A short distance to the last glacial coast best explains a Tasmanian centre of endemism
Atkinson, J and Kirkpatrick, JB, A short distance to the last glacial coast best explains a Tasmanian centre of endemism, Frontiers of Biogeography, 12, (4) Article e47438. ISSN 1948-6596 (2020) [Refereed Article]
At the small scales of world, continent and region, centres of local endemism have been hypothesised to be related to refugia and/or distinctive environmental conditions. We consider patterning of local endemics at a large scale to help test the validity of these two hypotheses for centres of local endemism recognised at smaller scales. Our study area was a centre of local endemism on the Tasman and Forestier peninsulas, Tasmania, Australia. We tested the distinctiveness of both the current climatic and edaphic conditions and the potential for refugia during Quaternary climatic fluctuations, using databases, published maps, and direct observation of climate. Inverse rarity analyses at 1 km2 showed a pattern of concentration of local endemics near the east and southeast coasts of the peninsulas. However, the ranges of species at a larger scale were largely non-overlapping. Climate did not differ from other coastal areas in southeastern Tasmania that lacked local endemics. Climatically similar areas to the centre of local endemism on and outside the peninsulas also had treeless vegetation on skeletal soils on dolerite and mudstone that were habitat for many of the species in the peninsulas centre of local endemism. The areas with high concentrations of local endemics on the peninsulas were located close to the coastline of the Last Glacial Maximum, unlike other areas with the same climatic and edaphic environments inside and outside the peninsulas. The conclusion that the centre of local endemism relates to a closely adjacent glacial refugium, rather than being a response to a distinctive environment, was reinforced by the non-overlapping distributions of the most locally endemic species at a large scale, and the variability in the habitat of the most locally endemic species. This study illustrates the value of investigating the causes of centres of local endemism at a range of scales and confirms the tight link between centres of endemism and refugia.