘natural’ forests, especially if they are tropical. We came across this when submitting a paper about the effects of prescribed burning on carabid populations in two sites in Portugal (Nunes et al., 2006).  We originally sent this to a well-known ecological journal who rejected it on the grounds of low replication, although we had also replicated it temporarily as well as geographically.  I was not impressed to see a paper published in this journal shortly after they had rejected our manuscript in which the authors had reported changes in insect communities after a one-off fire event in a tropical forest, without even the benefits of pre-fire baseline data.  We had in the meantime, given up on general ecology journals and submitted our paper to a local forestry journal.  Such is life.

I originally started this essay with the idea of bemoaning the fact that publishing studies based in production forests in more general journals was more difficult than publishing agriculturally based papers, but got diverted into writing about the way applied ecologists feel discriminated against by journals and pure ecologists.  I may or may not have convinced you about that.  To return to my original idea of it being more difficult for forestry–based ecologists to break out of the forestry journal ghetto than it is for agro-ecologists to reach a broader audience, I present the following data based on my own publication record, which very convincingly demonstrates that my original feeling is based on fact, albeit based on an n of one 🙂

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Numbers of agricultural and forestry based papers published by me in different journal categories.

I might also add that being an entomologist also limits where you can publish, so being an applied entomologist is something of a double whammy, and when it comes to getting research council funding, don’t get me started!

References

 Garratt, M.P.D., Wright, D.J., & Leather, S.R. (2010) The effects of organic and conventional fertilizers on cereal aphids and their natural enemies. Agricultural and Forest Entomology, 12, 307-318.

Hicks, B.J., Aegerter, J.N., Leather, S.R., & Watt, A.D. (2007) Differential rates of parasitism of the pine beauty moth (Panolis flammea) depends on host tree species. Scottish Forestry, 61, 5-10.

Leather, S.R. (1985) Oviposition preferences in relation to larval growth rates and survival in the pine beauty moth, Panolis flammea. Ecological Entomology, 10, 213-217.

Leather, S.R. (1986) The effect of neonatal starvation on the growth, development and survival of larvae of the pine beauty moth Panolis flammea. Oecologia, 71, 90-93.

Leather, S.R. (1993) Influence of site factor modification on the population development of the pine beauty moth (Panolis flammea) in a Scottish lodgepole pine (Pinus contorta) plantation. Forest Ecology & Management, 59, 207-223.

Leather, S.R. & Burnand, A.C. (1987) Factors affecting life-history parameters of the pine beauty moth, Panolis flammea (D&S): the hidden costs of reproduction. Functional Ecology, 1, 331-338.

Leather, S.R., Watt , A.D., & Barbour, D.A. (1985) The effect of host plant and delayed mating on the fecundity and lifespanof the pine beauty moth,  Panolis flammea (Denis & Schiffermuller) (Lepidoptera: Noctuidae): their influence on population dynamics and relevance to pest management. Bulletin of entomological Research, 75, 641-651.

Nunes, L.F., Silva, I., Pité, M., Rego, F.C., Leather, S.R., & Serrano, A. (2006) Carabid (Coleoptera) community change following prescribed burning and the potential use of carabids as indicator species to evaluate the effects of fire management in Mediterranean regions. Silva Lusitania, 14, 85-100.

Staley, J.T., Stewart-Jones, A., Pope, T.W., Wright, D.J., Leather, S.R., Hadley, P., Rossiter, J.T., Van Emden, H.F., & Poppy, G.M. (2010) Varying responses of insect herbivores to altered plant chemistry under organic and conventional treatments. Proceedings of the Royal Society of London B, 277, 779-786.

Walsh, P.J., Day, K.R., Leather, S.R., & Smith, A.J. (1993) The influence of soil type and pine species on the carabid community of a plantation forest with a history of pine beauty moth infestation. Forestry, 66, 135-146.

Watt, A.D., Leather, S.R., & Stoakley, J.T. (1989) Site susceptibility, population development and dispersal of the pine beauty moth in a lodgepole pine forest in northern Scotland. Journal of Applied Ecology, 26, 147-157.

Watt, A.D., Leather, S.R., & Evans, H.F. (1991) Outbreaks of the pine beauty moth on pine in Scotland: the influence of host plant species and site factors. Forest Ecology and Management, 39, 211-221.

 

Post script

The height of mature wheat and other cereals has decreased hugely over the last two hundred years.  Cereals were originally a multi-purpose crop, not just providing grain for humans, but bedding straw for stock and humans, winter fodder for animals, straw for thatching and if really desperate, you could make winter fuel out of discarded straw**.

applied-fig-8

John Linnell  – Wheat 1860  You wouldn’t have been able to see Poldark’s (Aidan Turner) manly chest whilst he was scything in this field!

aplied-fig-8

Pieter Breugel the Elder – Die Kornernter – The Harvesters  (1565) – Head-high wheat crops and not just because the average height was lower in those days.

 

*As I was writing this article I came across this paper (Friberg & Wiklund, 2016) which suggests that using excised plants may be justifiable.  Friberg, M. & Wiklund, C. (2016)  Butterflies and plants: preference/performance studies in relation to plant size and the use of intact plants vs. cuttings.  Entomologia experimentalis et applicata, 160, 201-208

**My source for this is Laura Ingalls Wilder – Little House on the Prairie, to be exact 🙂

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