A Spatially Explicit Distribution Model to Support Conservation Strategies for Isolated Small‐Ranged Species: A Case Study From Galápagos

Aim: This study aimed to test the effectiveness of a hierarchical, spatially explicit, Bayesian modelling framework combining Integrated Nested Laplace Approximation (INLA) with Stochastic Partial Differential Equation (SPDE) as an alternative to traditional Species Distribution Models (SDMs), particularly in cases where standard assumptions are violated, such as for small-ranged, data-limited species. Using the critically endangered Galápagos Pink Land Iguana (Conolophus marthae) as a case study, we also aimed to produce spatially explicit predictions to inform conservation strategies for this species. Location: The Galápagos Archipelago, Ecuador. Methods: We applied the INLA-SPDE model to address spatial autocorrelation in occurrence data, which is common when most observations originate from a limited number of surveys, as frequently happens with isolated, small-ranged species of high conservation priority. The model was used to identify environmental drivers of occurrence and to map both the current and potential distribution of C. marthae. We evaluated the predictive performance of the model through spatial cross-validation. Results: The model revealed that trophic resource availability, presence of open areas and terrain roughness are key factors limiting the distribution of C. marthae. Its current range was estimated at approximately 27 km2, while around 330 km2 of suitable areas were identified across three main sites outside its known distribution. The model showed good predictive performance (Cohen's K = 0.68; TSS = 0.70), with consistent predictor effects across model runs. Main Conclusions: Our findings demonstrated the utility of the INLA-SPDE approach in modelling distributions of small-ranged species, overcoming limitations of classical SDMs. The results obtained provided the first formal estimate of the range of C. marthae and identified new suitable areas, constituting an essential starting point to evaluate a species translocation, a key conservation strategy outlined in the Conservation and Management Plan for this species.