Species abundance distributions of selected communities in the Myristica swamp forests of southern Kerala

Abstract

The species abundance distribution (SAD) utilizes all the information gathered in a community and is the most complete mathematical description of the data. Myristica swamp forests are an endemic, highly fragmented ecosystem, naturally restricted due to systematic destruction and the special abiotic conditions required for their survival. Species diversity of amphibians, reptiles and trees in the Myristica swamp forests of southern Western Ghats in Kerala was documented using standard protocols for two years. Conventional species abundance distribution models could not be fitted into the datasets of this study. Graphical representations of the distribution of the dataset suggest that existence of multiple peaks on a log scale does not reject the universal hollow curve law on the arithmetic scale, but it will reject all SAD models producing unimodal curves. Various studies using SAD as a tool for community and ecosystem studies were reviewed and it was found that the presence of many species of intermediate abundance and decrease in rare species in our datasets could be an indication of natural distributions moving apart under disturbance and enrichment. Deconstruction and identification of resident and transient groups was done. We suggest that the Myristica swamps, which are situated in an area with high potential for rare species, may be in a transition due to disturbance and fragmentation. Ground truthing and previous studies already indicate these swamp forests as highly fragmented and disturbed.