Life history and population genetic structure of sea stars from the family Asterinidae

Life history can influence population genetic variation by altering patterns of gamete union and dispersal. Sea stars from the family Asterinidae have evolved similar life histories multiple times in parallel including planktonic feeding larvae, planktonic non-feeding larvae, development in benthic egg masses, and viviparity. In this thesis I first examine the population genetic structure of a widespread planktotrophic asterinid sea star from the East Pacific (Patiria miniata). I use mitochondrial sequence markers to determine whether extrinsic factors such as vicariance or intrinsic properties such as dispersal mode are driving patterns of population genetic variation in this species. I then examine patterns of population genetic variation among eight additional asterinid species from Australia using a mixed species pool of genomic microsatellite markers. I use these microsatellite markers to characterize the genetic variation within groups of brooded offspring associated with the unusual life histories of two live bearing asterinids from the genus Parvulastra. Lastly, I examine the evolution of life history among the asterinids and use the phylogenetic relationships among species to examine the correlation between life history and population genetic structure in this group. Ultimately, I find that the degree to which intrinsic life history properties of asterinids and extrinsic factors contribute to population genetic variation varies among species and among clades. In P. miniata patterns of population genetic variation are influenced by both intrinsic and extrinsic factors. Using microsatellite markers I find that in general between-population genetic variation is high in benthic species (benthic egg laying and live bearing) relative to species with planktonic larvae and that genetic variation within populations is lower in benthic species relative to planktonic species. Lastly, I find that the degree to which phylogeny constrains the coevolution of population genetic structure and life history varies among life history characters and among-population genetic parameters. This thesis suggests that in many cases variation in life histories among a closely related group of marine species can predict patterns of population genetic variation. However, extrinsic factors can in some cases, act with or override life history characteristics in driving patterns of population genetic variation.