Molecular Ecology of Peromyscus polionotus

Abstract

Lowe et al. (2004) describes ecological genetics as “the investigation of the origin and maintenance of genetic variation within and between populations, which ultimately leads to adaptation and speciation.” Thus, to gain a more complete understanding of a real world species an ecological genetics investigation must look across multiple levels and utilize different types of DNA markers as these processes occur on both a regional and microgeographic scale. A regional scale typically involves between population processes while the microgeographic level often investigates the same processes but at a much finer scale. Measures of genetic variation that are investigated at both scales include genetic diversity and genetic differentiation. Here, I investigated these two measures of genetic variation on both a regional and microgeographic scale using two different DNA markers (mitochondrial and nuclear DNA). First, mitochondrial DNA was used to investigate phylogenetic relationships within the species Peromyscus polionotus based on a previously proposed phylogenetic model. The relationships predicted using mtDNA genes cytochrome-b and the control region were incongruent with the previously proposed model. A revised model, then, indicates three distinct clades occupy the Gulf Coastal region of Florida and Alabama. Divergence among the clades may have occurred approximately 300 000 YBP. The Gulf Coastal region is comprised of two inland clades and a beach clade. Inland clades appear to integrate while beach subspecies are comprised of a single haplotype and do not appear to have recently integrated with adjacent inland populations. In fact, extant beach forms represent lineages that are older than the present dune systems they inhabit. Secondly, on a local or microgeographic scale, genetic diversity and differentiation was investigated using nuclear microsatellite markers. It was discovered that genotypes are partitioned on a microgeographic scale (< 1000 m). Genotype partitioning has several evolutionary implications and has been recognized as such for the majority of the past century. Partitioning was apparently temporal, deteriorating through annual population declines and reorganizing during birth pulses. Also, genotype partitioning reorganized following a hurricane that kept population densities low for four years. Importantly, partitioning of genotypes was demonstrated to slow the rate of genetic decay within the population of Alabama beach mice.