March 12 2015

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Department of Ecology and Evolutionary Biology

"Tar Pit Forensics: Exploring the Black Box of La Brea"

The still-active tar seeps of Rancho La Brea California have produced millions of fossils to date. The tar seeps represent an unusual taphonomic setting in that the skeletons recovered there are incomplete, disarticulated, and mixed together with little stratigraphic order. The large number and condition of the fossils have allowed previous researchers to hypothesize an entrapment scenario in which herbivores becan mired, were then later scavenged by carnivores, and were in turn subsequently trapped. However, the scenario lacks detail in the time period between the time the animals perished and their permeation with tar. It has been estimated that it took 17-20 weeks for carcasses to sink into the tar. Additionally, previous work has shown that skeletal elements moved apart from each other at least 1-3 meters but its unclear whether this movement occurred before or after the elements sank into the tar.A key missing estimate is how long it takes skeletons to become completely disarticulated in tar. I will present the outcome of placing several bobcat carcasses in a tar seep and a revised taphonomic scenario for La Brea tar seep fossils.

Department of Ecology and Evolutionary Biology

"Range Stability Predicts Lineage Persistence in a Ground Squirrel Species Complex"

Morphologically cryptic phylogeographic lineages are common throughout the natural world. Recent work has shown that if these divergent genetic lineages persist long enough in isolation, they ultimately gain reproductive isolation and can be considered valid species. However, hybridization and introgression between lineages can reverse this process, leading to the erosion of once distinct genetic entities. Range expansions caused by past climatic change can lead to secondary contact between lineages, providing opportunities for introgression. Here, we use species distribution modeling and an exon capture dataset to examine the impact of range stability on lineage persistence in a ground squirrel species complex (genus, Otospermophilus).















































































































































































































































































































































































































































































































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