Long-term climatic stability drives accumulation and maintenance of divergent lineages in a temperate biodiversity hotspot

Abstract

AbstractAimAnthropogenic climate change is forecast to drive regional climate disruption and instability across the globe. This issue is likely to be exacerbated within biodiversity hotspots, both due to the greater potential for species loss but also to the possibility that endemic lineages might not have experienced significant climatic variation in the past, limiting their evolutionary potential to respond to rapid climate change. We assessed the role of climatic stability on the accumulation and persistence of lineages in an obligate freshwater fish group endemic to a biodiversity hotspot.LocationSouthwest Western Australia (SWWA).TaxaWestern pygmy perch (Nannoperca vittata) and little pygmy perch (Nannoperca pygmaea).MethodsWe sampled 33 individuals from nine populations spanning the range of both study taxa to explore their phylogeographic history. Using a combination of genomic (ddRAD-seq) and environmental approaches, we investigated population divergence and phylogenetic relationships, delimited species and estimated changes in species distributions since the Pliocene.ResultsWe identified two deep phylogroups comprising three divergent clusters, which showed no historical connectivity since the Pliocene. We conservatively suggest these represent three isolated species with additional intraspecific structure within one widespread species. All lineages showed long-term patterns of isolation and persistence owing to climatic stability.Main conclusionsOur results highlighted the role of climatic stability in allowing the persistence of isolated lineages in the SWWA. This biodiversity hotspot is under compounding threat from ongoing climate change and habitat modification, which may further threaten previously undetected cryptic diversity across the region.