Many subspecies were described to capture phenotypic variation in wide-ranging taxa, with some later being found to correspond to divergent genetic lineages. We investigate whether currently recognized subspecies correspond to distinctive and coherent evolutionary lineages in the widespread Australian lizard Ctenotus pantherinus based on morphological, mitochondrial and genome-wide nuclear variation. We find weak and inconsistent correspondence between morphological patterns and the presumed subspecies ranges, with character polymorphism within regions and broad morphological overlap across regions. Phylogenetic analyses suggest paraphyly of populations assignable to each subspecies, mitonuclear discordance and little congruence between subspecies ranges and the distribution of inferred clades. Genotypic clustering supports admixture across regions. These results undermine the presumed phenotypic and genotypic coherence and distinctiveness of C. pantherinus subspecies. Based on our findings, we comment on the operational and conceptual shortcomings of morphologically defined subspecies and discuss practical challenges in applying the general notion of subspecies as incompletely separated population lineages. We conclude by highlighting a historical asymmetry that has implications for ecology, evolution and conservation: subspecies proposed in the past are difficult to falsify even in the face of new data that challenge their coherence and distinctiveness, whereas modern researchers appear hesitant to propose new subspecies.
Conservation efforts rely on robust taxonomic assessments that should be based on critical assessment of interspecific boundaries, infraspecific variation, and potentially distinctive peripheral populations. The meadow vole (Microtus pennsylvanicus) is widely distributed across North America, including 28 morphologically defined subspecies and numerous isolated populations. Because some subspecies are of high conservation concern, we examined geographic variation across the range of the species to test existing infraspecific taxonomy in terms of local and regional diversification. We sequenced mitochondrial DNA (mtDNA) from 20 subspecies of M. pennsylvanicus and contextualized infraspecific variation through comparison of pairwise genetic distances derived from an extended data set of 63 species of Microtus. We found strong support for at least three divergent clades within M. pennsylvanicus, with observed intraspecific clade divergence exceeding that between several pairwise comparisons of sister species within Microtus. Six nuclear genes were then sequenced to test the validity of mtDNA structure and to further evaluate the possibility of cryptic, species-level diversity using Bayes factor species delimitation (BFD) analyses. BFD consistently and decisively supported multiple species based on the multilocus approach. We propose that taxonomic revision of the meadow vole is required, with the eastern clade now identified as M. pennsylvanicus (Ord 1815), more »
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- Journal of Mammalogy
- Oxford University Press
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- National Science Foundation
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Subspecies at crossroads: the evolutionary significance of genomic and phenotypic variation in a wide-ranging Australian lizard ( Ctenotus pantherinus )
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