What makes an animal a specialist or a generalist?The Wehrle Lab at Bryn Mawr College uses the interplay of physiology, morphology, behavior, and ecology as tools to understand entire organisms in their natural context. Since diet and digestive physiology influence all aspects of an animal’s biology and survival, assessing what an animal eats and how it then digests and uses its food requires a multi-faceted approach considering the diet, organ structure and function, energetics, and ecological context.
Our questions broadly address:
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Digestive adaptations for herbivory
Thirty-six years after five breeding pairs of Podarcis sicula (Italian Wall Lizards) were moved from Pod Kopište to Pod Mrčaru in the Croatian Adriatic, Herrel et al. (2008, PNAS) revealed that the transplanted lizards on Pod Mrčaru had become mostly herbivorous and developed morphological adaptations for consumption of a plant diet, previously thought only to evolved over longer time scales. We found that shifts in digestive biochemistry were smaller than predicted and primarily localized to the hindgut, a pattern replicated in the lizard's microbiomes. Our published work on the physiology, however, covers just a small snapshot!
Our ongoing work with this system shows evidence of variation by season, sex, and year. Digestion is rarely investigated with respect to sex effects, be they related to internal processes or external conditions. Our lab is approaching these comparisons to see how these animals might use different strategies to meet the same goals. This research was largely funded through a Catalyzing New International Collaborations (CNIC) grant from NSF in major collaboration with Dr. Anthony Herrel and Dr. Zoran Tadic, advised by Dr. Donovan German. Integrative behavior of digestive enzymesOur work in collaboration with Dr. Kwasi Connor combines measurement of whole animal functional physiology with molecular tools and protein mapping to integrate how each level of biological organization informs the others. We are following up on findings that Mytilus californianus (California Mussels) modulate their digestive enzymes in response to tides, but that where a mussel is on the shore is tied to whether its enzymes can remain stable after a heat stress.
In our studies, we acclimated mussels to experimental diet treatments or fed/fasted feeding regimens, then exposed them to tidal events with or without heat added. Results from low tide show diet (but not temperature) effects on amylase activity. Preliminary data suggests amylase gene expression is much lower in the heat treatment across diets (but low overall in fasted mussels). A lower number of amylase transcripts during heat shock would support a decrease in amylase produced during heat stress. Acquisition and variation of gut microbes in an herbivorous lizardHerbivory in lizards and requires communities of symbiotic gut microbes and for >30 years, social interactions have been a hypothesized route of microbe transfer. Using Illumina sequencing in collaboration with the Earth Microbiome Project, we characterized the spatial, temporal, and social variation of these vital microbial communities in Green Iguanas (Iguana iguana). Generally, we found high variation in microbial community composition by each factor we investigated, including within recaptured individuals over time. Intergenerational microbial community transmission is unlikely to be as important as previously hypothesized based on the near absence of intergenerational associations and the dissimilarity in microbial community assemblages between hatchlings and adults/subadults. However, within-hatchling microbial admixing was common. This work was advised by Dr. Bobby Espinoza and supported by the Smithsonian Tropical Research Institute, Sigma Xi, SICB, SSAR, ASIH, and the Herpetologists League.
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