Aim
Freshwater crabs are ecologically vital benthic macroinvertebrates that sustain freshwater ecosystem functions, yet their limited dispersal and fragmented habitats make them highly vulnerable to human disturbance. Current global conservation assessments for freshwater crabs remain incomplete, as most studies focus only on species richness while neglecting phylogenetic diversity and systematic conservation gaps. This study aimed to characterize the global spatial patterns of freshwater crab species richness (SR) and phylogenetic diversity (PD), identify their key driving factors, and evaluate existing conservation coverage to identify priority areas for targeted freshwater biodiversity protection.

Location
Global

Results
Freshwater crab biodiversity exhibited a clear low-latitude aggregation pattern, with major SR and PD hotspots concentrated in tropical and subtropical regions including southern China, Southeast Asia, and northern South America. Mountain topography and stable hydrothermal conditions promoted crab diversity, whereas strong precipitation seasonality inhibited species accumulation. Large conservation gaps were identified across core hotspot regions, and current protected areas poorly cover freshwater crab diversity. Moderate spatial optimization of protected areas could greatly enhance conservation coverage under global protection targets.

Main conclusions
Global freshwater crab biodiversity patterns are shaped by coupled environmental and anthropogenic factors, with SR and PD showing heterogeneous spatial responses. Existing terrestrial-oriented protected areas cannot effectively conserve multi-dimensional freshwater crab biodiversity. Optimizing protected area spatial layout based on both species richness and phylogenetic diversity delivers more efficient conservation outcomes. This study demonstrates the importance of integrating evolutionary information into freshwater conservation planning and provides practical spatial priorities for filling global freshwater biodiversity conservation gaps.

We integrated global occurrence data for freshwater crabs, phylogenetic sequences, and multi-dimensional environmental and anthropogenic datasets. The obtained distribution data covered 95.83% of genera and 82.86% of species. Using an ensemble species distribution model, we predicted potential species distributions and mapped global patterns of SR and PD. Spatial generalized linear mixed models were applied to quantify the driving factors. We further identified biodiversity hotspots, evaluated conservation gaps, and pinpointed priority areas under the global land protection targets of 17% and 30%.