Phylogeography Of Moose (Alces Alces): Genetic Signatures Of Population History

Abstract

Through analysis of mitochondrial DNA (mtDNA) sequences, I examined phylogeographic relationships among moose (Alces alces) from Europe, Asia, and North America and inferred historic population trends explaining present-day structure of genetic variance. Diversity of nucleotide composition in cytochrome b was low worldwide, with no variation detected among North American moose. The North American lineage was more closely related to European than to Asian lineages, indicating a recent colonization of North America and refuting the theory of eastern and western races of moose. An analysis of the control region provided greater resolution, which revealed similar yet more detailed patterns, including detectable variation within North America subspecies. Patterns of genetic variation among regional populations identified central Asia as the source of extant lineages of moose. Moreover, a recent coalescence was indicated, with the most recent common ancestor dating to the last ice age. Two historic expansions of moose populations were detected: an initial expansion in Eurasia coincident with an interstade of the last ice age, and a second expansion in eastern Asia; and North America following the end of the last ice age. Data indicate a low effective population size in Eurasia during the peak of the last ice age followed by population and range expansion, likely facilitated by climate change. Haplotypes within North America formed a star phylogeny, indicative of recent expansion. Nucleotide and haplotype diversity were greatest in central North America and least in peripheral populations (Alaska, Colorado, and eastern North America). My data indicate a pattern of colonization consistent with a large central population providing founders for peripheral populations, perhaps resulting from leptokurtic dispersal. Low diversity in Alaska indicated a bottleneck subsequent to colonization and recent population expansion. Establishment of regional populations through small numbers of founders combined with selection pressure for smaller body size likely led to morphological differentiation among regional populations and likely was adequate for rapid development of subspecies. Nucleotide and haplotype diversity were low in southeastern Alaska, but were high in neighboring areas of British Columbia; there was little sharing of haplotypes occurred despite close proximity, indicating recent admixture of separate colonizing populations.