Desert spring refugia: museums of diversity or evolutionary cradles?

Abstract

Refugia play a critical role in preserving species unable to move or adapt to cope with environmental change. The role of refugia as ‘museums of diversity’ means these environments have a high conservation priority. Less well known, however, is the role that isolated and fragmented refugia can play in the generation of new diversity. Here, we examined the diversification and evolutionary history of a community of endemic invertebrates that inhabit Australian desert spring refugia. We compared the phylogenies of seven endemic groups (Haloniscus and Phreatomerus isopods, chiltoniid amphipods, Ngarawa ostracods, Trochidrobia and Fonscochlea snails and Gymnochthebius beetles) from these springs and examine the rates and timing of diversification and reconstructed the phylogeographic history of each taxon. Despite major life-history differences among these taxa, they demonstrate remarkable similarities in their evolutionary histories. All groups have multiple lineages that extend back to a time before the formation of present-day deserts, and significant geographic-based diversification since adapting to a refugial habitat. The results provide further evidence that refugia act as museums of biodiversity, preserving lineages that would have otherwise gone extinct. However, we also observed that isolation in refugia corresponds with significant diversification, leading to a recently evolved, novel endemic fauna, supporting the idea that fragmented refugia provide ideal conditions for the generation of future biodiversity hotspots.