ECOLOGICAL CONSTRAINTS DRIVE SOCIAL EVOLUTION IN THE AFRICAN MOLE-RATS

The African mole-rats (family Bathyergidae) are subterranean hystricom orph rodents occurring in a variety of habitats and displaying levels of sociality which range from solitary to eusocial, making them a uniq ue mammalian taxonomic group to test ecological influences on socialit y Here, we use an extensive DNA-based phylogeny and comparative analys is to investigate the relationship between ecology sociality and evolu tion within the family. Mitochondrial cytochrome-b and 12s rRNA trees reveal that the solitary species are monophyletic when compared to the social species. The naked mole-rat (Heterocephalus glaber) is ancestr al and divergent from the Damaraland mole-rat (Cryptomys damarensis), supporting previous findings that have suggested the multiple evolutio n of eusociality within the family. The Cryptomys genus is species-ric h and contains taxa exhibiting different levels of sociality, which ca n be divided into two distinct clades. A total of seven independent co mparisons were generated within the phylogeny, and three ecological va riables were significantly correlated with social group size: geophyte density (p <0.05), mean months per year of rainfall greater than 25 m m (p < 0.001), and the coefficient of rainfall variation (p = 0.001). These results support the food-aridity hypothesis for the evolution of highly social cooperative behaviour in the Bathyergidae, and are cons istent with the current theoretical framework for skew theory.