October 27 2011

5:00 pm 154 BSRB

EcoEvoPub Series

Graduate Student Presentations


Charles Boch, Ph.D.
Institute for Collaborative Biotechnologies, University of California, Santa Barbara
"Cascading Environmental Signals and the Acropora spp. Spawning Synchrony Response"

Spawning synchrony (i.e., synchronous release of gametes) is a ubiquitous phenomenon found in many marine organisms. Perhaps the most well known synchronized spawning event is the mass spawning behavior observed in the tropics where over a hundred coral species spawn within a few hours after sunset on the nights surrounding the full moon. These events involve the integration of circa-annual, circa-lunar, and circa-diel cues but the environmental signals that control these phenomenal events remain contentious in the literature. Therefore, the contributions of environmental signals to the time of coral spawning are compared at different temporal scales. Correlations of population spawning patterns with both solar insolation and sea surface temperature indicate that both environmental signals are important but spawning synchrony was shown to be more tightly dependent on the arrival of increasing sea surface temperatures. On the circa-lunar and circa-diel time scales, the unique features of the physical components of light dynamics were characterized and experimentally tested for their separate contribution to spawning synchrony. Spawning synchrony on the circa-lunar and circa-annual time scales was shown to be most dependent on photoperiod components of the lunar and solar cycles. The results of these studies are consistent with coral spawning models wherein coral spawning synchrony is driven by cascading environmental signals. Therefore, coral spawning synchrony is suggested to be controlled by a cascade of environmental signals starting with the seasonal arrival of maximum solar insolation and rising sea surface temperatures followed by lunar and solar photoperiod dynamics as proximate triggers.

Dept of Ecology and Evolutionary Biology, UCLA
"Emerging Infectious Diseases: Adaptation and Evolutionary Invasion Across Scales”

Data on evolutionary genetics of cross-species adaptation and epidemiological surveillance of zoonotic events are becoming increasingly available, but an explicit frameworkis needed to link these data to interpret the selection pressures influencing pathogen emergence. Hierarchical selection pressures may have differential correlations at different scales, e.g. increased pathogen replication at the within-host scale may have fitness costs at the population-level scale of transmission between hosts, affecting pathogen fitness in ways not obvious when studying evolution at a single scale. I will present a baseline model addressing the cross-scale hierarchy of selection under a stochastic framework, utilizing evolutionary and population genetic theory to explore the effects of selection acting across scales. At the between-host/transmission scale, multi-type branching processes are used as an approximation to the random processes of transmission and infection. The assumption of strong selection/weak mutation (SSWM), established by Gillespie (1984) is used as a first approximation for within-host dynamics. SSWM has been used extensively in empirical literature of adaptive landscapes and it is important to consider the consequences of this assumption in a cross-scale
framework. The basic cross-scale model presented supplies a mathematically tractable approach in which to initially analyze how a SSWM-dynamic within-host selection process interacts with between-host selection.











































































































































































































































































































































































































































































































































































































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