African shrews endemic to the Albertine Rift: two new species of Myosorex (Mammalia: Soricidae) from Burundi and the Democratic Republic of Congo.

Abstract

The genus Myosorex has a classic relict distribution within sub-Saharan Africa. Montane populations in eastern and western equatorial Africa are separated by ca. 2900 km. Until this study, the closest known populations in southern Africa were separated by nearly 2000 km from the closest populations in the Albertine Rift Valley. Here we document previously unknown populations of Myosorex, representing two new endemic taxa from montane forests adjacent to the Albertine Rift. In conjunction with additional data from Malawi, we fill in major gaps in our knowledge of the biodiversity and distribution of this genus in the areas of the Albertine and Malawi Rift Valleys. We demonstrate that this gap is an artefact of survey effort and collecting serendipity. The two new species described herein, as well as other species of Myosorex from north of the Zambezi River, exhibit limited distributions and are confined to montane habitats, typically above 1000 m. Our new species of Myosorex from Kahuzi-Biega NP (DRC) is the second known species of Myosorex from that park where it is syntopic with Myosorex babaulti. This is the first time that two species of Myosorex co-occur in any forest north of the Zambezi River. This suggests either sympatric speciation or a secondary re-invasion during times of climatic amelioration and forest expansion. The two species described here (Myosorex jejei and Myosorex bururiensis) are associated with two phenetically-defined species groups: the former with a more narrow hexagon-shaped skull, long-tail, and short claws (‘narrow-headed group’) and the latter with a more broad hexagon-shaped skull, short tail and long claws (‘broad-headed group’).

Keywords: African shrews; Myosorex; Albertine Rift; endemism; evolution; biogeography; Bururi Forest; Kahuzi-Biega National Park; conservation.