April 21 2009

12:00 154 BSRB

EcoLunch Series

Graduate Student Presentations by Keith Gaddis, Chris Johnson and Zac Harlow


Keith Gaddis
“Impact of isolation on gene flow in an African oasis plant-pollinator system"

How does fragmentation and isolation affect a historically isolated species? Are species that exist in harsh climate reproductively adapted to variable environments? In Saharan desert oases plants and animals have been experiencing increased environmental pressure for the last 60 years due to drought and rising global temperatures. How do species in these areas cope with these changes accompanied by advancing desert that decreases habitat size and increases isolation? Looking at a common desert tree species, Acacia senegal, I use molecular markers to identifying the population structure among oases combined with remote sensing data to identify current and past barriers to gene flow and its implication for the future of this area.

Chris Johnson
“Untangling Complex Foodwebs: Diversity Maintenance Mechanisms in the Serengeti”

Biodiversity is decreasing worldwide at a rate greater than it has during any of the historic mass extinction events. This makes it imperative to understand the mechanisms maintaining diversity in complex ecological communities. My research focuses on understanding the mechanistic basis of diversity maintenance and, in particular, determining whether diversity enhancing mechanisms are stable to atypical environmental changes such as climate warming. The impetus for this research comes from the complex ecological interactions observed in the plant-herbivore-predator community inhabiting the Serengeti. My goal is to develop a mathematical framework to elucidate the mechanisms by which species interactions and environmental variability interact to maintain diversity in complex ecological communities. Such a framework will not only provide a predictive conceptual basis for studying diversity maintenance, but it also provides the opportunity to develop computational methods for analyzing complex foodwebs in spatiotemporally variable environments and to utilize sophisticated statistical techniques to reduce the dimensionality of complex foodwebs to a core group of strongly interacting species.

Zac Harlow
"Aspects of Avian Communication revealed by sensor arrays and playback"

Birds use song to attract prospective mates and to deter potential rivals from their territories. In oscine passerines, males typically sing, but in some species the females also sing in tandem to produce a duet. Duetting more commonly occurs in tropical species that are sedentary year-round and form long-term pair bonds. Little is known about the spatial ecology of duetting birds in relation to rival pairs or intruders. I plan to use acoustic arrays and playback experiments to localize singing birds and better understand the function of duetting in the white-breasted wood-wren (Henicorhina leucosticta). I will also explore interactions of H. leucosticta with its sister species H. leucophrys where they come into contact along an elevational gradient in Central America.











































































































































































































































































































































































































































































































































































































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