Knowledge of the diets of animals is critical to identifying the ecological and evolutionary processes that shape their populations, as well as to developing effective conservation measures. However, such information is unavailable for many species because of difficulty in assessing food sources. The research conducted under this award will integrate bulk nitrogen isotope and compound-specific (amino-acid) nitrogen isotope data to examine the trophic positions and dietary breadth of three closely-related, but poorly understood, migratory bat species (Lasiurus cinereus, Lasiurus borealis, and Lasionycteris noctivagans). The work will be conducted in the lab of Dr. Naohiko Ohkouchi at the Department of Biogeochemistry at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which has pioneered the development and application of amino-acid nitrogen isotope analysis to the study of animal diet.
The proposed research provides an unparalleled opportunity to advance research concerning the degree of dietary specialization vs. flexibility of three bat species of conservation concern. It would also pioneer the application of established methodologies that not available at the U.S. home institution to a novel study system (bats). Prior studies differ greatly in their assessment of the degree of dietary specialization vs. flexibility that these species exhibit. One reason is that prior studies have been largely based on morphological analysis of the content of gut and/or fecal material, which is known to only detect persistent and identifiable prey parts from a recent meal. Stable isotope analysis overcomes this challenge, because it integrates dietary information over a longer period. Nitrogen isotope values increase from food source to consumer, which provides the basis for this approach. However, besides the trophic status of a consumer, nitrogen isotope values of bulk tissue can also be influenced by variation in the baseline nitrogen isotope values of a food web. Thus, I plan to integrate bulk tissue nitrogen isotope data with amino-acid specific nitrogen isotope data, which will allow me to distinguish such 'trophic' and 'source' effects. Based on (1) preliminary bulk nitrogen isotope data (collected at the home institution) and (2) existing knowledge of bat diet and foraging ecology, I hypothesize that the dietary habits of these bats will indicate varying degrees of specialization and dietary flexibility, as well as some degree of trophic differentiation. Greater insight into the feeding behavior and dietary flexibility these species across their ranges would aid efforts to better conserve them in the context of global environmental change.
This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.
