Effect of Inter-Habitat Matrix on Tropical Evergreen Forest Remnants: A Test of Matrix –Tolerance Hypothesis on Butterflies of Kodagu

Presented by: Deepak C K
Wildlife Institute Of IndiaAuthors
Deepakk C K, Dr. Gautam Talukdar, Dr. Bilal Habib, Dr. Krushnamegh Kunte

Introduction: What conservation problem or question does your study address?
Recent studies on habitat fragmentation has highlighted the importance of inter-habitat matrix and the need for a shift from traditional binary perspective to a ‘matrix composition’ perspective for understanding species diversity patterns in human modified landscapes. This study tested the matrix-tolerance hypothesis, according to which the abundance of a species in the matrix is inversely proportional to its vulnerability to fragmentation, on butterflies.

Methods: What were the main research methods you used?
The study was carried out in Kodagu region of Western Ghats. In order to test the matrix tolerance hypothesis sampling was carried out in 16 sites which included 7 in fragments (sacred groves), 7 in matrix (5 in coffee plantations, 2 in paddy field) and 2 in large contiguous forest (Reserve Forest). For abundance estimation of butterflies, time constrained surveys were carried out 3 times in each site between January 10 and April 8, 2013. An index related to fragmentation vulnerability was generated for each species using abundance data obtained from time-constrained surveys. The Fragmentation Vulnerability Index, FVI was defined as the ratio between average abundance of the species in the fragments and average abundance in the continuous patch. Spearman’s rank correlation was then used to test the association between rank FVI and rank matrix abundance. Effect of fragment size on the model was tested using ANCOVA.

Results: What are your most important results?
The present study shows that the relation between abundance of species in the inter-habitat matrix and its vulnerability to fragmentation is positive and significant (rs= 0.514, p = 0.001, N = 37). Species which are capable of tolerating the matrix are found to be less vulnerable to fragmentation.Fragment size didn’t have a significant effect on relation between matrix abundance and fragmentation vulnerability index (F=0.758, p=0.387, df=1)

Discussion: What are your important discussion points and what is the relevance of your results to conservation (if any)?
Some species deviate from the expected model in their response to habitat fragmentation which could possibly be explained by examining species specific traits. Fragment size didn’t have a significant effect on the model which could either be due to smaller range of fragment sizes in the present study or due to confounding factors like patch isolation and patch quality.