Cold‐adapted species are likely to have had more widespread ranges and greater population connectivity during the last glacial period than is the case today. This contrasts with the trend in many species for range and population size to increase during interglacials. We examined the pattern of genetic and morphological variation within an endemic, wingless, alpine grasshopper Sigaus australis (Orthoptera: Acrididae) in the Southern Alps of New Zealand, testing for isolation by distance using geometric morphometric and mitochondrial ND2 sequences to document variation. Presence/absence data were analysed to estimate the environmental envelope (niche) of Sigaus australis and the resulting model used to infer the extent of available habitat for the species during the last glacial maximum. Estimates of past range size were modified using models of montane ice extent during the LGM. Clinal patterns of pronotum shape variation and signatures of isolation by distance support the hypothesis of a formerly more connected species. A north/south division was observed in pronotum shape, but the phenotypic variation was not diagnostic, as one would expect within a single species. Although the current habitat area occupied by Sigaus australis is much smaller than estimates for the LGM from our climate model, we show that realised area differed less due to the extension of valley glaciers. However, the current distribution of S. australis is more fragmented than in the past. This and other flightless alpine species currently restricted to fragmented high elevation habitat demonstrate genetic lag but are subject to loss of diversity as anthropogenic climate warming proceeds.

Major aridification events in Australia during the Pliocene may have had significant impact on the distribution and structure of widespread species. To explore the potential impact of Pliocene and Pleistocene climate oscillations, we estimated the timing of population fragmentation and past connectivity of the currently isolated but morphologically similar subspecies of the widespread brushtail possum ( Trichosurus vulpecula ). We use ecological niche modeling (ENM) with the current fragmented distribution of brushtail possums to estimate the environmental envelope of this marsupial. We projected the ENM on models of past climatic conditions in Australia to infer the potential distribution of brushtail possums over 6 million years. D‐loop haplotypes were used to describe population structure. From shotgun sequencing, we assembled whole mitochondrial DNA genomes and estimated the timing of intraspecific divergence. Our projections of ENMs suggest current possum populations were unlikely to have been in contact during the Pleistocene. Although lowered sea level during glacial periods enabled connection with habitat in Tasmania, climate fluctuation during this time would not have facilitated gene flow over much of Australia. The most recent common ancestor of sampled intraspecific diversity dates to the early Pliocene when continental aridification caused significant changes to Australian ecology and Trichosurus vulpecula distribution was likely fragmented. Phylogenetic analysis revealed that the subspecies T. v. hypoleucus (koomal; southwest), T. v. arnhemensis (langkurr; north), and T. v. vulpecula (bilda; southeast) correspond to distinct mitochondrial lineages. Despite little phenotypic differentiation, Trichosurus vulpecula populations probably experienced little gene flow with one another since the Pliocene, supporting the recognition of several subspecies and explaining their adaptations to the regional plant assemblages on which they feed.

No abstract

Major aridification events in Australia during the Pliocene may have had significant impact on the distribution and structure of widespread species. To explore the potential impact of Pliocene and Pleistocene climate oscillations we estimated the timing of population fragmentation and past connectivity of the currently isolated but morphologically similar subspecies of the widespread brushtail possum (Trichosurus vulpecula). We use ecological niche modelling (ENM) with the current fragmented distribution of brushtail possum to estimate the environmental envelope of this marsupial. We projected the ENM on models of past climatic conditions in Australia to infer the potential distribution of brushtail possums over six million years. D-loop haplotypes were used to describe population structure. From shotgun sequencing we assembled whole mitochondrial DNA genomes and estimated timing of intraspecific divergence. Our projections of ENMs suggest current possum populations were unlikely to have been in contact during the Pleistocene. Although lowered sea level during glacial periods enabled colonisation of Tasmania, climate fluctuation during this time would not have facilitated gene flow. The most recent common ancestor of sampled intraspecific diversity dates to the early Pliocene when continental aridification caused significant changes to Australian ecology and Trichosurus vulpecula distribution was likely fragmented. Phylogenetic analysis revealed that the subspecies T. v. hypoleucus (koomal; southwest), T. v. arnhemensis (langkurr; north) and T. v. vulpecula (bilda; southeast) correspond to distinct mitochondrial lineages. Despite little phenotypic differentiation, Trichosurus vulpecula populations probably experienced little gene flow with one another since the Pliocene, supporting the recognition of several subspecies and explaining their adaptations to the regional plant assemblages on which they feed.

No abstract