Tag Archives: aphids

Ten more papers that shook my world – When it comes to plant-insect interactions its growth stage, not age that counts Watt (1979)

This is not just about a paper, but also about mentoring!  At the beginning of October 1977, I hesitantly knocked on the door of Professor Tony Dixon’s outer office in the School of Biological Sciences at the University of East Anglia, Norwich.  Tony was to become my PhD supervisor for the next three years and my friend and colleague for the next forty plus years, but until that day I had never met him, as my interview had been conducted entirely by telephone and in those pre-internet days, unless you had met someone at a conference you really only knew them by their papers and reputation.  I knew Tony because of his great little book, The Biology of Aphids which I had bought as an undergraduate in 1975, when I realised that aphids were really cool 😊 I told his secretary who I was and she directed me through to his office.  Tony looked up, said hello and asking me to follow him, took me down to the lab where I was to spend the next three years and introduced me to a tall, moustachioed Scotsman, Allan Watt, whom I was later to discover had a wicked sense of humour, and was to become not just a colleague and collaborator, but also a great friend, a friendship that continues to this day.  Tony’s introduction was roughly along the lines of “This is Allan, he’ll tell you what to do” and he did. Allan was just starting the final year of his PhD which was, like a number of us in Tony’s lab, on cereal aphids, in Allan’s case Sitobion avenae and Metopolphium dirhodum, the two major pests of cereals in the UK at the time.  My PhD was on a less abundant (in cereal crops), but equally problematic aphid, due to its ability to transmit Barley Yellow Dwarf Virus, the bird cherry-oat aphid Rhopalosiphum padi.  Having got my aphid cultures set up and done a couple of practice mini-experiments, I asked Allan what he was doing with his aphids.  He told me that he was looking at the effect of cereal growth stage on the survival and reproduction of his two aphid species and that the age of the plant had a significant effect on the aphids and that this varied between the two species, which he published a couple of years later (Watt, 1979).  Having been immersed in the cereal aphid literature for a couple of months, I knew that no one had done this for my aphid, and even then, being a great believer in “standing on the shoulders of giants” I figured that I could do the same for my aphid, but, in that never ending treadmill of adding novelty, also look at the effect of feeding position*. Allan’s advice and help stood me in good stead, and in due course I successfully published the results of my experiment (Leather & Dixon, 1981).

So, leaving aside me getting a publication as a result of Allan’s paper, how did this shake my World?  Well, first of all, it really drove home to me that plant phenological stage was incredibly important for insect-plant interactions and that unless you know the precise growth stage at which an interaction is happening it is difficult to compare other peoples’ results to yours and each other’s. As a result, it has led me as a reviewer and reader of papers, to be very scathing of phrases such as “ten-day old wheat plant”, “week old cabbage seedlings”, “young pea plant” (Leather, 2010).  It is deeply unhelpful for anyone wanting to repeat or compare similar work.  Just a few degrees difference in temperature over a week can move a plant from one phenological stage to another. There is no excuse for this type of sloppiness.

Two seven-day old wheat plants, same cultivar, same germination date, one reared at 20⁰C the other at 10⁰C. Growth stage 12 versus Growth stage 10 (Growth stages as described by Tottman & Makepeace, 1979).

The same two plants now fourteen day sold, GS 13 versus GS 12

It is not hard to find a solution.  The World has been blessed by the invention of the BBCH** system for coding plant phenological stages (Meier et al., 2009).  This system, which now exists for most major crop plants, including trees, means that there is no excuse for anyone to ever use the phrase “ten-day old plant” or similar wording. If by some chance, your plant does not yet have a BBCH description, either describe the growth stage that your plants are at in very precise terms or take the time to codify it yourself and submit it to a journal such as Annals of Applied Biology which has a long history of publishing such articles.

To be fair, before the BBCH system came into being, people had published descriptions of plant growth stages for some of the major crops, e.g. cereals (Feekes, 1941; Large, 1954), but they were not standardised, and in some cases, too broad-brush.  The stimulus for a standardised, decimal system of coding plant phenological stages was the publication of the Zadoks scale for cereals (Zadoks et al., 1974) and the illustrated follow-up a few years later (Tottman & Makepeace, 1979), the latter being the blueprint on which phenological growth stage papers are now based.

I look forward to the day when authors understand that a precise knowledge of plant growth stage is essential to understanding insect-plant interactions and I do NOT have to chide authors for not using the BBCH codification when I review their papers.

 

References

Feekes, W. (1941) De Tarwe en haar milieu. Vers. XVII Tech. Tarwe Comm. Groningen, 560-561.

Large, E.C. (1954) Growth stages in cereals. Plant Pathology, 3, 128-129.

Leather, S.R. (2010) Precise knowledge of plant growth stages enhances applied and pure research. Annals of Applied Biology, 157, 159-161.

Leather, S.R. & Dixon, A.F.G. (1981) The effect of cereal growth stage and feeding site on the reproductive activity of the bird cherry aphid Rhopalosiphum padi. Annals of Applied  Biology, 97, 135-141.

Meier, U., Bleiholder, H., Buhr, L., Feller, C., Hack, H., Hess, M., Lancashire, P.D., Schnock, U., Strauss, R., Vanden Boom, T., Weber, E. & Zwerger, P. (2009) The BBCH system to coding the phenological growth stages of plants – history and publications. Journal fur Kulturpflanzen, 61, S.41-52.

Tottman, D.R. & Makepeace, R.J. (1979) An explanation of the decimal code for the growth stage of cereals, with illustrations. Annals of Applied Biology, 93, 221-234.

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.

Watt, A.D. & Dixon, A.F.G. (1981) The effect of cereal growth stages and crowding of aphids on the induction of alatae in Sitobion avenae. Ecological Entomology, 6, 441-447.

Watt, A.D. & Wratten, S.D. (1984) The effects of growth stage in wheat on yield reductions caused by the rose grain aphid, Metopolophium dirhodum. Annals of Applied Biology, 104, 393-397.

Zadoks, J.C., Chang, T.T. & Konzak, C.F. (1974) A decimal code for the growth stages of cereals. Weed Research, 14, 415-421.

 

 

 

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*Rhopaloisphum padi, in contrast to Sitobion avenae, is usually found on the lower stem and leaves of cereals.

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The abbreviation BBCH derives from the names of the originally participating stakeholders: “Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie”. Allegedly, the abbreviation is said to unofficially represent the four companies that initially sponsored its development; Bayer, BASF, Ciba-Geigy, and Hoechst.

 

 

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Pick and Mix 33 – resilience, entomophagy, entomology, the windscreen phenomenon and writing habits

How resilent is your garden?

Angela Saini’s third book, Superior: The Return of Race Sciencemakes the compelling case that scientific racism is as prevalent as it has ever been, and explores the way such backward beliefs have continued to evolve and persist and here is a review

They may be small but they can move very large distances – insect migration in the news

Edible insects? Lab-grown meat? The real future food is lab-grown insect meat

Good advice from Megan Duffy on writing your discussion – to be sure

Aphids are wonderful – a long time ago they borrowed some virus genes to help them decide when to produce winged individuals

Here Stephen Heard defends the use of parenthicals

Botanists are arguing amongst themselves as to whether plants have brains or not – what do you think?

What sort of conservationist are you?

Manu Saunders on the windscreen phenomenon – another viewpoint on insect declines

 

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Pick and Mix 31 –  questions and answers

Sammy Borras Illustrator

 

Evelyn Cheeseman – entomologist extraordinaire in her own comic strip

Why I love aphids – soldiers, eusociality, plasterers

What’s the buzz about pollinators? Scott McArt from Conrell University explains in this video

Wildlife-friendly farming increases crop yield: evidence for ecological intensification

Tony Juniper wonders how Winston Churchill would have reacted to the threat of climate change

Jeff Olleton asks if the angry response of (some) environmentalists in the aftermath of the Notre Dame fire reasonable?

This one from Dynamic Ecology  on “Quantifying the life histories of ecological ideas”  is definitely for ecology nerds, but I found it very interesting J

How biodegradable is biodegradble plastic anyway?

What is the impact of journal impact factor on promotion, tenure and appointment of academics?

Terry McGlynn asks if some people are just innately smarter than others.  What do you think?

 

 

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Satiable curiosity – side projects are they worthwhile?

I’ve been meaning to write this one for quite a while.  It was stimulated by two posts, one from the incredibly prolific Steve Heard, the other by the not quite so prolific, but equally interesting,  Manu Saunders.  First off, what is a side project?  To me, a side project is one that is not directly funded by a research council or other funding agency or, in some cases, one that you do in your spare time, or to the horror of some line-managers, is not strictly in your job description 🙂 The tyranny of modern research funding dictates that projects must have specific research questions and be accompanied by hypotheses and very specific predictions; most proposals I referee, even contain graphs with predicted results and almost all have ‘preliminary data’ to support their applications.   This is not necessarily a bad thing but to directly quote Manu Saunders from her blog post

“Whittaker’s (1952) study of ‘summer foliage insect communities in the Great Smoky Mountains’ is considered one of the pioneer studies of modern community ecology methods. The very short Introduction starts with the sentence “The study was designed to sample foliage insects in a series of natural communities and to obtain results of ecological significance from the samples.” No “specific research questions” and the hypotheses and predictions don’t appear until the Discussion” Sounds like bliss.

The central ethos of my research career which began in 1977, can be summed up by this quotation uttered by the character ‘Doc’ in John Steinbeck’s novel Sweet Thursday “I want take everything I’ve seen and thought and learned and reduce them and relate them and refine them until I have something of meaning, something of use” (Steinbeck, 1954).* The other thing that has driven me for as long as I can remember, and why I ended up where I am,  is something I share with Rudyard Kipling’s Elephant Child, and that is a “satiable curiosity”:-) Something that has always frustrated me, is that, in the UK at least, most funded research tends to be of a very short duration, usually three years, often less than that**, and if you are very lucky, maybe five years.  If you work on real life field populations, even if you work on aphids, these short term projects are not really very useful; laboratory work is of course a different matter.

I got my first ‘permanent’ job in 1982 working for UK Forestry Commission Research based at their Northern Research Station (NRS) just outside Edinburgh.  My remit initially was to work on the pine beauty moth, Panolis flammea and finally, on the large pine weevil, Hylobius abietis.  As a committed aphidophile, I was determined, job description or not, to carry on working with aphids. I decided that the easiest and most useful thing to do was to set up a long-term field study and follow aphid populations throughout the year.  My PhD was on the bird cherry-oat aphid, Rhopalosiphum padi, a host alternating aphid, the primary host of which is the bird cherry, Prunus padus, with which  Scotland is very well supplied, and fortuitously, just down the road from NRS was Roslin Glen Nature Reserve with a nice healthy population of bird  cherry trees.  I chose ten suitable trees and started what was to become a ten-year once a week, lunch time counting and recording marathon.  I also decided to repeat a study that my PhD supervisor, Tony Dixon had done, record the populations of the sycamore aphid, Drepanosiphum platanoidis.  In the grounds of NRS were five adjacent sycamore tree, Acer pseudoplatanus, and these became my early morning study subjects, also once a week. I had no articulated hypotheses, my only aim was to count and record numbers and life stages and anything else I might see. Anathema to research councils but exactly what Darwin did 🙂

Although it was a ‘permanent’ job, after ten years I moved to Imperial College at Silwood Park and immediately set up a new, improved version of my sycamore study, this time a once weekly early morning*** walk of 52 trees in three transects and with much more data collection involved, not just the aphids, their natural enemies and anything else I found and on top of all that, the trees themselves came in for scrutiny, phenology, growth, flowering and fruiting, all went into my data sheets.  I also set up a bird cherry plot, this time with some hypotheses articulated 🙂

As a result of my weekly walk along my sycamore transects, a few years later I set up yet another side project, this time an experimental cum observational study looking at tree seedling survival and colonisation underneath different tree canopies. At about the same time, initially designed as a pedagogical exercise, I started my study of the biodiversity of Bracknell roundabouts.

One might argue that most undergraduate and MSc research projects could also come under the heading of side projects, but I think that unless they were part of a long term study they aren’t quite the same thing, even though some of them were published.  So, the burning question, apart from the benefits of regular exercise, was the investment of my time and that of my student helpers and co-researchers worth it scientifically?

Side project 1.  Sycamore aphids at the Northern Research Station, 1982-1992

I collected a lot of aphid data, most of which remains, along with the data from Side project 2, in these two notebooks, waiting to be entered into a spreadsheet.  I also collected some limited natural enemy data, presence of aphid mummies and numbers killed by entomopathogenic fungi.  Tree phenological data is limited to bud burst and leaf fall and as I only sampled five trees I’m not sure that this will ever amount to much, apart from perhaps appearing in my blog or as part of a book.  Nothing has as yet made it into print, so a nil return on investment.

Raw data – anyone wanting to help input into a spreadsheet, let me know 🙂 Also includes the data for Side project 2

 

Side project 2.  Rhopalosiphum padi on Prunus padus at Roslin Glen Nature Reserve 1982-1992

I was a lot more ambitious with this project, collecting lots of aphid and natural enemy data and also a lot more tree phenology data, plus noting the presence and counting the numbers of other herbivores.  I have got some of this, peak populations and egg counts in a spreadsheet and some of it has made it to the outside world (Leather, 1986, 1993: Ward et al., 1998).  According to Google Scholar, Ward et al., is my 6th most cited output with, at the time of writing, 127 citations, Leather (1993) is also doing quite well with 56 citations, while Leather (1986) is much further down the list with a mere 38 citations.  I have still not given up hope of publishing some of the other aphid data.  I mentioned that I also recorded the other herbivores I found, one was a new record for bird cherry (Leather, 1989), the other, the result of a nice student project on the bird cherry ermine moth (Leather & MacKenzie, 1994).  I would, I think, be justified in counting this side project as being worthwhile, despite the fact that I started it with no clear hypotheses and the only aim to count what was there.

 

Side project 3.  Everything you wanted to know about sycamores but were afraid to ask 1992-2012

As side projects go this was pretty massive.  Once a week for twenty years, me and on some occasions, an undergraduate research intern, walked along three transects of 52 sycamore trees, recording everything that we could see and count and record, aphids, other herbivores, natural enemies and tree data, including leaf size, phenology, height, fruiting success and sex expression.  My aim was pretty similar to that of Whittaker’s i.e.   “…to sample foliage insects in a series of natural communities and to obtain results of ecological significance from the samples”  truly a mega-project.  I once calculated that there are counts from over 2 000 000 leaves which scales up to something like 10 000 000 pieces of data, if you conservatively estimate five data observations per leaf. Quite a lot of the data are now computerized thanks to a series of student helpers and Vicki Senior, currently finishing her PhD at Sheffield University, but certainly not all of it. In terms of output, only two papers so far (Wade & Leather, 2002; Leather et al., 2005), but papers on the winter moth, sycamore and maple aphids and orange ladybird are soon to be submitted.  On balance, I think that this was also worthwhile and gave me plenty of early morning thinking time in pleasant surroundings and a chance to enjoy Nature.

The sycamore project – most of the raw data, some of which still needs to be computerised 🙂

 

Side project 5. Sixty bird cherry trees 1993-2012

This project has already featured in my blog in my Data I am never going to publish series and also in a post about autumn colours and aphid overwintering site selection.  Suffice to say that so far, thanks to my collaborator Marco Archetti, two excellent papers have appeared (Archetti & Leather, 2005; Archetti et al., 2009), the latter of which is my third most cited paper with 101 cites to date and the former is placed at a very respectable 21st place.  I don’t really see any more papers coming out from this project, but I might get round to writing something about the study as a whole in a natural history journal. On balance, even though only two papers have appeared from this project, I count this as having been a very worthwhile investment of my time.

All now in a spreadsheet and possibly still worthwhile delving into the data

 

Side project 5.  Urban ecology – Bracknell roundabouts 2002-2012

This started as a pedagogical exercise, which will be the subject of a blog post in the not too distant future. The majority of the field work was done by undergraduate and MSc students and in the latter years spawned a PhD student, so a side project that became a funded project 🙂 To date, we have published seven papers from the project (Helden & Leather, 2004, 2005; Leather & Helden, 2005ab; Helden et al., 2012; Jones & Leather, 2012; Goodwin et al., 2017) and there are probably two more to come.  Definitely a success and a very worthwhile investment of my time.  The story of the project is my most requested outreach talk so also gives me the opportunity to spread the importance of urban ecology to a wider audience.

The famous roundabouts – probably the most talked and read about roundabouts in the world 🙂 Sadly Roundabout 1 i n o longer with us; it was converted into a four-way traffic light junction last year 😦

 

Side project 6.  Testing the Janzen-Connell Hypothesis – Silwood Park, 2005-2012

I mentioned this project fairly recently so will just link you to it here.  So far only one paper has come out of this project (Pigot & Leather, 2008) and I don’t really see me getting round to doing much more than producing another Data I am never going to publish article, although it does get a passing mention in the book that I am writing with former colleagues Tilly Collins and Patricia Reader.  It also gave undergraduate and MSc project students something to do.  Overall, this just about counts as a worthwhile use of my time.

Most of this is safely in a spreadsheet but the data in the notebooks still needs inputting

According to my data base I have published 282 papers since 1980 which given that I have supervised 52 PhD students, had 5 post-docs, and, at a rough estimate, supervised 150 MSc student projects and probably 200 undergraduate student projects doesn’t seem to be very productive 😦 Of the 282 papers, 125 are from my own projects, which leaves 139 papers for the post-docs and PhD students and 17 from the side projects.  Three of the papers published from the side projects were by PhD students, so if I remove them from the side projects that gives an average of 2.3 papers per side project and 2.4 papers per post-doc and PhD student.   So, in my opinion, yes, side projects are definitely worth the investment.

 

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.

Archetti, M., Döring, T.F., Hagen, S.B., Hughes, N.M., Leather, S.R., Lee, D.W., Lev-Yadun, S., Manetas, Y., Ougham, H.J., Schaberg, P.G., & Thomas, H. (2009) Unravelling the evolution of autumn colours: an interdisciplinary approach. Trends in Ecology & Evolution, 24, 166-173.

Goodwin, C., Keep, B., & Leather, S.R. (2017) Habitat selection and tree species richness of roundabouts: effects on site selection and the prevalence of arboreal caterpillars. Urban Ecosystems, 19, 889-895.

Helden, A.J. & Leather, S.R. (2004) Biodiversity on urban roundabouts – Hemiptera, management and the species-area relationship. Basic and Applied Ecology, 5, 367-377.

Helden, A.J. & Leather, S.R. (2005) The Hemiptera of Bracknell as an example of biodiversity within an urban environment. British Journal of Entomology & Natural History, 18, 233-252.

Helden, A.J., Stamp, G.C., & Leather, S.R. (2012) Urban biodiversity: comparison of insect assemblages on native and non-native trees.  Urban Ecosystems, 15, 611-624.

Jones, E.L. & Leather, S.R. (2012) Invertebrates in urban areas: a review. European Journal of Entomology, 109, 463-478.

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

Leather, S.R. (1989) Phytodecta pallida (L.) (Col., Chrysomelidae) – a new insect record for bird cherry (Prunus padus). Entomologist’s Monthly Magazine, 125, 17-18.

Leather, S.R. (1993) Overwintering in six arable aphid pests: a review with particular relevance to pest management. Journal of Applied Entomology, 116, 217-233.

Leather, S.R. & Helden, A.J. (2005) Magic roundabouts?  Teaching conservation in schools and universities. Journal of Biological Education, 39, 102-107.

Leather, S.R. & Helden, A.J. (2005) Roundabouts: our neglected nature reserves? Biologist, 52, 102-106.

Leather, S.R. & Mackenzie, G.A. (1994) Factors affecting the population development of the bird cherry ermine moth, Yponomeuta evonymella L. The Entomologist, 113, 86-105.

Leather, S.R., Wade, F.A., & Godfray, H.C.J. (2005) Plant quality, progeny sequence, and the sex ratio of the sycamore aphid, Drepanoisphum platanoidis. Entomologia experimentalis et applicata, 115, 311-321.

Pigot, A.L. & Leather, S.R. (2008) Invertebrate predators drive distance-dependent patterns of seedling mortality in a temperate tree Acer pseudoplatanus. Oikos, 117, 521-530.

Steinbeck, J. (1954) Sweet Thursday, Viking Press, New York, USA.

Wade, F.A. & Leather, S.R. (2002) Overwintering of the sycamore aphid, Drepanosiphum platanoidis. Entomologia experimentalis et applicata, 104, 241-253.

Ward, S.A., Leather, S.R., Pickup, J., & Harrington, R. (1998) Mortality during dispersal and the cost of host-specificity in parasites: how many aphids find hosts? Journal of Animal Ecology, 67, 763-773.

Whittaker, R.H. (1952) A Study of summer foliage insect communities in the Great Smoky Mountains. Ecological Monographs, 22, 1-44.

 

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I was so impressed by this piece of philosophy that it is quoted in the front of my PhD thesis 🙂

**

My second post-doc was only for two years.

***

You may wonder why I keep emphasising early morning in relation to surveying sycamore aphids.  Sycamore aphids are very easy to disturb so it is best to try and count them in the early morning before they have a chance to warm up and become flight active.

 

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Ten more papers that shook my world – Plant growth formulae for entomologists – Radford (1967) and Wyatt & White (1977)

Plant growth formulae for entomologists, what a great title for a paper or even a book J These two papers, separated by a decade had a great influence on my PhD and subsequent entomological career, or at least the lab based part of it. I started my PhD at the University of East Anglia on October 2nd 1977, where I was lucky enough to be supervised by that doyen of the aphid world, Professor Tony Dixon.  I was, and still am, convinced that the sooner you get started on practical work the better and that is what I tell my students.  Yes, reading is important but getting to know your organism early on, is just as, if not more, important. You can catch up on your in-depth reading later, but that early ‘hands on’ experience, even if what you first do is not publishable, is invaluable.  I see from my lab notebooks that my first experiments* were examining the effects of host plant on the fecundity and longevity of my study aphid, Rhopalosiphum padi.

My first experiment as a PhD student!

It was doing these very simple experiments, collecting development, survival and reproductive data that introduced me to the idea of measuring life history parameters in the round,

One of my first data sheets – not used in my thesis but gave me invaluable experience for later on.

rather than as single factors, akin to how ecologists move from measuring species diversity as a simple species count to using diversity indices that combine other attributes and describe the community more holistically. So it was with me and growth and reproductive rates. I wanted to be able to infer what my laboratory results might mean in the field and to develop faster methods of screening for host plant effects.  I came across, or was pointed in the direction of, two papers that had great influence on my research, Radford (1967)** about measuring growth rates, albeit of plants, and Wyatt & White (1977) on how to measure intrinsic rates of increase rm without having to go through the very laborious and time-consuming methods devised by Birch (1948); working on aphids makes you do things in a hurry 😊

Ian Wyatt and his colleague Peter White did a series of painstaking laboratory experiments to obtain reproductive figures for aphids and mites and came up with a simplified version of the Birch equation such that

rm = 0.738(lnMd)/d

 where Md = the number of offspring produced over a period of time equal to the pre-reproductive period D and 0.738 is a constant (Wyatt & Wyatt, 1977)

The Radford paper, reinforced by reading a paper by another great aphidologist, Helmut van Emden, Professor of Horticulture at the University of Reading (van Emden, 1969) convinced me that Mean Relative Growth Rate (MRGR) was the way to go to obtain comparative measures of host plant suitability for my aphids.  To save you looking it up, MRGR is calculated as follows:

The beauty of this, especially if you are working with very small animals such as aphids, is that you don’t need to weigh them at birth, you can if you want, just measure weights between two time periods.

Screening plants for resistance to aphids is an integral part of developing sustainable and environmentally friendly ways of protecting your crops.  At the time I started my PhD several methods were in use, ranging from measuring direct fecundity and developmental time (Dean, 1974), to short cuts such as counting the number of mature embryos at adult moult (Dewar, 1977) and of course Mean Relative Growth Rate (van Emden, 1969).  Although I tended to measure life-time fecundity and longevity for almost all my experiments, having the short cut of MRGR and in many cases the fecundity achieved in the first seven days of reproduction*** (e.g. Leather & Dixon, 1981) were useful tools to have.  What was the world shaking discovery for me, and something that in retrospect, I find surprising that no one else cottoned on to, was that MRGR was highly correlated with fecundity and that this meant that MRGR was correlated with the intrinsic rate of increase (Leather & Dixon, 1984).  This means that you can screen host plants and predict population trajectories with experimental observations that take less than half the time using the traditional measurements.  That paper proved very popular and is Number 7 in my citation list, with, at the time of writing, 80 citations.   A few years later, when I had moved on to working with other insect orders, I found that the relationship between MRGR and rm applied to Lepidoptera and that different insect orders followed the same rules (Leather, 1994).

Lepidoptera and aphids, singing from the same data sheets (Leather, 1994).

So truly, a paper that shook my world.

References

Birch, L.C. (1948) The intrinsic rate of natural increase of an insect population.  Journal of Animal Ecology, 48, 15-26.

Dean, G.J.W. (1974) Effect of temperature on the cereal aphids, Metopolphium dirhodum (Wlk.), Rhoaplosiphum padi (L.) and Macrosiphum avenae (F.) (Hem., Aphididae).  Bulletin of Entomological Research, 63, 401-409.

Dewar, A.M. (1977) Assessment of methods for testing varietal resistance to aphids in cereals.  Annals of Applied Biology, 87, 183-190.

Fisher, R.A. (1921) Some remarks on the methods formulated in a recent article on ‘The quantitative analysis of plant growth’. Annals of Applied Biology, 7, 367-372.

Leather, S.R. & Dixon, A.F.G. (1981) The effect of cereal growth stage and feeding site on the reproductive activity of the bird cherry-oat aphid, Rhopalosihum padiAnnals of Applied Biology, 97, 135-141.

Leather, S.R. & Dixon, A.F.G. (1984) Aphid growth and reproductive rates. Entomologia experimentalis et applicata, 35, 137-140.  80 cites number 7 in my list

Leather, S.R. (1994) Insect growth and reproductive rates. In Individuals, Populations and Patterns in Ecology (ed. by S.R. Leather, A.D. Watt, N.J. Mills & K.F.A. Walters), pp. 35-43. Intercept, Andover.

Radford, P.J. (1967) Growth analysis formulae – their use and abuse. Crop Science, 7, 171-175.

van Emden, H.F. (1969) Plant resistance to Myzus persicae induced by a plant regulator and measured by aphid relative growth rate. Entomologia experimentalis et applicata, 12, 125-131.

Wyatt, I. J. & White, P. F. (1977) Simple estimation of intrinsic increase rates for aphids and tetranychid mites. Journal of Applied Ecology 14, 757-766.

 

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and boy was I quick off the mark.  I started my PhD on October 2nd and here I am 24 days later with cereal plants at GS 12 ready to receive aphids J

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it is only fair to point out that Radford owed his inspiration to the work of that great statistician, Ronald Fisher (Fisher, 1921)

***

aphids like many insects produce over half their progeny in the first week or so

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Aphids galore, les pucerons à gogo – UK-France Joint Meeting on Aphids – April 3rd to 5th 2019

The giant aphid – a fitting start to an aphid conference, albeit taxonomically suspect 😊

I have just returned from a very enjoyable two-day meeting at Rothamsted Research Station in Harpenden.  This was a follow-up to the very enjoyable meeting we had in Paris in 2015 which made me ask somewhat facetiously, if pea aphids ruled the world 😊 As with the Paris meeting, this recent meeting was jointly organised by Jean-Christophe Simon and Richard Harrington with some input by me.  There were ninety delegates, and not just from France and the UK; we had a keynote speaker from Japan, Tsutomu Tsuchida, and also speakers from Belgium, the Czech Republic, Germany, Ireland and Switzerland.

Tsumato Tsuchida, me, Richard Harrington, Julie Jaquiéry, Jean-Christophe Simon and Richard Blackman.

Our other three keynote speakers included two of the doyens of the aphid world, Roger Blackman and Helmut van Emden   and Julie Jaquiéry from the University of Rennes.  As with the Paris meeting, many of the talks were about the pea aphid and symbionts.  Other aphids did, however, get mentioned, including my favourite aphid, Rhopaloisphum padi, which featured in an excellent talk by PhD student Amma Simon from Rothamsted, who is supervised by one of my former students, Gia Aradottir.  There was an excellent poster session, a tribute to the late great, Ole Heie from Mariusz Kanturski, a fabulous film by Urs Wyss, which included shocking scenes of lime aphids being torn apart by vicious predators, and of course the conference dinner.

It would take too long to describe all the talks, so I will let the pictures tell the story of a very enjoyable meeting.  Hopefully we will all meet again in France in 2023.

Great talks and a packed lecture theatre

Food and chat

Very animated poster sessions

Three senior aphidologists in action,  Helmut Van Emden, Hugh Loxdale and Roger Blackman

Richard Harrington presenting Roger Blackman and ‘Van’ van Emden with the Award of the Golden Aphid – the lighting in the conference dining area was very peculiar 😊

Strange lighting at the conference dinner

From the Urs Wyss film– lime aphid moulting

The giant aphid having a quick snack

And in case you wondered, there were embryos inside the giant aphid 🙂

Many thanks to the Royal Entomological Society and BAPOA/INRA for funding.

And here are most of the delegates on the final day

Aphid SIG 2019

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Not all aphids are extant – fossil aphids

Mention the word fossil and most people immediately think of dinosaurs, ammonites, early hominids and perhaps plants from the carboniferous.  For those of you who have coal-burning fires, have a look in your coal-scuttle, you may be surprised at what you find.  What most people don’t realise is that there are fossil insects and these include those fabulous insects, aphids 🙂

A beautifully preserved aphid, Mindarus harringtoni, named after, and owned by my friend, and fellow aphid enthusiast, Richard Harrington.

The oldest fossil of a true insect dates back to the Pragian (early Devonian) era (396-407 million years ago (Mya)) implying that they can, almost certainly, be dated back to the earlier Silurian period (434 Mya) (Engel & Grimaldi, 2004). Aphids, being relatively soft-bodied animals, tend to be less commonly found as stone fossils, but there are some fine examples in existence.  The oldest aphid fossil found so far is Vasegus triassicus from the Vosges area of France and dating back to 174-163 Mya (Szwedo & Nel, 2011).  I have a great admiration for taxonomists in general, but paleoentomologists really are worthy of worship, working as they do, with material, especially that found in rock deposits, of an extremely taxing nature.

Wing of the aphid Vosegus triassicus  (Szwedo & Nel, 2011)

A more recognisable aphid wing from the Lower Cretaceous (140 Mya).  https://jurassiccoast.org/fossilfinder/1338-aphid-wing/

Another contender for the oldest aphid was found in the Daohugou beds in China on the boundaries of the provinces of Inner Mongolia, Hebei and Liaoning (Huang et al., 2015).  These deposits have been dated back to about 165 Mya.  Given the inevitable distortion caused by the squashing, the fossils do look like some modern aphids and I am pretty certain that I can see the cauda which is one of the distinguishing characteristics of aphids.

Daopaphis magnalata with a visible cauda? (Huang et al., 2015)

Somewhat younger, a mere 15 000 000 years old, Palaeogreenidea rittae, which displays the other dead giveaway that tells you that you are looking at an aphid, the siphunculi.

Palaeogreenidea rittae, note the distinctive siphunculi.  Middle Miocene from Nevada (approximately 15 Mya) (Heie, 2006).

Amber, fossilised tree resin, is, however, where you are most likely to find ancient aphids.  Tree resin is a carbohydrate-based extremely sticky secretion of trees, particularly conifers. It is part of their defence system and is used to seal wounds and to trap and encapsulate any insect intent on forcing an entry into the heart of the tree. The majority of the insects found in resin have arrived there by accident; they have landed on it and found themselves trapped.  They gradually become engulfed by the resin and die a slow and lingering death, unless a bird plucks them from their sticky surroundings as a tasty snack.  Go into a pine forest or look at the resin bleeds that you often find on fruit trees and you will very soon find some hapless insect victims. Over time the resin hardens and becomes a substance known as copal.  This can then find its way into the soil; the tree falls over or the copal becomes detached and falls to the round. Once in the soil, the copal has the chance, over several million years, to harden further still and eventually become resin.  Any insect trapped in resin is perfectly preserved, ready for the intrepid palaeoentomologist to discover and name or entrepreneur to sell to curio collectors.

A very fine specimen with a very long stylet; presumably this fed on the trunk of trees.  Germaraphis spp. (Pemphigidae)    http://www.fossilmuseum.net/Fossil-Amber/antaphid/amber-86.htm 

 

A very recognisable aphid indeed, the antennal tubercles, siphunculi and cauda are all very clear.  Photo from Ross (2009).

Not all aphids in amber are as easy to identify as the two specimens above.  The example below is why I have such a great admiration for palaeoaphidologists.

I am told that this is an aphid.  Photographed and found by Gracie Price a placement student at Oxford University Museum of Natural History, reproduced with thanks to Darren Mann.

I have written earlier about the close relationships that many aphids have with ants and it seems from the number of times ants and aphids have been found in close proximity in amber inclusions, that this association has been in existence for at least 73 million years especially with Germaraphis dryoides (Heie, 1967; Perkovsky, 2009).

Ant and aphid in amber. It will cost you €100 if you want to own this specimen.  http://www.amberinclusions.eu/ant-and-aphid-symbiosis-in-baltic-amber-4809#prettyPhoto

Another association, perhaps not so pleasant for the aphid, and also immortalised in amber, is that of a nematode parasite from 100 million years ago (Poinar, 2017).

Aphid in amber with nematode parasite (Poinar, 2017).

What can we learn from these amber inclusions?  First, by comparing them with modern aphids, we can make inferences about their life styles.  As Ole Heie (1967) pointed out, aphids with clawed tarsi (feet) and long mouth parts are almost certainly not only to be tree dwellers, but ones that fed through the bark on the stems or trunks.  Aphids that live on the underside of leaves need neither of these adaptations.  Are there any other inferences to be made? I have already pointed out that, the fossil evidence suggests the ant-aphid mutualism has been long-established.

Fossil aphids also allow us infer that as aphids are largely found in temperate zones, the climate in those sites where amber is easily found must also have been temperate when they were trapped by the then, fresh tree resin (Heie, 1967).  Palaeobiologists have attempted to reconstruct ancient ecosystems from fossils including insects.  A recent and innovative study comparing arthropods found in trapped in modern tree resins, sticky traps and Malaise traps with those in fossil amber suggests that amber inclusions reflect the insects closely associated with trees but not necessarily the overall community (Kraemer et al., 2018).  We can’t get DNA out of amber as suggested in Jurassic Park, but we can certainly get a lot of other biological information from this fantastic window into the past.

I’ll end on a cautionary note. Not all amber is real amber.  Fakes abound.  Plastic is often used as fake amber and is sold with insect inclusions or as jewellery.  An easy way to test if it is plastic or amber, is to see if it floats in a saturated salt solution, if it does it is probably amber. More difficult to detect, is fake amber that has been produced by melting down real amber or copal, and then had modern insects embedded in it while it is still liquid.  If your insect inclusion is very nicely and symmetrically arranged, then you can be sure it is a fake.  Not all such inclusions are sold as genuine, most openly advertise exactly what they are; I have several, gifts from families and students.

Modern insect embedded in plastic.

 

References

Engel, M.S. & Grimaldi, D. (2004) New light shed on the oldest insect. Nature, 427, 627-630.

Heie, O. (1967) Studies on Fossil Aphids (Homoptera: Aphidoidea) Especially in the Copenhagen Collection of Fossils in Baltic Amber. Spolia Zoologica Musei Hauniensis, Copenhagen.

Heie, O.E. (2006) Fossil aphids (Hemiptera: Sternorrhyncha) from Canadian Cretaceous amber and from the Miocene of Nevada. Insect Systematics & Evolution, 37, 91-104.

Huang, D., Wegierek, P., Żyła, D. & Nel, A. (2015) The oldest aphid of the family Oviparosiphidae (Hemiptera: Aphidoidea) from the Middle Jurassic of China. European Journal of Entomology, 112, 187-192.

Kraemer, M.M.S., Declos, X., Clapham, M.E., Arillo, A., Peris, D., Jäger, P., Sebner, F., Peñalver, E. (2018) Arthropods in modern resins reveal if amber accurately recorded forest arthropod communities. Proceedings of the National Academy of Sciences, USA, 115, 6739-6744

Perkovsky, E.E. (2009) On finding a single-clawed aphid, Germaraphis ungulata (Homoptera, Aphidinea), in a syniclusion with the ant Monomoroium mayrianum (Hymenoptera, Formicidae) in the Saxonian amber.  Paleontological Journal, 43, 1006-1007.

Poinar, G.O. (2017) A mermithid nematode, Cretacimermis aphidophilus sp. n. (Nematoda: Mermithidae) parasitizing an aphid (Hemiptera: Burmitaphididae) in Myanmar amber: a 100 million year association.  Nematology, 19, 509-513.

Ross, A. (2009) Amber – The Natural Time Capsule. NHM, London.

Szwedo, J. & Nel, A. (2011) The oldest aphid insect from the Middle Triassic of the Vosges, France. Acta Palaeontologica Polonica, 56, 757-766.

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Aphids don’t suck sap! (usually)

Aphids are sap feeding, most of the time they feed from the phloem, or sieve elements, that part of the plant responsible for transporting the food made in the leaves by photosynthesis, around the plant.  Aphids face three problems arising from their phloem feeding habit. First, the phloem sap is largely composed of sugars, with a few trace elements and nitrogen in the form of soluble amino acids.  The aphids are mainly interested in the nitrogen and that poses the second problem, the amino acids are mainly non-essential ones.  Thirdly, the phloem is under pressure, figures range from 2 to 40 Bars* (about twice to forty times atmospheric pressure) (e.g. Mittler, 1957; Rogers & Peel, 1975; Barlow & Randall, 1978; Wright & Fisher, 1980).  Imagine that you are trapped in an air-tight room and your only source of air is an inflated tractor tyre.   You have a sharp metal straw which you can stick into the tyre to release the air into your mouth.  If you put one end of the straw in your mouth and then pierced the tyre wall, your head would explode.

Sadly I couldn’t find a picture of an exploding aphid and my cartoon version was a failure, so this is it 🙂

Aphids face the same sort of pressure. Fortunately evolution has provided them with a very strong pharyngeal pump and incorporated a series of valves in their mouth-parts (stylets = straw) with which they are able to control the flow of the phloem into their bodies.  The last thing they want to do when plugged into the phloem is suck, it would be the last thing they did 🙂 and that’s why aphidologists get upset when people describe aphids as sap-suckers!

 

Aphid feeding apparatus – adapted from McLean & Kinsey (1984)

To be fair, we are being somewhat pedantic, the fluid transported in the xylem tubes, largely water, is also colloquially known as plant sap. The xylem, unlike the phloem is not under pressure (Sperry et al., 1996), so on those rare occasions when the aphid does need to drink water, they do have to suck sap (Spiller et al., 1990).  The other occasion on which aphids need to suck rather than regulate the flow of sap is when they are feeding in very artificial laboratory situations, on leaf discs or on artificial diets where the nutrient solution is between two pieces of Parafilm™.  In both these cases there is negative pressure and the cibarial pump does then come into operation. Interestingly, it is sometimes quite difficult to get aphids to feed on artificial diets unless a phagostimulant is included to overcome their reluctance to feed on sap that is not under pressure (Mittler & Dadd, 1963), but that’s a story for a future post.

Aphids feeding on leaf discs, in this case for insecticide assays at Rothamsted Research

 

Aphids feeding on artificial diet through Parafilm™. Photo Meena Haribal https://www.sciencedaily.com/releases/2015/12/151216151742.htm

 

References

Barlow, C.A. & Randolph, P. A.  (1978) Quality and quantity of plant sap available to the pea aphid.  Annals of the Entomological Society of America, 71, 46-48.

McLean, D.L. & Kinsey, M.G. (1984) The precibarial valve and its role in the feeding behavior of the pea aphid, Acyrthosiphon pisum. Bulletin of the Entomological Society of America, 30, 26-31.

Mittler, T.E. (1957) Studies on the feeding and nutrition of Tuberolachnus salignus (Gmelin) (Homoptera, Aphididae) I. The uptake of phloem sap. Journal of Experimental Biology, 34, 334-341.

Mittler, T.E. & Dadd, R.H. (1963) Studies on the artificial feeding of the aphid Myzus perslcae (Sulzer) – I. Relative uptake of water and sucrose solutions. Journal of Insect Physiology, 9, 623-645.

Sperry, J.S., Saliendra, N.Z., Pockman, W.T.,  Cochard, H., Cruiziat, P., Davis, S.D., Ewers, F.W. & Tyree, M.T. (1996) New evidence for large negative xylem pressures and their measurement by the pressure chamber method. Plant, Cell & Environment, 19, 427-436.

Rogers, S. & Peel, A.J. (1975) Some evidence for the existence of turgor pressure gradients in the sieve tubes of willow Planta (Berl.) 126, 259-267.   

Spiller, N.J., Koenders, L. & Tjallingii, W.F. (1990) Xylem ingestion by aphid – a strategy for maintaining water balance.  Entomologia experimentalis et applicata, 55, 101-104.

Wright, J.P. & Fisher, D.P. (1980) Direct measurement of sieve tube turgor pressure using severed aphid stylets. Plant Physiology, 65, 1133-1135.

 

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The Natural World in Haiku Form – Volume 2

Nature versified.

Haikus from the year gone by

To enjoy or not.

 

Cryptic and not

Grasshoppers blend in;

 Busy ants don’t care at all

 If you see them there

17th August 2018 Vinca

 

Ants

Mountainous thunder

Sends ants scuttling to their nest.

Seeds await the wind

 

Ants again – Reverse Haiku

Ants, sensing distant thunder,

Scuttle to their nest,

While seeds pods wait for the wind.

22nd May 2018 Vinca

 

Aphids

 

Aphids are so cool.

Three generations, making

One clonal body

25 December 2017

 

Raucous Rooks

Starkly black on blue.

Rudely cawing rooks disturb

My morning coffee

15 February 2018

 

Raucous rooks railing.

Sable, swooping, skyward sailing,

Disturb my morning

26th February 2018

 

Mountain

Sunny Canigou,

Snowy peak shining brightly.

Winter in Vinca

20th January 2018

 

Malham Tarn

Rising from the rain

Summer mist, slowly rolling,

Hides Malham Tarn

July 16th 2018

 

Prunella

Commonly overlooked,

 Elastically plastic;

Purple Prunella

July 17th 2018

 

Four Brothers?

Four trees in a row
Standing smallest to tallest.
What is their story?

August  20th 2018, Vinca

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Global Insect Extinction – a never ending story

I have had an unexpectedly busy couple of weeks talking about declines in insect populations.  Back in November of last year I wrote a blog about the sudden media interest in “Insect Armageddon” and followed this up with a more formal Editorial in Annals of Applied Biology at the beginning of the year (Leather, 2018).  I mused at the time if this was yet another media ‘storm in a teacup’ but it seems that the subject is still attracting attention.  I appeared on television as part of TRT World’s Roundtable programme and was quoted quite extensively in The Observer newspaper on Sunday last talking about insect declines since my student days 🙂 At the same time, as befits something that has been billed as being global, a similar story, featuring another veteran entomologist appeared in the New Zealand press.

The TV discussion was quite interesting, the panel included Nick Rau from Friends of the Earth, Lutfi Radwan, an academic turned organic farmer, Manu Saunders from Ecology is Not a Dirty Word and me.  If they had hoped for a heated argument they were out of luck, we were all pretty much in agreement; yes insects did not seem to be as abundant as they had once been, and this was almost certainly a result of anthropogenic factors, intensive agriculture, urbanisation and to a lesser extent climate change.  Unlike some commentators who firmly point the finger at the use of pesticides as the major cause of the declines reported, we were more inclined to towards the idea of habitat degradation, fragmentation and loss.  We also agreed that a big problem is a lack of connection with Nature by large sections of the population, and not just those under twenty.  We also felt very strongly that governments should be investing much more into research in this area and that we desperately need more properly replicated and designed long-term studies to monitor the undeniable changes that are occurring.  I had, in my Editorial and an earlier blog post, mentioned this point and lamented the paucity of such information, so was pleasantly surprised, to receive a couple of papers from Sebastian Schuh documenting long-term declines in Hemiptera and Orthoptera in Germany (Schuh et al., 2012ab), although of course sad, to see yet more evidence for decreasing insect populations.

The idea that insects are in terminal decline has been rumbling on for some time; more than a decade ago Kelvin Conrad and colleagues highlighted a rapid decline in moth numbers (Conrad et al., 2006) and a few years later, Dave Brooks and colleagues using data from the UK  Environmental Change Network revealed a disturbing decline in the numbers of carabid beetles across the UK (Brooks et al., 2012).   In the same year (2012) I was asked to give a talk at a conference organised by the Society of Chemical Industry. Then, as now, I felt that pesticides were not the only factor causing the biodiversity crisis, but that agricultural intensification, habitat loss and habitat degradation were and are probably more to blame.  In response to this quote in the media at the time:

“British Insects in Decline

Scientists are warning of a potential ecological disaster following the discovery that Britain has lost around 7% of its indigenous insect species in just under 100 years.

A comparison with figures collected in 1904 have revealed that around 400 species are now extinct, including the black-veined white butterfly, not seen since 1912, the Essex emerald moth and the short-haired bumblebee. Many others are endangered, including the large garden bumblebee, the Fen Raft spider, which is only to be found in a reserve on the Norfolk/Suffolk border, and the once common scarlet malachite beetle, now restricted to just three sites.

Changes to the insects’ natural habitats have been responsible for this disastrous decline in numbers. From housing and industrial developments to single-crop farming methods, Britain’s countryside has become increasingly inhospitable to its native insects.”

I chose to talk about “Forest and woodland insects: Down and out or on the up?” I used data from that most valuable of data sets, the Rothamsted Insect Survey to illustrate my hypothesis that those insects associated with trees were either doing better or not declining, because of increased tree planting over the last fifty years.  As you can see from the slides from my talk, this does indeed seem to be the case with moths and aphids that feed on trees or live in their shade.  I also showed that the populations of the same species in northern Britain, where agriculture is less intensive and forests and woodlands more prevalent were definitely on the up, and this phenomenon was not just confined to moths and aphids.

Two tree aphids, one Drepanosiphum platanoidis lives on sycamore, the other Elatobium abietinum, lives on spruce trees; both are doing rather well.

Two more tree-dwelling aphids, one on European lime, the other on sycamore and maples, both doing very well.  For those of you unfamiliar with UK geography, East Craigs is in Scotland and Newcastle in the North East of England, Hereford in the middle and to the west, and Starcross in the South West, Sites 2, 1, 6 and 9 in the map in the preceding figure.

Two conifer feeding moth species showing no signs of decline.

On the up, two species, a beetle, Agrilus biguttatus perhaps due to climate change, and a butterfly, the Speckled Wood Pararge aegeria, due to habitat expansion and climate change?

It is important however, to remember that insect populations are not static, they vary from year to year, and the natural fluctuations in their populations can be large and, as in the case of the Orange ladybird, Halyzia sedecimguttata, take place over a several years, which is yet another reason that we need long-term data sets.

The Orange ladybird Halyzia sedecimguttata, a mildew feeder, especially on sycamore.

It is obvious, whether we believe that an ecological catastrophe is heading our way or not, that humans are having a marked effect on the biodiversity that keeps our planet in good working order and not just through our need to feed an ever-increasing population.  A number of recent studies have shown that our fixation with car ownership is killing billions of insects every year (Skórka et al., 2013; Baxter-Gilbert et al.,2015; Keilsohn et al., 2018) and that our fear of the dark is putting insects and the animals that feed on them at risk (Eccard et al.,  2018; Grubisic et al., 2018).  We have a lot to answer for and this is exacerbated by our growing disconnect from Nature and the insidious effect of “shifting baselines” which mean that succeeding generations tend to accept what they see as normal (Leather & Quicke, 2010, Soga & Gaston, 2018) and highlights the very real need for robust long-term data to counteract this dangerous and potentially lethal, World view (Schuh, 2012; Soga & Gaston, 2018).  Perhaps if research funding over the last thirty years or so had been targeted at the many million little things that run the World and not the handful of vertebrates that rely on them (Leather, 2009), we would not be in such a dangerous place?

I am, however, determined to remain hopeful.  As a result of the article in The Observer, I received an email from a gentleman called Glyn Brown, who uses art to hopefully, do something about shifting baselines.  This is his philosophy in his own words and pictures.

 

References

Baxter-Gilbert, J.H., Riley, J.L., Neufeld, C.J.H., Litzgus, J.D. & Lesbarrères, D.  (2015) Road mortality potentially responsible for billions of pollinating insect deaths annually. Journal of Insect Conservation, 19, 1029-1035.

Brooks, D.R., Bater J.E., Clark, S.J., Monteith, D.T., Andrews, C., Corbett, S.J., Beaumont, D.A. & Chapman, J.W. (2012)  Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss in insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Conrad, K.F., Warren. M.S., Fox, R., Parsons, M.S. & Woiwod, I.P. (2006) Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis. Biological Conservation, 132, 279-291.

Eccard, J.A., Scheffler, I., Franke, S. & Hoffmann, J. (2018) Off‐grid: solar powered LED illumination impacts epigeal arthropods. Insect Conservation & Diversity, https://onlinelibrary.wiley.com/doi/full/10.1111/icad.12303

Estay, S.A., Lima, M., Labra, F.A. & Harrington, R. (2012) Increased outbreak frequency associated with changes in the dynamic behaviour of populations of two aphid species. Oikos, 121, 614-622.

Grubisic, M., van Grunsven, R.H.A.,  Kyba, C.C.M.,  Manfrin, A. & Hölker, F. (2018) Insect declines and agroecosystems: does light pollution matter? Annals of Applied Biology,   https://onlinelibrary.wiley.com/doi/full/10.1111/aab.12440

Keilsohn, W., Narango, D.L. & Tallamy, D.W. (2018) Roadside habitat impacts insect traffic mortality.  Journal of Insect Conservation, 22, 183-188.

Leather, S.R. (2009) Taxonomic chauvinism threatens the future of entomology. Biologist, 56, 10-13.

Leather, S.R. (2018) “Ecological Armageddon” –  more evidence for the drastic decline in insect numbers. Annals of Applied Biology, 172, 1-3.

Leather, S.R. & Quicke, D.J.L. (2010) Do shifting baselines in natural history knowledge therten the environment? The Environmentalist, 30, 1-2.

Schuh, S. (2012) Archives and conservation biology. Pacific Conservation Biology, 18, 223-224.

Schuh, S., Wesche, K. & Schaefer, M. (2012a) Long-term decline in the abundance of leafhoppers and planthoppers (Auchenorrhyncha) in Central Europe protected dry grasslands. Biological Conservation, 149, 75-83.

Schuh, S., Bock, J., Krause, B., Wesche, K. & Scgaefer, M. (2012b) Long-term population trends in three grassland insect groups: a comparative analysis of 1951 and 2009. Journal of Applied Entomology, 136, 321-331.

Skórka, P., Lenda, M., Moroń, D., Kalarus, K., & Tryjanowskia, P. (2013) Factors affecting road mortality and the suitability of road verges for butterflies. Biological Conservation, 159, 148-157.

Soga, M. & Gaston, K.J. (2018) Shifting baseline syndrome: causes, consequences and implications. Frontiers in Ecology & the Environment, 16, 222-230.

 

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