MULTIVARIATE ANALYSIS SHOWING IMPACT OF DIFFERENT ENVIRONMENTAL FACTORS ON SPECIES RICHNESS AND SPECIES DENSITY OF FRESHWATER MOLLUSC COMMUNITIES INHABITING WATERS OF NORTH-WEST HIMALAYASSUNEHA UTTAM, SEEMA LANGER, CHAKSHU GUPTA, MENAKSHI DHARAbstract Freshwater molluscs face extreme threat due to anthropogenic stress which is reflected in their changing population structure over time. The extent of this phenomenon needs to be monitored and proper management of freshwater ecosystem should be done. In the present communication, an approach was undertaken to study the effect of ten different physical and chemical factors affecting mollusc density and mollusc richness in both lentic and lotic water bodies of North-West Himalayas. A total of 10 species of gastropods and 3 species of bivalves were recorded. Bivalves remained absent from both lentic bodies while gastropods dominated in both lotic waters in terms of taxa richness. On subjecting physical and chemical parameters to a multivariate analysis, 7 out of 10 factors were found significant after univariate Analysis of Variance (p<0.05). Principal component analysis showed that all the study stations varied in terms of physical and chemical conditions in different seasons. Canonical correspondence analysis revealed that dissolved oxygen, depth, alkalinity, Calcium ions and Chloride ions were the variables that significantly associated with the distribution of molluscs. The regression analysis revealed that the concentration of chloride ions was the common factor that was negatively related to both taxa richness and taxa density. |