360 C. Azat et al.


institutions, local communities, NGOs and the private sec- tor; Supplementary Table 2), to enhance collaboration for the conservation of Darwin’s frogs. The Alliance is led by members of the Amphibian Specialist Group, and endorsed by the Chilean and Argentinian Ministries of Environment.


Threat assessment


The status reviewsupported previous claims that the decline of Darwin’s frogs has been largely driven by habitat loss, chytridiomycosis and climate change (Bourke et al., 2010, 2012, 2018; Soto-Azat et al., 2013a, 2013b; Uribe-Rivera et al., 2017;Valenzuela-Sánchez et al., 2017). Here we provide a brief synthesis of this review.


Status of populations Using species distribution modelling, Bourke et al. (2012) identified areaswith potential remnant R. rufum populations, providing guidance for future efforts to rediscover this species. Soto-Azat et al. (2013a) dated its ex- tinction to 1982 (95%CI: 1980–2000) using historical sight- ings. In contrast, R. darwinii is found in small and isolated populations (Soto-Azat et al., 2013a; Valenzuela-Sánchez et al., 2015). During the development of the strategy, we iden- tified 56 extant populations in Chile and 10 in Argentina (Fig. 1). In Chile, R. darwinii has recently disappeared from, or drastically declined in, many localities where it was abun- dant only decades ago (Crump & Veloso, 2005; Soto-Azat et al., 2013a). Thesizeof extantpopulations is c. 10–145 re- productive individuals (Crump, 2002;Soto-Azat et al., 2013a; Valenzuela-Sánchez et al., 2014, 2017, 2019a). In Argentina, the species has been less well studied but, based on museum collections, it was probably much more abundant in the past (Úbeda & Pastore, 2015).


Habitat loss The original habitats of R. rufum, the Coastal Mediterranean and Maulino deciduous forests (32–36 °S), have been almost completely replaced by exotic pine and eu- calypt plantations and agriculture, with,7%ofMaulino for- est remaining (Smith-Ramírez, 2004;Echeverría etal., 2006). The Valdivian temperate rainforest (36–47 °S) is the typical habitat of R. darwinii. To the north, the situation for R. dar- winii is similar to that for R. rufum, but further south the native forest becomes more continuous as the coverage of protected areas increases, thus providingmore suitable habi- tat for the species.


Amphibian chytridiomycosis Caused by the fungus Batr- achochytrium dendrobatidis, this emerging disease is known for its catastrophic and ongoing impacts on amphibian populations worldwide (Scheele et al., 2019). This pathogen has been identified from museum specimens of wild


FIG. 3 Boxplot (median, 25th, and 75th percentiles) of relative changes in the extent of potential habitat (suitable and accessible) of R. darwinii, projected to two temporal windows (2050 and 2080) and two climate change scenarios (Relative Concentration Pathway 4.5 and 8.5; IPCC, 2014). The dashed line represents a scenario of no change compared to the present situation.


Chilean amphibians collected since the 1970s (Soto-Azat et al., 2013b). This coincides with the documented onset of South American amphibian declines (Scheele et al., 2019). Surveys in Chile have demonstrated that B. dendrobatidis is infecting R. darwinii in the wild (Bourke et al., 2010), with evidence of lethal chytridiomycosis (Soto-Azat et al., 2013b), which leads to extirpation of infected populations (Valenzuela-Sánchez et al., 2017).


Climate change Because of its specific habitat requirements (Valenzuela-Sánchez et al., 2019a), slow life-history strategy (Valenzuela-Sánchez et al., 2017) and dispersal limitations (Valenzuela-Sánchez et al., 2014, 2019b), Rhinoderma spp. are expected to be particularly susceptible to climate change (Soto-Azat et al., 2013a). Using a dispersal-constrained species distribution model, Uribe-Rivera et al. (2017) estimated that during 1970–2010, climate change led to a reductionof suitable habitat for this species by 23–40%. Bourke et al. (2018)pre- dicted an expansion of climatically suitable areas for R. dar- winii by 2080, especially in the south of its range. However, unless assisted by translocations, R. darwinii would not nat- urally colonize most of the emerging suitable areas (Uribe- Rivera et al., 2017). Incorporating dispersal limitations analyses of climate change projections for 2050 and 2080 show reductions of 33–56% in the potential distribution of R. darwinii (Fig. 3; Uribe-Rivera et al., 2017).


Other threats


Collection of wild Rhinoderma spp., mainly for hobbyists and museums, was common in the past (J.C. Ortiz, pers.


Oryx, 2021, 55(3), 356–363 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001236


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