[Brno, 24th of January 2023] – The breakthrough study, led by Czech scientists, has revealed how biological diversity originated in one of the world’s most significant biodiversity centres. The most extensive genetic study of African small insectivores, shrews, published in the Journal of Biogeography, unveiled secrets related to the origin, spreading patterns, and unusual diversification of mountain mammals in sub-Saharan Africa.
The East Afromontane Biodiversity Hotspot is known for its unique ecological features and enormous biological diversity, stretching from Saudi Arabia and Yemen to Mozambique and Zimbabwe. The largest part of this range is formed by the Ethiopian Highlands. It has provided a stable refuge for mountain flora and fauna during climatic fluctuations over the last 30 million years. In contrast, many mountains south of Ethiopia, including isolated volcanoes like Mount Kilimanjaro, were formed relatively recently during the Pleistocene (about 2 million years). The unique diversity of mountain fauna and flora in East Africa results from the complex geomorphology of the East African Rift and the influence of climate changes over the past few million years.
Given the area’s size and stability, it might be expected that the extensive Ethiopian Highlands would host the highest biological diversity. However, the highest numbers of formally described species were found in former British colonies, such as the mountains of Uganda or Kenya, where British taxonomists were active in the early 20th century. Evolutionary studies based on biological patterns from the entire area have been lacking until now.
In the recently published work, scientists focused on shrews, small insectivorous mammals with over 220 described species, making them the most species-rich mammal genus globally. Half of these species are found in Africa. Biologists from the Institute of Vertebrate Biology of the Czech Academy of Sciences (IVB CAS) and Masaryk University, along with colleagues from other countries, gathered genetic data from 511 shrew samples from across the East Afromontane Biodiversity Hotspot. It is the most extensive genetic dataset on African insectivores to date.
“Based on genomic analyses, we revealed six distinct evolutionary groups. Five of them were endemic to the Ethiopian Highlands, meaning that this was the place where the initial diversification of these shrews occurred. Subsequently, during two migration waves, they spread to other areas in Africa,” explains Josef Bryja, the head of the mammalian evolutionary genetics research group at IVB CAS. He continues, “Our analyses unveiled several new species in the Ethiopian Highlands, Kenya, and Uganda. Some of them, with a size of less than 5 cm and a weight of 3 grams, are among the smallest mammals globally. On the other hand, we proposed the synonymization of several species that are essentially not genetically different. This will now allow us to assess better the level of biological diversity in different areas of sub-Saharan Africa. Moreover, many species of insectivores can host dangerous pathogens, so the obtained data might have epidemiological consequences.”
“Our results clarify how geomorphology and climate changes influenced the spread and diversification of these small mammals. Climate cooling led to the expansion of mountain forests from higher altitudes to lowlands, enabling connections between mountain ranges that were previously separated by dry ecosystems like deserts. Through shrews and their kinship relationships, we can observe that species living in the mountains were able to descend to lower altitudes and also overcome extensive areas that are now uninhabitable for them,” adds Malahat Dianat, a Ph.D. student at the Department of Botany and Zoology at Masaryk University and the first author of the study.
However, our story does not end with shrews. The insights from the study apply to other organisms in this unique area. “Countless species of plants and animals are waiting to have their stories revealed. We have unequivocally demonstrated that evolutionary diversity in the Ethiopian Highlands is far higher than elsewhere in East Africa. Unfortunately, one of the fastest-growing human populations in the world lives here, irreversibly damaging the exceptional nature, leading to the extinction of many species, some of which we probably haven’t even described yet,” concludes Malahat Dianat.
DOI: DOI: 10.1111/jbi.14748