Abstract:
During their evolutionary radiation, mammals have colonized diverse habitats. Arguably the subterranean niche is the
most inhospitable of these, characterized by reduced oxygen, elevated carbon dioxide, absence of light, scarcity of food,
and a substrate that is energetically costly to burrow through. Of all lineages to have transitioned to a subterranean niche,
African mole-rats are one of the most successful. Much of their ecological success can be attributed to a diet of plant
storage organs, which has allowed them to colonize climatically varied habitats across sub-Saharan Africa, and has
probably contributed to the evolution of their diverse social systems. Yet despite their many remarkable phenotypic
specializations, little is known about molecular adaptations underlying these traits. To address this, we sequenced the
transcriptomes of seven mole-rat taxa, including three solitary species, and combined new sequences with existing
genomic data sets. Alignments of more than 13,000 protein-coding genes encompassed, for the first time, all six
genera and the full spectrum of ecological and social variation in the clade. We detected positive selection within the
mole-rat clade and along ancestral branches in approximately 700 genes including loci associated with tumorigenesis,
aging, morphological development, and sociality. By combining these results with gene ontology annotation and
protein–protein networks, we identified several clusters of functionally related genes. This family wide analysis of molecular
evolution in mole-rats has identified a suite of positively selected genes, deepening our understanding of the
extreme phenotypic traits exhibited by this group.
