The spider fauna in the rice agricultural landscape of Hainan Island, China: Composition, abundance and feeding structure

The project "Conserving Arthropod Biodiversity and Ecosystem Services in Rice Environments" was conducted on the island of Hainan located at the southernmost part of China, the second largest island off the coast with a tropical biodiversity-rich region in arthropods. Spider biodiversity exploration, the first activity executed in selected areas in August 2010 yielded 10,426 specimens made up of spiderlings, subadults and adults. The composition represented 167 species under 97 genera and 19 families. Of these, 21 species in seven families, namely: Araneidae (2 spp.), Clubionidae (3 spp.), Lycosidae (5 spp.), Salticidae (2 spp.), Theridiidae (7 spp.) and one each in Thomisidae and Zodariidae were discovered as new to science and their taxonomic treatment will be dealt with separately. Sixty-six species, 40 genera and two families were added to Hainan spider biodiversity checklist. Pooled samples showed six families as most abundant in decreasing order, namely: Oxyopidae (4,259 specimens) > Araneidae (3,380) > Tetragnathidae (1113) > Thomisidae (548) > Lycosidae (518) and Salticidae (383). In terms of species, the immatures of the lynx spider, Oxyopes spp. (Oxyopidae) and orb-web, Araneus inustus (Araneidae) were most dominant keystone speci es that were likely to have exerted strong ecological services in the rice environment by preying on planthoppers, leafhoppers and leaffolder moths. Across sites, the trend in total spider abundance was Danzhou (4,036 specimens in 17 families) > Lingshui (3,904 spiders in 14 families) > Sanya (1,254 spiders in 9 families) > Haikou (1,231 spiders in 11 families). Four families - Oxyopidae, Araneidae, Tetragnathidae and Salticidae were most abundant in Danzhou while Araneidae, Oxyopidae, Lycosidae and Thomisidae in Lingshui. Three families - Tetragnathidae, Oxyopidae and Araneidae dominated Sanya while Oxyopidae and Lycosidae in Haikou. Two claw types - trionychus or 3-clawed (9,454 specimens in 10 families or 90.7% of all spider catch) vs. dionychus or 2-clawed (972 in 9 families or 9.3%) and two feeding structures - hunters (5,833 specimens in 13 families, 55.95%) vs web builders (4,593 specimens in 6 families, 44.05%) characterized the spiders from Hainan island. All these hunting and web-building spiders - ecological service promoters in nature were predators and constituted a sizeable amount of arthropod biodiversity catch from the island. Spider conservation through abandonment of insecticide use and growing of flowering plants around rice fields is highly recommended to maintain rich biodiversity.