Metabolic Diversity of a Widely Distributed Tropical Freshwater Crab Is Not Underpinned by Genetic Differences

ABSTRACT Aim The aim of this study was to understand the interplay between local and regional factors as drivers of population physiological diversity in a tropical freshwater crab species. Location Western Ghats, south‐west India. Taxon Barytelphusa cunicularis, Brachyura, Crustacea. Methods We applied an integrative approach combining population genetics and whole animal physiology, using the tropical freshwater crab Barytelphusa cunicularis as our model species. We tested for effects of population location (e.g., latitude, altitude), season (as a proxy for rainfall and water temperature) and/or warming on indices of whole animal respiratory physiology (metabolic rate, MO 2 ) and hypoxic performance (P crit , i.e., the PO 2 at which routine MO 2 can no longer be sustained) in five widely distributed populations of this species. We also generated population genetic data (mtDNA COI and nDNA histone H3 sequences) to determine the extent of any population genetic structuring and/or cryptic species diversity present to verify that we were investigating a single species. Results Despite a high level of genetic structuring between the different populations of B. cunicularis examined, the genetic distances observed were consistent with intra‐ and not interspecific differences in freshwater crabs. Populations varied in the diversity of the physiological (MO 2 ) responses observed. There were significant effects of season and population on respiration in response to temperature and P crit in response to acute hypoxia. Main Conclusions We conclude that local environmental factors are important in shaping physiological diversity between populations in tropical freshwater species and systems. This highlights the need to include population‐level responses in any projections we make on how biodiversity will respond to ongoing and future environmental changes, including those caused by climate change.