抄録
Geographic variation of a Japanese harvestman species, Leiobunum montanum Suzuki 1953 was
studied in Tottori Prefecture and adjacent areas in the Chugoku Mountains in Honshu, Japan. In addition to the
Mt. Daisen race, occurrence of two new local races were found: “Ohginosen race” which bears typically elongated
abdomen and “Chizu-Wakasa race” characterized by having male palps with prehensile structures. The
number of chromosomes varied from 2n =18 to 2n = 22 with several populations which show polymorphic for
the number. There were many populations that were polymorphic for 2n=20/21/22 in the Chizu and Wakasa
areas, southeastern part of Tottori Pref., though no populations fixed for 2n = 22 were found. Populations from
Mt. Daisen to the western rim of the Chizu area is characterized by having 2n =18 karyotype, though a population
was found to be polymorphic 2n = 18/20. Leiobunum montanum and L. hiraiwai, both of which are members
of the curvipalpe-group of Leiobunum, show an exclusive pattern in their distribution except for a few
populations where the two occur sympatrically on the northwestern slope of Mt. Hyonosen. This is the case
of sympatry found for the first time for two bisexual species of the curvipalpe-group. Leiobunum montanum
has body size similar to L. hiraiwai but populations of the Ohginosen race which is sympatric with L. hiraiwai
are clearly larger than it. It is likely that the body size difference serves to the sympatric occurrence of the two
species.
