May 23 2013

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Mairin Balisi
Department of Ecology and Evolutionary Biology

"Ecomorphological specialization and the coexistence of North American fossil dogs"

Approximately 34 to 15 million years ago, as many as 25 contemporaneous species of canids inhabited North America. This peak diversity is remarkable, given that the maximum species richness of canids on any continent today is 12 and, in North America, is only 9. Furthermore, this period hosted representatives of all three canid subfamilies: Hesperocyoninae and Borophaginae, now extinct, as well as the earliest representatives of Caninae, the sole remaining subfamily. Unlike today, canid feeding specializations in Oligo-Miocene North America appear to have spanned hypocarnivory to hypercarnivory, suggesting that the coexistence of so many canid species resulted in part from ecomorphological specialization. Using morphological adaptations as indicators of filled ecological niches in four North American fossil communities, I propose to examine the potential role of ecomorphological specialization in species richness during the period of coexistence among the three canid subfamilies.

Ryan Ellingson
Department of Ecology and Evolutionary Biology

"Time-calibrated phylogeny of North Pacific bay gobies reveals adaptive convergence, ecological diversification, and relictual endemism"

North Pacific bay gobies inhabit bays, beaches, and estuaries of temperate Asia and North America, but are absent from the northernmost latitudes of the central Pacific. Morphological characters have conventionally subdivided the clade into two informal groups – an elongate infaunal Astrabe group, and a deeper-bodied benthic Chasmichthys group – each with a disjunct East-West (amphi-) Pacific distribution. A multi-locus phylogeny reveals basal divergence of the tree coincident with a dramatic global cooling event at the Eocene/Oligocene transition, with no evidence of subsequent trans-Pacific migration. These results suggest that several morphological characters previously used to define the Astrabe and Chasmichthys groups have arisen independently on both sides of the Pacific, revealing convergence of ecologically adaptive characters within a geographically divided clade. Inferences of vicariance via biogeographic events are used to time-calibrate this phylogeny. Divergence time estimates are used to compare and contrast potential mechanisms of bay goby diversification on either side of the Pacific. Speciation in the West Pacific has been driven largely by interstitial colonization of gravel beaches of varying grain size, and by invasion of freshwater streams around the Sea of Japan. In the East Pacific, diversification appears to be related to an intense upwelling regime combined with isolation in large Miocene-era embayments on the coast of California. Divergence times also provide strong evidence for relictual endemism in the Gulf of California, as speciation of three out of four Gulf-endemic gobies substantially predates tectonic formation of the Gulf itself.

THURSDAY, May 23, 2013















































































































































































































































































































































































































































































































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