Spatial pattern of freshwater habitats and their prioritization using additive partitions of beta diversity of inhabitant piscine assemblages in the Terai-Dooars ecoregion of Eastern Himalayas

摘要

Underlying spatial and habitat attributes of a river network are crucial to comprehend the bio-spatial arrangements within it, the study of which suffers from a paucity of information. Despite several reports on various piscine assemblages, no study contributes to understanding the characteristic attributes of the freshwater habitats of the sub-Himalayan Terai-Dooars ecoregion. Therefore, this study aims to uncover such underlying features through a precise understanding of the spatial profile of freshwater habitats and additive partitions of piscine beta diversity. A significant spatial association is found in the upper stretches of most of these torrential freshwater reaches confined to the eastward of the River Teesta basin to the tributaries of River Jaldhaka. Such a pattern is aligned with a higher local contribution to beta diversity (LCBD) values. The spatial map of LCBD indicates that the mid-altitude (100 > elevation > 2000 m) region contains unique or rare species assemblages. This fact is further confirmed by the spatial aggregation of characteristically adapted hill stream fish species with higher species contribution to beta diversity (SCBD) values. The results are further explained by relevant climatic, topographic, nutrients (sediments), and habitat attributes of which climate, topographic, substrate, and land cover features are the most contributory factors. Such variables are subjected to severe modulation following increasing anthropogenic pressure and changing climatic conditions, leading to the jeopardy of these freshwater habitats. Therefore, prime importance should be accorded to the ecological restoration value of these spatially structured torrential freshwater habitats for conservation and monitoring in the coming days.