Diversification in Caucasian Epeorus (Caucasiron) mayflies (Ephemeroptera: Heptageniidae) follows topographic deformation along the Greater Caucasus range

Abstract

The evolution and distribution of mountain biota are closely linked with mountain formation and topographic complexity. Here we explore the diversification of cold‐tolerant mayflies of the subgenus Epeorus (Caucasiron) in the south‐eastern Greater Caucasus, an area of dynamic changes in topography since the Miocene, driven by the convergence of the Greater and Lesser Caucasus. We hypothesized that orogenic processes promoted the diversification of E. (Caucasiron) and that the resultant diversification pattern followed the timing and progress of mountain formation along the range. A new evolutionary lineage of E. (Caucasiron) distributed in the central‐eastern Greater Caucasus was found and described as Epeorus (Caucasiron) tripertitus sp.n. It consists of three clades clearly differentiated based on mitochondrial sequence data, but indistinguishable by morphological traits. Based on a time‐calibrated phylogeny using mitochondrial (COI, 16S) and nuclear (EF, wg, 28S) markers, we found that a gradual allopatric diversification of the ancestral population of E. (C.) tripertitus sp.n. dated to a period lasting from the late Miocene to the Pleistocene spread eastward along the range. This pattern corresponded with the process of topographic deformation which started in the central part of the range in the Miocene and progressed to the east during the Pliocene/Pleistocene. The results implied the dominant role of mountain building on the biotic diversification of this region and continuing recent speciation in the south‐eastern part of the mountains.