Climatic fluctuations and orogenesis as motors for speciation in E ast A frica: case study on Parepistaurus K arsch, 1896 ( O rthoptera)

Mechanisms of speciation of flightless grasshoppers in mountainous and coastal E ast A frica are inferred considering (i) phylogenies estimated with a combination of molecular markers ( 16S rRNA locus, COI and H 3 ), (ii) ecological data and (iii) the geographic distribution of Parepistaurus species. The study suggests that coastal taxa of Parepistaurus belong to ancestral lineages from which evolved the high diversity of species found in the E astern A rc M ountains of T anzania and K enya, which are geologically ancient mountain formations. Network analyses and a molecular clock approach, calibrated with the geological age of the volcanoes, suggested that speciation was boosted by climatic fluctuations affecting large areas of E ast A frica. With the aridification beginning 2.8 Ma, forest taxa were isolated due to forest fragmentation and populations were separated by extended grasslands, which are avoided by Parepistaurus species. However, a humid period between 2.7 and 2.5 Ma triggered a spread of coastal taxa along the E astern A rc M ountains. Forests expanded again and riparian vegetation along rivers draining into the I ndian O cean probably served as corridors for the dispersal of coastal taxa to the hinterland. The inland volcanoes such as M ount K ilimanjaro are therefore good time markers because their geological age is known, limiting the available time for speciation processes of mountainous Parepistaurus in the area to a maximum of about 1–2 Ma. A third humid but cold period between 1.1 and 0.9 Ma probably further boosted the spread of several flightless and montane‐adapted O rthoptera taxa.