Unveiling cryptic macroinvertebrate sentinels to enhance biomonitoring in tropical rivers: Bridging traditional approaches with DNA barcoding in the Indo-Burma biodiversity hotspot.

Human activities present significant threats to tropical freshwater ecosystems, notably in many global biodiversity hotspots, threats that are further increased by inadequate taxonomic knowledge and the lack of appropriate biomonitoring tools. This study integrates globally validated biomonitoring approaches with DNA-based identification methods to create a macroinvertebrate-based tool for diagnosing ecosystem health and assessing the biodiversity of tropical river ecosystems in Myanmar (Indo-Burma bioregion). To evaluate river site degradation, comprehensive data on water and habitat quality, as well as land use information, were collected. Riverine macroinvertebrates were sampled by kick sampling, and subsequent DNA barcoding analysis was used to establish molecular taxonomic units (MTUs) for key bioindicator groups, including Ephemeroptera, Plecoptera, Trichoptera, Coleoptera, and Odonata (EPTCO) as species-level identification nomenclature was lacking. Tolerance scores for the local fauna were derived along an environmental degradation gradient to enable comparisons with widely adopted global assessment tools relying on macroinvertebrate metrics. In both study areas, the upper parts of the river networks were generally undisturbed by human activities while stressors associated with urban and agricultural land use were evident in the lower parts of the catchments. The highest precision for assessment of river health was found when establishing tolerance scores adjusted to local species composition in each study area separately. Although a family-level-based multimetric approach was significantly related to the main environmental degradation gradient, assessments utilizing cryptic species-level data (MTUs) emerged as the being most precise indicator in both areas. Our study highlights the synergistic benefits of merging traditional biomonitoring with DNA-based methods for species identification for biomonitoring in tropical river ecosystems. To halt biodiversity decline and curb the extent of the escalating nature crisis, such integrated approaches will be highly valuable in understudied and biodiversity-rich aquatic ecosystems.