Distribution of an endangered burrowing spider Lycosa ishikariana in the San'in Coast of Honshu, Japan (Araneae: Lycosidae)

抄録

We surveyed habitats of an endangered burrowing wolf spider Lycosa ishikariana (Saito 1934) along the San'in coast of Tottori and Shimane Prefectures, southwestern Honshu, Japan. The species was found from eight sites covering seven different beaches from Inasa Beach (Izumo City) in the east to Toda Beach (Masuda City) in the west in Shimane Prefecture for the first time. This extends the southwestern limit of the species' range ca. 160 km westward from the Yumigahama Beach of Tottori Prefecture, the present southernmost record. In the coast of Tottori Prefecture, the species was found from 17 sites that exceed known number of records in the area. The apparent increase of the number of habitats of the species in Tottori Prefecture is probably due to a shift of survey season from the mid summer to June when density of the burrows culminates by the recruit of newly hatched spiderlings. Simple logistic regression analyses suggested that presence/absence of the species is related to any of the sand grain sizes, sorting indices, areas, lengths and maximum widths of the sandy beaches, though a multiple logistic regression analysis revealed that beach areas and sand grain size were the most significant factors. According to the models obtained, requirements for the occurrence of species were estimated to be areas>0.0313 km² (total length>985 m, width>60 m) of sandy beach, and sand grain diameter>0.33 mm.