Study of spider order araneae diversity on selected sites adjoining the tributaries of bharatapuzha in Kerala

Abstract

Riparian habitats act as ecotones integrating the neighbouring terrestrial and aquatic ecosystems. These habitats are exhibit variation with respect to the nature of both the contributing ecosystems. Bharatapuzha, the second longest river in Kerala has a paramount importance in moulding biodiversity of central Kerala. A lot of anthropogenic interventions brought irrecoverable damage to the river, hence to the associated riparian habitats. Riparian spiders are highly versatile with respect to their trophic roles; being both predators and prey. Present study extended for a period of two years could document a total of 7151 individuals belonging to 27 families, 90 genera and 133 species. Around 44 % of the families reported from the country were represented in this sampling study. Standard sampling procedures like line transect method were followed. World Spider Catalogue version 25.0 was the reference for identification and scientific names. For convenience, the sampling was done from five selected sites adjoining distinct tributaries of the river, located in Palakkad and Malappuram districts. The samplings were carried out in three seasons, pre monsoon, monsoon and post monsoon. A considerably significant difference was found to exist among the sites and seasons. Both the abundance and richness were higher during post monsoon season. Habitat wise, site 1, Malampuzha recorded higher abundance and richness. Salticidae was the most dominant family followed by Araneidae and Tetragnathidae. Highest relative abundance value was recorded for Hyllus semicupreus. Species accumulation curve reached the asymptotic level indicating satisfactory coverage of the species distribution. Rarefaction curve corresponding to post monsoon season of Malampuzha reached the highest peak. Considering AIC values, Zipf – Mandelbrot was chosen as the best fit model. All the eight feeding guilds were represented in the study; other hunters were the most dominant one. No new species were reported in this study.