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February 11, 2021

5:00pm Zoom

EcoEvoPub Seminar Series
Department of Ecology and Evolutionary Biology, UCLA

" Graduate Student Presentations "

Eva Horna Lowell and Sean O’Fallon

Department of Ecology and Evolutionary Biology, UCLA, Pinter-Wollman and Nonacs Labs

Effects of environment, genes and evolution on nest architecture

An animal’s genes, environment, and evolutionary history all contribute in different ways to the expression of behavior. Nest architecture is an extended phenotype of ant colonies that results from a dynamic interaction between the environment and the collective nest building behaviors of the ants. Nest architecture differs among ant species and among colonies within a species, but the source of these differences remains an open question. To investigate the impact of colony identity (genetics), evolutionary history (species), and the environment on nest architecture, we compared how two species of harvester ants construct their nests in different environmental conditions. For each species, we collected workers from four colonies and allowed them to excavate a nest in environments that differed in temperature and humidity. After allowing the ants to excavate a nest for seven days, we created casts of each nest and quantified them. We compared nest structures among colonies and between species. Our results reveal differences in nest structure among colonies of the same species and between species. Interestingly, environmental conditions did not have a strong influence on nest structure in either species. Our results suggest that extended phenotypes are shaped more strongly by genes and evolutionary history and are less plastic in response to the abiotic environment, like many physical and physiological phenotypes.

Chris Kyriazis

Department of Ecology and Evolutionary Biology, UCLA, Wayne and Lohmueller Labs

Modeling inbreeding depression and recovery potential in the vaquita

A growing body of research has highlighted the ways in which inbreeding depression can drive extinction in small wildlife populations. For species that have experienced severe declines, a question therefore arises of whether recovery is possible, or if it is instead impeded by inbreeding depression. A prime example of this is the vaquita, a highly-endangered porpoise that is endemic to the Gulf of California. Over the past several decades, the vaquita has experienced a dramatic decline in population size driven by high bycatch mortality, with roughly 10 individuals remaining. Recently, it has been argued that the vaquita is doomed to extinction due to its low levels of genetic diversity, and that we should no longer devote scarce conservation resources towards its recovery. In this study, we generated a whole genome sequence dataset for the vaquita to explore extinction risk and recovery potential. Using this dataset, we first demonstrate that low genetic diversity in the vaquita is a consequence of its long-term small population size rather than the recent bottleneck. Next, we use this dataset to parameterize stochastic simulations exploring recovery potential under various scenarios over the next 50 years. We find that recovery is possible if bycatch mortality is immediately and dramatically halted; however, extinction rates remain high even at modest rates of bycatch mortality. Furthermore, we demonstrate that vaquita recovery may in fact be enabled by its small historical population size, which could translate to a low strength of inbreeding depression. Our results demonstrate hope for vaquita recovery, and highlight the utility of genomic tools in conserving a species on the brink of extinction.