Topography, climate, land cover, and biodiversity: Explaining endemic richness and management implications on a Mediterranean island

TL;DR

This study uses machine learning to identify key environmental factors influencing endemic plant richness on Crete, highlighting the importance of topography and climate for conservation planning.

Contribution

It quantifies the relative importance of topography, climate, and land cover in shaping endemic richness using neural networks, providing a novel framework for island conservation strategies.

Findings

Elevation range and climatic variability are key predictors of endemic richness.

Endemic hotspots only partially overlap with total species richness areas.

Prioritizing mountainous, climatically variable regions benefits conservation and ecosystem services.

Abstract

Island endemism is shaped by complex interactions among environmental, ecological, and evolutionary factors, yet the relative contributions of topography, climate, and land cover remain incompletely quantified. We investigated the drivers of endemic plant richness across Crete, a Mediterranean biodiversity hotspot, using spatially explicit data on species distributions, topographic complexity, climatic variability, land cover, and soil characteristics. Artificial Neural Network models, a machine learning tool, were employed to assess the relative importance of these predictors and to identify hotspots of endemism. We found that total species richness, elevation range, and climatic variability were the strongest predictors of endemic richness, reflecting the role of biodiversity, topographic heterogeneity, and climatic gradients in generating diverse habitats and micro-refugia that promote speciation and buffer extinction risk. Endemic hotspots only partially overlapped with areas of high total species richness, indicating that total species richness was the optimal from the ones examined, yet an imperfect surrogate. These environmentally heterogeneous areas also provide critical ecosystem services, including soil stabilization, pollination, and cultural value, which are increasingly threatened by tourism, renewable energy development, land-use change, and climate impacts. Our findings underscore the importance of prioritizing mountainous and climatically variable regions in conservation planning, integrating ecosystem service considerations, and accounting for within-island spatial heterogeneity. By explicitly linking the environmental drivers of endemism to both biodiversity patterns and ecosystem function, this study provides a framework for evidence-based conservation planning in Crete and other Mediterranean islands with similar geological and biogeographic contexts.