A global analysis of fish biodiversity using environmental DNA (eDNA) has revealed how human activity and climate have influenced biodiversity patterns in river ecosystems.
Adjunct Associate Professor Deirdre Gleeson, from The University of Western Australia's School of Agriculture and Environment, was co-author of the study led by Professor Florian Altermatt from the University of Zurich and Professor Xiaowei Zhang from Yunnan University, which combined eDNA data from 113 river systems across five continents.
The data covered nearly 2,000 freshwater sampling sites, ecosystems that cover less than 1 per cent of Earth's surface but sustain nearly 10 per cent of known species.
"Unlike traditional methods involving gillnets or electrofishing, eDNA monitoring does not require fish to be actively captured," Associate Professor Gleeson said.
"We extract DNA directly from water samples and sequence it to identify species-specific genetic signatures, enabling us to infer which species are present in an ecosystem."
Published in Nature Ecology & Evolution, the study identified global patterns in riverine fish biodiversity, revealing catchments in warmer climates consistently accumulated greater biodiversity as catchment size increased.
While the findings highlighted the crucial role of climate in shaping biodiversity patterns, researchers found the positive relationship weakened in areas with higher levels of human activity.
"This suggests human activity could alter large-scale biodiversity patterns by constraining fish biodiversity across river catchments," Associate Professor Gleeson said.
The study revealed that not only species richness, but also other measures of biodiversity, including functional diversity and genetic sequence diversity, showed stronger negative responses to human activity in larger river catchments.
For example, phylogenetic diversity, which reflects the evolutionary relationships among species, was particularly affected by human activity, especially in smaller river catchments.
The study demonstrated the potential of eDNA as an effective tool for rapid, large-scale biodiversity monitoring.
"Climate change and weather events combined with human activity are threatening biodiversity worldwide," Associate Professor Gleeson said.
"Our findings can help understand how it is changing ecosystems and can be used to inform conservation management and policymakers."
