Intrinsic and extrinsic effects on the population connectivity of asterinid sea stars

Abstract

Genetic connectivity determines the evolutionary independence of populations and plays an important role in governing both micro-and macroevolutionary processes. In this dissertation, I use mtDNA sequences, nDNA sequences, and microsatellite loci to examine extrinsic and intrinsic factors that influence marine population connectivity, utilizing five species of Asterinid sea stars. First, I used a seascape genetics framework to show high and significant correlations between anthropogenic pollution variables and the genetic structure of Patiria miniata, a ubiquitous, non-harvested species with high levels of genetic diversity, indicating that coastal pollution is limiting pelagic larval dispersal. Second, I examined the rapid divergence of two species, Cryptasterina hystera and Cryptasterina pentagona, to infer the genetic consequences of the loss of pelagic larval development. I discovered the fastest known marine faunal speciation event, and showed that the associated transition to live-bearing from planktonic development as well as the potential to self-fertilize had severe consequences for genetic diversity, heterozygosity, and population connectivity. Next, I demonstrate the utility, accuracy, and cost and time effectiveness of a new multiplexing methodology using 454 (Roche) technology to simultaneously sequence five nuclear DNA loci in two species across 16 sampled localities. Finally, I used this methodology along with traditional methods in a comparative framework to demonstrate that benthic larval development has a profound effect on the genetic connectivity of sympatric asterinid species. I show the species with benthic development, Parvulastra exigua, has lower levels of genetic diversity across all markers, has more inferred genetic clusters, and higher levels of genetic structure compared to the lecithotrophic species, Meridiastra calcar. Additionally, I show that the genetic architectures of these two species are consistent with predicted dispersal abilities with P. exigua showing a distinct pattern of extirpation during the LGM with subsequent recolonization and M. Calcar showing a distinct pattern of persistence and isolation during the LGM with subsequent post Pleistocene introgression. In short, I find that extrinic factors, such as coastal pollution, and instrinsic factors, such as the location of larval development, can fundamentally structure the population connectivity and genetic diversity of asterinid sea star species.