Evolution in the dark: A study of cave crickets in Southern Appalachia
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In 1978 Hubbell and Norton described nine species of crickets in the Tribe Hadenoecini found in caves or forest litter in the Southern Appalachians. According to the model proposed by these authors new species formed during glaciation. Hubbell and Norton (1978) suggested that the crickets are thermophile relicts that dispersed in the area before and after glaciation but, during glaciation, formed new species in allopatric refugia of caves or forests south of their normal ranges. Our mitochondrial DNA sequence data—the first obtained for members of this group--tested several hypotheses: 1) The Tribe Hadenoecini is a monophyletic clade when compared with outgroups from their sister Tribe Dolocopodini, 2) The two genera Euhadenoecus and Hadenoecus are both monophyletic, 3) The forest Euhadenoecus and the trogloxenic Euhadenoecus are each monophyletic, 4) The two trogloxenes from Kentucky form a single clade, and the three most cave-adapted trogloxenes in Tennessee form a single clade. Our preliminary results support all four of these hypotheses. Our data, however, suggest that the divergence between the two genera and between the two clades of Hadenoecus occurred well before the Pleistocene and that only speciation within the two Hadenoecus clades occurred in the mid to late Pleistocene as suggested by Hubbell and Norton (1978).
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