Globally, ecosystems are becoming increasingly degraded. As a result, many organisms are becoming vulnerable to extinction. However, many organisms are poorly known, so identifying species at risk of extinction and effectively managing populations is problematic. In the absence of detailed ecological data, macroecological relationships could be a useful tool for identifying species at risk of extinction and areas of conservation concern.
Freshwater ecosystems are particularly imperiled and poorly known. Using Australian freshwater fish as a model system, we investigate the relationship between range size and body size for all Australian freshwater fish and how this relationship changes with dispersal capacity and conservation status. We then test whether this macroecological pattern can be used to detect potentially vulnerable, but currently unprotected, species. Lastly, we mapped the distribution of currently unlisted freshwater fish that share traits with currently listed species to reveal unrecognized hotspots of freshwater fish conservation concern across Australia and areas where there is a mismatch between research effort and extinction risk.
Results/Conclusions
We found a positive, triangular relationship between range size and body size. Potamodromous species and species endemic to New Guinea and Australia had the largest geographic ranges, while, in contrast to previous studies, diadromous and globally widespread species had the smallest Australian geographic ranges. For a given body size, conservation listed species had a range less than one-tenth the size of unlisted species. Based on this relationship, we identified 55 species that may be vulnerable to extinction but currently receive no conservation protection. Most of these species are restricted to northern Australia, a climatically sensitive and poorly researched region on the verge of major development.
Despite differences in environments, levels of connectivity and life-history strategies, freshwater fishes exhibit a positive relationship between geographic range size and body size consistent with that found in terrestrial fauna. By identifying northern Australia as a hotspot of potentially vulnerable species, we provide an important context for guiding targeted research and informing future conservation management of Australia’s freshwater fishes. We suggest macroecological relationships are useful for identifying species at risk of extinction across most taxa when detailed ecological data are absent.