June 1, 2022

12:00pm, PST 158 HH and Zoom

Graduate Student Presentations
UCLA, Dept of EEB

" Graduate Student Presentations "

SAM DEGREGORI

Department of Ecology and Evolutionary Biology, Barber Lab

UCLA

“Delineating Ecological and Evolutionary Controls on Coral Reef Gut Microbiomes”

Gut microbes provide vital functions for animal hosts. While it is known that host ecology and evolutionary history play a role in shaping gut microbiomes, a majority of studies have focused on mammal hosts. Other vertebrates, including fish, have received little attention. Coral reef fish, in particular, exhibit a wide range of distinct feeding behaviors and evolutionary histories that likely correlate with gut microbiome composition and diversity. Furthermore, comparing fish gut microbiomes to those of mammals may reveal host-microbe dynamics that have converged between distantly related hosts. My thesis leverages a large unprecedented coral reef fish gut microbiome dataset (N=550), where I sampled the gut microbiomes of 20 host species of fish with robust replication spanning three islands across the South Pacific, to better understand how host phylogeny, host diet, and host environment shape fish gut microbiomes and whether the observed trends are comparable in other vertebrate hosts. For this talk, I will be focusing on some striking similarities I found between fish and mammal gut microbiomes and discussing the ecological and evolutionary implications.

CHRIS KYRIAZIS

Department of Ecology and Evolutionary Biology, Lohmueller Lab

UCLA

“Understanding the Genomic Threats to Extinction in Small Populations”

Anthropogenic pressures have resulted in an abundance of small and isolated wildlife populations facing an elevated risk of extinction. In these populations, extinction risk can often be exacerbated by genetic factors, such as inbreeding depression. The aim of my dissertation was to apply novel genomic and simulation tools to deepen our understanding of the factors influencing risk of extinction due to inbreeding depression. In my first dissertation chapter, I used computational genetic simulations to explore how historical population size influences the severity of inbreeding depression. My results demonstrate that historically-large populations with high genetic diversity face an elevated risk of extinction following a population contraction due to these populations harboring high levels of recessive strongly deleterious variation. In my subsequent work, I examined the consequences of this phenomenon for modelling extinction risk and recovery potential in the critically endangered vaquita porpoise. The vaquita has been heavily impacted by illegal fishing in the Gulf of California and currently numbers ~10 individuals, causing some to argue that the species is doomed to extinction. Using a genomics-informed simulation model, I demonstrate that the vaquita has a low risk of inbreeding depression and high potential for recovery in the absence of continued bycatch. This low risk of inbreeding depression is enabled in part by the species’ small historical populations size. Overall, my results illustrate the central role of historical population size as a determinant of extinction risk due to inbreeding depression, with important implications for the growing number of small and isolated populations worldwide.

 

Wednesday, June 1, 2022

12:00pm, PST

Host: Colin Kremer