title: Factors determining species displacement of related predatory mite species (Acari: Phytoseiidae).
abstract: Neoseiulus womersleyi (Acari: Phytoseiidae) used to be the dominant species in fruit-tree orchards throughout Japan, but starting in the 1990s, N. womersleyi began to be displaced by Neoseiulus californicus in central and southwestern Japan. The present study was conducted to examine factors explaining the displacement of N. womersleyi by N. californicus. First, we confirmed under laboratory conditions that N. californicus could exclude N. womersleyi if they initially coexisted in a 1:1 ratio. During a 2-h continuous observation period, none of the heterospecific pairs had copulated and after 5 days together with heterospecific males, none of the females had laid eggs. When these females were placed with conspecific males, normal numbers of offspring were produced. Moreover, conspecific matings were not substantially disturbed in the presence of heterospecific males or females. Total fecundity was significantly lower in N. womersleyi than in N. californicus, but their r m values did not differ from each other. On the other hand, the frequency of intraguild predation by N. californicus on N. womersleyi was significantly higher than vice versa. From these results, we concluded that not reproductive interference nor differential female fecundity but asymmetrical intraguild predation seemed to explain the competitive exclusion of N. womersleyi by N. californicus.
authors: Laboratory of Applied Entomology and Zoology, Faculty of Agriculture, Ibaraki University, Ami, Ibaraki, 300-0393, Japan, gotoh@mx.ibaraki.ac.jp.
authors: Tetsuo
authors: T
authors: Gotoh
authors: Masumi
authors: M
authors: Hanawa
authors: Sayaka
authors: S
authors: Shimazaki
authors: Natsuki
authors: N
authors: Yokoyama
authors: Chun-Qing
authors: CQ
authors: Fu
authors: Reo
authors: R
authors: Sugawara
authors: Shuichi
authors: S
authors: Yano
mesh_terms: D000818:Animals; D003163:Competitive Behavior; D005260:Female; D008297:Male; D008925:Mites / Q000254:growth & development*; D011235:Predatory Behavior; D012098:Reproduction