Biotopical Distribution of Orb-Weaver Spiders (Aranei: Araneidae) in the Ridge-top Zone of the South Sikhote-Alin Mountains

Until recently, the study of spiders in the mountainous conditions of the Primorsky Region of Russian Far East was carried out only with the example of ground dwelling spiders. The purpose of this work is to reveal the species composition and features of the biotopic distribution of orb-weaver spiders (Aranei: Araneidae) in the ridge-top zone of the Southern Sikhote-Alin mountains (Primorsky Region). The field material was collected from may to october in 2016 and 2017 at key sites located on different mountain ranges and their spurs in the altitude range from 1000 to 1560 m above sea level. Within each key sites, transect-sites with a size of 3 x 25 m were laid. The spider's collections were by the hands collecting and sweeping method. A total of 305 specimens of spiders belonging to 10 species from 7 genera were caught. Comparison of species lists of spiders was carried out by cluster analysis methods (unweighted pair group method with arithmetic mean, UPGMA) using the Jacquard coefficient. For automatic calculations data processing program Past v. 2.17 is used. The maximum diversity of spiders is observed among the herbage-reed meadows, which do not form a continuous belt of vegetation at altitudes of 1000–1400 m above sea level. seas. Seven species belonging to 6 genera were caught here. The minimal diversity is noted among the continuous open stony debris, devoid of vegetation. Here is the only species caught – Aculepeira matsudae. The species Plebs sachalinensis and Araniella yaginumai are most numerous and widespread in the ridge-top zone of the Southern Sikhote-Alin. The high abundance of Araniella yaginumai is achieved due to favorable conditions for this species in the herbage-reed grass lands. In all the studied biotopes in the ridge-top zone of the mountains the density of the orbweaver spiders is low and does not exceed 2.04 specimens per 10 m2.