Range contractions and reduced body mass predicted for endemic skinks of the Cameroon volcanic line with future warming

Aim The vulnerability of montane species to environmental change has been
increasingly recognized over the past decade. However, most of these
species are regionally endemic with restricted ranges, limiting dispersal
necessary for avoiding extinction. Threats posed for montane lizards could
be further complicated in species following Bergmann’s rule, where body
size increases with altitude. In this study, we applied a bioclimatic and
body mass trait-based species distribution model approach to identify
areas suitable for montane endemic skink species of the Cameroon Volcanic
Line (CVL) under current and future climates. Location Cameroon Volcanic
Line Methods We recorded occurrence records and measured body mass in the
field for skink species endemic to the CVL. We additionally supplemented
our occurrence data with records from an online repository. We projected
habitat suitability in the region by implementing the occurrence data in
the bioclimatic species distribution models. We further integrated both
occurrence and body mass information in our trait-based model to project
potential body mass. Results Projected currently suitable ranges were
limited to higher elevation regions, which are inhabited by numerous other
threatened amphibian and reptile species. We found that, for our two skink
species following Bergmann clines in body mass, trait model predictions
covered a slightly larger geographic range than bioclimatic estimates.
Under future warming, both models predict substantial contractions in
suitable areas, potentially constraining species to mountain tops. Through
the trait-based approach, we further detected potential warming-induced
body mass reductions in projected suitable areas. Main conclusions We thus
demonstrate how combining occurrence records with species trait
information in predictive modelling can reveal complementary trends for
more comprehensive climate change impact assessments. Overall, these
challenges towards the persistence of CVL-endemic skink species should
prompt urgent responses in national conservation management and local
community engagement.