Geographic variation of <i>Gagrellula ferruginea</i> (Opiliones: Sclerosomatidae) in Tottori Pref., Honshu, with special reference to a hybrid zone between two geographical races

Geographic variation of a Japanese harvestman species, Gagrellula ferruginea (Loman 1902) was studied in Tottori Prefecture and adjacent areas in Honshu, Japan.Two geographical races, the Daisen race and the Kinki race, were distinguished by the coloration of the body and legs.The both forms intergrade one another at the boundary of their ranges making a hybrid zone of ca.20 km wide.The diploid number of chromosomes was 12 in the seven western populations of 26 populations studied, while the number was 14 in the 18 eastern populations from the Hino River, irrespective of the variation in coloration.The number of noduli on the second femur varied from 1 to 5, though the mode was three except for a single population (Yabara predominated by 2).There was a slight increase of the mean noduli number toward east (Spearman rank correlation, r s = 0.15, P<0.001).Legs became shorter with the increase of altitude in each of the areas around Mt. Daisen, Mt.Mikuniyama and Mt.Hyonosen, though the populations around Mt. Daisen always had shorter legs than those in the other areas.Response to altitude of body length differed between populations around Mt. Hyonosen and those around Mt. Mikuniyama and Mt.Daisen.Body became smaller with the increase of altitude in the populations around Mt. Daisen and Mt.Mikuniyama, but the trend was unclear in the populations around Mt. Hyonosen.