Predictive Modelling for Anuran Responses to Climate Change in Tropical Montane Ecosystems

Climate change poses a serious threat to many species globally. Potential responses are shifting range, adapting (e.g., phenological changes) or face extinction. Tropical montane ecosystems are particularly vulnerable to shifts in future climate due to rapid land use change, high population growth and multiple changes in the climate system, such as shifts and intensity of seasonality. Climate Change Vulnerability Assessment (CCVA) through Species Distribution Modelling (SDMs) provides a means of spatially assessing the potential impact of climate change on species ranges, but SDMs are limited in application by incomplete distribution data, a particularly acute challenge with rare and narrow ranging species. Malagasy amphibians exemplify the problems of SDMs in CCVA: two-thirds (166 species) have insufficient distribution data to run an SDM. This thesis developed a Trait Distribution Model (TDM) framework to spatially assess the climate-change vulnerability of data-poor, threatened Malagasy amphibians for the first time. By grouping species into trait complexes and then pooling distribution records, TDMs were used to assess the distributions of amphibian communities along environmental gradients. Threatened species clustered into three complexes; arboreal specialists, understorey species and habitat specialists. TDMs predicted the spatial distribution of all species in the landscape, but that ability improved as species’ range sizes and distribution data decreased. Correlations between trait complexes and water deficit suggested high levels of climate vulnerability for Malagasy amphibians by 2085, particularly arboreal species. However, omission of habitat variables led to spatial over-prediction, by up to 60%, for specialised species under current climate conditions. Subsequent ‘climate+habitat’ models revealed that up to eight threatened amphibian species face heightened extinction risk from climate change. Species losses are concentrated in lowland and mid-altitudinal zones, with no projected losses of tropical montane species. TDMs can indicate habitat management at the community level and be part of conservation planning under projected climate change.