Interspecies interference of oviposition behaviour in the cowpea weevils Callosobruchus rhodesianus (Pic) and Callosobruchus maculatus (F.)

Abstract

The total number of eggs laid by Callosobruchus rhodesianus (Pic.) and Callosobruchus maculatus (F.) females in the presence of single and mixed species populations of males at different densities were counted. Increasing male density significantly reduced the realised fecundity of C. maculatus but not C. rhodesianus females. In the presence of C. maculatus males, however, the number of eggs laid by C. rhodesianus was greatly reduced. The reduction in egg laying and observations on mating behaviour indicates direct physical interference between weevils and competition for mates. An adequate number of beans were provided so competition for oviposition sites by females was unlikely. The ability of C. maculatus to inhibit oviposition of C. rhodesianus is suggested as one reason for its superiority over the latter when the two species compete for limited resources.Resume-Le nombre d'oeufs pondus par Callosobruchus rhodesianus (Pic.) et Callosobruchus maculatus (F.) en presence de differentes densities de males d'especes unique ou mixtes hlrent compte. L'augmentation des densities de males ont reduit de fagon significative la fecondite realisee de C. maculatus mais non celle de C. rhodesianus. Par contre en presence de males de l'espece C. maculatus, le nombre d'oeufs pondus par C. rhodesianus fut grandement reduit. La reduction d'oeufs pondus inique une interference physique directe entre les charancpns ainsi qu'une competition pour l'accouplement. Une qualite suffissante de feves fut fournie afin que la competition entre les femelles pour les sites d'oviposition soit improbable. La capacite d'inhiber l'oviposition de C. rhodesianus par C. maculatus est suggeree comme une raison pour sa superiorite sur C. rhodesianus lorsque les deux especes competitione pour des ressources limitees.

Demographic consequences of reproductive interference in multi-species communities

“… 15 , 68 – 70 ]. As a result, it should be easier to detect demographic RI when the starting frequencies of species are highly skewed because fitness loss from RI will be amplified when the rarer species experiences proportionally more harmful heterospecific encounters [ 70 – 72 ]. Consequently, our experimental design is conservative with respect to being able to detect demographic RI, which likely explains why we observed demographic RI for only some experimental treatments.…”

Reproductive interference: ecological and evolutionary consequences of interspecific promiscuity

“…Assuming reciprocal reproductive interference between two closely related species, relatively more abundant species inflicts stronger effect on the fitness of the other species (Giga and Canhão 1997;Liu et al 2007;Kishi et al 2009), because as the number of individuals increases, harassing males become more abundant. In addition, increased conspecific abundance is advantageous for females, because it dilutes the effect of mating attempts by heterospecifics on individual females (Kyogoku and Nishida 2012).…”

Why Callosobruchus rhodesianus causes limited damage during storage of cowpea seeds in a tropical humid zone in Togo

“…The C. maculatus larvae could eliminate C. rhodesianus larvae after larval fights or could inhibit the development of its competitor. The ability of C. maculatus to inhibit the oviposition of C. rhodesianus (Giga & Canhao, 1997) and the reduced chances of survival of C. rhodesianus larvae in interspecific competition still decreased the developmental capacities of this species under storage conditions. In interspecific competition with Callosobruchus chinensis , C. maculatus also appears to be the better competitor, and several studies have demonstrated its ability to exclude its competitor in mixed cultures (Bellows, 1990).…”

“…Interspecific competition with the sympatric species C. maculatus could be a disadvantage for C. rhodesianus. Giga & Canhao (1997) observed that the number of eggs laid by C. rhodesianus was greatly reduced in the presence of males of C. maculatus. They suggested that the ability of the latter species to inhibit oviposition of C. rhodesianus could explain its superiority in interspecific competition.…”