Molecular phylogeography of the troglobiotic millipede Tetracion Hoffman, 1956 (Diplopoda, Callipodida, Abacionidae)
2011
Loria, Stephanie F. | Zigler, Kirk S. | Lewis, Julian J.
More than 85 species of cave-obligate (troglobiotic) millipede have been described from North America. Understanding the patterns and processes that determine their distribution in this region is an area of recent research. Here, we present the first molecular phylogeographic study of troglobiotic millipedes. Millipedes of the genus Tetracion Hoffman, 1956 (Callipodida: Abacionidae) inhabit caves on the Cumberland Plateau in Tennessee and Alabama, a global hotspot for cave biodiversity. Three species have been described: Tetracion jonesi Hoffman, 1956, Tetracion antraeum Hoffman, 1956, and Tetracion tennesseensis Causey, 1959. To examine genetic divergence within and between species of Tetracion we sequenced part of the mitochondrial cytochrome oxidase 1 gene from 53 individuals from eleven caves across the range of Tetracion tennesseensis and in the northern part of the range of Tetracion jonesi. We found: (1) little variation within species (six haplotypes in Tetracion tennesseensis and four haplotypes in Tetracion jonesi, with a maximum of 1.4% intraspecific divergence between haplotypes), (2) that gene flow between caves is limited (7 of 10 haplotypes were restricted to a single cave, and FSᵀ > 0.80 and P < 0.05 for fifteen of eighteen comparisons between caves), and (3) significant genetic divergence between species (8.8% between Tetracion tennesseensis and Tetracion jonesi). Our results are consistent with previous morphology-based species definitions showing Tetracion tennesseensis and Tetracion jonesi belonging to distinct taxa. Our research contributes to the growing body of phylogeographic information about cave species on the Cumberland Plateau, and provides a point of comparison for future studies of troglobionts and millipedes.
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