Habitat Expansion, but Population Isolation. The Impact of Climate Change on an Endemic Frog of Patagonia

Abstract

The Rio Negro Frog (Atelognathus nitoi) is an amphibian species endemic to Patagonia, shared between Argentina and Chile. Currently, it is classified as Vulnerable (IUCN) and is mainly threatened by anthropogenic pressures such as habitat alteration and climate change. Due to its life history and habitat requirements, primarily determined by temperature and precipitation, climate change may particularly influence the species' distribution. We evaluated how climate change may affect geographic range by producing a Species Distribution Model (SDM), generating a habitat suitability map and calculating its Extent of Occurrence (EOO). Projections were made for the period 2041–2060 under the Shared Socioeconomic Pathways SSP1-2.6 and SSP5-8.5, representing optimistic and pessimistic climate change scenarios, respectively. A set of five atmosphere–ocean general circulation models was used to reduce uncertainty. We evaluated the degree of connectivity of the lagoons with records of the species by applying Lin's functional linkage index, allowing comparisons in terms of their relative importance for the system's connectivity. Our results indicate an increase in suitability area over time, with a westward distribution shift in future scenarios. However, local extinctions are projected at the northern and southern margins of the species' range. Therefore, although the EOO is expected to expand, the species' life-cycle characteristics, limited dispersal capacity and low connectivity between the populations analysed should be taken into account when planning conservation actions.