Abstract:
Previous studies of African mole-rats of the genera Heliophobius and Fukomys (Bathyergidae)
in the regions of East and south central Africa have revealed a diversity of
species and vicariant populations, with patterns of distribution having been influenced
by the geological process of rifting and changing patterns of drainage of major river
systems. This has resulted in most of the extant members of the genus Fukomys being
distributed west of the main Rift Valley. However, a small number of isolated populations
are known to occur east of the African Rift Valley in Tanzania, where Heliophobius
is the most common bathyergid rodent. We conducted morphological, craniometric
and phylogenetic analysis of mitochondrial cytochrome b (cyt b) sequences of two
allopatric populations of Tanzanian mole-rats (genus Fukomys) at Ujiji and around
Mount Hanang, in comparison with both geographically adjacent and more distant
populations of Fukomys. Our results reveal two distinct evolutionary lineages, forming
clades that constitute previously unnamed species. Here, we formally describe and
designate these new species F. livingstoni and F. hanangensis respectively. Molecular
clock-based estimates of divergence times, together with maximum likelihood inference
of biogeographic range evolution, offers strong support for the hypothesis that vicariance
in the Western Rift Valley and the drainage patterns of major river systems has
subdivided populations of mole-rats. More recent climatic changes and tectonic activity
in the ``Mbeya triple junction'' and Rungwe volcanic province between Lakes Rukwa
and Nyasa have played a role in further isolation of these extra-limital populations of
Fukomys in Tanzania.
