Investigating the role of dispersal on the genetic structure of wild populations

Abstract

The movement of individuals among populations (dispersal) is an ecological process that can affect the genes of populations. Identifying the role this process plays in the wild can be difficult due to uncertainty caused by other genetic and ecological processes. Here, I present three studies investigating the role of dispersal in wild populations of Weddell seals (Leptonychotes weddellii), mule deer (Odocoileus hemionus) and westslope cutthroat trout (Oncorhynchus clarkii lewisi). Each of these studies presents, to my knowledge, novel statistical approaches within this discipline that account for the uncertainty caused by other genetic and ecological processes when investigating the role of dispersal. In the second chapter I present a study that uses a two-step maximum likelihood analysis, fit with the data cloning algorithm, to incorporate uncertainty in estimating the probability that an individual has multiple copies of the same gene from a given ancestor into estimates of the association between this probability and the number of pups a female Weddell seal will produce in her life. This study did not find strong support for the hypothesis that increased similarity of an individual's genes reduced the number of pups she would produce across her lifetime. In the third chapter I use individual based genetic distance measures to investigate the association between features of the landscape and the genetic similarity of mule deer. This study found no detectable barriers to dispersal of mule deer across Montana. The fourth chapter presents a study comparing the dispersal rate between samples of westslope cutthroat trout from Glacier National Park that have interbred with introduced rainbow trout (Oncorhynchus mykiss) to samples that have not. There was no detectable difference in the dispersal rate of westslope cutthroat trout that have interbred with introduced rainbow trout relative to those that have not. In conclusion, dispersal is an important ecological process affecting the genes of populations, but understanding the role it plays across a landscape requires adequately accounting for the uncertainty due to other genetic and ecological processes. The three studies presented highlight different ways of addressing this problem when investigating the role of dispersal in the wild.