Spatial ecology and conservation of New World Crocodylians

Crocodylians are apex predators that play a critical role in the stability, resilience, and functioning of terrestrial, marine, and freshwater ecosystems across tropical and subtropical ecoregions of the Americas. Besides their ecological importance, they possess inherent potential as conservation promoters, which can be constrained by the scarcity of research aimed at understanding their natural history and ecology. This thesis aimed to provide a comprehensive assessment of the spatial ecology, niche dynamics, and conservation status of all 11 New World crocodylians: Alligator mississippiensis, Crocodylus acutus, Caiman crocodilus, Crocodylus intermedius, Caiman latirostris, Crocodylus moreletii, Crocodylus rhombifer, Caiman yacare, Melanosuchus niger, Paleosuchus palpebrosus, and Paleosuchus trigonatus. To achieve this, I performed ecological niche analyses integrated species distribution models (SDMs), species abundance models (SAMs), and joint species distribution modeling (JSDMs) to explore (i) the predictive performance and transferability of distribution models across space and time, (ii) the degree of niche conservatism among species and its phylogenetic underpinnings, (iii) the relationship between habitat suitability and species abundance, and (iv) the potential impacts of climate change on future distributions and the effectiveness of current protected areas. In Chapter 2, I developed and compared SDMs across multiple sets of environmental predictors, assessing model performance via independent temporal and spatial evaluations. Results indicated high internal accuracy, but model transferability was species- and context-dependent, highlighting the need for careful predictor selection and high-quality occurrence data. Chapter 3 assessed niche conservatism among species, revealing weak phylogenetic niche conservatism across both geographic and environmental dimensions in New World crocodylians. Chapter 4 combined SDMs and SAMs to assess the relationships between predicted habitat suitability and species abundances, and evaluate whether these abundance and suitability patterns vary with distance from both geographic and environmental niche centroids. I found that most species displayed weak or context-dependent correlations, highlighting the need for caution when using suitability as a surrogate of abundance, and emphasizing that both metrics independently contribute insights to understand spatial ecology and population dynamics. Finally, Chapter 5 projected future distributions under climate change using SDMs and JSDMs, quantifying habitat retention within the existing protected area network. While some species maintained suitable habitat within protected areas, others faced substantial contractions, and differences between SDM and JSDM projections reflected the influence of interspecific interactions and latent ecological processes. Overall, this research provides high-resolution, standardized assessments of New World crocodylian distributions, highlights the importance of integrating species-specific, ecological, abundance, and community-level information for conservation planning, and identifies species and regions at greatest risk under future climate scenarios. The findings demonstrate that reliable predictions of species distributions require careful attention to model structure, predictor selection, and validation approaches, while also emphasizing the limitations of relying solely on suitability metrics for abundance or conservation assessments. These results establish a strong baseline for future ecological studies, inform evidence-based management strategies, and support the long-term conservation of crocodylians and their associated ecosystems across the New World.