Drying microclimates threaten persistence of natural and translocated populations of threatened frogs

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ORIGINAL PAPER

Drying microclimates threaten persistence of natural and translocated populations of threatened frogs Emily P. Hoffmann1 Nicola J. Mitchell1



Kim Williams2 • Matthew R. Hipsey3



Received: 20 July 2020 / Revised: 6 October 2020 / Accepted: 7 October 2020 Ó The Author(s) 2020

Abstract Defining species habitat requirements is essential for effective conservation management through revealing agents of population decline and identifying critical habitat for conservation actions, such as translocations. Here we studied the habitat-associations of two threatened terrestrial-breeding frog species from southwestern Australia, Geocrinia alba and Geocrinia vitellina, to investigate if fine-scale habitat variables explain why populations occur in discrete patches, why G. alba is declining, and why translocation attempts have had mixed outcomes. We compared habitat variables at sites where the species are present, to variables at immediately adjacent sites where frogs are absent, and at sites where G. alba is locally extinct. Dry season soil moisture was the most important predictor of frog abundance for both species, and explained why G. alba had become extinct from some areas. Sites where G. alba were present were also positively associated with moss cover, and negatively with bare ground and soil conductivity. Modelling frog abundance based exclusively on dry season soil moisture predicted recent translocation successes with high accuracy. Hence, considering dry season soil moisture when selecting future translocation sites should increase the probability of population establishment. We propose that a regional drying trend is the most likely cause for G. alba declines and that both species are at risk of further habitat and range contraction due to further projected regional declines in rainfall and groundwater levels. More broadly, our study highlights that conservation areas in drying climates may not provide adequate protection and may require interventions to preserve critical habitat. Keywords Amphibian conservation  Climate  Habitat  Population decline  Soil moisture  Geocrinia

Communicated by Dirk Sven Schmeller. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10531-02002064-9) contains supplementary material, which is available to authorized users. & Emily P. Hoffmann [email protected] Extended author information available on the last page of the article

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Biodiversity and Conservation

Introduction Defining the environmental factors that determine species distributions is invaluable for effective species conservation and management. Population declines due to environmental change are prevalent worldwide (Pereira et al. 2012) and so understanding the environmental limits of species is critical for predicting future biodiversity. Species-habitat associations can be used to identify threatening processes and enable management actions that may halt or reverse declines, and ultimat