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.

"水稻生境节肢动物多样性与生态系统服务保护"项目于中国最南端的海岛海南岛开展，该岛为中国沿海第二大岛，是节肢动物物种丰富的热带生物多样性区域。2010年8月在选定区域启动的蜘蛛多样性调查为项目首项活动，共采集到10426号标本，涵盖幼蛛、亚成体与成体，隶属于19科97属167种。其中7科共计21种为科学新种，分别为园蛛科（Araneidae）2种、袋蛛科（Clubionidae）3种、狼蛛科（Lycosidae）5种、跳蛛科（Salticidae）2种、球蛛科（Theridiidae）7种，以及蟹蛛科（Thomisidae）和狡蛛科（Zodariidae）各1种，相关分类学研究将另行开展。本次调查新增66种、40属及2科至海南岛蜘蛛多样性名录。
按标本量从高到低排序，优势类群依次为：猫蛛科（Oxyopidae，4259号标本）>园蛛科（Araneidae，3380号）>肖蛸科（Tetragnathidae，1113号）>蟹蛛科（Thomisidae，548号）>狼蛛科（Lycosidae，518号）>跳蛛科（Salticidae，383号）。物种层面，猫蛛属（Oxyopes spp.，Oxyopidae）的幼体与园蛛属物种Araneus inustus（Araneidae）为优势关键物种，它们通过捕食稻飞虱、叶蝉和稻纵卷叶螟，极可能在水稻生境中发挥了重要的生态服务功能。
各采样点的蜘蛛总丰度趋势为：儋州（17科，4036号标本）>陵水（14科，3904只蜘蛛）>三亚（9科，1254只蜘蛛）>海口（11科，1231只蜘蛛）。不同采样点的优势类群各有差异：儋州以猫蛛科、园蛛科、肖蛸科和跳蛛科为优势类群；陵水以园蛛科、猫蛛科、狼蛛科和蟹蛛科为主；三亚以肖蛸科、猫蛛科和园蛛科占主导；海口则以猫蛛科和狼蛛科为优势类群。
海南岛蜘蛛类群可分为两种爪型：三爪型（trionychus，10科共9454号标本，占总捕获量的90.7%）与二爪型（dionychus，9科共972号标本，占9.3%）；同时可按取食结构划分为两类：游猎型（hunters，13科共5833号标本，占55.95%）与结网型（web builders，6科共4593号标本，占44.05%）。上述游猎型与结网型蜘蛛均为捕食性天敌，是海南岛节肢动物生物多样性捕获样本中的重要类群，亦是自然生态服务的推动者。本研究强烈建议通过停用杀虫剂及在稻田周边种植显花植物开展蜘蛛保护工作，以维持区域丰富的生物多样性。