Monthly Archives: September 2019

We can’t all be groundbreakers – we need bricklayers too

Groundbreaker – someone who changes the way things are done, especially by making new discoveries

Groundbreaking – new and original, not like anything seen before from the Cambridge Dictionary

All of us who aspire to publishing our hard-won data will recognise the phrases below, taken from the overview pages of highly reputable ecological and entomological journals. Everyone wants to push back the frontiers of

Anonymised quotes from journal overview pages – I am sure that you will recognise some of them

knowledge, but I feel that the focus by journals and funding bodies on ‘novelty’ is bad for science and bad for researchers.  I am certainly not the first one to say it, but it bears repeating, there is a tyranny of novelty pervading the research community and this has also infected the way that science is reported. This focus on ‘novelty’ and its link to promotion, grant application success and job tenure, can mean that careers are damaged, research areas ignored (Leather & Quicke, 2009), an imbalance of disciplines within university departments leading to piece-meal degrees and the dilemma of where to publish. The dilemma being do you publish where it does the most good for science and wide access or for your career, which are often mutually incompatible.

Looking at the selection of journal guidelines above, for me, this particular phrase is the most disturbing, “Confirming or extending the established literature, by for example showing results that are novel for a new taxon, or purely applied research, is given low priority.”   In terms of science, at the very least, this stance leads to nobody checking to see if a study is truly valid or just a statistical artefact or, as is very likely, a special case. A recent paper suggests that in ecology, less than 0.03% of published papers are true replicates of previously published studies (Kelly, 2019), while in behavioural ecology, the figure is a round zero, although about 25% of studies are partial replicates (Kelly, 2006).

Although I am not a great believer in the Open Access author pays dogma (after all, in the world of novelists and poets, only those who can’t find publishers pay and we term that ‘vanity publishing’), the publishing ethos of  PLOS ONEWe evaluate submitted manuscripts on the basis of methodological rigor and high ethical standards, regardless of perceived novelty”, is very welcome. It is a shame that more journals, particularly those where publication is free of charge, have not adopted the same principle.  The preoccupation with ‘novelty’ also has the consequence that academics, particularly those at the start of their careers or those working in institutions where ‘novelty’ is seen as the only way to gain advancement or retain one’s position,  feel under pressure to only publish in certain journals and to emphasise ‘novelty’.  This can, and I am sure it is inadvertent in the majority of cases, result in authors limiting their search for previous work to the immediate horizon rather than diving deeper into the ocean of past literature, and often ‘reinventing’ the wheel’ (Lawton, 1991; Leather, 2004), which does past academics and science a great disservice.

An alternative title to this post might have included the phrase “standing on the shoulders of giants”, often attributed to Isaac Newton but according to Wikipedia almost certainly older than that.  As some of you may know, one of the categories on my blog is “Ten papers that shook my world” (now supplemented by Ten more papers that shook my world), in which I discuss papers that have had a major influence on my scientific development and publication list.  According to the Web of Science I have written 210 papers*, of which, in my opinion, only one is truly ‘novel’**. I hypothesised from field evidence (Leather, 1988), and later demonstrated experimentally (Leather, 1993), that insects sharing the same host plant could, by altering plant architecture, compete, despite being separated temporally and spatially.  Actually, now that I reflect upon it, even this idea could be said to be based on the ‘apparent competition’ hypothesis put forward by Bob Holt (Holt, 1977).  I should add that neither of those ‘novel’ papers of mine have made the big time, both have been cited a mere eleven times, in contrast to those papers where I was inspired by the work of others.

To end on yet another building metaphor or two; I have, in my forty-two years as a research scientist, never felt that I have wasted my time. I have been content with adding bricks to the scientific edifice, grouting in between entomological and ecological tiles and adding pieces to the vast jigsaw of life. Yes, there is a problem in that some institutions are reluctant or unwilling to recognise the contributions made by those of us who reinforce the various academic structures, but my message to you is Illegitimi non carborundum, don’t give up and be proud of what you have achieved.  There may be times when you feel unappreciated, or indeed, as I have at times, rather angry, but remember, they need us, for without us, the whole structure will fall into ruins.

People say, what is the sense of our small effort? They cannot see that we must lay one brick at a time, take one step at a time. A pebble cast into a pond causes ripples that spread in all directions. Each one of our thoughts, words and deeds is like that. No one has a right to sit down and feel hopeless. There is too much work to do.” Dorothy Day

References

Gish, M. & Inbar, M. (2018) Standing on the shoulders of giants: young aphids piggyback on adults when searching for a host plant.  Frontiers in Zoology, 15, 49.

Holt, R.D. (1977) Predation, apparent competition, and the structure of prey communities.   Theoretical Population Biology, 12, 197-229.

Kelly, C.D. (2006) Replicating empirical research in behavioural ecology: how and why it should be done but rarely is. The Quarterly Review of Biology, 81, 221-236.

Kelly, C.D. (2019) Rate and success of study replication in ecology and evolution. PeerJ:e7654

Lawton, J. H. (1991). Warbling in different ways. Oikos, 60, 273–274.

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

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

Leather, S.R. (2004) Reinventing the wheel: on the dangers of taxon parochialism and shallow reference trawling!  Basic & Applied Ecology, 5, 309-311.

Leather, S.R. & Quicke, D.L.J. (2009) Where would Darwin have been without taxonomy? Journal of Biological Education, 43, 51-52.

Murphy, S.M., Vidal, M.C., Hallagan, C.J., Broder, E.D., Barnes, E.E., Hornalowell, E.S. & Wilson, J.D. (2019) Does this title bug (Hemiptera) you? How to write a title that increases your citations. Ecological Entomology, 44, 593-600.

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.

 

*

my own publication list has me at 298, but that includes books, conference papers, research notes and popular articles; Google Scholar has me at 235.

**

I have not included a paper that I am a co-author on (Ward et al., 1998), as although ‘novel’, it was not my idea.  I supplied the data and the whisky and acted as a sounding board during one very long evening of mathematical inspiration by Seamus Ward 😊 The following day I made a blood donation and fainted shortly afterwards, resulting in a nasty head wound and a visit to the local hospital!

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Green Islands – mining cytokinins

A little while ago I wrote about the phenomenon of  “green islands” caused by ants keeping insect herbivores away from trees.   If, however, you work on leaf miners, the term green islands means something else entirely.  Instead of referring to a feature of the landscape, it refers to a feature of the leaf, which unless you are Toby*, is definitely not a landscape-level phenomenon 😊

While some insects, aphids for example, induce senescence to improve the quality of their host plant and some plants induce senescence and early leaf-fall in those leaves that have been colonised by gall aphids in order to reduce their infestation load (Williams & Whitham, 1986), there are other insects that try desperately to prevent senescence so as to prolong their feeding life on what would otherwise be a dead leaf.

Green island leaf mine of the moth, Stigmella atricapatella – Many thanks to Mike Shurmer for the photographs.

The phenomenon of the green islands in autumn leaves associated with leaf mining Lepidoptera has been known about for some time (Hering, 1951), but although the adaptive value of this was easy to see, the causal mechanism remained unknown for some time. Similarly, plant pathologists had also noticed that one of the symptoms of powdery mildew infections is the appearance of a green ring around the necrotic spot caused by the fungus (von Tubeuf, 1897); if not a green island, a green atoll 😊

Green island or green atoll? Powdery mildew on wheat https://slideplayer.com/slide/9073461/27/images/14/Green+island+on+wheat+infected+with+wheat+powdery+mildew.jpg

That fungi produced secretions containing plant growth substances such as the auxin (plant hormones) indole acetic acid has been known since the 1930s (Thimann, 1935) and it was later hypothesised that the levels present in the surrounding leaf tissue were associated with the resistance or lack thereof, to the fungal agent (e.g. Shaw & Hawkins, 1958). A further class of plant growth substances, initially termed kinins because of their similarity to kinetin (a cell growth promoting plant hormone, but later renamed cytokinins** (Skoog et al., 1965)) were discovered by Folke Skoog and co-workers (Miller et al., 1956) and linked to the production of green islands by plant pathogens (reviewed by Skoog & Armstrong, 1970).

“What about the leaf miners?” I hear you ask. You will be pleased to know that entomologists were not too far behind. Lisabeth Engelbrecht working on Nepticulid leaf miners on birch (Betula pendula) and Aspen (Populus tremula) set up a study (Engelbrecht, 1968) to test her hypothesises that the green islands were caused as a result of insect saliva or by the larvae physically cutting the leaf veins that would otherwise have delivered the chemical signal responsible for beginning leaf senescence. She discovered that the green islands contained large concentrations of cytokinin  (Engelbrecht, 1968) and working with other colleagues discovered that the labial glands of leaf mining larvae also contained cytokinin, but was unsure as to whether the cytokinin originated from the larvae or were formed in the leaf in response to chemicals in the saliva or frass of the larvae (Engelbrech et al., 1969), although if you read the paper it is quite clear that she is convinced that the source of the cytokinin is from the larvae and not the plant.

After all this excitement about insect produced cytokinin and green islands things seemed to go a bit dead.  I found a couple of passing references to the possibility that leaf mining Lepidopteran larvae use cytokinin to produce a green island to extend larval life after leaf abscission (Miller, 1973; Faeth, 1985) and an opinion piece discussing the possible adaptive role of using green islands to prolong larval life after leaf fall (Kahn & Cornell, 1983), but, surprisingly, nothing experimental to test this hypothesis. Oddly, I did find a paper testing the idea that early leaf abscission was an induced defence against leaf miners, where green islands were mentioned in the introduction but not mentioned again (Stiling & Simberloff, 1989).

Don’t get me wrong, plant pathologists and entomologists working on insect galls were still writing about the role of cytokinin (e.g. Murphy et al., 1997: Mapes & Davies, 2001), but leaf miner green island research seemed to have died.  Suddenly, however, in the mid-2000s the French ‘discovered’ leaf miners and David Giron and colleagues, showed how the leaf miner Phyllonorycer blancardella manipulates the nutritional quality of their host leaves by increasing the levels of cytokinin in the surrounding leaf tissue (Giron et al., 2007).

‘Green island’ formed by Phyllonorycter blancardella (From Giron et al., 2007).

 

As we know from aphids, where insects play, bacterial symbionts are never far away, and sure enough it wasn’t long before it was shown that Wolbachia ‘infections’ were helping the leaf miners produce their ‘green islands’. Wilfried Kaiser and colleagues treated leaf miner larvae with antibiotics to remove the symbiont and found that the ‘cured’ larvae, although still able to feed and form leaf mines, were unable to produce ‘green islands’ and the levels of cytokinin were much lower than that found in the ‘green islands’ formed by untreated leaf miners (Kaiser et al., 2010).

Influence of Wolbachia on green island formation. To the left, infected leaf miners (Phyllonorycter blancardella) happily surrounded by nutritious plant tissue; to the right, ‘cured’ by antibiotics, the leaf miner soon runs out of food (Kaiser et al., 2010)

The same group have also documented the mechanism by which the leaf miners and their symbionts work together (Body et al., 2013) and also, using molecular phylogenies and ecological trait data, shown that the existence of the ‘green island’ phenotype and Wolbachia infections are associated with the evolutionary diversification of the Gracillarid leaf miners (Gutzwiller et al., 2015).

You might expect that these findings would have stimulated renewed interest in the ‘green island’ phenomenon, but you would be wrong.  Despite the fact that at the time of writing this article (September 10th 2019) Kaiser et al. (2010) had, according to the Web of Science, been cited 105 times, only three papers dealing with this phenomenon have been published, the most recent appearing in early 2018 (Zhang et al., 2018) and, incidentally, by the same group that published the Kasier et al. (2010) study. It would appear that as with ‘green islands’, the study of the phenomenon is also very localised.

References

Allen, P.J. (1942) Changes in the metabolism of wheat leaves induced by infection with powdery mildew. American Journal of Botany, 42, 425-435.

Body, M., Kaiser, W., Dubreuil, G., Casas, J. & Giron, D. (2013) Leaf-miners co-opt microorganisms to enhance their nutritional environment. Journal of Chemical Ecology, 39, 969-977.

Engelbrecht, L. (1968) Cytokinin in den ,,grunen Inseln” des Herbstlauibes. Flora oder Allgemeine botanische Zeitung. Abt. , Physiologie und Biochemie, 159, S, 208-214.

Englebrecht , L., Orban, U. & Heese, W. (1969) Leaf-miner caterpillars and cytokinins in the “green islands” of autumn leaves. Nature, 223, 319-321.

Faeth, S.H. (1985) Host leaf selection by leaf miners: interactions among three trophic levels. Ecology, 66, 870-875.

Gutzwillner, F., Dedeine, F., Kaiser, W., Giron, D., & Lopez-Vaamonde, C. (2015) Correlation between the green-island phenotype and Wolbachia infections during the evolutionary diversification of Gracillariidae leaf-mining moths. Ecology & Evolution, 5, 4049-4062.

Hering, E.M. (1951) Biology of the Leaf Miners, Dr W Junk, The Hague, Netherlands

Herrick, G.W. (1922) The Maple Case-Bearer Paraclemensia Acerifoliella Fitch. Journal of Economic Entomology, 15, 282-288.

Kahn, D.M. & Cornell, H.V. (1983) Early leaf abscission and folivores: comments and considerations. American Naturalist, 122, 428-432.

Kaiser, W., Huguet, E., Casas, J., Commin, C. & Giron, D. (2010)  Plant green-island phenotype induced by leaf-miners is mediated by bacterial symbionts. Proceedings of the Royal Society B, 277, 2311-2319.

Mapes, C.C. & Davies, P.J. (2001) Cytokinins in the ball gall of Solidago altissima and in the gall forming larvae of Eurosta solidaginis. New Phytologist, 151, 203-212.

Miller, C. O., Skoog, F., Okumura, F. S., Von Saltza, M. H., & Strong, F. M. (1956). Isolation, structure and synthesis of Kinetin, a substance promoting cell division. Journal of the American Chemical Society, 78, 1375–1380.

Miller, P.F. (1973) The biology of some Phyllonorycter species (Lepidoptera: Gracillariidae) mining leaves of oak and beech. Journal of Natural History, 7, 391-409.

Murphy, A.M., Pryce-Jones, E., Johnstone, K. & Ashby, A.M. (1997) Comparison of cytokinin production in vitro by Pyrenopeziza brassicae with other plant pathogens. Physiological & Molecular Plant Pathology, 50, 53-65.

Shaw, M. & Hawkins, A.R. (1958) the physiology of host-parasite relations V. A preliminary examination of the level of free endogenous Indoleacetic acid in rusted and mildewed cereal leaves and their ability to decarboxylate exogenously supplied radioactive indoleacetic acid. Canadian Journal of Botany, 34, 389-405.

Skoog, F. & Armstrong, D.J. (1970) Cytokinins. Annual Review of Plant Physiology, 21, 359-384.

Skoog, F., Strong, F.M. & Miller, C.O. (1965) Cytokinins. Science, 148, 532-533.

Stiling, P.D. & Simberloff, D. (1989) Leaf abscission – induced defense against pests or response to damage ? Oikos, 55, 43-49.

Thimann, K.V. (1935) On the plant growth hormone produced by Rhizopus suinus. Journal of Biological Chemistry, 109, 279-291.

Von Tubeuf, K.F. (1897) Diseases of Plants, Longmans, Green & Co, London.

Walters, D.R., McRoberts, N. & Fitt, B.D.L. (2008) Are green islands red herrings? Significance of green islands in plant interactions with pathogens and pests. Biological Reviews, 83, 79-102.

Williams, A.G. & Whitham, T.G. (1986) Premature leaf abscission: an induced plant defense against aphids. Ecology, 67, 1619-1627.

Zhang,  H., Dubreuil, G., Faivre, N., Dobrev, P., Kaiser, W., Huguet, E., Vankova, R. & Giron, D.  (2018) Modulation of plant cytokinin levels in the Wolbachia‐free leaf‐mining species Phyllonorycter mespilella. Entomologia experimentalis et applicata, 166, 428-438.

 

*Toby Alone (La Vie Suspendue) by Timothée de Fombelle, is a fantastic novel, which I only fairly recently discovered, but can heartily recommend.

** Cytokinins are a class of plant growth substances that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence. Wikipedia

 

 

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Pick & Mix 36 – something for everyone?

May Berenbaum has written an excellent editorial on the many failings of journal impact factors

Wow, a caterpillar that ‘shouts’ at would be predators

Ray Cannon writes about the wonders of dragonfly wings

More on insect declines, their causes and ways to minimise them

A pair of researchers found evidence that the insect population in a Puerto Rican rainforest was in free fall. But another team wasn’t so sure.

Failing exams doesn’t stop you becoming a professor

Why you should get out more – Visitors to urban greenspace have higher sentiment and lower negativity on Twitter

The Understory – excerpted from Robert MacFarlane’s recent book, Underland: A Deep Time Journey, “The Understory” is an examination of the life beneath the forest floor.

A fun visual time-line highlighting 100 years of UK forestry

Lovely obituary of a forest entomology legend – C.S. (Buzz) Holling

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