Carnivores and carotenoids…a new paper by Jeremy Heath

PhD student Jeremy Heath had something additional to be thankful for this Thanksgiving. His manuscript entitled “Carnivores and carotenoids are associated with adaptive  behavioural divergence in a radiation of gall midges” was just officially published (online) in the journal Ecological Entomology. In this paper, Jeremy and coauthors explore adaptive phenotypic divergence in populations of the galling midge Asteromyia carbonifera that coexist on the same host plant, the goldenrod Solidago altissima. He goes beyond analyses of gall morphology (which has been explored in previous papers), to examine variation in “ovipositional phenotype” (essentially where they midges deposit their eggs) and carotenoid constituents of  salivary and accessory glands (orange-colored chemicals important in all sorts of biological processes), and how this may influence interactions with both host plants and parasitoid enemies (I won’t give it all away, read the paper!). It is a dense paper, chock full of experiments, tantalizing results, and interesting possibilities. I invite you to take a look at it, there is something in there for everybody (I am sure Jeremy (heath.22@wright.edu) would be happy to send you a pdf).

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Enemy mine

Bob Kula and colleagues (Oscar Dix-Luna and Scott Shaw) recently published a revision of the braconid genus Ilatha. These are relatively large, often brightly colored braconid wasps found exclusively in the New World tropics. They are certainly attractive wasps, but the most fascinating thing about them (to me) is that they are hyper-parasitoids of tachinid flies. That is, they are parasitoids of tachinid flies, which are themselves parasitoids of caterpillars. Apparently, adult female wasps locate caterpillars that already contain a developing tachinid and lay an egg with their piercing ovipositors through the caterpillar into the tachinid larva. The juvenile braconid then bides its time while the tachinid proceeds to devour the caterpillar (from the inside). Eventually, the tachinid kills the host and emerges to pupate, at which time the braconid proceeds to devour the tachinid (from the inside). It’s like those Russian dolls. Totally cool (except that they are eating my beloved tachinid flies!)

Some of the specimens that Kula et al. used in their species descriptions were reared as part of our collaborative NSF Biological Surveys and Inventories project focused on Caterpillars and Parasitoids of the Eastern Andes(on which Scott Shaw is a Principal Investigator). For attempting to identify some of the tachinid hosts of Ilatha from puparia, the authors honored me by naming one species (right) Ilatha stiremani. I am truly honored to have such an interesting and beautiful (at least in my eyes) wasp bear my name – even if it is a mortal enemy of my tachinid brethren. Thanks Guys!

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Beth Stayrook receives award

Beth Stayrook, undergraduate research assistant extraordinare in the Stireman lab, was recently awarded a $1500 scholarship award from the Women in Science Giving Circle at Wright State University. Beth is a seriously smart, dual major in Biology and Chemistry. Way to go Beth! You Rock!

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Tachinid flies and the final frontier…

Forest canopies are often referred to as one of the “final frontiers” of biodiversity exploration. We know astonishingly little about what organisms and ecological interactions occur in forest canopies, primarily due to the difficulty in sampling and studying them. In recent years there have been many initiatives to begin exploring the flora and fauna of forest canopies, particularly in the tropics. These efforts have revealed diverse communities inhabiting the upper reaches of tree canopies, often quite distinct from those occurring near ground-level in the same areas.

In a recently published study in the journal Insect Conservation and Diversity led by Pierfilippo Cerretti (Univ. Roma), we analyzed the diversity and composition of tachinid flies in the canopy and understory of a temperate forest in Italy (Bosco Fontana, right). Using 14 Malaise traps (7 suspended), we found that the canopy hosted a distinct community of tachinid flies.

Overall, more tachinids (were collected from understory traps (36) than from canopy traps (28), but the canopy traps had higher evenness and high diversity values. A number of species occurred solely or primarily in just one of the habitats and many of those that occurred in both habitats showed strong sex biases in one habitat or the other. This is one of the very few studies that have ever examined a canopy parasitoid communities, and the only rigorous quantitative study examining vertical stratification of forest tachinids. We hope to pursue more such studies of tachinid and other insect communities in this “last” frontier.

Stireman, J.O. III, Cerretti, P., Whitmore, D., Hardersen, S. and Gianelle, D. 2012. Composition and stratification of a tachinid (Diptera: Tachinidae) parasitoid community in a European temperate plain forest. Insect Conservation and Diversity 5:346-357.
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Paper on adaptive radiation in gall midges published in Journal of Evolutionary Biology

Stireman, collaborator Patrick Abbot, and Lab technician Hilary Devlin have just published a paper analyzing the extraordinary radiation of Asteromyia carbonifera gall midges on their Solidago hosts across North America. We show that this nominal species is actually comprised of a multitude of distinct evolutionary lineages that differ in host plant use and gall morphology. However, there is very little genetic structure related to geography.

These results suggest that A. carbonifera has undergone a very recent, rapid adaptive radiation, driven by ecological selective pressure from both lower trophic levels (host plant suitability and defenses) and higher ones (parasitoids, which select on gall morphology). Interestingly, divergence in gall morphology and host-plant associations appear to evolve relatively rapidly, with similar gall forms evolving multiple times, and host plants being repeatedly colonized by different lineages.

This is a fascinating example of very recent, even current, adaptive radiation in which we can still perceive the selective forces driving phenotypic divergence. However, this paper primarily focuses on patterns observed in the genetic structure of populations, and much more needs to be done confirming the processes responsible.

Please e-mail Stireman (john.stireman@wright.edu) if you would like a pdf of this paper
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Stireman attends the International Congress of Entomology in South Korea

For a first real report from the Stireman lab, I thought I might say a few words about my recent trip to South Korea to attend the XXIV International Congress of Entomology. This meeting, my first ICE actually, was held at the EXCO convention center in the city of Daegu, which is located in Southwest S. Korea. I cannot begin to describe the diversity of interesting talks and posters. There were many concurrent sessions covering everything from genomics to biogeography. A few of the general oral sessions were eclectic assemblages such as, my favorite title, “Ecology: Genetics, pollution, symbionts & prey-predator interaction.”

I spoke about our recently funded NSF proposal to study the phylogeny and evolution of tachinid flies in a symposium on the evolution and phylogeny of Diptera (flies) organized by Brian Wiegmann and David Yeates (thanks guys!). Of course, tachinids are awesome, diverse, and understudied parasitoids that are the focus of much work in the lab. At some point, I should write about them here, but for now, you can check out Jim O’Hara’s great introduction. As we are just getting underway on this project (with collaborators Jim O’Hara, Pierfilippo Cerretti, Kevin Moulton, and Isaac Winkler), my talk was a little light on results, but I hope I convinced the audience that tachinids are a group that sorely needs modern systematic work and that there are many interesting evolutionary questions that we can explore with them.

This was my first trip to any Asian country, so of course I found it very interesting; the language, the food, the culture, all pretty novel. The Korean people were very friendly and helpful, which is good, because even after spending over a week there, I was still working on “hello” (안녕하세요, annyeonghaseyo) and “Thank you” (감사합니다, kamsahamnida).

Although there were many great talks, the highlight of the meeting for me was a brief trip up to Palgongsan Natural Park where we walked through the forest up to a giant stone Buddha and saw amazing temples. Although it was mostly rainy, The fog covered peaks and echoing buddhist chanting lent the experience a mystical quality (and there were tachinids too!).

Buddhist temple in Palgongsan area

Korean limacodid with tachinid eggs!

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New lab page (in progress)

This is the *New* web page for the Stireman lab in Biological Sciences at Wright State University. I though perhaps the blog format might encourage more frequent updates, as my old lab web page has not been updated for a couple of years. This is a work in process, as I need to get all the main pages up, so check back for further additions.

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