Cg. Faulkes et al., ECOLOGICAL CONSTRAINTS DRIVE SOCIAL EVOLUTION IN THE AFRICAN MOLE-RATS, Proceedings - Royal Society. Biological Sciences, 264(1388), 1997, pp. 1619-1627
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.