Knowledge shortfalls on the edge effects on amphibians and reptiles: research gaps and trends

Abstract Landscape transformation reduces the size of remaining natural patches and intensifies edge effects. These effects alter environmental conditions and vegetation structure, degrading remnant habitats. Amphibians and reptiles (herpetofauna) are especially vulnerable to edge effects because of their ecophysiological traits (e.g., critical temperatures, dehydration rates), making them valuable indicators of habitat change. We evaluated biodiversity knowledge shortfalls across 100 studies published from 1968 to 2025 that assessed edge effects on herpetofauna worldwide. Our results reveal pronounced geographic gaps: research is concentrated in the Nearctic (33%) and Neotropical (32%) regions, whereas the Palearctic, Sino-Japanese, Oriental, and Madagascan regions, as well as highland systems more broadly, remain underrepresented. Within regions, studies are concentrated at low elevations (74% conducted below 500 m a.s.l.) and in tropical moist broadleaf forests and temperate broadleaf–mixed forests (47% and 35%, respectively). Analysis of taxonomic bias shows a predominance of squamates and anurans (48 and 47 studies, respectively), whereas Testudines are rarely studied, and Gymnophiona and Crocodylia are entirely absent. Regarding the response variables analyzed in the studies, the literature most consistently addressed Prestonian-related dimensions, with 93% of studies focusing on abundance or occupancy-related variables. In contrast, major gaps remain in the study of functional traits and diversity (Raunkiæran shortfall; 11 studies), thermal tolerances (Hutchinsonian shortfall; 9 studies), biotic interactions (Eltonian shortfall; 8 studies), and evolutionary history (Darwinian shortfall; only 1 study on phylogenetic diversity). Studies are strongly biased toward edge interfaces between exotic pastures and old-growth forest interiors, or between secondary forests and old-growth forest interiors, while rapidly expanding urban, infrastructure-related, and agroforestry edges remain largely understudied. By integrating geographic, taxonomic, and ecological response variables, this synthesis reveals multidimensional knowledge shortfalls that constrain our ability to predict species responses to anthropogenic edges and to develop effective conservation strategies for vulnerable herpetofauna in fragmented landscapes.