A functional perspective for global amphibian conservation
Introduction
A functional view of biodiversity offers a link between species traits (which are ultimately expressed in the phenotypes of individual organisms), the role they fulfill in ecosystems and their response to human disturbance (Diaz and Cabido, 2001). Such perspectives have changed the way we look at traditional conservation, given that it integrates biodiversity not only by its evolutionary history but also by its role in ecosystems functioning, and therefore, plan its conservation accordingly (Brum et al., 2017).
For anurans, in particular, habitat preference and requirements exert a strong influence on morphological evolution, being the cause of adaptive convergences in phenotypes (Moen et al., 2016; Moen and Wiens, 2017). Five microhabitat-related ecomorphs (i.e. aquatic, arboreal, burrowing, terrestrial and torrential) have evolved repeatedly in different times and locations, and species within these ecomorphs share phenotypic traits relating to vertical stratification and microhabitat use (Moen and Wiens, 2017; Oliveira and Scheffers, 2018). The geographical distribution of these microhabitat-related ecomorphs is strongly related to patterns of precipitation and temperature, and with variations in vegetation structure at a global scale (Oliveira and Scheffers, 2018). Most ecomorphs (aquatic, arboreal or semi-arboreal) are diverse only in tropical regions with a high precipitation and low annual seasonality, while some ecomorphs (as semi-aquatic or terrestrial) are climatically generalist and therefore widely distributed. In contrast, burrowing species only occur in climatic regimes with a high annual precipitation seasonality, and so, has a peculiar distribution. Finally, there is a very restricted ecomorph (torrential), distributed in some particular tropical regions (Oliveira and Scheffers, 2018). Thus, ecomorphs represent a relevant functional trait for understanding amphibian diversity based on microhabitat use. Despite the fact that amphibians are the focus of many studies in biological conservation (Hof et al., 2011; Nori et al., 2015; Stuart, 2004), as far as we know, none of them are based on the functional perspective at a global scale.
The study of causes and consequences of the global decline in amphibian populations has become a relevant research topic in conservation biology since the 90s (Wake, 1991). Amphibians are undergoing an extinction crisis; out of the 7876 living extant species (Frost, 2018), nearly 40% are currently threatened with extinction (Hoffmann et al., 2010; Jenkins et al., 2013; Pimm et al., 2014; Stuart, 2004). On top of that, it is well documented that the global network of protected areas (PAs) could be much more efficient than they really are today in protecting threatened amphibians (Nori et al., 2015; Rodrigues et al., 2004; Sánchez-Fernández and Abellán, 2015). Besides, more than 40% of non-threatened amphibians are still poorly known by science, and presumably most of them face the same threats (Hof et al., 2011; Howard and Bickford, 2014; Morais et al., 2013; Nori and Loyola, 2015; Nori et al., 2018).
Currently, the main threat to vertebrate species is the degradation (and eventually the loss) of their original habitats, with land conversion for agriculture expansion being the main driver of population decline and species loss (Grooten and Almond, 2018). Amphibians are not an exception (IUCN, 2018; Stuart, 2004). In fact, most clades are heavily threatened (Nori et al., 2015), and respond negatively (Nowakowski et al., 2017) to these activities. Considering that land-use changes are unevenly distributed across the globe and are strongly related with landscape characteristic and climatic regimes, it is expected that human modifications in the environment will affect differently anurans microhabitat-related ecomorphs. These idiosyncratic responses, coupled with a low performance of PAs (Jones et al., 2018; Watson et al., 2014) could constrained diversity of functional forms.
Here, using detailed geographical information on distribution pattern of 3138 amphibian species (categorized into seven ecomorphs), combined with land-use scenarios, for both current and future periods, we aim to: (1) describe the general patterns of species richness for amphibian ecomorphs; (2) analyze the overlap between patterns of amphibian ecomorph richness and different modified scenarios (3) estimate the role of the current global network of PAs in the long-term protection of the ecomorphs across the amphibian distribution; and (4) determine key regions to maximize amphibian life forms representation. Through these analyses we aim to provide new evidences about priority conservation areas for amphibians in a functional sense, taking into account global species patterns and different biological diversity aspects, that can guide futures conservation decision-making processes and the establishment of efficient areas for the long-term protection of amphibian.
Section snippets
Spatial data
We downloaded digital range maps (extent of occurrence maps) for 6476 amphibian species available at the IUCN database (https://www.iucnredlist.org/; IUCN, 2018, accessed on May 07th, 2018), and associated species range maps with the list of ecomorphs using the spatial join tool of ArcGIS 10.3. The list of ecomorphs had the scientific names of the species and their corresponding ecomorphs (Moen et al., 2016; Moen and Wiens, 2017).
In Moen et al. (2016), the authors defined ecomorphs based on
Results
There were a varied number of total species within each ecomorph, ranging from 108 species (aquatic) to 1151 species (arboreal; Table 1). Ecomorphs holding the largest number of species per pixel were arboreal (56 species) and terrestrial (46 species), whereas ecomorphs with the lowest number of species per pixel were aquatic (6 species) and torrential (10 species; Table 1).
The torrential ecomorph showed the highest level of geographical restriction patterns across their ranges. In fact,
Discussion
Historically, research on amphibian conservation has had a strong taxonomical basis, focusing exclusively on the vulnerability/protection of different taxa (mainly at species level; Jenkins et al., 2013; Nori et al., 2015; Rodrigues et al., 2004) or the effect of the lack of knowledge on their conservation (Howard and Bickford, 2014; Nori and Loyola, 2015; Nori et al., 2018), without attending to the possible differential vulnerability of distinct amphibian functional forms. Here, we highlight
CRediT authorship contribution statement
Bruna E. Bolochio: Conceptualization, Methodology, Formal analysis, Investigation, Writing - original draft, Visualization, Funding acquisition. Julián N. Lescano: Conceptualization, Methodology, Writing - review & editing, Supervision. Javier Maximiliano Cordier: Formal analysis, Investigation, Visualization. Rafael Loyola: Writing - review & editing, Supervision. Javier Nori: Conceptualization, Methodology, Software, Formal analysis, Investigation, Resources, Writing - original draft, Writing
Declaration of competing interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: FONCYT – PICT 2018-2666 and SeCyT UNC.
Acknowledgements
We thank Rodrigo Tinoco for providing the photos of anurans presented here. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. JN thanks FONCyT (PICT 2017-2666) and SeCyT, UNC for financial support. RL research is funded by CNPq (grant #306694/2018-2). This paper is a contribution of the INCT in Ecology, Evolution and Biodiversity Conservation founded by MCTIC/CNPq (grant #465610/2014-5) and FAPEG (grant #
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