February 2 2017

5:00 pm 1100 TLSB

EcoEvoPub Series

Graduate Student Presentations


Christine Scoffoni
Department of Ecology and Evolutionary Biology, UCLA

"Outside-xylem vulnerability, not xylem embolism, controls leaf hydraulic decline during dehydration

Leaf hydraulic supply is crucial to enable the maintenance of open stomata for CO2 capture and plant growth. During drought-induced leaf dehydration, the capacity for water flow through the leaf (Kleaf) declines, a phenomenon attributed for over fifty years to the formation of gas bubbles in the leaf veins, neglecting potential dynamics of the outside-xylem (mesophyll) pathways. We quantified and visualized the hydraulic vulnerability of the xylem and outside-xylem pathways and estimated their influence on whole-plant water transport. The response of outside-xylem pathways determined the vulnerability of the leaf and plant hydraulic system, protecting the xylem throughout the plant from tensions that would drive cavitation. These findings pinpoint the leaf mesophyll as a central locus for the control of water transport during progressive drought.

Tyler McCraney
Department of Ecology and Evolutionary Biology, UCLA

"Ecological drivers of speciation and size evolution in gobiiform fishes"

Why are some taxa more diverse than others? Understanding the causal mechanisms that have resulted in variable species richness and morphological diversity across the Tree of Life is fundamental to evolutionary biology. Behavioral, morphological, and geological factors have been hypothesized to drive diversification by providing ecological opportunities that reduce competition among lineages, but testing these predictions has often been limited to small, geographically restricted taxa, or sparsely sampled radiations of diverse taxa. Here I use a time-calibrated megaphylogeny and macroevolutionary modeling of speciation and morphological rates to identify ecological drivers of diversification across the globally distributed gobiiform fishes. I find elevated rates of body size evolution for freshwater fishes and greater speciation rates in mutualistic lineages, but no relationship between reef-association, diversification, and phenotypic evolvability. These results support the role of aquatic habitats and cooperative behaviors as major drivers of diversification in gobies.















































































































































































































































































































































































































































































































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