December 5 2013

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Kenneth Chapin
Department of Ecology and Evolutionary Biology

"The Evolution of Incipient Sociality in Cave Cannibals"

Rarely do two environments transition as abruptly and with such starkly different evolutionary pressures as those of cave and surface habitats, making them a particularly interesting system to study evolution and behavioral ecology. In numerous species, however, there are no physical barriers between cave and surface environments and considerable gene flow may occur across habitats. This presents tension between gene flow and divergence. In the case of cave and forest dwelling whip spiders of Puerto Rico, cave selection pressures have resulted in distinct behavioral differences: cave populations exhibit incipient sociality, while forest conspecifics are solitary cannibals. Studying this system addresses two hotly debated questions in biology: What selection pressures result in incipient sociality, and how does gene flow constrain divergence of cave populations? Presented is preliminary research on the behavioral divergence of one cave population, future directions to understand whip spider population genetics and sociality, and an overview of concurrent research.

Abby Curtis
Department of Ecology and Evolutionary Biology


Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Mammals that exhibit aquatic behavior are generally characterized by the loss of paranasal sinuses along with flattened skull roofs, and large, dorsally shifted eyes and nostrils. Loss of paranasal sinuses in aquatic species is attributed to the risk of their collapse due to greater pressures while diving. However, there are fully aquatic early whales that appear to have had sinuses as well as several extant, fully terrestrial mammals that lack sinuses. We investigated how sinuses vary in size and shape among species that vary in the amount of time they spend foraging in water, focusing specifically on arctoid carnivorans. Arctoid species show marked disparity in skull size and shape and range in behavior from being exclusively terrestrial, to semi-terrestrial or semi-aquatic. Moreover, three distinct lineages independently evolved aquatic habits. Results show that sinuses are either lost or reduced in semi-terrestrial and semi-aquatic species, and that sinus size is related to skull size and shape. We found several terrestrial species that lacked sinuses, indicating that factors other than negative pressures associated with diving, such as limited space due to skull size and shape, also can limit sinus size and presence.











































































































































































































































































































































































































































































































































































































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