Diversity and Structure of Spider Assemblages in Sirumalai Hills, Dindigul District, Tamilnadu
A pilot study was conducted to reveal the spider diversity in Sirumalai hills of Dindigul district. The study was conceded out in Sirumalai Hills which is the western offshoot of the Eastern Ghats, lying between 10°07' - 10°18' N latitude and 77°55' - 78°12'. The annual rainfall is around 1200 mm per year, with approximately 75 rainy days in two seasons. The maximum rainfall is recorded from the North-East monsoon (October-November). April- June is noted as the hot summer season. The humidity is maximum in the rainy months (91%) and minimum in the summer months (68%). A total of 112 species of spiders belonging to 78 genera of 35 families were collected from this area during this study period (June 2014- May2015). The maximum and minimum temperatures were recorded in the months of May (29.2°C) and January (18.3°C) respectively. This represents 10% of the total families recorded in India. Guild structure analysis of the collected spiders revealed 6 feeding guilds viz., orb-web builders, foliage hunters, ground hunters, sheet web builders, scattered line weavers and ambushers. The families Araneidae, Tetragnathidae, Salticidae and Thomisidae exhibited maximum species diversity. The dominant family was Araneidae with 17 species. Shannon index, Simpson index, and Margalef Richness index evaluated were 1.06, 0.103 and 8.4 respectively. Spiders belonging to different feeding guild and population were higher during monsoon and winter season. Because of the complex interaction of various climatic factors such as high rainfall and humidity, with topographical features, Sirumalai hills holds many smaller but diverse environmental niches which make this an important centre of speciation in Eastern Ghats.
Keywords - Spider diversity, Eastern Ghats, Sirumalai Hills, Araneidae