Asymmetrical reproductive interference between two sibling species of tea looper: Ectropis grisescens and Ectropis obliqua

Abstract

AbstractEctropis grisescensWarren andEctropis obliqua(Prout) are two morphologically similar sibling species with overlapping ranges. In this study, manipulative laboratory experiments were conducted to examine the possibility of reproductive interference in sympatric populations ofE. grisescensandE. obliquaand the potential consequences of the mating interaction. Our results showed that the presence of males or females of different species could incur mating interference and significant reduction ofF1offspring. The reduction was not significant relevant to the initial relative abundance ofE. grisescensandE. obliqua. Detailed observations of mating opportunity showed that female mating frequencies of both species were not significantly affected by the absolute species density, but the mating success ofE. obliquafemales with conspecific males depended on species ratio. In addition, adding males to the other species resulted in lower number of offspring suggesting that the males’ behaviour might be linked with mating interference. Males of bothE. grisescensandE. obliquacould interfere the intraspecific mating of the other species, but the impact of the mating interference differed. These combined data indicated that asymmetric reproductive interference existed inE. grisescensandE. obliquaunder laboratory conditions, and the offspring of the mixed species were significantly reduced. The long term outcome of this effect is yet to be determined since additional reproductive factors such as oviposition rate and progeny survival to adulthood may reduce the probability of demographic displacement of one species by the other in overlapping niches.