Phylogeography of the pallid kangaroo mouse,Microdipodops pallidus: a sand‐obligate endemic of the Great Basin, western North America

Abstract

Aim Kangaroo mice, genus Microdipodops Merriam, are endemic to the Great Basin and include two species: M. pallidus Merriam and M. megacephalus Merriam. The pallid kangaroo mouse, M. pallidus, is a sand-obligate desert rodent. Our principal intent is to identify its current geographical distribution and to formulate a phylogeographical hypothesis for this taxon. In addition, we test for orientation patterns in haplotype sharing for evidence of past episodes of movement and gene flow.Location The Great Basin Desert region of western North America, especially the sandy habitats of the Lahontan Trough and those in south-central Nevada.Methods Mitochondrial DNA sequence data from portions of three genes (16S ribosomal RNA, cytochrome b, and transfer RNA for glutamic acid) were obtained from 98 individuals of M. pallidus representing 27 general localities sampled throughout its geographical range. Molecular sequence data were analysed using neighbour-joining, maximum-parsimony, maximum-likelihood and Bayesian methods of phylogenetic inference. Directional analysis of phylogeographical patterns, a novel method, was used to examine angular measurements of haplotype sharing between pairs of localities to detect and quantify historical events pertaining to movement patterns and gene flow.Results Collecting activities showed that M. pallidus is a rather rare rodent (mean trapping success was 2.88%), and its distribution has changed little from that determined three-quarters of a century ago. Two principal phylogroups, distributed as eastern and western moieties, are evident from the phylogenetic analyses (mean sequence divergence for cytochrome b is c. 8%). The western clade shows little phylogenetic structure and seems to represent a large polytomy. In the eastern clade, however, three subgroups are recognized. Nine of the 42 unique composite haplotypes are present at two or more localities and are used for the orientation analyses. Axial data from haplotype sharing between pairwise localities show significant, non-random angular patterns: a north-west to south-east orientation in the western clade, and a north-east to south-west directional pattern in the eastern clade.Main conclusions The geographical range of M. pallidus seems to be remarkably stable in historical times and does not show a northward (or elevationally upward) movement trend, as has been reported for some other kinds of organism in response to global climate change. The eastern and western clades are likely to represent morphologically cryptic species. Estimated times of divergence of the principal clades of M. pallidus (4.38 Ma) and between M. pallidus and M. megacephalus (8.1 Ma; data from a related study) indicate

Phylogeography of the dark kangaroo mouse, Microdipodops megacephalus: cryptic lineages and dispersal routes in North America’s Great Basin

“…For this test, unique haplotypes of M. megacephalus were identified as the focal group and all unique haplotypes of M. pallidus (Hafner et al , 2008) as the outgroup. Data from the non-coding 16S gene were presumed to meet the assumption of selective neutrality.…”

“…The partition homogeneity test (PHT; Farris et al , 1994) was conducted as in Hafner et al (2008) using paup * 4.0b10 (Swofford, 2003) to further evaluate phylogenetic congruence. A non-significant PHT result ( P =0.98) permitted combination of the three mtDNA gene fragments.…”

“…Maximum-parsimony analyses followed the methods of Hafner et al (2008). Nodal support for the consensus tree was evaluated using 1000 bootstrap pseudoreplicates (Felsenstein, 1985) and Bremer support values (Bremer, 1994) were obtained by using paup * 4.0b10 and T ree R ot 2 (Sorenson, 1999).…”

“…Hafner et al , 2008). Although there is a dearth of detailed information on the ecology and general natural history of these rodents, available data indicate that kangaroo mice are ecological specialists that are restricted to open, sandy habitats (Hall, 1941; Hafner et al , 1996).…”

Isolation and characterization of 17 polymorphic microsatellite loci in the kangaroo mouse, genus Microdipodops (Rodentia: Heteromyidae)

“…As a result of these climatic events in conjunction with restricted habitat preferences, populations of both M. megacephalus and M. pallidus are often isolated. In fact, several recent studies have revealed that some of these isolated populations may represent unique genetic clusters (Hafner et al 2006(Hafner et al , 2008 resulting in conservation concerns for both M. megacephalus and M. pallidus. Microsatellite markers will be used to help elucidate how Microdipodops populations responded to past climatic changes as well as gain a better understanding of the interactions among extant populations of M. megacephalus and M. pallidus.…”