Cytochrome b sequence analysis reveals differential molecular evolution in African mole-rats of the chromosomally hyperdiverse genus Fukomys (Bathyergidae, Rodentia) from the Zambezian region

Abstract

African mole-rats (Bathyergidae, Rodentia) of the (eu)social genus Fukomys are one of the most speciose mammal genera endemic to Sub-Saharan Africa. Fukomys distributed in the Zambezian phytochorion is characterized by extreme chromosomal variation (2n = 40-78). We inferred a molecular phylogeny of Zambezian Fukomys to resolve the interrelationships and the evolutionary history of the known chromosomal races. We sequenced the entire cytochrome b gene (1140 bp) for a total of 66 specimens representing 18 karyotypical races from Zambia. An additional 31 sequences were retrieved from GenBank including data on all other chromosomal races. The haplotypes belonging to a small chromosomal race from Salujinga cluster with the Fukomys mechowii (Giant mole-rat) haplotypes. Differential degrees of chromosomal variation are observed among the major mole-rat clades, which is most pertinent when comparing the central Zambezian Fukomys micklemi and the northern Zambezian Fukomys whytei clades. The karyotypically hyper-diverse (12 known chromosomal races) Fukomys micklemi clade shows low levels of cytochrome b sequence divergence. Within the F. whytei clade we find a more conservative pattern of chromosomal diversification (three known chromosomal races) while the levels of sequence divergence are much higher then in the F. micklemi clade. Our results suggest that chromosomal changes may drive phyletic divergence and, eventually, speciation. The observed cladogenetic events during the Plio-Pleistocene within the F. mechowii, F. whytei, F. damarensis and F. micklemi clades appear to coincide with climatically mediated speciation bursts in other savannah dwelling mammals, including hominids. Based on the molecular data presented, combined with morphological and chromosomal data, the taxonomic implication seems to be that Fukomys may contain several (undescribed) cryptic species.

Chromosomal phylogeny and evolution of the African mole-rats (Bathyergidae)

“…The coding of adjacent syntenies with no mention of centromeres (strategy (i) in Material and Methods) or the coding of adjacent syntenies and centromere positions in two different characters (strategy (ii) in Material and Methods) both resulted in a single tree that failed to retrieve Fukomys monophyly (not shown). This is in marked contrast to the strong support for this clade by DNA sequences (Faulkes et al 2004, Ingram et al 2004, Van Daele et al 2007b. Moreover, we note that strategy (ii) tends to introduce over-weighting of characters since where a centromere position disrupts an adjacent synteny it is coded 1 and the synteny is also coded 1 (i.e., the centromere cannot be present without the adjacent synteny being present as well).…”

African Mole-rats (Bathyergidae): A Complex Radiation in Tropical Soils

“…Preliminary data obtained from a geometric morphometrical analysis of the ventral side of the cranium of a number of closely related chromosomal races belonging to the F. micklemi phylogroup suggest that during raciation small localized shape changes (shape changes of so-called non-uniform origin; Zelditch et al 2004) could modify the integration of structures with shifts in functionality. As expected, these shape changes do not seem to follow the cladogenetic sequence of events as depicted by a cyt b phylogeny (Van Daele et al 2006). This fact could be further exploited to understand how either plastic responses to immediate ecological conditions (cf.…”

Plasticity and constraints on social evolution in African mole-rats: ultimate and proximate factors

“…(b-d) Represent alternative hypotheses for convergent gains and losses in solitarity/sociality, dependent on the status of the common ancestor of the family: (b) with a solitary common ancestor, sociality arises independently twice in Heterocephalus and the common ancestor of Fukomys/Cryptomys, with further elaboration to eusociality in extant H. glaber and F. damarensis; with a social common ancestor, either sociality is lost in the common ancestor of Heliophobius and descendent lineages to re-emerge in Fukomys/Cryptomys (c), or retained in common ancestors with loss and the evolution of a solitary lifestyle in lineages leading to Heliophobius, Bathyergus and Georychus (d ). Other, less parsimonious explanations are also possible (data adapted from earlier studies [3][4][5][6][7][8]). …”