Spatial heterogeneity within habitat indicates the community assemblage pattern and life strategies

Abstract

Abstract The problem of life strategies in relation to the alteration of habitat quality remains one of the fundamental questions in ecology and evolution. Spatial analysis of community assemblage for organisms could be a useful insight to resolve this issue. An important tropical riverine ecosystem, the Ganges, has been considered for this study. The River Ganges supports a diverse fish fauna, with about 300 fish species reported for Indian waters. The emergence and maintenance of life strategy of fish are naturally regulated in response to the variation of abiotic factors in different ways. Here, we formulate a spatial model using Self Organizing map (SOM), with monthly surveys of local fisheries from nine principal landing sites along the lower stretch of the Ganges. We explored the conditions for selecting life history strategies based on prevailing abiotic factors of habitat. Parameters of water quality incur heterogeneity within a continuous habitat. It is already reported that the fishery in this area is at a stake due to over exploitation and the catch per unit effort (CPUE) is declining as an invariable outcome. Thus, an assessment of community assemblage of this area is of principal importance for managing aquatic resources in the lower Ganges. The primary goal is to test the hypothesis that fish faunal community structure and assemblage along with their life strategy can change along the gradient of water quality parameters down the stretch of lower Ganges. Data on average annual yield (total mean monthly catch) was considered for analysis. Statistical ordination revealed associations between assemblage composition and abiotic factors. Patterns of fish community composition are associated with species life-history strategies which, in turn, are influenced by their quality of habitat. Therefore, the anthology of abiotic factors, controlling the immediate habitat of organisms, has paramount role to serve as the indicators of habitat quality and life history strategies following eco-evolutionatry aspects.