February 27 2014

5:00 pm 154 BSRB

EcoEvoPub Series

Graduate Student Presentations


Rachel Chock
Department of Ecology and Evolutionary Biology

"Interspecific Competition and the Reintroduction of the Endangered Mouse"

Captive breeding and population reintroduction are last resort measures that are increasingly necessary to save endangered species from extinction. Success rates have improved slowly since early reintroductions, with greater attention now paid to habitat type, food availability, dispersal, and predation risk. Theory predicts that persistence of a reintroduced population is more likely when competition is low; however, competitive relationships are rarely considered when planning reintroductions. Direct and indirect competition can lead to either competitive exclusion (local extinction) or stable coexistence. To achieve stable coexistence, there must be a difference in species’ interference competition ability that counteracts a difference in species’ exploitative competition ability. If one species in a pair were superior in both, competitive exclusion would occur. I ask how the Pacific pocket mouse (Perognathus longimembris pacificus, PPM), a small, specialist forager, maintains a stable population in a community of larger generalist competitors. Determining which species is the closest competitor of PPM will aid in management of the endangered pocket mouse and contribute to the selection and competitor management of reintroduction sites for captive bred PPM populations.

Richard Hedley
Department of Ecology and Evolutionary Biology

"Probabilistic Syntactical Rules Define the Songs of Cassin’s Vireos"

The songs of birds are amongst the most acoustically complex signals in the natural world. Given relatively few primary functions – mate attraction and territory defense – the most perplexing aspect of bird song is its apparent redundancy. Males of some species possess repertoires of several hundred song types, while others achieve similar ends by repeating a single song type. I recorded the song repertoires of several Cassin’s Vireos, and investigated the rules governing the sequential arrangement of songs. My analysis showed that songs were arranged non-randomly, with transitions between some phrase-types being rather common, while others were rare or never recorded. Several aspects of their song delivery suggest considerable redundancy in their songs, and their delivery style does not fit into the predictions of any single theory of the evolutionary pressures on bird songs. Are their songs simply poorly adapted for their presumed functions, or might there be more information in their songs than has been previously appreciated? I will discuss my findings in light of this question, and present preliminary results regarding the influence of social context on singing behavior.











































































































































































































































































































































































































































































































































































































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