Being inspired by the BES

This week (20th July) I have had the privilege of being able to interact with 50 undergraduates (mainly just finished their first year) under the auspices of the British Ecological Society’s new undergraduate summer school held at the Field Studies Council’s Malham Tarn Centre. The scheme enables aspiring ecologists to have “an opportunity to enhance their existing knowledge with plenary lectures from senior ecologists, fieldwork, workshops, careers mentoring and more at a week-long residential course” This was especially pleasurable for me because as a school boy and student I spent several enjoyable camping holidays at Malham and it gave me an opportunity to take part in a field course again, something I have missed since leaving Silwood Park where I ran the now defunct annual two-week long Biodiversity & Conservation field course. The programme included two ecological luminaries and old friends of mine, Sue Hartley from the University of York and plant scientist and author, Ken Thompson formerly of Sheffield University and also Clare Trinder from the University of Aberdeen.  Also in the programme was conservation biologist, Stephanie Januchowski-Hartley,  and additional input from the Chartered Institute of Ecology & Environmental Management (CIEEM), microbial ecologist, Dr Rob Griffiths from CEH and ecologist Dr Peter Welsh of the National Trust.

I arrived mid-morning of the Tuesday, having driven up from Shropshire to Yorkshire the night before, having taken the opportunity to stay in the old family home in Kirk Hammerton before it is put up for sale. Whilst there I also set a few pitfall traps to collect some insects that we might not catch otherwise. As it happened they were a dismal failure, returning mainly spiders, harvestmen and woodlice, plus one nice carabid beetle, more of which later. The weather didn’t look all that promising for an insect sampling session but I kept my fingers crossed and hoped that it wouldn’t rain as much as it did almost 40 years ago when my best friend from school and I aborted our camping holiday at nearby Malham Cove after three days of solid rain ;-)

Malham Tarn

Malham Tarn – not quite raining

  I was greatly amused on arriving to be greeted by a very large arachnid lurking on an outhouse.

Malham spider

We breed them big in Yorkshire!

Malham Tarn FSC

Malham Tarn Field Studies Centre

After checking my equipment and locating suitable sampling sites I joined the students, Karen Devine, the BES External Affairs manager and some of the PhD mentors for lunch. After lunch it was my slot, a chance to infect (sorry, inspire), fifty ecologically included undergraduates with a love of insects. After being introduced by Karen I launched into my talk to a very full room of students.

Karen Devine

Karen instilling order and attention ;-)

Ready to be inspired

Ready and waiting to be inspired

The undergraduates came from thirty different UK universities with a strong female bias, 34:16. Exeter University had four representatives, with Reading, Liverpool John Moores, UCL and Bristol with three each. I was sorry to see that there were no students from my Alma mater Leeds, or from my former institution, Imperial College, once regarded as the Ecological Centre of the UK, although UEA where I did my PhD, had two representatives.  There was also one representative from my current place of work, Harper Adams University. Incidentally one of the students turned out to have gone to the same school that I did in Hong Kong, King George V School, albeit almost fifty years apart; a small world indeed.

I set the scene by highlighting how many insect species there are, especially when compared with vertebrates.

The importance of insects

The importance of insects and plants

Number of animal species

Or to put it another way

After a quick dash through the characteristics of insects and the problems with identifying them, exacerbated by the shortage of entomologists compared with the number of people working on charismatic mega-fauna and primates, I posed the question whether it is a sound policy to base conservation decisions on information gained from such a small proportion of the world’s macro-biota.

Then we were of into the field, although not sunny, at least it was not raining so I was able to demonstrate a variety of sampling techniques; sweep netting with the obligatory head in the bag plus Pooter technique, butterfly netting, tree beating and, as a special treat, motorized suction sampling, in this instance a Vortis.

Sampling

With aid of the PhD mentors and Hazel Leeper from the Linnaen Society, the students were soon cacthing interesting things (not all insects) and using the Pooters like experts.

Students sampling

Getting close up with the insects

I also let some of the students experience the joy of the Vortis, suitably ear-protected of course. All good things come to an end and it was then time to hit the microscopes, wash bottles, mounted pins and insect keys.

In teh lab

Getting stuck in – picture courtesy Amy Leedale

Down the microscope

What’s this?

I was very impressed with how well the students did at getting specimens down to orders and families and have every confidence that there are a number of future entomologists among them. After the evening meal, Kate Harrison and Simon Hoggart from the BES Publications Team introduced the students to the tactics of paper writing and publishing which I think they found something of an eye-opener. The students, after a rapid descent on the bar, enjoyed a Pub Quiz whilst I relaxed with a glass of wine until it was dark enough for me to demonstrate the wonders of using fluorescent dust to track our solitary carabid beetle using my UV torch before heading off to bed.

Fluorescent carabid Eloise Wells

Glow in the dark carabid beetle – the bright lights of Malham Tarn – photo courtesy of Eloise Wells

I was sorry to have to leave the next morning, it would have been great fun to have stayed the full week, but next year I do hope to be able to be there for at least two days and nights so that we can do pitfall trapping and light trapping and of course, have more fun with fluorescent insects.

I hope the students found the whole week inspirational and useful, I was certainly inspired by their obvious enjoyment and interest and will be surprised I if do not come across some of them professionally in the future.

Well done BES and congratulations to Karen and her team for providing such a great opportunity for the students. I am really looking forward to next year and being able to see great Yorkshire features like this in the sunshine ;-)

Yorkshire grit

 

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When did research diversity stop being a good thing? Another threat to UK applied agricultural sciences

If, as is well documented, lack of diversity in cropping systems is bad for agricultural production (Johnson et al, 2006: Iverson et al., 2014), then those running the BBSRC should ask themselves why it is a good idea to reduce the number of UK universities they fund that are capable of first class work in the agricultural sciences, particularly crop protection.

Monoculture

http://heckeranddecker.wordpress.com/2008/10/14/feeding-the-next-city/

 

Normally at this time of year I am desperately putting the finishing touches to a couple of applications for BBSRC Industrial CASE studentships (iCASE).   In past years, at the beginning of May, those of us in the majority of UK universities without access to Doctoral Training Partnership funding, make our way to the BBSRC Industrial CASE studentship page to check when the closing date for applications are.  Imagine my shock to find that “this inclusive, very successful and effective programme  appears to have been hi-jacked by the fat cats of the UK university sector.  Yet another example of the “haves” getting more at the expense of the “have-nots”.

BBSRC will no longer operate an annual competition for industrial CASE (iCASE) studentships, instead allocating the majority of these studentships to the BBSRC Doctoral Training Partnerships (DTP) for awarding alongside their standard studentships.  

“The decision to cease the annual iCASE competition for individual studentship projects was taken for a number of strategic and operational reasons, primarily in recognition that the cohort-based approach, as exemplified by the DTPs, provides the gold standard in modern bioscience training, and one which BBSRC was keen to ensure all our funded students had the opportunity to take advantage of”

A more cynical reading of this is ‘it saves the BBSRC administrative time and the costs associated with having to have the applications reviewed by the Training Awards Committee’.   I also take exception to the implication that the only universities in the UK that have a cohort-based training approach are those in receipt of a DTP.  At Harper Adams University we have a well-established cohort-based doctoral training system.  I would be very surprised indeed if we are unique in this aspect of our PhD training amongst the other 100 UK universities outwith the BBSRC DTP programme.

The BBSRC web site goes on to stare “In addition, it was agreed that devolving responsibility for the recruitment and selection of students and collaborators to the DTP partner organisations (of which there are in excess of 45 within 12 partnerships across the UK higher education and public sector research sectors) would improve links between them and local companies, and increase the ability of institutions to act quickly and agilely in allocating projects to these companies, without the delays associated with a large national competition.”

Having moved from a university with a BBSRC Doctoral Training programme and seeing the difficulty and lack of willingness that staff in the other Departments within the School had in finding industrial partners I lack confidence in the ability of such departments to improve links.  As applied, whole organism ecologists/biologists, my former colleagues and I, benefitted immensely from our more molecular-based colleagues’ lack of real industrial contacts and were able to make good use of their unused CASE allocations.  The named grant holder of the DTP grant at the time, told me during a coffee break at a BBSRC Training Awards Committee meeting that he felt the whole CASE scheme was a waste of money.

The iCASE scheme was an opportunity for first class researchers from DTP excluded universities and from ‘Cinderella’ disciplines, e.g. entomology, integrated pest management, non-molecular plant sciences, such as plant pathology, plant nematology, weed science and forestry, which are incidentally recognised by the BBSRC and other learned bodies as being nationally vulnerable ‘skill sets’ to obtain funding that they would otherwise not have access to.  It is a sad fact of life that the universities that hold BBSRC DTP grants long ago decided that possessors of the above vulnerable skill sets did not publish in high enough impact journals and either made them redundant or did not replace them when they retired.

The decision by the BBSRC to further disenfranchise those many excellent applied agricultural scientists is perverse and much to the detriment of UK agriculture.  Given the growing need for sustainable farming systems worldwide it is hard to understand or justify the thought processes that led to this very ill-judged decision.

Ironically it is not just those of us in universities without BBSRC DTP provision that found the removal of the iCASE scheme bothersome.  A day or so after my discovery of the death of iCASE I received an email from a friend of mine at another UK university which is part of a DTP.

 “On a separate issue – no doubt you’ll have registered BBSRC removing the iCASE fund.  Allegedly we will now absorb more projects into our regional  “Doctoral Training Partnership”, but as these are only 2.5 years  for the main project (after all the associated training) it doesn’t always lend itself to the same sorts of projects as iCASE”

And finally, just to highlight the vulnerable skills-sets issue that the BBSRC seems determined to worsen.  I am, as some of you may know, Editor-in-Chief of the Annals of Applied Biology.  I recently received this email from one of my Editorial Board, a whole organism plant pathologist with field experience.

“Dear Simon

 I think that the time has come for me to step down from the editorial board of the Annals of Applied Biology.  I have been doing this for fourteen or fifteen years and I am due to retire from my current post in the Agri-Food & Biosciences Institute in the next few months.

 It has been a privilege, and at most times, highly enjoyable to be part of the editorial board of Annals which is a really good journal.  In a highly competitive world AAB has maintained and indeed increased its reputation.  The standard of papers published is very high and the range of papers received from across the globe is sometimes astonishing.  It has certainly been frustrating at times identifying suitable referees for papers, and as research scientists seem to be under more and more pressure of time it is easy to understand why they are often reluctant to take on extra duties.  However peer review is at the very centre of how science works so it is important that everyone takes their responsibility seriously.

 I would love to be able to recommend a replacement but just now plant pathologists, certainly in the UK, are very thin on the ground.”

I contacted the President of the British Society of Plant Pathologists to see if he could offer me any suitable suggestions for a mid-career plant pathologist with field experience.  Sadly, the majority of  UK Plant Pathologists in the right age range with suitable publishing experience, are molecular biologists.  I eventually filled the gap, but had to appoint a Plant Pathologist from a US university, where happily, universities still recognise the need for field and whole organism plant pathologists and their importance in ensuring global food security; something that most research intensive UK universities and the BBSRC seem to have forgotten.

References

Iverson, A. L., Makin, L. E., Ennis, K. K., Gonthier, D. J., Connor-Barrie, B. T., Remfret, J. L., Cardinale, B. J. &Perfecto, I. (2014). Do polycultures promote win-win or trade-offs in agricultural ecosystem services?  A meta-analysis. Journal of Applied Ecology 51: 1593-1602.

Johnson, M. T. J., Lajeunesse, M. J. &Agrawal, A. A. (2006). Additive and interactive effects of plant genotypic diversity on arthropod communities and plant fitness. Ecology Letters 9: 24-34.

 

Post script

As I knew we were expecting a visit from Jackie Hunter the Chief Executive of the BBSRC, I deliberately held back posting this until I had had a chance to ask her directly about the demise of the iCASE scheme. Jackie was very willing to speak to me about this issue.  The main reason for the removal of the scheme appeared to be the costs of administration and of reviewing the proposals. She assured me that the interests of people like me had been taken into account by giving more money to the ten companies  which hold grants in their own right and also by expecting greater flexibility from the existing University DTP grant holders, by which I took to mean that they would be encouraged to collaborate with the ‘have-nots’. This may seem laudable were it not for two facts; of the ten industrial DTP holders, five are pharmaceutical companies holding just under half of the grants and the academic DTP grant holders are greatly lacking in agricultural expertise. I also suspect, given the shortage of available PhD studentships in comparison with staff numbers within most university departments, that a big stick will be needed to encourage any cross-fertilization with non-DTP holders. I will, however, wait and see if Jackie’s optimism is well-founded, although I will not be holding my breath ;-)

Post post script

 The importance of diversification in research funding is not just a hobby-horse of mine.  See for example, this excellent post by Stephen Heard writing on why it is a bad strategy to centralise research funding.

 

 

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Insect egg mimics – plant parts that pretend to be insect eggs

Back in the 1980s I was a forest entomologist working for the UK Forestry Commission at their Northern Research Station based just outside Edinburgh.  I was working on two important pests of Lodgepole pine (Pinus contorta), the pine beauty moth, Panolis flammea and the European pine sawfly, Neodiprion sertifer.  The pine beauty moth lays its eggs in short rows on the upper surface of pine needles in late spring/early summer.

Panolis eggs

Eggs of the pine beauty moth, Panolis flammea  (Image courtesy of Stanislaw Kinelski, Bugwood.org http://www.invasive.org/browse/detail.cfm?imgnum=1258002).

They are pale yellow when first laid and gradually darken as they mature becoming a deep violet colour just before they hatch.  The eggs of Neodiprion sertifer are also laid on the upper part of the pine needles, but are ‘injected’ just under the cuticle of the needle.  After a few days a small necrotic patch develops at the oviposition site.

Neodiprion eggs

Eggs of the European pine sawfly, Neodiprion sertifer (image courtesy of A. Steven Munson, USDA Forest Service, Bugwood.org http://www.forestryimages.org/browse/detail.cfm?imgnum=1470178)

Spring field work for me was several days of rather tedious egg counting and as I scrutinised hundreds of pine needles, I noticed that some of the needles had little flecks or balls of resin on them,

Resin flecks

Resin flecks on bristlecone pine, Pinus arsitata – often confused with scale insect infestations (Photo by Hans G. Oberlack via Wikipedia).

which were, especially on gloomy days in the depths of the forest, quite easy to confuse with pine beauty moth eggs.  Other needles had discoloured areas that looked like pine sawfly eggs or also a bit like pine beauty moth eggs, depending on how they were arranged.

Egg mimics

Possible insect egg mimics on pine needles

Long days working alone in a forest allow one the time to think and it occurred to me one day that if I was being fooled by these ‘pseudo eggs’ then perhaps egg-laying pine beauty moths and pine sawflies might also be getting confused and avoiding laying eggs on these apparently already infested needles.   I wondered if there was any evidence to support my far-fetched hypothesis and to my delight found a paper by (Williams & Gilbert, 1981) that demonstrated quite convincingly that passion-fruit vines, produce structures resembling eggs of Heliconius butterflies and that these deter them from laying eggs on them.

Egg mimics 2

Egg mimics on passion flower leaf – Photo by Lawrence Gilbert http://plantmimicrybz2820.blogspot.co.uk/2015/04/the-passiflora-genus.html

I also found papers that showed that other Lepidoptera (Rothschild & Schoonhoven, 1977; Nomakuchi et al., 2001) and beetles (Mappes & Mäkelä, 1993), are able to discriminate between leaves that already have eggs laid on them and avoid laying more eggs on those leaves, thus reducing larval completion.

Although I never formally checked it, I got the impression that needles bearing ‘egg mimics’ had fewer pine beauty moth eggs or pine sawfly eggs laid on them than those without.  Another question that could be easily looked at is whether pine trees in areas that have had outbreaks have more speckled needles than those in non-outbreak areas.  I always meant to do some formal sampling and a proper experiment to back up my feelings, but never found the time to do it.  I am pretty certain that I am unlikely to get round to doing this in the near future (if ever), but I would like to know if this is indeed another example of  a plant mimicking insect eggs.  I would be very happy indeed if any of you feel like testing my hypothesis and look forward to seeing the results in print.

 

References

MacDougal, J.M. (2003)  Passiflora boenderi (Passifloraceae): a new egg mimic passionflower from Costa Rica.  Novon, 13, 454-458

Mappes. J. & Mäkelä, I. (1993)  Egg and larval load assessment and its influence on oviposition behaviour of the leaf beetle Galerucella nymphaeae.  Oecologia, 93, 38-41

Nomakuchi, S., Masumoto, T., Sawada, K., Sunahra, T., Itakura, N. & Suzuki, N. (2001) Possible Age-Dependent Variation in Egg-Loaded Host Selectivity of the Pierid Butterfly, Anthocharis scolymus (Lepidoptera: Pieridae): A Field Observation .  Journal of Insect Behavior, 14, 451-458.

Rothschild, M. & Schoonhoven, L.M. (1977) Assessment of egg load by Pieris brassicae (Lepidoptera: Pieridae). Nature, 266, 352-355.

Williams, K.S. & Gilbert, L.E. (1981) Insects as selective agents on plant vegetative morphology: egg mimicry reduces egg laying by butterflies. Science, 212, 467-469.

 

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Journals of Irreproducible Research – downgrading reproducibility and fact checking

As far as I am concerned, good science is about communication and reproducibility, or, as Stephen Heard argues, at least being able to believe that it is reproducible.  I would argue a bit more strongly than Stephen, in that I think you should, at the very least, be able to be confident that you could reproduce the experiment without having to contact the author(s) and that you can also easily check the cited literature.   In this context, there are two things that really annoy me about some of the so-called ’high impact’ established print journals and their on-line would be rivals.  First, the way in which the methods and materials section is relegated to the end of the paper, often in smaller font, and in some cases to the supplementary material section  In other journals e.g. Nature, the methods section is also very minimal and I defy anyone to repeat those experiments!  My second bugbear is the habit that some journals have, possibly to reduce space, in making you use numbers to denote references, placing them either in parentheses or superscript in the main text.

Perhaps I am alone in this, but I do like to know whose work is being cited without having to constantly refer to the references section.  What  particularly annoys me, are those journals that not only insist on numbered references but then list them in number order and not in alphabetical order!  I once wrote a review paper for Annual Review of Entomology, which has the numbering system, but subverted it by listing my references alphabetically – the editor never noticed ;-)

You may say that what all these journals are doing is merely structuring the paper in the order that people tend to read them which is, I admit, a valid point. To me however, they are saying to the scientific community, perhaps not overtly, but certainly subliminally, that methods and materials are something you don’t really need to bother about, somewhat akin to those things that you store in an attic or basement, just in case you might want them at some time in the future, but probably not often, if at all.

Hidden methods

This sends a strong and erroneous message to authors that despite the methodology being the most important part of how we do our science, as long as they report the general gist of how they did things it is fine.  To referees the subversion of the methods section sends an equally strong signal; you don’t really need to spend a lot of time reading about the methodology as long as the rationale for the work is justified and that the results are significant and well presented.

As someone who works on insect-plant interactions I constantly come across inadequate methods and materials sections both as a referee and as a reader of published work.  The thing that perhaps causes me the most annoyance are descriptions of plant phenology.   Herbivorous insects have a very intimate relationship with their host plants and the growth stage of their host plant or the age of the plant tissue that they are feeding on can have very marked effects on their development, survival and fecundity (Awmack & Leather, 2002).  I so often came across methods descriptions along the lines of “10 day-old cabbage seedling” “ 3 week old pepper plant”,  “2 week-old wheat plant”, that in desperation I wrote an editorial (Leather, 2010) explaining how important it was to use a measure that didn’t depend on the temperature,  photoperiod, nutrient or water status that the plants were grown at i.e. the BCCH scale.  I also compiled a virtual issue of Annals of Applied Biology, with relevant examples drawn from the journal which has a long and distinguished history in publishing such articles.  If you can’t find your host plant in past issues of the Annals you will find that most plants have a published version somewhere, even if only on Wikipedia.  Despite my efforts however, I still often have to remind authors to describe the phenological stage of their host plants accurately and precisely.

Methods and materials, please come back, we need you!

 

References

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

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

 

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Ten Papers that Shook My World – Owen & Weigert (1976) – The things that eat you are good for you

Journal clubs have been around a long time, but as a new PhD student in 1977 it was a new experience for me.  I was thus somewhat uncertain about what was expected from me when my supervisor presented me with a copy of Owen, D.F. & Wiegert, R.G. (1976) Do consumers maximise plant fitness? Oikos, 27, 488-492, and informed me that I was going to present my views on the paper the following month.  In those days organised PhD training programmes in the UK did not exist. Nowadays, PhD students in the UK follow a programme of lectures and workshops ranging from statistics, presentation skills, paper writing, ethics, use of social media, how to run tutorials, IPR, critical appraisal,  etc. etc. Given my lack of experience,  I was a little apprehensive to say the least.  Luckily I had the chance to see how the older members of our research group dealt with their papers in the preceding weeks and was somewhat moe confident about what was expected of me.  I duly read the paper and highlighted the areas that I wanted to critique.

O&W1O&W2O&W3

Parts of the Owen & Weigert (1976) paper showing the bits that I highlighted for my critique.

Owen & Weigert’s hypothesis was, that contrary to accepted doctrine, consumers, especially those feeding on trees, were beneficial to their host plants and not harmful.  Coming fresh from an agriculture department where I had been taught that anything that ate a plant was a pest, this was a startling and heretical concept for me to digest!  I remember at the time that I was not particularly convinced by the arguments and that within the group the general consensus was that Denis Owen was a bit of an eccentric.  In fact, the senior members of the group entered into a printed debate in the popular scientific press (McLean et al., 1977; Owen, 1977) which resulted in what I still consider to be the best ever front cover of New Scientist ;-)

New Scientist cover

Arguably the best ever front cover of New Scientist

 We were not the only ones who expressed scepticism about Owen’s hypothesis, although experimental rebuttals of Owen’s claim that aphids and trees were in a mutualistic relationship via honeydew production did not appear until some years later (Petelle, 1980; Choudhury, 1984, 1985).  These papers resulted in a series of spirited responses from Owen (Owen & Wiegert, 1982a, b, 1985, 1987).  Some years later, however, Joy Belsky provided further evidence against Owen’s hypothesis (Belsky, 1986,1987; Belsky et al., 1993) and I too entered the fray (Leather, 1988,2000).

Thus by the end of the last century it appeared that all the evidence indicated that if you were a plant, being eaten was not good for you.  On the other hand, if Owen had posed his hypothesis at a population or group level, he might have been able to make a better case for herbivores increasing plant fitness. In an earlier post, in which I wrote about the plant immune response and how plants communicate with each other when attacked and warn their neighbours of potential attack, one could definitely make a stronger case for plants benefitting from being eaten.  Induced resistance can even work at an individual level, some recent work (McArt et al., 2013) has shown that evening primroses (Oenothera biennis) attacked early in the season by the Japanese beetle, Popillia japnonica, become more resistant to attack from seed predators than those that escape early season defoliation. As a result the beetle attacked plants produce more seed than those that escaped attack.  Given that a general measure of fitness is reproductive success (i.e. how many seeds are produced) then in this case, consumers do maximise plant fitness and Denis Owen can have the last word.

References

Belsky, A.J. (1986) Does herbivory benefit plants? A review of the evidence. American Naturalist 127, 870-892

Belsky, A.J. (1987) The effects of grazing: confounding of ecosystem, community and organism scales. American Naturalist, 129, 777-783.

Belsky, A.J., Carson, W.P., Jensen, C.L. & Fox, G.A, (1993) Overcompensation by plants – herbivore optimization or red herring. Evolutionary Ecology, 7, 109-121.

Choudhury, D. (1984) Aphids and plant fitness – a test of Owen and Wiegert’s hypothesis. Oikos, 43, 401-402.

Choudhury, D. (1985) Aphid honeydew – a re-appraisal of Owen and Wiegert’s hypothesis. Oikos, 45, 287-289.

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

Leather, S.R. (2000) Herbivory, phenology, morphology and the expression of sex in trees: who is in the driver’s seat? Oikos, 90, 194-196.

McArt, S.H., Halitschke, R., Salminen, J.P. & Thaler, J.S. (2013)  Leaf herbivory increases plant fitness via induced resistance to seed predators.  Ecology, 94, 966-975.

McLean, I., Carter, N., & Watt, A. (1977) Pests out of Control. New Scientist, 76, 74-75.

Owen, D.F. (1977) Are aphids really plant pests? New Scientist, 76, 76-77.

Owen, D. F. (1980). How plants may benefit from the animals that eat them. Oikos 35: 230-235.

Owen, D.F. & Wiegert, R.G. (1976) Do consumers maximise plant fitness? Oikos, 27, 488-492

Owen, D.F. & Wiegert, R.G. (1982) Beating the walnut tree: more on grass/grazer mutualism. Oikos, 39, 115-116.

Owen, D.F. & Wiegert, R.G. (1982) Grasses and grazers: is there a mutualism ? Oikos, 38, 258-259.

Owen, D.F. & Wiegert, R.G. (1984) Aphids and plant fitness. Oikos, 43, 403.

Owen, D.F. & Wiegert, R.G. (1987). Leaf eating as mutualism. In Insect Outbreaks (ed. by P. Barbosa & J.C. Schultz), pp. 81-95. Academic Press, New York.

Petelle, M. (1980) Aphids and melezitose: a test of Owen’s 1978 hypothesis. Oikos, 35, 127-128.

 

Post script

Denis Owen died at a relatively young age and for those interested in his career and life, his obituary can be found here.

 

 

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Re-examining external examining and the evolution of humans

External examining 2

Last year I wrote about my first year of being external examiner for the BSc Zoology degree at University College Dublin and some of the reasons why I enjoy the process.  This year I again visited Dublin to undertake my annual review of the zoology degree and was reminded of another reason why I find being an external examiner so rewarding.

Normally I go through all the exam scripts looking at how well they are annotated by the first marker, if they are signposted to help the second marker, e.g. marked as outside reading (OR) and check if they have been moderated and if the mark given has been justified in accordance with the marking criteria.  I also check if the marking across and between modules is consistent and fair.  For many of the modules this is really all I can do as I may not know a great deal about the subject, e.g. epithelial transport.  On the other hand there are some modules that I know a lot about, such as insect-plant interactions or biodiversity, where the questions asked are often very similar to the ones that I set for my own students. In these cases I read each answer and mark them before looking at what the actual mark given was and if they are similar this gives me confidence that all is well.

I often find myself learning new things when I read through the research projects of the students that I am going to viva; this year ranging from molecular biology, to phylogenetics, to elucidating the genes associated with inflammation of the brain of Irish greyhounds, to vertebrate behaviour to marine invertebrates and of course not forgetting entomology.  In respect to the projects this year the experience was no different.  What was different this year was that I had enough time to become engrossed with the scripts of the Evolution of Humans module.  One of the questions asked students to review the evidence that supports or refutes the theory that bipedalism in humans arose from adopting wading behaviour in a humid woodland environment. As a teenager, heretical as it may seem to my fellow entomologists, I was very interested in human evolution, reading and being influenced by Robert Ardrey, especially his book African Genesis and of course by the work of the Leakeys.  On reaching university and afterwards however, I became much more focused on invertebrates and my reading on human evolution became somewhat limited, although I do remember being unconvinced, rightly it seems, by the Aquatic Ape Hypothesis and sticking with the African savannah origin hypothesis.

I was thus fascinated to read about The Amphibian Generalist Theory (Niemitz, 2002) in which Carsten Niemitz put forward the idea that our hominid ancestors lived in trees in forested habitats as had been suggested earlier (Clarke & Tobias, 1995) but moved from there to forage along the nearby coasts and river banks from which they waded into the water in pursuit of the rich food sources available. The buoyancy given by the water and the need to keep their heads above water helped develop bipedalism.

Wading monkeys

Modern wading quadruped primates adopting bipedal locomotion whilst wading.  ‘Borrowed’ from Niemitz (2010).

Gorilla wading

Looks more like what happens when you get into water that is colder than you expect than foraging for food!

At the same time as the forests were fragmenting, the savannahs were forming and these were also able to be exploited by these early hominids. I found the student essays fascinating and they stimulated me to download lots of the papers that they referred to in their exam answers.  So as a direct result of external examining I have updated my knowledge of human evolution, and rekindled my interest in the subject.

This is, I think, a salutary message to us all, that by becoming too engrossed in our own subjects we run the risk of losing an all-round appreciation of the world in general.  Talking and listening to people from other disciplines is very important and can lead to very productive and exciting collaborations.  As an example, our entomology group at Harper Adams have  begun to develop some collaborative work with a psychologist, Claudia Uller, from Kingston University which will hopefully generate some very exciting projects.

And my final take-home message; if you are offered the chance to become an external examiner, jump at the opportunity and and not just auditing the process, take the time to read the essays and projects that are not directly in your area of expertise.  You will be pleasantly surprised.

References

Clarke, R.J., and Tobias, P.V. (1995) Sterkfontein member 2 footbones of the oldest South African hominid. Science 269:521–524

Niemitz, C. (2002) A theory on the habitual orthograde human bipedalism—the “Amphibische Generalistentheorie”. Anthropologischer Anzeiger, 60:3–66

Niemitz, C. (2010) The evolution of the upright posture and gaita review and a new synthesis.  Naturwissenschaften, 97:241–263

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Mellow Yellow – Not all aphids live on green leaves

I have written before about aphids and how their quest for the ideal food plant may explain the evolution of host alternation; we find that most aphid species tend to be associated with rapidly growing meristems, or newly flushing leaves (Dixon, 2005). Some aphids are so keen on young plant tissue that they ‘engineer’ youth in their host plants, injecting salivary compounds and forming leaf–rolls, pseudo-galls and galls, all of which act as nutrient sinks and lengthen the time that the modified leaves stay green and nutrient-rich

leaf roll Rhopalosiphum

 Leaf-roll caused by Rhopalosiphum padi on bird cherry, Prunus padus.

Leaf roll Myzus cerasi

Pronounced leaf roll pseudo-gall caused by Myzus cerasi on Prunus avium.

Non host-alternating (autoecious) aphids, such as the sycamore aphid Drepanosiphum platanoidis, the maple aphid, Periphyllus testudinaceus, or the birch aphid, Euceraphis punctipennis, have no such escape route; they are confined to their tree host for the year, albeit, they can, if they ‘wish’, fly to another tree of the same species, but essentially they are held hostage by the their host plant. As the season progresses, leaf nutritional and physical properties change; going from young tender green leaves, with high nitrogen and water contents, to mature, tough leaves, low in nitrogen and water to yellow senescing leaves with again, higher nitrogen levels (Awmack & Leather, 2002) and finally of course, dead brown leaves of no nutritional value.

Seasonal changes

Sycamore and maple aphids, enter a state of suspended animation ‘summer aestivation’ (Essig, 1952; Dixon, 1963), whilst birch and poplar aphids, whose hosts plants often produce new growth during the year, ‘track’ these new leaves (Wratten, 1974; Gould et al., 2007). As far as these aphids are concerned young tissue is their best food source, with senescent tissue being second best and mature leaves being least favoured. During the summer they will, however, take advantage of mature leaves that are prematurely senescing, such as those attacked by leaf diseases such as tar spot. I have often found sycamore aphids feeding and reproducing on these infected leaves whilst those aphids on neighbouring mature leaves remain in aestivation.

Tar spot 2

Effects of tar spot on sycamore leaves

Host-alternating (heteroecious) aphids on the other hand are somewhat different. As their life cycle includes a programmed migration back to their primary tree host in autumn, those autumn morphs (oviparae) are adapted to senescent tissue (Leather & Dixon, 1982, Kundu & Dixon, 1993, 1994). Similarly, the spring morphs (fundatrices and fundatrigeniae) are adapted to young leaves and find it difficult or impossible, to make a living on senescent leaves.
Morphs and host age

There are yet other aphids, such as the green spruce aphid Elatobium abietinum, the pine aphid, Eulachnus agilis and the black pecan aphid, Melanocallis caryaefoliae, that are senescence specialists. In contrast to the flush specialists, these aphids engineer senescence, also using salivary compounds,  and are unable to survive on young foliage (Bliss, 1973; Fisher, 1987; Cottrell et al., 2009).

Elatobium in action

Elatobium abietinum ‘engineering’ senescence on spruce needles and avoiding young flushing tissue.

It is interesting to speculate that perhaps these tree-dwelling non host-alternating aphids are secondarily derived from the autumn part of the life-cycle of host-alternating aphids. After all, if non host-alternating aphids on herbaceous host plants are off-shoots of the summer part of the host-alternating life-cycle why not the other way round. There is just so much more to learn about aphids. Yet another reason why I love aphids so much ;-)

References

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

Bliss, M., Yendol, W.G., & Kearby, W.H. (1973) Probing behaviour of Eulachnus agilis and injury to Scotch pine. Journal of Economic Entomology, 66, 651-655.

Cottrell, T.E., Wood, B.W. & Ni, X. (2009) Chlorotic feeding injury by the Black Pecan Aphid (Hemiptera: Aphididae) to pecan foliage promotes aphid settling and nymphal development. Environmental Entomology, 38, 411-416.

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

Dixon, A.F.G. (2005) Insect Herbivore-Host Dynamics. Cambridge University Press, Cambridge.

Fisher, M. (1987) The effect of previously infested spruce needles on the growth of the green spruce aphid, Elatobium abietinum. Annals of Applied Biology, 111, 33-41.

Gould, G.G., Jones, C.G., Rifleman, P., Perez, A., & Coelman, J.S. (2007) Variation in Eastern cottonwood (Populus deltoides Bartr.) phloem sap content caused by leaf development may affect feeding site selection behaviour of the aphid, Chaitophorous populicola Thomas (Homoptera: Aphididae). Environmental Entomology, 36, 1212-1225.

Kundu, R. & Dixon, A.F.G. (1993) Do host alternating aphids know which plant they are on? Ecological Entomology, 18, 61-66.

Kundu, R. & Dixon, A.F.G. (1994) Feeding on their primary host by return migrants of the host alternating aphid, Cavariella aegopodii. Ecological Entomology, 19, 83-86.

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

Wratten, S.D. (1974) Aggregation in the birch aphid, Euceraphis punctipennis (Zett.) in relation to food quality. Journal of Animal Ecology, 43, 191-198.

 

Post script

A lot of what I describe comes from a talk I gave in 2009 at a workshop in Oxford on autumn colours (the output of which was 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. I always meant to write the talk up as an Opinion piece but procrastination set in badly. I was somewhat annoyed with myself when earlier this year this excellent piece by the legendary ecologist and entomologist, Tom White, appeared; I have only myself to blame, six years is a very long bit of procrastination ;-)

White, T.C.R. (2015) Senescence-feeders: a new trophic sub-guild of insect herbivores Journal of Applied Entomology, 139, 11-22.

 

Post post script

This post is dedicated to my eldest son, Sam, who died quietly in his sleep, at a tragically young age, December 23rd 2010.   It would have been his birthday on the 21st May.  Despite being a molecular biologist, (he worked at the Sanger Institute), he was as green as you can get, a great naturalist and conservationist, with an incredibly gentle soul. He strongly believed in conserving the World’s natural resources and amused colleagues by sticking up signs in the toilets at the Sanger, which read “If its yellow let it mellow, if its brown flush it down”.

Sampsa

 

He is sorely missed by us all. He also had more Nature papers than me ;-)

Parkhill, J., Achtman, M., James, K.D. et al., (2000) Complete DNA sequence of a serogroup A strain of Neisseria meningitides. Nature, 404, 502-506

Parkhill, J., Dougan, G. , James, K.D. (2001) Complete genome sequence of a multiple drug resistant Salmonella enterica serovar Typhi CT18. Nature, 413, 848-852.

Parkhill, J., Wren, B.W., Thomson, N.R. et al., (2001) Genome sequence of Yersinia pestis, the causative agent of plague. Nature, 413, 523-527.

Parkhill, J., Sebaihia, M., Preston, A. et al., (2003) Comparative analysis of the genome sequences of Bordetella pertussis,   Bordetella parapertussis and Bordetella bronchiseptica. Nature Genetics, 35, 32-40

Wood, V., Gwilliam, R. Rajandream, M.A. et al., (2002) The genome sequence of Schizosaccharomyces pombe . Nature, 415, 871-880

 

 

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Distant Elephants and Low-Hanging Fruit – confessions of a procrastinator

elephant vsmall

verb; procrastinate – delay or postpone action; put off doing something

I hate writing full-blown grant applications. The thought of sitting down with a blank page in front of me, and justifying why I want to do the research, saying how well it fits the remit of the research council, demonstrating how great I am (track record of applicant), articulating my hypotheses, outlining the work packages, writing an impact statement, getting costings to draw up a budget, justifying the resources requested, and so on and so on, and all with the knowledge that there is an about 1 in 5 chance of getting funded, does not fill me with any great enthusiasm. It also takes up a huge amount of my time and to do it properly you really do need to sit down and exclude all other activities.

I also find it difficult to start writing a paper from scratch, or get to work on a new presentation;  I should, for example, be getting my plenary lecture for ENTO15 ready, but as it only May 11th and I am not speaking until September 2nd I am finding it difficult to get started on that. This is despite the fact that it was only by a superhuman effort before Christmas I got the written version submitted to Ecological Entomology on the required day (now available on Early View if you are interested).  Of course I am steadfastly ignoring the fact that I will be on holiday from July 24th until August 17th and that on my return I will be marking several MSc project reports!

elephant small

I have several delaying (apparently according to Microsoft Word, procrastinatory doesn’t exist) tactics, or low-hanging fruits, that I can pick

Low-hanging fruit

when faced with things I don’t really like doing; I can tidy my desk,

Desk

I can go to check my aphid cultures (a very useful 800 m walk to the glasshouses), I can walk to the Postgraduate Office to check applications (450 m from my office), do a sweep round the PhD offices (also 450 m away from my office) to see how my students are doing, check my email (again and again), accept a request to review a paper, although this then necessitates writing a report ;-) , and as an Editor, I have the very useful excuse that I need to log on to the journal site to check what is happening; the list is long and can certainly fill my day.

elephant medium

In our defence, procrastinators are actually very useful for the academic community; we are the people who agree to review papers, agree to be external examiners, sit on internal and external committees, do a lot of teaching and generally act as good citizens, although perhaps not as altruistically as our colleagues might think, after all we do have an ulterior motive.

Is there a cure?

There are things that we can do; a colleague of mine, does not open her emails on a Monday, I don’t have the will power to do this, I find it difficult enough to ignore my email for two-hour periods, which is my attempt at giving myself a chance to get really into doing some writing. Some people (those who are sociable and find it hard not to go to coffee or chat with colleagues) work from home; again this does not work for me as I then find household chores to distract me. I once went on a time management course in which the use of a daily To Do List was suggested. I dutifully began one of these but found that because of reactive tasks my proactive list just carried on to the next day and never seemed to get completed so that didn’t work for me either, but perhaps I should have said no to the reactive tasks or been less ambitions with the number of things on my To Do List? If anyone has further suggestions please let me know.

So how is that I complete anything substantial? For external tasks this is easy, I promise to deliver, and because I take my solemn promises to other people very seriously indeed, the task gets done, no matter how much I would rather not do it. Unfortunately, promises to myself I find much easier to break, so things that I regard as non-life or career-threatening, do tend to fall by the wayside.

elephant big

 

All in all, I’m very lucky as my procrastinatory (it does exist Microsoft – see here) habits are relatively mild and surmountable, and I have managed to get this far in life without any serious failures.

There are, however, some people who procrastinate because of fear of failure, they set themselves the impossible goal of perfection (unless of course you are a gymnast or diver). This can lead to some very serious failures; for example, students who don’t answer any questions in an exam because they are afraid that their answers will be wrong and hand in a blank answer book, despite having it pointed out to them that if they don’t write anything they will definitely fail. I have also known students who find it almost impossible to hand in written work because they are afraid that it won’t be good enough, despite being told that unless I can see something I can’t help them improve it. To a non-sufferer the solution seems incredibly simple, just get out there and do something, how difficult can it be? It is, however, not simple at all, it can actually be a serious psychological problem that needs very sympathetic and supportive handling, ranging from sharing the task with a friend, colleague or even a suitably sympathetic supervisor, to professional counselling. It is not something to be dismissed lightly as an exasperating foible. Please, please remember this the next time you come across a colleague or student who persistently fails to complete tasks on time. They are not doing it on purpose.  Talk to them about the problem and address the issues sympathetically and with compassion and recommend them to seek psychological help if you feel it is necessary.
Post script

Apropos my latest attempt at writing a major grant proposal, the closing date is 17th May and given that I am writing this on the 11th May and I have, so far only written the opening paragraph of a ten page proposal, I fear that the elephant is about to arrive and trample me ;-)

elephant large

Post post script

It amazes me how many times you hear or see, people using the word prevaricate when they mean procrastinate; they are very different in meaning and not something you would want to own up to in public. Prevaricate means to act or speak in an evasive way (for great examples listen to a politician being interviewed), which to me at least, implies dishonesty.

elephant large

 

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The UK needs more forest health specialists

Last week (April 22nd and 23rd 2015) I had the pleasure of attending the Institute of Chartered Foresters’  National Conference in Cardiff.  The theme of the conference was Tree health, resilience and sustainability.

ICF conference

 The PowerPoint versions of the presentations are available here.

It was very well attended with over 150 delegates and divided into six sessions; Setting the Scene, Overseas Experience, Perspectives on Risk, Searching for Resilience and Sustainability, Practical Responses in the Field and finally Messages for Government and the Profession.  The speakers came from a range of backgrounds; universities, research institutes, the forest industry and others.  Dr John Gibbs, a former colleague of mine from Forest Research opened the formal talks with a masterly review of how forest health problems were tackled in the last century, using Dutch Elm Disease as his focal organism. He was followed by Professor James Brown from the John Innes Institute discussing how lessons from agriculture could be used to develop strategies to combat tree diseases.  Both these speakers pointed out that there was a grave shortage of forest pathologists and entomologists in the UK, particularly in the university sector.   James Brown commented that he had been shocked to discover he had only been able to count seven people in the sector working on tree diseases and added that this did not make them forest pathologists.  We had talks from overseas speakers such as Professor Mike Wingfield from South Africa on global forest health threats, Jim Zwack from the USA speaking on the Emerald Ash Borer as an urban pest problem and Catherine St-Marie highlighting the fact that climate change was aiding and abetting the spread of the Mountain Pine Beetle in Canada.

There was a surprisingly interesting talk on the problems of insuring forests against pests and disease form Phil Cottle of Pardus Underwriting Limited and an enlightening presentation from Professor David Ball from Middlesex University talking about uncertainty and decision-making.  Again both these speakers highlighted the need for further information about pests and diseases.

Day 2 had us searching for resilience and sustainability within the UK forestry sector with a very entertaining talk from Jo O’Hara, Head of Forestry Commission Scotland.  Her talk really drove home to me how much UK forestry has changed over the last 30 years; when I joined the Forestry Commission in 1982 they had only just appointed their first woman District Officer, and now a woman runs FC Scotland – a very welcome sign of change.  Tariq Butt from Swansea University spoke about the use of entomopahogenic fungi as biological control agents in forestry, something increasingly moving higher on the agenda as we face the loss of even more conventional pesticides in the next few years and Martin Ward, the Director-General of EPPO asked us to consider how global plant health arrangements could be improved to protect trees more effectively.  Again the message was that we need more forest health specialist, and not just in the UK.   After the morning coffee break, Joan Webber, the Principal Pathologist for Forest Research UK, spoke about detection and precautionary measures to combat biosecurity threats and yet again highlighted the need for further research and eyes on the ground; in other words more specialist staff are required.  Neil Strong from Network Rail drew our attention to the problems caused by trees to our railway system and then Bill Mason extolled the virtues of increasing species and structural diversity when planting new forests and managing older ones, to improve resilience.

The afternoon session kicked off with Clive Potter from Imperial College talking about understanding what the public’s concerns about tree health are and how certain events can amplify risk perception among the public.  The public outcry about Chalara and Ash Dieback being a particularly good example of the phenomenon.  I followed with a talk about the needs for professional education which gave me the opportunity to point out what subject areas should be covered in an aspiring forester’s education.

Essential skills

I was also able to remind my audience that the number of UK universities providing specific forestry training at undergraduate level had dwindled to less than a handful and that despite offering modules purporting to cover forest health problems, only two employ specialist staff in those areas.  At postgraduate level there is only one course that deals specifically with forest health issues in the UK, the MSc in Conservation & Forest Protection that I run at Harper Adams University.

My take-home messages to a very receptive audience was that students need more emphasis on identification skills and much more practical experience, that current forestry professionals need to keep their eyes open and practice looking for pests and diseases as well as taking any opportunity to refresh their training and that UK universities offering forestry related courses need to employ more forest entomologists and forest pathologists.  Even more importantly, the UK government need to make sure that there are financial incentives to encourage universities to employ more forest entomologists and forest pathologists by increasing targeted research funding in those areas and once increased, maintain those levels of funding.  There also needs to be a clear signposting of career opportunities for the next generation of forest health scientists and if we as a country are serious about safeguarding our native woodlands and forest estate, then more jobs need to be created.

As I have written elsewhere, we cannot afford to sit back and hope that things will get better on their own.  Versions of this slide appeared on the screen several times during the course of the conference.  We are under attack and we need more suitably qualified people to help repel and contain the invaders.

Forest pests

 

Additional reading

Leather, S.R. (2014) Current and future threats to UK forestry. Outlooks on Pest Management, 25, 22-24.

Leather, S.R. (2014) How prepared is the UK to combat future and current threats to forests? Commonwealth Forestry Association Newsletter, 64, 10-11.

 

Post script

I am very grateful indeed to the Institute of Chartered Foresters for giving me the opportunity to speak at the conference and for providing generous hospitality.  It was one of the most engaging and interesting conferences that I have been to for a very long time.  Well done ICF.

 

Post post script

It was also good to see Twitter being used very successfully with the #Treehealth hashtag.  We even had participants from the Canadian Forestry Service!

ICF tweets

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Not all aphids take the same risks

In 1970 an entomologist working on the black bean aphid, Aphis fabae, at Rothamsted Experimental Station (as it then was),  noted that he could categorise the winged individuals as either migrants, flyers or non-flyers; the former flying before they reproduced, the second flying after they reproduced and the final category, never flying (Shaw, 1970).  To describe this phenomenon he used the phrase “migratory urge” a term previously only used in the ornithological literature.

A few years later a group of PhD students in Tony Dixon’s lab at the University of East Anglia started dissecting aphids and counting their ovarioles, finding that unlike most other insects, ovariole number was variable within a species and not related to adult weight (Dixon & Dharma, 1980; Wellings et al., 1980; Leather, 1983).  Generally speaking, in insects, including aphids, the heavier they are, the more fecund they are, although in some instances this is not always true (Leather, 1988).

Ovarioles Fig 1

Figure 1 taken from http://www.aphidsonworldsplants.info/Cloning_Experts_3.htm

Ovarioles Fig 2

Figure 2 What aphid ovarioles really look like Dombrovsky  et al. BMC Research Notes 2009 2:185   doi:10.1186/1756-0500-2-185

What we found then (Wellings et al., 1980), and later (Leather et al., 1988), was that aphids with wings (alatae) even those from the same clone, had much more variability in the number of ovarioles contained within them than those without wings (apterae) (Leather et al., 1988), and that the more ovarioles an aphid contained the more fecund it was, although as mentioned earlier the number of ovarioles appeared to be independent of weight (Leather & Wellings, 1981).

So what does this have to do with migratory urge in Aphis fabae? In the early 1980s Keith Walters was working on migration in cereal aphids (Sitobion avenae and Rhopalosiphum padi) and discovered, that as with Aphis fabae these two species also produced alatae with different flight attributes (Walters & Dixon, 1983).  Building on what we in our group had discovered about ovarioles, Keith was able to show that the degree of migratory urge in aphids was determined by the number of ovarioles they contained. The greater the number of ovarioles the more reluctant they were to take flight (Figure 3ab).

Ovarioles Fig 3a

Figure 3a Relationship between number of ovarioles and time to take-off (minutes) in Sitobion avenae  (Drawn from data in Walters & Dixon, 1983).

Ovarioles Fig 3b

Figure 3b Relationship between number of ovarioles and time to take-off (minutes) in Rhopaloisphum padi  (Drawn from data in Walters & Dixon, 1983).

 He also found that the fewer the number of ovarioles, the steeper the angle of take-off was (Figure 4) i.e. aphids with few ovarioles climbed faster and more steeply and were thus more likely to end  up higher in the air, and thus more likely to travel further than those

Ovarioles Fig 4

Figure 4 Relationship between number of ovarioles and angle of take-off (degrees) in Rhopalosiphum padi (drawn from data in Walters & Dixon, 1983).

taking off at a shallower angle.  He also showed that resistance to starvation was greater in those aphids with fewer ovarioles and that they could also fly for longer periods of time.  Given that alatae of Aphis fabae also have a variable number of ovarioles, 6-12 (Leather et al., 1988), we can see that this fits in very well with Shaw’s classification of migrants, flyers and non-flyers.

This is yet another great example of the flexibility (plasticity) of the aphid clone.  By producing offspring that have different flight capabilities and propensities, the clone is able to hedge its bets in times of adversity; alate aphids in many aphid species are produced in response to crowding and/or poor nutritional quality (Dixon, 1973).  This deterioration in living conditions could be very local i.e. restricted to the plant on which the aphid is feeding or its immediate neighbours, slightly more widespread, i.e. at a field scale or at a much more widespread landscape scale.  Given that long distance aphid migration is very costly (only a tiny proportion survive, Ward et al, 1998) the best option is to spread the risk between the members of your clone.  Those individuals with more ovarioles and greater potential fecundity make the low risk short-distance hops (trivial flights), but take the chance that the next door plant might be just as bad as the one left behind and also within easy reach of natural enemies, but with a higher chance of arriving and reproducing.

Ovarioles Fig 5

A risk taking aphid!

 

At the other end of the scale, those clone members with fewer ovarioles and reduced potential fecundity make the long distance migratory flights, with the risk of not finding a suitable host plant in time, but with the chance that if they do, it will be highly nutritious and natural enemy-free.  A really good example of not putting all your eggs in one basket and yet again a demonstration of what fantastic insects aphids are ;-)

 

References

Dixon, A.F.G. (1973) Biology of Aphids Edward Arnold, London.

Dixon, A.F.G. & Dharma, T.R. (1980) Number of ovarioles and fecundity in the black bean aphid, Aphis fabae. Entomologia Experimentalis et Applicata, 28, 1-14.

Leather, S.R. (1983) Evidence of ovulation after adult moult in the bird cherry-oat aphid, Rhopalosiphum padi. Entomologia experimentalis et applicata, 33, 348-349.

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

Leather, S.R. & Welllings, P.W. (1981) Ovariole number and fecundity in aphids. Entomologia experimentalis et applicata, 30, 128-133.

Leather, S.R., Wellings, P.W., & Walters, K.F.A. (1988) Variation in ovariole number within the Aphidoidea. Journal of Natural History, 22, 381-393.

Shaw, M.J.P. (1970) Effects of population density on the alienicolae of Aphis fabae Scop.II The effects of crowding on the expression of migratory urge among alatae in the laboratory. Annals of Applied Biology, 65, 197-203.

Walters, K.F.A. & Dixon, A.F.G. (1983) Migratory urge and reproductive investment in aphids: variation within clones. Oecologia, 58, 70-75.

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.

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

 

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