Space partitioning among the wolf spider Pardosa amentata species group in Hokkaido, Japan

Abstract

Summary There are 4 species belonging to the wolf spider Pardosa amentata species group in Hokkaido. The 4 species have separately occurred in Hokkaido in general, but a few species have sometimes occurred together at the same sites. Their biology at the coexisting sites, with special reference to partitioning of space was studied. P. agraria mainly inhabited fields and occurred widely in Hokkaido. P. hokkaido, P. brebivulva and P. lugubris inhabited the vicinity of forests and occurred in southern Hokkaido and on the side of the Sea of Japan in Hokkaido, all over Hokkaido excent the side of the Sea of Japan in central Hokkaido, and the lowlands and highlands in northern and eastern Hokkaido and mainly the highlands in other regions, respectively. In eastern Hokkaido where P. brevivulva and P. lugubris have coexisted, as the number of spiders detected and the number of localities of the former were less than those of the latter, it was concluded that the former occurred mainly in southern Hokkaido and the Hidaka region. In southern Hokkaido where P. hokkaido and P. brevivulva have coexisted, few individuals of both species were collected together at the same sites, and they were distributed allotopically. In short, the partitioning of space among the P. amentata species group occurring in Hokkaido was clear. From investigations on the coexisting sites and some other reports, it was considered that food, life cycle and diel activity periodicity among Pardosa occurring in Hokkaido were similar to one another. This may be one of the causes of the clear space partitioning among Pardosa. Since Pardosa is a raptorial predator that does not weave but wanders on the ground and uses space horizontally, available prey resource for Pardosa would be limited. It was therefore conjectured that the spider would be prone to space segregation, even if the spider could segregate the other niche dimensions. The partitioning of space between P. agraria and P. hokkaido inhabiting distinct habitats was loose when it was compared with that between species inhabiting similar habitats. As most of the spiders observed in the overlapping areas were females with egg cocoons, which required little food, the reduced feeding was considered to have allowed the loose partitioning.

Ecological Studies on Wolf Spiders(Araneae: Lycosidae) in a Northwest Area of Kanto Plain, Central Japan: Diel Activity and Habitat Preference Observed by Pitfall Trapping.

“…The three lycosids of Pardosa were collected only in daytime. They may be diurnal like the Pardosa lycosids in previous papers (DONDALE et al, 1972;YEARGAN, 1975;SuwA, 1986). Pirata yaginumai and Pirata piratoides showed slightly diurnal tanakai, and nocturnal tendency, respectively, but Arctosa fujiii, Pirata procurvus and P, and probably also Pirata clercki and Tricca japonica, can be regarded as aperiodic.…”

“…Some of these lycosids segregated their main habitats especially from other species of the same genus. Pardosa agraria in Hokkaido, northern Japan, is most abundant in meadows of forest edges (SuwA, 1986), but they were replaced by P, graminea in the study area. The absence or low frequency of P. graminea in Lsl and Ls2, and of P. astrigera in Bs2 suggests the exclusion by P, agraria or Pirata yaginumai.…”

“…2d---2f). They were tougher and larger than traps of Type A, and were used from 1983to 1986(Mar. 12 -Jul .…”

“…This paper shows interspecific differences of diel activity and habitat preference observed in pitfall samples. Some lycosids change diel activity (DONDALE et al, 1972) or habitat preference (EDGAR, 1971;HOLLANDER & L OF, 1972;DONDALE, 1977;SUWA, 1986;EUBANKS & MILLER, 1992) after their maturation and/or ovipositions. These changes were also examined.…”

“…For the substrata, bare soil, live plants, dead plants (or litter), and their water contents are probably selected (NORGAARD,1951;VLIJM & KESSLER-GESCHIERE, 1967;SCHAEFER, 1972;ROVNER & KNOST, 1974;DONDALE, 1977;UETZ, 1977;GREENSTONE, 1980). Specific composition of plants or animals was excluded from the elements of this classification, because there are no obvious relationships between lycosids and any particular species of plants or food animals (KUENZLER, 1958;MIYASHITA, 1968;EDGAR, 1969;HALLANDER, 1970;YEARGAN, 1975;DONDALE & BINNS, 1977;SUWA, 1986;UETz et al, 1992).…”