The Ethiopian Highlands are a vast mountain range with many potential ecological niches, characterized by a high level of endemism among small mammals. Ethiopian endemics include 12 species of shrews of the genus Crocidura, represented exclusively by forest or alpine forms. This number of endemic species clearly demonstrates that the Ethiopian Highlands is an important center of species diversity and adaptive radiation for this genus. However, the currently available molecular genetic data on the relation of endemic Ethiopian species to each other, as well as with a similar endemic group from Tanzania, are limited by a small number of studied species, small sample sizes, and the lack of studies based on nuclear gene sequences.
The staff of the Laboratory of Microevolution of Mammals of the A.N.Severtsov IEE RAS together with colleagues from the M.V. Lomonosov Moscow State University have carried out a phylogenetic analysis of an extended set of species of this genus and an assessment of the times of divergence between the main clades. The obtained phylogenetic patterns made it possible to propose an evolutionary scenario according to which the Ethiopian Highlands is the primary center of diversification for the Ethiopian-Tanzanian shrew clade. The territories south of the Ethiopian Highlands were probably settled by members of this group as a result of a single colonization event (1.3–0.7 Ma).
The modern distribution of C. macmillani can be explained by the secondary re-colonization of the Ethiopian highlands. The results of the analysis of mitochondrial and nuclear markers made it possible to confirm the previously put forward assumption that the features of the divergence process between the sister taxa C. thalia and C. glassi correspond to the predictions of the gradient (ecological) speciation model based on the possibility of diversification of forms (without interrupting the gene flow between them) until they reach species status due to different directions of selection on a pronounced gradient of natural conditions.
Original publication:
Bannikova A.A., Zemlemerova E.D., Lebedev V.S., Lavrenchenko L.A., 2021. The phylogenetic relationships within the Eastern Afromontane clade of Crocidura based on mitochondrial and nuclear data. Mammalian Biology, 101(6): 1005–1018. https://doi.org/10.1007/s42991-021-00120-7
Link to article: https://link.springer.com/article/10.1007%2Fs42991-021-00120-7