Multidimensional niche partitioning in a parasitoid guild parasitizing Xylotrechus stebbingi (Coleoptera: Cerambycidae) in its native Indian Himalayan range: New host records and ecological interactions
摘要
Three parasitoid wasps associated with the cerambycid beetle Xylotrechus stebbingi were recorded from the Kashmir Himalayas: the doryctine braconids Neurocrassus palliatus and Parallorhogas pallidiceps, and the ichneumonid Xorides xylotrechi. Clear temporal segregation in oviposition behaviour was observed, with N. palliatus exhibiting exclusively nocturnal activity, whereas X. xylotrechi and P. pallidiceps were diurnal. Host size preferences differed significantly among parasitoids, with P. pallidiceps attacking smaller hosts (13.4 ± 4.07 mm) compared with X. xylotrechi (20.5 ± 1.45 mm) and N. palliatus (21.9 ± 2.77 mm). Reproductive strategies also differed: X. xylotrechi was solitary (one egg per host), whereas N. palliatus and P. pallidiceps were gregarious. In the gregarious species, host larval size was strongly positively correlated with clutch size (r > 0.90), with a steeper clutch size increase in N. palliatus (1.63 eggs mm⁻1 host size) than in P. pallidiceps (1.00 eggs mm⁻1). All species exhibited significantly female-biased sex ratios (76.2–86.0%) and female-biased sexual size dimorphism (SDI: + 0.175 to +0.339), although the degree of female bias did not differ significantly among species. Development time varied significantly, with X. xylotrechi requiring 40–44 days to complete development compared with 21–28 days for the two doryctine species. These findings indicate differences among parasitoids associated with X. stebbingi and provide baseline information on their occurrence in Himalayan ecosystems. Further studies on host range, non-target effects, and field performance are required to assess their potential for biological control.