May 5 2009

12:00 154 BSRB

EcoLunch Series

Graduate Student Presentations by Raul Sedano,Ranjan Muthukrishnan and Pamela Thompson


Raul Sedano
"Patterns of historical and contemporary evolution in mountain Tanagers from the Tropical Andes"

The underlying processes along altitudinal and latitudinal gradients promoting diversification in the tropical Andes are a topic of much interest. My study has three objectives for exploring the patterns of historical and contemporary diversification in Andean birds. First, I aim to investigate patterns of trait macroevolution along the Andes using the phylogeny of a group of Neotropical Tanagers. In order to do this I will to examine the evolution of body size in mountain Tanagers to explore the role that the Andean orogeny has had in shaping ecology and morphology. Second, I aim to investigate the contemporary role of isolation and climate change in montane birds using coalescent-based models and ecological-niche modeling. Third, I aim to test the relative contribution of gene flow between divergent populations across the elevational gradient in mountain tanagers. For this talk I will present the general questions, the methodological approach and data used to address the objectives of my research.

Ranjan Muthukrishnan
"Coral-algal phase shifts: a look at the effects of multiple anthropogenic stressors and a test of alternate stable states theory"

Coral reefs are a globally threatened ecosystem of large economic and cultural significance. Coral declines are often associated with a phase-shift toward macroalgal dominance on reefs. A number of anthropogenic influences, including overfishing, nutrient loading and increased sedimentation have been linked to these transitions though their relative and interactive effects are uncertain. In addition it has been suggested that coral-dominated and algae-dominated reefs may represent alternate stable states of reef ecosystems. In order to test the hypothesis that alternate stable states are occurring I surveyed the distribution of coral and algae to see if it matched characteristic patterns predicted by alternate stable states and I evaluated mechanisms that could stabilize the alternate states. To test the role of different stressors in the transition toward algal-dominated reefs I experimentally manipulated herbivore, nutrient and sedimentation levels and monitored reef condition over the course of 6 months.

Pamela Thompson
Impact of Landscape Change on Bat-Plant Interactions in a Tropical Dry Forest

Human driven habitat fragmentation is one of the biggest threats to healthy ecosystems worldwide. Ecological processes such as plant-animal interactions are particularly vulnerable, because changes in landscape structure that affect one species will most likely affect the other. My research focuses on pollination by bats in a tropical dry forest in Mexico. Specifically, I am investing the effects of landscape change on the pollen dispersal by nectar-feeding bats in two landscape types: undisturbed riparian areas (arroyos), and arroyos surrounded by fragmented forest. First, I will compare the abundance, diversity, and foraging of nectar-feeding bats in these two landscape types. Second, I will test the hypothesis that gene flow of a bat-pollinated plant species (Crescentia alata) is reduced in fragmented landscapes, using molecular markers and a statistical model developed for landscape genetics. Understanding how forest fragmentation has impacted plant-pollinator interactions, as seen through the effect on both the bats and the plant, will strengthen conservation planning in these organisms and the region, as well as highlight the role that bats play in maintaining connectivity between plant sub-populations.











































































































































































































































































































































































































































































































































































































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