No Disturbance Please! Butterfly Community Response to Disturbance and Other Environmental Factors

Singh, Pragya (2015) No Disturbance Please! Butterfly Community Response to Disturbance and Other Environmental Factors. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Pragya Singh (10MS59)) Pragya_Singh.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Intensive land use has substantially changed the community patterns of many insects and mammals. Increasing land use and human disturbance has led to an ever increasing turnover of plant community and a decrease in the number of ecological niches available to certain insects including butterflies. There is a substantial gap in our knowledge about how the insect communities respond to the different degrees of human disturbance in landscapes and how it shapes their community structure. In my thesis I wanted to study the butterfly diversity and their community structure and how it is affected by different environmental factors. The factors included a human disturbance index, plant richness, patch size and the habitat type. I also investigated their co-occurrence patterns and abundance across the disturbance gradient and looked at the ecological basis for the clustering of butterfly species. I also looked at the characteristics of the butterflies which occurred in the same module. Butterflies were sampled from August 2014 to October 2014 using transect sampling method. I investigated butterfly communities at 12 sites in Nadia District, West Bengal, India. Human disturbance level of a site was calculated and ranked based on several factors like presence of human and cattle, plant and trees turnover rates, proximity to human settlement and roads similar to the method of Index of Biological Integrity. Multivariate analysis showed that patch size and plant richness significantly affected both butterfly richness and diversity whereas disturbance had a significant effect only on butterfly richness but not on diversity. Principal Component Analysis showed that butterfly communities differ in composition with respect to forests and other habitat type. The butterflies had significant co-occurrence patterns and their co-occurrence network comprised of a main network where four modules were connected together and five other isolated modules. The isolated network modules responded differently from the main network modules to disturbance suggesting that disturbance may have a substantial effect in shaping community structure of butterfly species with different responses from different species. This work is relevant in the current Indian scenario where there is an urgent need to reconcile conservation plans with changing landscape uses like widespread forest conversion and agricultural intensification, and to make use of these heterogeneous agro-landscapes for conservation.

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