Correlates of extinction risk in squamate reptiles: the relative importance of biology, geography, threat and range size

Abstract

34 Aim 35Evaluating the relative roles of biological traits and environmental factors that predispose 36 species to an elevated risk of extinction is of fundamental importance to macroecology. Results 54Range size was the most important predictor of extinction risk, reflecting the high frequency 55 of reptiles assessed under range-based IUCN criteria. Habitat specialists occupying accessible 56 ranges were at a greater risk of extinction: although these factors never contributed more than 57 10% to the variance in extinction risk, they showed significant interactions with range size. 58Predictive power of our global models ranged between 23 and 29%. The general overall 59 pattern remained the same among geographic, taxonomic and threat-specific data subsets. Main conclusions 62Proactive conservation requires shortcuts to identify species at high risk of extinction.

Species traits explaining sensitivity of snakes to human land use estimated from citizen science data

“…For example, imperilment has been shown almost universally to increase with body size for most species (e.g., Purvis et al, 2000;Cardillo et al, 2008), including reptiles (Tingley et al, 2013;Böhm et al, 2016). Nevertheless, a direct link between body size in vertebrates and sensitivity to habitat loss or human land use has proven elusive across many taxa (Swihart et al, 2003;Meyer et al, 2008;Thornton et al, 2011;Vetter et al, 2011;Quesnelle et al, 2014), and our results agree with these earlier findings.…”

“…Small range size is a factor commonly linked to increased imperilment in many species (Jones et al, 2003;Tingley et al, 2013;Böhm et al, 2016). This increased imperilment has been attributed to multiple Fig.…”

“…As a measure of "diet breadth", we included a count of the number of all taxonomic Classes reported as prey in species accounts in Ernst and Ernst (2003). As an index of habitat specialization/breadth ("habitat breadth"), we followed Böhm et al (2016) and used a count of the number of habitat types inhabited by each species reported in IUCN species accounts (www.iucnredlist.org accessed 15 January 2016). We calculated the proportion of these habitats that were aquatic for each species as an index of the degree to which each species uses aquatic habitats ("aquatic index"), the results of which agreed well with life history accounts in Ernst and Ernst (2003) and the authors' personal observations.…”

“…To date, several traits have been linked to increased extinction vulnerability in commonly studied vertebrates. For instance, extinction risk often increases with increasing habitat specialization, body size, and trophic level, but decreases with increasing range size and fecundity (Gaston and Blackburn, 1995;Purvis et al, 2000;Jones et al, 2003;Cardillo et al, 2005;Cardillo et al, 2008;Davidson et al, 2012;Tingley et al, 2013;Böhm et al, 2016). Ultimately, however, different suites of traits may underlie how species respond to a given threat (e.g., habitat loss, disease, overharvesting; Murray et al, 2014).…”

“…Additionally, of those species that have been evaluated, 20% of them have been deemed data deficient (Böhm et al, 2013). This is troubling given recent concerns that reptiles may be experiencing global declines on par with those in other taxa (Gibbons et al, 2000;Böhm et al, 2016). Among reptiles, snakes perhaps best epitomize the problem of both a considerable lack of data and recent enigmatic declines across several continents (Winne et al, 2007;Reading et al, 2010;Todd et al, 2010).…”