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Genomic distinctness despite shared color patterns among threatened populations of a tiger beetle

Citation

French, Rowan et al. (2021), Genomic distinctness despite shared color patterns among threatened populations of a tiger beetle, Dryad, Dataset, https://doi.org/10.5061/dryad.k6djh9w5t

Abstract

Conservation biologists have long debated the value of subspecies, which are morphologically and geographically identifiable but not necessarily evolutionarily distinctive. One example of a controversial subspecies is Cicindela formosa gibsoni, a tiger beetle that is nationally listed as threatened in Canada and whose taxonomic status is based primarily on its unique elytral (forewing) color pattern. To determine whether C. f. gibsoni represents one or more genetically distinctive units, we sampled 14 populations within or near this subspecies’ disjunct North American range and assessed their genetic differentiation from neighboring and phenotypically distinctive populations of C. f. formosa and C. f. fletcheri. Instead of clustering by color pattern, analyses of mitochondrial and nuclear markers recovered three geographically structured genetic groupings: a northern cluster from Canada, a southwestern cluster from northwestern Colorado, and a southeastern cluster of US populations east of the Continental Divide. These data, coupled with previously documented differences in larval morphology, suggest that populations of C. formosa in western Canada and northwestern Colorado may have independently evolved similar color patterns. Thus, we consider C. f. gibsoni to be endemic to Canada and describe the novel subspecies C. f. gaumeri ssp. nov. from northwestern Colorado. Both subspecies are evolutionarily significant units, and each deserves consideration for conservation listing. Collectively, our results reveal general congruence between mitochondrial and nuclear genetic data but conflict with color pattern, the conventional basis for subspecies designations in tiger beetles.

Funding

Natural Sciences and Engineering Research Council of Canada, Award: RGPIN-2018-04920

Natural Sciences and Engineering Research Council of Canada, Award: USRA-540997-2019