Abstract
East African mountains constitute a network of isolated habitat islands among dry savannah and are thus ideal for studying species diversification processes. This study elucidated the phylogenetic and phylogeographic relationships of all bushcricket species comprising the genus Aerotegmina. Our analysis indicated that large-scale climatic and topographic processes in Africa are likely to have driven speciation in this group, and revealed the cytogenetic traits of the species. Molecular phylogeny supported the monophyly of Aerotegmina and showed that the genus probably originated in the old Eastern Arc Mountains of Tanzania and Kenya. Two lineages were distinguished: small- and large-sized species with geographically distinct habitats. The underlying processes are thought to be eight dispersals, ten vicariance events, and one extinction event linked to repeated fragmentation of the African rainforest. Those processes, in conjunction with habitat change, probably also led to the spatial separation of the species into a northern clade with a diploid number of chromosomes 2n = 32 + X0 or 2n = 30 + neo-XY and a southern clade with a reduced number of chromosomes (2n = 28 + X0 or 24 + neo-X1X2Y). Karyotype analysis suggests that Aerotegmina is currently in the process of speciation.
Highlights
Tropical montane rainforests are hotspots of species richness and offer diverse habitats for many endemic taxa[1,2]
We provide comprehensive information on the molecular phylogeny and cytogenetics of this genus and discuss the ecological processes leading to species diversification and the current biogeography of the group
Three molecular markers were used for reconstructing the interspecific relationships of Aerotegmina: cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S), and histone 3 (H3), which have proved useful in previous studies of closely related groups of East African bushcrickets (e.g.,14–16,28,29)
Summary
Tropical montane rainforests are hotspots of species richness and offer diverse habitats for many endemic taxa[1,2]. It has been suggested that the climate changes of the past one to three million y ears[13] enhanced speciation in East Africa, as seen in various genera with arrays of morphologically and molecularly closely related species, e.g., in the subtribe Karniellina (subfamily: Conocephalinae14–16), the genus Peronura (subfamily: P haneropterinae17), the genus Parepistaurus (subfamily: Coptacridinae18), and the family Lentulidae[19,20]. Most inland mountains, such as Mt. Kilimanjaro, adjacent to the geologically old northern branch of the Eastern Arc Mountains, can serve as time markers since their geological age is known.
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