Selection becomes visible: enforced sexual dimorphism caused by sexual selection in the weevilRhopalapion longirostre(Olivier 1807) (Coleoptera: Curculionoidea: Brentidae)

Abstract

Extremely divergent traits between males and females are often the result of different requirements and behaviours of the sexes and will evolve relatively rapidly under selection forces. Sexual dimorphism in Rhopalapion longirostre is predominately manifested in the length and structure of the rostrum. To estimate how sexual selection shapes mating success in this weevil we compared paired and unpaired individuals collected from three populations in Austria. The mating process in this species is complex and lengthy. Statistical analyses based on detailed observations of their mating behaviour revealed that matched pairs show functional affinities in body size. Females and males with larger elytra, as well as males with large overall body size, are favoured mating partners, while males that are too small have no mating success. This arrangement ensures copulation and consequently successful egg deposition. For efficient egg channel boring into the flower buds of the host plant, Alcea rosea, the extremely long female rostrum is a crucial tool. Natural selection promotes longer rostra in females whereas sexual selection favours the shorter rostra in males. The major evolutionary forces, natural and sexual selection, enhance the sexual dimorphism in this species.

Mating Behavior and Sexual Selection in Monochamus saltuarius (Gebler)

“…In the hollyhock weevil Rhopalapion longirostre (Olivier), individuals with large elytra are favored by the opposite sex. Prior to mounting, the prospective male R. longirostre seeks a large female with a long elytra, and females with a larger elytra enable males to crawl better and promote mating success [39], which is consistent with our results. The elytra length showed a significant positive correlation with the elytra width and other morphological characteristics of females.…”

“…Sexual dimorphism in R. longirostre is attributed to the interplay of two forces: natural selection, favoring larger females, and sexual selection, which stabilizes the size of male hind legs. This pattern has been observed and studied in this species [39]. In Nicrophrus orbicollis Say, the length of the male tarsus (especially the fore tarsus) is selected by females [79].…”

Opposites attract: Multiple evidence of sexual antagonistic coevolution driving extreme male-biased sexual size dimorphism inPanopeus meridionalis

“…The male biased sexual size dimorphism (MBSSD) of P. meridionalis ranks among the highest reported in animals, jointly with that of other crustaceans, some primates, mustelids and ungulates (Fairbairn, 1997; Janicke & Fromonteil, 2021). While the evolution of larger males is often attributed to enhanced performance in male-male competition for mating and female preference, the fact that the larger males are better able to force females to copulate is often overlooked as a concomitant powerful evolutinary driver (Shine & Mason, 2005; Wilhelm et al ., 2015). Although we did not test for the size related outcome of male-male contests, there is a great deal of evidence that positive correlation between body size and hierarchy is almost ubiquitous among crabs (Swartz, 1976; Van Der Meeren, 1994; Sneddon et al ., 1997; Brown et al ., 2005; Daleo et al ., 2009; Sal Moyano et al ., 2016) so it is reasonable to think that P. meridionalis is not an exception and intrasexual competence is operating.…”

“…Character displacement between the sexes resulting from natural selection acting differentially in each sex, which is often reffered as Sexually Antagonistic Selection (Parker, 2006; Connallon & Hall, 2018; De Lisle, 2019), should not be overlooked as either the sole or a concurrent force driving sexually divergent evolution. Indeed, trait variation between sexes is very often shaped by a synergistic combination of drivers of natural and sexual selection, each bearing variable weight along their co-evolutionary trajectories (Wilhelm et al ., 2015; De Lisle, 2019). A prime example of this is sexual size dimorphism (Connallon & Hall, 2018; Janicke & Fromonteil, 2021).…”

Excavation mechanics of the elongated female rostrum of the acorn weevil Curculio glandium (Coleoptera; Curculionidae)

“…Our observations suggest that females actively push their rostra into acorns and seemingly control the orientation of excavating channels. In addition to this, females of the brentid weevil species Rhopalapion longirostre excavate channels while carrying male partners, and it can happen that another male tries to copulate at the same time [27]. The females, therefore, may encounter unexpected loads and be abruptly moved during excavation.…”