Tag Archives: feeding

Ten more papers that shook my world – complex plant architecture provides more niches for insects – Lawton & Schroeder (1977)

Some years ago I wrote about how one of my ecological heroes, Sir Richard Southwood (later Lord Southwood), influenced my research and stimulated what has become a lifelong interest of mine, island biogeography, in particular the iconic species-area relationship. Apropos of this it seems apposite to write about another huge influence on my research, Sir John Lawton.  I first encountered John*, as he was then, at the tender age of 17, when our Sixth Form Science class were bussed from Ripon Grammar School to York University to hear a very enthusiastic arm-waving young ecologist, yes John Lawton, talking about food webs. Excellent as it was, it wasn’t, however, this talk that inspired me :-), but a paper that he and Dieter Schroeder wrote a few years later (Lawton & Schroeder, 1977), in which they showed that structurally more diverse plants potentially hosted more insect species per unit range than those plants with less complex architecture.  A couple of years later Strong & Levin (1979) showed that this also applied to fungal parasites in the USA.  The mechanism behind the finding was hypothesised to be based on apparency – the bigger you are the easier you are to find, the bigger you are, the more niches you can provide to be colonised, pretty much the same reasoning used to explain geographic island biogeography and species-area accumulation curves (Simberloff & Wilson, 1969). John Lawton, Don Strong and Sir Richard Southwood also highlighted this in their wonderful little book (Strong et al, 1984) which has provided excellent material for my lectures over the years.

As someone who is writing a book, theirs is an excellent example of how you can improve on other people’s offerings.  Staying with the theme of plant architectural complexity, Strong et al (1984) brilliantly reported on Vic Moran’s masterly study on the relationship between Opuntia growth forms and the number of insects associated with them (Moran, 1980).  Vic’s study was an advance on the previous studies because he examined one family of plants, rather than across families, so reducing the variance seen in other studies caused by phylogenetic effects. I should also point out that this paper was also an inspiration to me.

The figure as shown in Victor Moran’s paper.

The revamped Moran as shown in Strong & Lawton (1984).

Okay, so how did this shake my world? As I have mentioned before, my PhD and first two post-docs were on the bird cherry-oat aphid, Rhopalosiphum padi, a host-alternating aphid that uses bird cherry, Prunus padus, as its primary host.  Never being one to stick to one thing, I inevitably got interested in bird cherry in general and as well as eventually writing a paper about it (Leather, 1996) (my only publication in Journal of Ecology), I also, in due course, set up a long term experiment on it, the outcome of which I have written about previously. But, I digress, the first world shaking outcome of reading Lawton & Schroeder, was published in Ecological Entomology (incidentally edited by John Lawton at the time), in which I analysed the relationships between the insects associated with UK Prunus species and their distribution and evolutionary history, and showed that bird cherry had a depauperate insect fauna compared with other Prunus species (Leather, 1985).

I’m not working with very many points, but you get the picture (from Leather, 1985). Bird cherry (and also Gean, the common wild cherry. Prunus avium) hosts fewer insect species than would be expected from its range and history.

This in turn led me on to an even more ambitious project.  Inspired by a comment in Kennedy & Southwood (1984) that a better resolution of the species-plant range relationship would result if the analysis was done on a taxonomically restricted group of plants and by the comment in Southwood (1961) that the Rosaceae were a very special plant family, I spent several months wading through insect host lists to compile a data set of the insects associated with all the British Rosaceae.  Once analysed I submitted the results as two linked papers to the Journal of Animal Ecology.  Having responded to Southwood’s demand that “this manuscript be flensed of its too corpulent flesh” it was eventually published (Leather, 1996).  My somewhat pompous introduction to the paper is shown below.

“This relationship is modified by the structure or complexity of the plant, i.e. trees support more insect species than shrubs, which in turn support more species than herbs (Lawton & Schroder 1977; Strong & Levin 1979; Lawton 1983).”

“Kennedy & Southwood (1984) postulated that if taxonomically restricted groups of insects and/or plants were considered, the importance of many of these variables would increase. Few families of plants cover a sufficiently wide range of different growth forms ranging from small herbs to trees in large enough numbers to give statistically meaningful results. The Rosaceae are a notable exception and Southwood (1961) commented on the extraordinary number of insects associated with Rosaceous trees. It would thus appear that the Rosaceae and their associated insect fauna provide an unparalleled opportunity to test many of the current hypotheses put forward in recent years concerning insect host-plant relationships.”

Cutting the long story short (I am much better at flensing nowadays), I found  that Rosaceous trees had longer species lists than Rosaceous shrubs, which in turn had longer lists than herbaceous Rosaceae.

Rather messy, but does show that the more architecturally complex the plant, the more insect species it can potentially host (from Leather, 1986).

Flushed by the success of my Prunus based paper, I started to collect data on Finnish Macrolepidoptera feeding on Prunus to compare and contrast with my UK data (I can’t actually remember why this seemed a good idea).  Even if I say so myself, the results were intriguing (to me at any rate, the fact that only 19 people have cited it, would seem to suggest that others found it less so), in that host plant utilisation by the same species of Macrolepidoptera was different between island Britain and continental Finland (Leather, 1991).

 

 

From Leather (1991) Classic species-area graph from both countries but some intriguing differences in feeding specialisation.

Despite the less than impressive citation index for the UK-Finland comparison paper (Leather, 1991), I would like to extend the analysis to the whole of Europe, or at least to those countries that have comprehensive published distributions of their Flora.  I offer this as a project to our Entomology MSc students, every year, but so far, no luck ☹

Although only four of my papers can be directly attributed to the Lawton & Schroeder paper, and taking into account that the insect species richness of Rosacea paper, is number 13 in my all-time citation list, I feel justified in counting it as one of the papers that shook my World.

References

Kennedy, C.E.J. & Southwood, T.R.E. (1984) The number of species of insects associated with British trees: a re-analysis. Journal of Animal Ecology, 53, 455-478.

Lawton, J.H. & Schroder, D. (1977) Effects of plant type, size of geographical range and taxonomic isolation on numbers of insect species associated with British plants. Nature, 265, 137-140.

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

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

Leather, S.R. (1991) Feeding specialisation and host distribution of British and Finnish Prunus feeding macrolepidoptera. Oikos, 60, 40-48.

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

Moran, V.C. (1980) Interactions between phytophagous insects and their Opuntia hosts. Ecological Entomology, 5, 153-164.

Simberloff, D. & Wilson, E.O. (1969) Experimental zoogeography of islands: the colonization of empty islands. Ecology50, 278-296.

Southwood, T.R.E. (1961) The number of species of insect associated with various trees. Journal of Animal Ecology, 30, 1-8.

Strong, D.R. & Levin, D.A. (1979) Species richness of plant parasites and growth form of their hosts. American Naturalist, 114, 1-22.

Strong, D.R., Lawton, J.H. & Southwood, T.R.E. (1984) Insects on Plants – Community Patterns and Mechanisms. Blackwell Scientific Publication, Oxford.

 

 

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Thrip, thrips, thripses – A thrips by any other name

As well as the more well-known EntoPub*, the Harper Adams entomologists also indulge in Entolunch**, when we gather in one of our larger offices to eat our packed lunches and keep up to date with what we are doing, covering research, teaching and day-to-day life. This is not because we are anti-social or are averse to mixing with other disciplines, but because our offices are almost 500 m away from the Staff Common Room and nearest food outlet.  Last week our conversation turned to the Thysanoptera, more commonly known as thrips or thunder bugs.

Thrips1

Some fine examples of thrips, including the common thunder bug.

According to Lewis (1997) they were first described by DeGeer in 1744 under the name Physapus, but in 1758, Linneaus, ignoring this, placed the then four known species in a genus Thrips, later elevated to Order by Haliday in 1836.  Why Linneaus decided to call them thrips is a bit of a mystery, as according to the Oxford English Dictionary, thrips is derived from the Latin via Greek, meaning woodworm!

Thrips are tiny little insects, the giants among them, (mainly tropical) can reach lengths of up to 15 mm but most are round about 1-2 mm long (Kirk, 1996; Moritz, 1997).  Although they are not bugs, their feeding process can be described as “piercing-sucking or punch and suck” (Kirk, 1997).

Thrips2

 

There are about 8000 species of thrips worldwide (Lewis, 1997), although probably less than 200 in the UK (Kirk, 1996). Although many are important plant pests (Lewis, 1997), they can also be pollinators and fungivores (Kirk, 1996) or even very effective biological control agents (Gilstrap, 1995).    Some are gall-formers, and these, like some galling aphids, also have fights to the death with their rivals (Crespi, 1988).  All in all, almost as wonderful as aphids 🙂

But I digress, our conversation that lunchtime was not about the biology of thrips, but about the singularity (or plurality) of their name. Thrips are (in)famous for being like sheep, they are thrips whether you are speaking of one or of many, which has, and does, cause some debate among entomologists and others.

Thrips3

http://mxplx.com/memelist/keyword=end

We quite liked thripses although it does conjure visions of Gollum and his precious.

Thrips4

Who knew that Gollum was an entomologist?

Intrigued by the linguistic puzzle of thrips I wondered what it was in other languages. Using Google Translate, and possibly risking a Tolkienesque mistranslation, I found that in most cases, even French, it was boringly enough, thrips.

There were some languages where thrips was not thrips, but not many:

German               thripse

Swedish               trips

Italian                  tripidi

Catalan                 els trips

Estonian               ripslased

Polish                    wciornastki

Czech                    třásněnka

 

Perhaps my favourite was the Afrikaans, blaaspootjies. On breaking it down into parts it turns out that blaas means bladder and pootjies, legs, which doesn’t seem to make a lot of sense.

Bengali, Chinese and Japanese, were quite picturesque.

 

Bengali              থ্রিপস্ (thripas)

Chinese             牧草虫 (mùcǎo chóng)

Japanese          アザミウマ (azamiuma)

 

But the most ornate was Tamil

Thrips5

(llaippēṉ)

Which is quite a long word for such small insects, but very pretty all the same.  If anyone has any more suggestions for the naming of thrips, do feel free to comment.

 

References

Crespi, B.J. (1988) Risks and benefits of lethal male fighting in the colonial, polygynous thrips Hoplothrips karnyi (Insecta: Thysanoptera).  Behavorial Ecology & Sociobiology, 22, 293-301.

Gilstrap, F.E. (1995) Six-spotted thrips: a gift from nature that controls spider mites. [In] Thrips Biology and Management, pp 305-316, (ed. B.L. Parker, M. Skinner & T. Lewis),  Plenum Press, New York.

Kirk, W.D.J. (1996)  Thrips,  Naturalist’s Handbooks, Richmond Publishing Co. Ltd., Slough UK. [A very nice and simple introduction to the wonderful world of thrips]

Kirk, W.D.J. (1997) Feeding, [In] Thrips as Crop Pests, pp 119-174 (ed T Lewis), CAB International, Wallingford Oxford

Lewis, T. (1997) Pest thrips in perspective, [In] Thrips as Crop Pests, pp 1-13 (ed T Lewis), CAB International, Wallingford Oxford

Moritz, G. (1997) Structure, growth and development.  [In] Thrips as Crop Pests, pp 15-63 (ed T Lewis), CAB International, Wallingford Oxford

 

Post script

Slapped wrist for me – Elina Mäntylä has pointed out that in Finnish, thrips is ripsiäinen, probably to do with the wing structure.  I should have known that having lived and worked in Finland at the Pest Investigation Department.  interestingly, Google Translate thinks it is Thrips in Finnish – but if you do Finnish to English it does indeed translate ripsiäinen to thrips.

 

Glossary

*EntoPub            Drinks and a meal in a local hostelry organised by one of the Harper Adams Entomologists but not confined solely to entomologists.  We do like to mix with non-entomologists occasionally 🙂  Held at approximately 10 day intervals.

**EntoLunch     A communal occasion when the Harper Adams entomologists get together in office AY02 and eat their packed lunches whilst chatting, usually with some entomological connection.  Again this is not entirely confined to entomologists, we are usually joined by a couple of soil and water scientists who share our exile on the edge of the campus 🙂  A daily event during the working week.

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The Curious Case of the Shark-finned Aphid

The large (giant) willow aphid, Tuberlolachnus salignus, is, in my opinion, one of the world’s greatest unsolved mysteries.  This aphid is sometimes regarded as being the largest aphid in the world.  It can reach a length of 5 mm, can weigh up to 13 mg as an adult and the new-born nymphs weigh about 0.25 mg (Hargreaves & Llewellyn, 1978).  You can get an idea of how big it is from the picture below.

willow aphid on finger

http://www.rothamsted.ac.uk/PressReleases.php?PRID=100

This is pretty big for an aphid, although not quite as big as one of my former PhD students (Tilly Collins) liked to pretend!  The picture below used to appear on her website and was the envy of a number of Texan entomologists.  Tuberolachnus salignus, as you might expect, since it feeds through the bark and not on leaves, has rather a long set of stylets, up to  1.8 mm, more than a third of it’s body length (Mittler, 1957).

tilly on aphid

This picture emphasises the first mystery: what is the function of the dorsal tubercle, which so closely resembles a rose thorn, or to me, a shark’s fin.  Nobody knows.  Is it defensive? Unlikely, since T. salignus being a willow feeder is stuffed full of nasty chemicals and very few predators seem to want, or be able to feed on it.  They feed in large aggregations on the stems of their willow tree hosts and can have serious effects on tree growth (Collins et al., 2001).  As the aphids produce a lot of honeydew, they are often ant-attended  (Collins & Leather, 2002) and these also deter potential predators.  In fact the aphid colonies produce so much honeydew in the summer that they attract huge numbers of vespid wasps that are in search of energy-rich sugar sources at that time of year.  These too are likely to make potential predators and parasitoids think twice about approaching the aphids.

Tuberolachnus

Photograph courtesy Dr Tilly Collins

The wasps also cause a problem for researchers and when Tilly was doing her PhD, she used to have to confine her fieldwork to those times of day when the wasps were not around.   In addition, if you crush one of the aphids you will discover that it stains your fingers bright orange and that this stain will last several days if you don’t try too hard to wash it off.  If you get this aphid ‘blood’ on your clothes they will be permanently marked and Tilly used to say that she ought to be paid an extra clothing allowance.

Tuberolachnus salignus, is as far as we can tell, anholocyclic, no males have been recorded and no matter how hard people have tried to induce the formation of males and sexual females, they have not been successful.  This is however, not the second mystery.  The mystery is that every year, in about February, it does a disappearing act and for about four months its whereabouts remain a mystery (Collins et al., 2001).  So we have an aphid that spends a substantial period of the year feeding on willow trees without leaves and then in the spring when most aphids are hatching from their eggs to take advantage of the spring flush, T. salignus disappears!  Does it go underground?  If so, what plant is it feeding on and why leave the willows when their sap is rising and soluble nitrogen is readily available?

So here is a challenge for all entomological detectives out there.  What is the function of the dorsal tubercle and where does T. salignus go for the spring break?

Truly a remarkable aphid and two mysteries that I would dearly love to know the answers to and yet another reason why I love aphids so much.

Collins, C.M. & Leather, S.R. (2002) Ant-mediated dispersal of the black willow aphid Pterocomma salicis L.; does the ant Lasius niger L. judge aphid-host quality. Ecological Entomology, 27, 238-241. http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2311.2002.00390.x/full

Collins, C. M., Rosado, R. G. & Leather, S. R. (2001). The impact of the aphids Tuberloachnus salignus and Pterocomma salicis on willow trees. Annals of Applied Biology 138, 133-140 http://onlinelibrary.wiley.com/doi/10.1111/j.1744-7348.2001.tb00095.x/abstract.

Hargreaves, C. E. M. & Llewellyn, M. (1978). The ecological energetics of the willow aphid, Tuberolachnus salignus:the influence of aphid Journal of Animal Ecology, 47, 605-613. http://www.jstor.org/discover/10.2307/3804?uid=3738032&uid=2&uid=4&sid=21101920521473

Mittler, T. E. (1957). Studies on the feeding and nutrition of Tuberolachnus salignus (Gmehn) (Homoptera, Aphididae). I. The uptake of phloem sap. Journal of  Experimental Biology, 34, 334-341  http://jeb.biologists.org/content/34/3/334.full.pdf

Other resources

http://influentialpoints.com/Gallery/Tuberolachnus_salignus.htm

http://www.nhm.ac.uk/nature-online/life/insects-spiders/common-bugs/aphid-watch/

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