May 22 2014

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Allison Fritts-Penniman
Department of Ecology and Evolutionary Biology

"A Genomic Approach to Elucidating Speciation Processes in the Nudibranch Genus Phestilla"

Corals often host other invertebrates and fishes in mutualistic or parasitic relationships. The evolution of new or more specific associations between corals and other reef organisms may lead to the creation of new species. Previous work on coral-associated nudibranchs shows that host switching has occurred during the evolution of the genus Phestilla, but the relationship between host switching and speciation is still unknown. Mitochondrial DNA reveals ongoing divergence between populations collected from different host species, but a genomic approach is required to determine whether this ecological process also acted in past speciation events. Using RADseq, we are comparing the degree and distribution of genomic divergence between population and species pairs hosted by different coral species to provide insight into whether species diversity in this genus can be attributed to host-driven selection.

Shenyue Jia
Department of Geography

"Environmental Variability and Fluctuation of Coccidioidomycosis (Valley Fever) In California: Based on a New Framework Involving Arthospore Life Cycle"

Coccidioidomycosis (valley fever), caused by inhalation of spores from Coccidiodes immitis (C. immitis) and Coccidioides posadasii (C. posadasii), is a disease endemic to arid regions in the southwest US, as well as parts of Central and South America. With a projected increase of drought in this region, an improved understanding of environmental factors behind the outbreaks of coccidioidomycosis will enable the prediction of coccidioidomycosis in a changing climate regime. Previous research shows the infections correlate with climate conditions including precipitation, temperature, and dust. However, most studies focus only on the environmental conditions of fungus growth, which is the first stage in the life cycle of arthospores. In contrast, we extend the analysis to the following two stages in the life cycle, arthrospore formation and dispersal, to form a better model to predict the disease outbreaks. Besides climate conditions, we use relative spectral mixture analysis (RSMA) based on MODIS MOD43 nadir BRDF adjusted reflectance (NBAR) data to derive the relative dynamics of green vegetation, non-photosynthetic vegetation and bare soil coverage as better indicators of soil moisture, which is important for arthospore formation and dispersal. After detecting the hotspots of disease outbreaks, we correlate seasonal incidence from 2000 to 2010 with the environmental variables zero to eight seasons before to obtain candidates for stepwise regression. Regression result shows a seasonal difference in the leading explanatory variables. Such difference indicates the different seasonal main influential process from arthospore life cycle. C. immitis (fungus responsible for coccidioidomycosis outbreaks in California) growth explains outbreaks in winter and fall better than other two stages in the life cycle, while arthospore formation is more responsible for spring and summer outbreaks. As the driest season, summer has the largest area related with arthospore dispersal.
The seasonal difference of main influential process relates to the length of lags between the outbreaks and stages in life cycle of arthospores. During wet seasons of California including winter and fall, outbreaks are less correlated with the short-lag process such as dispersal of arthospores because of high soil moisture. In contrast, the long-lag process like C.immitis growth is influential on outbreaks in wet seasons. The arthospore formation, especially during the latest dry season (with a lag less than one year), is more responsible for outbreaks in spring and summer, when the influence of C. immitis growth is dampened by time. However, arthospores formed and preserved years ago may introduce uncertainty to the seasonal lag patterns. The long lags also exist in outbreaks related to arthospore formation. By including all three stages of arthospore life cycle, we formed a more comprehensive framework in explaining the relationship between environmental conditions and disease outbreaks. Such analysis can be extended to a finer temporal resolution (e.g. per month) to obtain a clearer picture between environmental variability and coccidioidomycosis fluctuation.















































































































































































































































































































































































































































































































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