Abstract
Tropical and subtropical freshwater habitats are among the most biodiverse ecosystems worldwide, containing a characteristic fauna and high numbers of endemic species. However, exploitation of organisms, global climate change, pollution and the introduction of invasive species are severely threatening this diversity. Implementation of appropriate conservation and protection measures in tropical freshwater systems depends on comprehensive knowledge of state and change in biodiversity, which however, has been barely feasible due to logistic, technical and taxonomic challenges abound in tropical and subtropical ecosystems. Here we use a single environmental DNA (eDNA) multi-site sampling campaign distributed evenly through the 200,000 km2 Chao Phraya river basin, Thailand, to provide key information on freshwater fish diversity. We found a total of 108 fish taxa and identified key biodiversity patterns within the river network with respect to alpha- and beta-diversity patterns. By using a hierarchical clustering, we grouped the fish communities of all sites across the catchment into distinct clusters. Mapping these clusters over the catchment not only accurately matched the topology of the river network, but also revealed distinct groups of sites which should each be considered of high conservation value. Our study demonstrates a key application of large-scale monitoring (via eDNA) to identify distinct areas within a catchment 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
Summary
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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