Herbivorous Insect Dietary Specialization
In light of decades of research, an outstanding debate persists over the relative influence of escape from natural enemies, co-evolutionary arms race with plant defensive, and more recently, microbes in shaping herbivorous insect diets. Over 40% of the world's non-microbial diversity consists of intimate relationships between plants and the herbivorous insects that eat them. A great deal remains to be discovered about the relative proximate and ultimate forces responsible for this global trend.
The question that I am interested in is why are the vast majority of insects highly specialized upon their host plants? Is the need to escape from natural enemies? Is it a co-evolutionary relationship with plant defensive chemistry? How do microbes influence these interactions?
These questions compel many fascinating predictions! By synthesizing complimentary observational and experimental approaches with a solid foundation in natural history my collaborators and I work with tri-trophic experimental systems for tackling this research topic.
The question that I am interested in is why are the vast majority of insects highly specialized upon their host plants? Is the need to escape from natural enemies? Is it a co-evolutionary relationship with plant defensive chemistry? How do microbes influence these interactions?
These questions compel many fascinating predictions! By synthesizing complimentary observational and experimental approaches with a solid foundation in natural history my collaborators and I work with tri-trophic experimental systems for tackling this research topic.
My PhD study system compares ecology and chemistry of sympatric Heliconius caterpillars and Passiflora flea beetles across latitudes ranging from Central Texas to Costa Rica. This comparative framework allows me the opportunity to design comparative experiments that with the potential to disentangle the relative drivers of host specialization and patterns of host occupancy between two ecologically similar, but phylogenetically distinct, groups of herbivorous insects.
My colleague, John Smiley, with me on the STR in front of the former saba tree featured in Plant Earth.
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Mated pair of Heliconius charitonia at our butterfly rearing facility at UT's Brackenridge Field Lab in Austin, TX.
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John Smiley planted this Passiflora garden in the La Selva lab clearing years ago. This is a huge magnet for the Passiflora flea beetles that w study! This resource allows us the opportunity to make many novel interactions right at the station.
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John Smiley and I have been using a simple field method to quantify cyanide concentrations in Passiflora tissue, a key trait for mediating herbivory. Using these measurements, I have established a well-replicated common garden that contains all 12 species of Passiflora found at La Selva. This garden captures the amazing variation in cyanide chemistry characteristic of our focal plant species. It will be very well-studied before I get my PhD!
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Ptocadica bifasciata larva consuming Passiflora biflora, a host with highly variable cyanide concentrations among individuals. This flea beetle has been recorded consuming several species of Passiflora at La Selva. We hypothesize that Passilfora herbivores with more generalized diets, like P. bifasciata, are preferentially occupying individual passifloras with low cyanide concentrations.
Disonycha quinquelineata is another Cost Rican flea beetle with an apparently more generalized diet. We have successfuly maintained this species in captivity at our UT Austin facility. Among others. a reason that this species is interesting to us is that it's sister species, D. stenosticha is found in Deep South Texas. We have also established this species in culture. They are very similar in ways (e.g. morphology, life history) but they perform quite differently on hosts native to their respective ranges.
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Pedillia nov sp. "red" adults consuming a highly ephemeral resource - fresh Passiflora pittieri foliage. This host is highly cyanogenic, fresh foliage is rare, and this species is an exclusive consumer of it. Heliconius hewitsoni has a highly similar relationship with this host, but it is only found on the Pacific side of Costa Rica. These intimate interactions are of great interest to us.
My major advisor, Larry Gilbert, and many former member of our lab have pushed our understanding of Heliconius biology to a very high level. Genetics of adaptive phenotypes, population ecology, chemical ecology, meta-population dynamics, etc. This work establishes a fantastic system for me to come in and compare with the Passiflora flea beetles. AND there's still lots of valuable natural history to learn about Helioconius in their natural context! I am very fortunate to have such a rich and interesting system to employ for my dissertation research.
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Prior to beginning my PhD at UT I explored this host plant specialization in a system centered around tropical tortoise beetles (Coleoptera: Chrysomelidae: Cassidinae), a cosmopolitan group of herbivorous insects that are characterized by high levels of dietary specialization.
Acromis sparsa on Merremia ummbellata
Stolas plagiata on Ipomoea phillomega
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Chelymorpha alternans metallic color morph.
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My most impactful scientific experience to date was learning about ecology and evolution of plant-insect interactions in the greater Dyer-Smilanich-Richards lab group at the University of Nevada, Reno. I earned my undergraduate degree at UNR and was afforded the opportunity to work as a lab technician for Lee Dyer for five years. We synthesized approaches from chemical ecology, natural history, field experiments and modeling to further understanding of tri-trophic interactions. I became clear that his was the approach I was going to take in investigating nature.
My friends and colleagues in this fantastic research group influenced my choice of research program significantly. |
AMNH Southwest Research Station - Portal, AZ. I came to the SWRS with the lab and wonderful teams of Earthwatch volunteers every year between 2013-2015 to collect caterpillars, host plants and parasitoids. This is one of my favorite places in North America.