Global warming leads to habitat loss and genetic erosion of alpine biodiversity

Aim: Species living on steep environmental gradients are expected to be
especially sensitive to global climate change. Here, we combined genetic,
ecological niche modelling and climatic niche comparisons to investigate
the influence of climate on the biogeography of three alpine species with
overlapping ranges. Location: Te Waipounamu (South Island) Aotearoa–New
Zealand. Taxon: Endemic alpine-adapted Cataontopinae grasshoppers.
Methods: We used niche modelling to estimate and project the potential
niche of three focal species under past and future climate scenarios.
Vulnerability assessments were performed using niche factor analyses.
Demographic trends and phylogeographic structure were investigated using
samples from 15 mountain tops to generate mitochondrial DNA haplotype
networks and population genetic statistics. Results: Niche models and
genetic data suggest suitable habitat for all three alpine species was
more widespread and contiguous in the past than today. Demographic
analyses indicate in situ survival rather than post-Pleistocene
colonisation of current habitat. Population structuring and genetic
divergence suggest that mountain uplift during the Pliocene and
environmental barriers during Pleistocene glacial and interglacial stages
shaped contemporary population structure of each species. Though
geographically overlapping, niche analyses suggest these alpine species
are not ecologically identical, and each shows similar but distinct
responses to environmental change, but all will lose intraspecific
diversity through population extinction. Main conclusions: Climatic,
biological and geophysical factors controlled population structuring of
three cold-adapted species during the Pleistocene with a legacy of
spatially separate intraspecific lineages. Ecological niche models for
each species emphasise distinct combinations of environmental proxies, but
all are expected to experience severe habitat reduction during climate
warming. Increased global temperatures drive available habitat to higher
elevation resulting in population contractions, range shifts, habitat
fragmentation, local extinctions, and genetic impoverishment. Despite
alpine species not being ecologically identical, we predict all mountain
biota will lose significant genetic diversity due to global warming.