Abstract

Large tropical and subtropical rivers are among the most biodiverse ecosystems worldwide, but also suffer from high anthropogenic pressures. These rivers are hitherto subject to little or no routine biomonitoring, which would be essential for identification of conservation areas of high importance. Here, we use a single environmental DNA multi-site sampling campaign across the 200,000 km2 Chao Phraya river basin, Thailand, to provide key information on fish diversity. We found a total of 108 fish taxa and identified key biodiversity patterns within the river network. By using hierarchical clustering, we grouped the fish communities of all sites across the catchment into distinct clusters. The clusters not only accurately matched the topology of the river network, but also revealed distinct groups of sites enabling informed conservation measures. Our study reveals novel opportunities of large-scale monitoring via eDNA to identify relevant areas within whole river catchments for conservation and habitat protection.

Highlights

  • Tropical and subtropical regions are among the most biodiverse systems g­ lobally[1,2]

  • After bioinformatic clean-up and removal of low frequency reads, across all samples a total of 5,825,212 and 4,927,576 reads were assigned to Fish Taxa found in the custom-built reference database for Kelly and MiFish primers, respectively

  • Of the 108 fish taxa (FT) found in the combined dataset, 67 (62%) FT were found with both primer pairs, 15 (14%) were unique to the Kelly dataset and 26 (24%) were unique to the MiFish dataset

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Summary

Introduction

Tropical and subtropical regions are among the most biodiverse systems g­ lobally[1,2]. Freshwater rivers in these regions are particular hotspots of biodiversity, with up to a third of global freshwater fish species found in the Amazon, Congo and Mekong river basins alone, most of which are endemic to these ­areas[3] These extraordinary systems contribute strongly to global biodiversity, they provide essential ecosystem services, such as drinking water and are a key protein source for local human ­populations[4]. The selection of suitable PCR primers allows the identification of species from specific taxonomic groups present in an e­ cosystem[20] This approach has been used to assess species richness of fish in different temperate aquatic ­systems[21,22,23,24,25], providing crucial information for fisheries and conservation ­management[26]. Non-invasive to the taxa being detected, and allowing prediction of diversity patterns across whole riverine s­ ystems[33,34], it is offering an unprecedented opportunity to monitor freshwater habitats on a landscape scale

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