Biased research reveals major gaps in fragmentation studies on the Spanish fauna

Abstract

Habitat loss and fragmentation globally threat biodiversity and ecosystem services. However, major research biases and knowledge gaps in biogeographical regions, taxonomic groups, landscape metrics and species’ biological responses studied, are recurrent in fragmentation studies. Detecting these biases and associated gaps is crucial to steer future research efforts and to guide applicable conservation policies. We conducted a systematic literature review and extracted data from 107 articles to evaluate biogeographic, taxonomic and ecological biases in fragmentation research on the highly-diverse terrestrial fauna in peninsular Spain. We observed that research was biased towards mountain ranges, southeastern drylands and nearly largest cities. Specifically, the Cantabrian Range comprised the highest density of studies, while open dehesas in western Spain and Atlantic coastal forests in the northwest were overlooked. We also found an overrepresentation of studies (77%) on vertebrates and a high positive relative bias for birds, while several invertebrate taxa were neglected in the literature. Fragmentation was more frequently considered than habitat loss. Habitat degradation and patch size reduction were the most studied metrics, while patch isolation, edge effect and matrix contrast were underrepresented. Assemblage-level species responses (abundance and richness) comprised 86% of studies, while interspecific interactions, genetics and individual conditions were largely underrepresented. Our findings indicate major gaps in the studies focused on the effects of habitat loss and fragmentation on the Spanish fauna. We recommend that fragmentation research in this diverse region from southern Europe needs to consider undersampled taxa, further fragmentation metrics and biological responses to avoid inappropriate inferences for conservation actions.