This page summarizes my PhD thesis research other projects in progress.
nutritional physiology and trophic ecology
I am broadly interested in how nutritional needs and physiology are related to trophic ecology. Since beginning my PhD, I have focused on the nutritional ecology of highly unsaturated omega-3 fatty acids (HUFA). For my PhD candidacy exam, I synthesized the existing literature on HUFA, which resulted in a review paper. In my review, I discussed the importance of HUFA for animals, the dichotomy between HUFA availability at the base of aquatic and terrestrial food webs, and the ecological implications of mismatches between HUFA supply and demand.
I am also interested in understanding how evolutionary history and local food quality as well as trophic ecology influence animals' ability to convert the HUFA precursor ALA into HUFA and in animals' dietary HUFA needs in nature. Riparian insectivorous birds have provided me with an excellent system in which to begin understanding these processes. For example, I've found that Tree Swallows (Tachycineta bicolor) chicks are able to convert ALA to HUFA, but that the efficiency of this process and availability of ALA in their prey is such that HUFA are ecologically essential nutrients for them in natural systems. Compound-specific carbon stable isotope tracers are a key tool that I use in this area of my research.
More broadly, I am broadly interested in understanding how evolutionary history (i.e., phylogenetic relationships), trophic ecology, and habitat interact to determine species' nutritional requirements at a genetic level. For example: Is being an herbivore or does living in a marine environment exert a greater influence over whether a species is able to convert ALA to HUFA? Does being an insectivore within a family of granivores suggest that a species may that a species has lost this ability? I am currently working to answer these questions with collaborators.
Twining, C. W., J. T. Brenna, N. G. Hairston, and A. S. Flecker. 2016. Highly unsaturated fatty acids in nature: what we know and what we need to learn. Oikos 125:749-760.
Twining, C. W., P. Lawrence, D. W. Winkler, A. S. Flecker, and J. T. Brenna. 2018. Conversion efficiency of alpha linolenic acid to omega-3 highly unsaturated fatty acids in aerial insectivore chicks. Journal of Experimental Biology 221(3).
Limnology for the ornithologist
I started out my scientific training in limnology, but have been moving into the terrestrial realm by using my background in aquatic ecology to ask questions in avian ecology. In this research I also use tools from nutrition including fatty acid composition analyses, bulk stable isotopes, and compound-specific stable isotopes. In my dissertation, I studied the following in riparian aerial insectivores, Eastern Phoebes (Sayornis phoebe), and their prey in natural systems around Ithaca, NY:
- Do emergent aquatic insects contain more HUFA than terrestrial insects and how does their fatty acid composition vary at a landscape level?
- Where do riparian aerial insectivores get their overall diet from and how does this vary at a landscape level? (Bulk stable isotopes)
- Where do riparian aerial insectivores get their HUFA and how does this vary vary at a landscape level? (Compound-specific stable isotopes)
HUFA Effects on developmental performance
During my PhD, I also studied the effects of HUFA on performance for riparian aerial insectivore chicks. I found that increasing HUFA in diet increased growth rates and body condition, in both Tree Swallows and Eastern Phoebes. I also found that decreasing HUFA increased metabolic rates (even after size correction) and that HUFA also increased immunocompetence in Tree Swallows.
Twining, C. W., J. T. Brenna, P. Lawrence, J. R. Shipley, T. N. Tollefson, and D. W. Winkler. 2016. Omega-3 long-chain polyunsaturated fatty acids support aerial insectivore performance more than food quantity. Proceedings of the National Academy of Sciences 113:10920-10925.