Mitochondrial DNA Variation and the Phylogeny of African Mole Rats (Rodentia: Bathyergidae)

Abstract

Patterns of mitochondrial DNA (mtDNA) variation were evaluated within and between six species in the five genera of the endemic African mole rats in the family Bathyergidae. A total of 493 distinct restriction fragments was produced by digestion of bathyergid mtDNAs with 15 restriction enzymes. Of these fragments, 126 provided phylogenetic information. The magnitude of mtDNA sequence divergence among the five genera of bathyergids indicates an ancient origin and agrees with levels of nuclear sequence divergence estimated from allozymes. Two sister groups, Georychus/Heliophobius and Cryptomys/Heterocephalus, are apparent based on phylogenetic analyses of the mtDNA data. Although the two species of Bathyergus are closely aligned, this genus is very divergent from the other four genera and is associated with either the Georychus/Heliophobius group or represents a more basal lineage. Two isolated populations of Georychus capensis are as divergent from one another as the genus Heliophobius is from Georychus. mtDNA, allozyme, and chromosomal variation among the three subspecies of Cryptomys hottentotus suggests that C. h. damarensis should be raised to specific rank. The phylogenetic relationships suggested by the mtDNA variation are used to evaluate two aspects of bathyergid evolution. First, the current distribution of bathyergids may be the result of range expansions and vicariant events related to increasing aridity along a corridor between east and southern Africa during past geological time. Second, the sister group relationship of Heterocephalus and Cryptomys suggests that the common ancestor of the eusocial species, Heterocephalus glaber was possibly colonial rather than solitary.