The phylogenetic relationships within the Eastern Afromontane clade of Crocidura based on mitochondrial and nuclear data

Eastern Afromontane region is a well-known hotspot of biodiversity and endemism; however, the relationships between groups of organisms inhabiting different highland areas are still poorly understood. Herein, the phylogenetic relationship between endemic Crocidura from Ethiopia and Tanzania was assessed using mitochondrial and nuclear data. At the genus scale, all analyses supported the monophyly of the Eastern Afromontane clade. Within this clade, most of the Ethiopian endemics form a group, which is paraphyletic relative to a more compact Tanzanian clade. The Ethiopian C. macmillani was found to be closely related to Tanzanian species. In fact, according to the mitochondrial DNA data, it may be a descendant of the C. montis–C. luna clade. The molecular dating results suggest that the Ethiopian–Tanzanian clade diverged at ca. 3.4 Mya while the onset of radiation within the clade corresponds to Early Pleistocene (ca. 2 Mya). The inferred phylogenetic pattern is consistent with the scenario that has Ethiopia as the primary centre of diversification for the Eastern Afromontane clade. The areas southwards from Ethiopia were found to be colonized through a single dispersal event at 1.3–0.7 Mya; the distribution of C. macmillani might be explained by a secondary re-colonization of Ethiopia. Collectively, the nuclear and mitochondrial data revealed a low divergence between morphologically distinct and elevationally parapatric C. thalia and C. glassi, thereby aligning with the gradient model of speciation.