Relic populations ofFukomysmole-rats in Tanzania: description of two new speciesF. livingstonisp. nov. andF. hanangensissp. nov.

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.

Phylogeny and biogeography of the African Bathyergidae: a review of patterns and processes

“…Divergence between Cryptomys and Fukomys follows the Zambezian and the Kalahari-Highveld phytochoria and was likely driven by the pattern of flow of the paleo-Zambezi River (the upper Zambezi River was linked to the Orange- or Limpopo Rivers; Thomas & Shaw, 1988). This flow pattern isolated ancestors of the two genera, with Cryptomys radiating southward while Fukomys spread north and west to attain a large distribution in south-central and West Africa (also see Ingram, Burda & Honeycutt, 2004; Faulkes et al, 2017).…”

“…The early divergence of the East African Heterocephalus and Heliophobius appears independent of rifting (also see Faulkes et al, 2017), while the divergence between the two generic complexes of Georychus / Bathyergus and Cryptomys / Fukomys may have followed the spatial separation of a common ancestor via different routes of dispersal from East Africa. Within the Georychus / Bathyergus complex, a widespread common ancestor likely diverged parapatrically, with Georychus evolving in the South African interior and Bathyergus diverging within sandy areas of south and south-western South Africa.…”

“…Fukomys includes a divergent and widespread collection of distinct genetic lineages (also see Faulkes et al, 1997, 2004, 2017; Ingram, Burda & Honeycutt, 2004; Van Daele et al, 2007b; Deuve et al, 2008) consisting of several species complexes of various evolutionary ages and with various degrees of divergence (Fig. 6; also see Van Daele et al, 2007b; Faulkes et al, 2017). The evolutionary progression within this groups suggests a West African origin, with subsequent migrations to the east and south (Fig.…”

“…Because of their eusocial nature (relatively uncommon amongst mammals), Heterocephalus and Fukomys have received much attention (Bennett & Jarvis, 1988; Nevo & Reig, 1990; Sherman, Jarvis & Alexander, 1991; Jarvis & Bennett, 1993; Nevo, 1999; Bennett & Faulkes, 2000; Lacey, Patton & Cameron, 2000; Faulkes & Bennett, 2007, 2009), leaving the other genera largely under-investigated by comparison (but see Honeycutt et al, 1987; Allard & Honeycutt, 1992; Faulkes et al, 1997; Walton, Nedbal & Honeycutt, 2000; Huchon & Douzery, 2001). Recent systematic/phylogeographic studies have hinted that diversity within the family is notably under-represented (Faulkes et al, 2004; Ingram, Burda & Honeycutt, 2004; Visser, Bennett & Jansen van Vuuren, 2014, 2018, 2019) and as a result, several species have recently been described (Honeycutt et al, 1991; Aguilar, 1993; Macholan et al, 1998; Burda et al, 1999; Chitaukali, Burda & Kock, 2001; Gippoliti & Amori, 2011; Van Daele et al, 2013; Faulkes et al, 2017), with further suggestions of possibly undescribed species in Heliophobius (Faulkes et al, 2011), Georychus , Bathyergus and Cryptomys (Visser, Bennett & Jansen van Vuuren, 2019).…”

“…Given the spate of phylogeographic investigations across wide geographic areas (Faulkes et al, 2004, 2011, 2017; Van Daele et al, 2007b; Visser, Bennett & Jansen van Vuuren, 2014, 2018, 2019), sufficient information now exist to synthesize a comprehensive systematic and biogeographic review for the Bathyergidae based on comprehensive geographic coverage and including all the bathyergid genera. In doing so, we construct a comprehensive phylogeny for the group to review genealogical relationships and timing of diversification events, and identify and review biogeographic patterns and broad historical processes driving speciation.…”