Going underground is not an evolutionary dead end - at least in the Pyrenees

Abstract

The high degree of specialization of cave organisms, with extreme morphological and physiological modifications, has attracted the attention of naturalists and evolutionary biologist for more than two centuries. The common assumption is that the lost of eyes and wings and the lack of regulatory mechanisms to avoid dehydration typical of cave organisms confine them to the deep subterranean environment, in an evolutionary dead end with extinction as the only possible outcome. Recent work on two Pyrenean groups of subterranean beetles (Trechini and Leptodirini) suggests that, far from being a dead end, the colonization of the subterranean environment may represent an opportunity for diversification. We illustrate this with two examples drawn from our recent work: In the first, a genus deeply nested within a clade of exclusively subterranean species is shown to have expanded its range from the Pyrenees to colonize some karstic areas of the Catalonian coast, and subsequently radiate in them. In the second, we found that one of the most extreme adaptations of subterranean insects, the contraction of the life cycle with the development of a large, single instar non-feeding larva had a unique origin dating back to early Miocene. This implies that diversification occurred after the development of this specialization - and at a higher rate that that of the non-modified lineages that retained the ancestral state of an active larvae with several instars.