Diversity of spiders as influenced by cultivation techniques in rice

Abstract

Field studies were carried out in wet seasons of 2014 and 2015 in rice fields of College Farm, Rajendranagar, Hyderabad to understand the abundance and biodiversity of spiders in varied rice cultivation systems. Design of the experiment was split plot with three main modules, viz., transplanted, broadcasted and drum sown rice and subtreatments under each main module included three plant protection methods viz., organic protection, farmers’ practices and ‘no protection’ practices. Results showed that predator numbers in ‘no protection’ and organic protection plots of all main treatments were more than in farmers’ practices indicating the impact of the chemical pesticides. A total of 22 genera of spiders belonging to 12 families were recorded which comprised of seven guilds based on their hunting strategies and microhabitats. Shannon diversity index ranged between 1.83 and 2.26 and Pielou's evenness index was 0.59–0.72 in two years of study indicating a stable ecosystem and even species distribution in rice crop at Rajendranagar. Study of the guild assemblage indicated that orb-weavers constituted 28.1% of the population, ground runners 23.51%, space web builders 18.38%, sheet-web builders 13.12%, stalkers 8.04% and ambushers made upto 0.38% of the spider population. Understanding the vertical stratification of various spider genera on the plant gave further insight into the prey preferences of these predators.