Spider Diversity in Kavvayi River Basin , Kerala , Southern India

Kavvayi river basin is a typical lateritic biotope situated in the Northern part of Kerala, which holds various ecological units such as lateritic vegetation, agro-ecosystems, seasonal pools, Grass lands, Kanams, Sacred groves, Mangrove-marsh and riparian vegetation. Many of these microhabitats are unique in character and poorly documented. A preliminary study was conducted to document the diversity of spider fauna inhabiting in the different ecosystems of Kavvayi river basins.India is having 1,686 species of spiders belonging to 60 families and 438 genera, which constitutes 3.6% of world’s spider population. The present study resulted in the documentation of 112 species of spiders belonging to 81 genera and 21 families. Araneidae was the most dominant family which constitutes 21.5% of the total spider species collected. The second dominant family was Salticidae which constitutes 19.5% of total spider population. Guild structure analysis of the collected spiders revealed seven feeding guilds, namely stalkers, orb web builders, ambushers, foliage runners, space web builders, ground runners and wandering sheet weavers. The spider fauna of this ecosystem is qualitatively rich due to varied microhabitats, which supports high floral and faunal diversity. The present study suggests a detailed investigation at ecosystem level to understand the role of spiders in ecosystem function. Current World environment Journal Website: www.cwejournal.org ISSN: 0973-4929, Vol. 13, No. (1) 2018, Pg. 100-112 ContACt Ashtamoorthy Sreejith dr.sreejithnamboodiri@gmail.com Kerala Forest Research Institute, Peechi, Thrissur, Kerala


Introduction
As one of the most widely recognized group of arthropods, spiders make up a diverse portion of the world's invertebrates 1 .They are distributed on every continent except Antarctica and have adapted to all known ecological environments except air and open sea 2 .Spiders globally include about 47,099 described species in 4,073 genera and 113 families 3 .They are unique among all organisms in their modes of silk production and usage and of reproduction.
Spiders are clearly an integral part of the global biodiversity since they play an important role in ecosystems as predators and source of food for other creatures 4 .They primarily feed on insects, but also eat other arthropods, including other Araneae.They are suitable biological indicators of ecosystem changes and habitat modifications due to their small body size, short generation time, and high sensitivity to temperature and moisture changes 5 .
Spiders form one of the most diverse groups of organisms existing in India.Previous conservation efforts in India have focused on the larger vertebrates while invertebrates were largely ignored.There is now a growing need to conserve all species and not only the larger vertebrates 6 .Documentation of spider fauna is more important because they play a significant role in the regulation of insects and other invertebrate populations in most ecosystems.A comprehensive data on diversity and distribution of spiders from Kerala region is sparse as compared to other regions of the country.India is having 1,686 species of spiders belonging to 60 families and 438 genera, which constitutes 3.6% of world's spider population 7 .Very little work has been done on spider diversity of Kerala 8,9,10 .Joseph et al., 11 reported 20 species of spiders from Periyar Tiger Reserve.Patel B.H. 12 described 91 species of spiders from Parambikulam tiger reserve.Sudhikumar et al., 13 reported 75 species of spiders from Mannavan shola forest areas and Sunil et al., 14 reported 147 species of spiders from Parambikulam tiger reserve.Most recently Sudhikumar 15 listed 210 species of spiders from Nelliyampathy hill ranges of Western Ghats.This is higher than the number recorded from any other regions surveyed in Kerala.The present study is carried out in Kavvayi River Basin, which is in Northern Kerala.This region is abundantly blessed with rich flora and fauna.The only reported study from this area on spiders was Palot and Balakrishnan 16 in which they reported 17 species from Madayipara, a lateritic hill of Northern Kerala.The aim of this study was to compile the first checklist of spiders of the Kavvayi river basin and to determine the percentage of species protected.

Study Area
We conducted our study in the Kavvayi river basin, located between 12 0 05' to 12 0 15' North latitude and 75 0 05' to 75 0 20' East longitude.It spread over an area of 164.76 km 2 spreads over nine local administrative bodies in the districts of Kannur and Kasaragode.The Kavvayi River emerges from the Cheemeni laterite hills at an elevation of 119 m above MSL having a length of 31 Km and directly flows into the Kavvayi backwater.The river basin is topographically complex, biodiversity-rich, fragmented and densely populated cultural landscape.Even though the Kavvayi River is prominent among the 14 rivers originating in midland in Kerala there is no reserved forest patch in the river basin.According to land use or land cover pattern, the study area has major subdivisions such as Lateritic exposed area, Sacred Groves, Kaanams, Plantations and Agroecosystems, Mangrove or marsh (Figure -i).

Sampling
The study has been carried out during the month of January to December 2014 in the Kavvayi river basin of Kerala.Two surveys were conducted per month at selected areas of the river basin.Spider collection was done during the morning (7.00 am to 11.00 am) and evening (16.00 pm to 18.00 pm) time to maximize the species richness.An all out search method was used for spider collection and the collection was conducted mainly by handpicking and beating methods.Pitfall sampling was also employed for spider collection.Spider microhabitats like fallen logs and leaf litters were thoroughly checked for ground-dwelling spiders while leaves of trees and visible webs were searched for arboreal spiders.Smaller spiders were collected by leading them into tubes containing alcohol with the help of brush dipped in alcohol.Most of the spiders were photographed in the field itself with the help of SLR Camera Canon EOS 5D Mark-III.Identification was done at the Centre for Animal Taxonomy and Ecology (CATE), Dept. of Zoology, Christ College, Irinjalakuda.The specimens were preserved in 70% alcohols with proper labeling of locality, date of collection and other notes of importance.The mature specimens were identified up to the species level with the help of stereo zoom microscope (Magnus MSZ TR) and also with available literature 17,18,19,20,21 .

Results and Discussion
A total of 112 species of spiders belonging to 81 genera and 21 families were collected(Table 1) during the study period.The genera such as Oxyopes and Neoscona show high species diversity.Out of the 438 genera reported from Indian region 7 , 81 genera were collected from Kavvayi River Basin.Maximum generic diversity was found in families including Salticidae (18), Araneidae (14), Theridiidae (9) and Thomisidae (8).Out of the 60 families recorded from the Indian region, 21 families were collected from Kavvayi river basins.This represents 35% of the total families reported from India.Araneidae was the most dominant family corresponding 24 species from 14 genera constituting 21.5% of total spider population.The second dominant family was Salticidae with 22 species from 18 genera constituting 19.5% of the total population.The relative species abundance of various families recorded during the study can be represented as Salticidae>Theridiidae >Thomisidae Tetragnathidae>Oxyopidae>Lycosidae =Uloboridae>Pholcidae=Sparassidae=Pisauridae> Ctenidae=Gnaphosidae= Linyphiidae=Eutichuridae =Scytodidae>Corinnidae=Eresidae=Hersilidae =Philodromidae=Theraphosidae (Figure -ii)..The spiders collected from the study area can be divided into seven functional groups or guilds based on the classification system proposed by Uetz et al., 22 ..In 1991, Uetz 24 reported that structurally more complex shrub can support a more diverse spider community.
At present, the study area is facing unprecedented levels of fragmentation.The changes in land use pattern led to over exploitation of ecologically important land classes like Laterite exposed area, mangrove -marsh lands, paddy cultivation, ecogroves, etc.., without considering its importance.Due to the scarcity of woody species or forest cover the lateritic exposed regions in the study area appear devoid of vegetation in remote sensing images and often considered as 'wastelands' that's why miners easily get the permission from the authorities for mining and reclamation of the area but, in reality, these landscape units having high biodiversity value and ecological significance.At present only a small portion of the lateritic exposed area remains undisturbed.There is no reserve or protected forest in the study area that's why no parts of the river basin other than some sacred groves got authorized protection, sacred groves got cultural or religious protection from the local people.Considering their ecological importance there is an urgent need to conserve the critical ecosystems in the river basin.
Our study provides baseline information of spiders inhabiting in this ecosystem.The habitat destruction is at its peak, this type of valuable scientific information would help to create proper conservation and management strategies of this landscape

Fig. i :
Fig. i: location map of Kavvayi river basin showing critical land cover