Multivariate sexual selection in a rapidly evolving speciation phenotype

Abstract

Estimating the fitness surface of rapidly evolving secondary sexual traits can elucidate the origins of sexual isolation and thus speciation. Evidence suggests that sexual selection is highly complex in nature, often acting on multivariate sexual characters that sometimes include non-heritable components of variation, thus presenting a challenge for predicting patterns of sexual trait evolution. Laupala crickets have undergone an explosive species radiation marked by divergence in male courtship song and associated female preferences, yet patterns of sexual selection that might explain this diversification remain unknown. We used female phonotaxis trials to estimate the fitness surface for acoustic characters within one population of Laupala cerasina, a species with marked geographical variation in male song and female preferences. Results suggested significant directional sexual selection on three major song traits, while canonical rotation of the matrix of nonlinear selection coefficients (g) revealed the presence of significant convex (stabilizing) sexual selection along combinations of characters. Analysis of song variation within and among males indicated significantly higher repeatability along the canonical axis of greatest stabilizing selection than along the axis of greatest linear selection. These results are largely consistent with patterns of song divergence that characterize speciation and suggest that different song characters have the potential to indicate distinct information to females during courtship.

Multivariate sexual selection on male tegmina in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: Haglidae)

“…Both centroid size and PC3 covaried with dominant frequency (Tables and B), which was under strong stabilizing selection (Ower et al ., ). Multivariate stabilizing sexual selection on dominant frequency has also been reported in Australian black field crickets, Teleogryllus commodus (Brooks et al ., ) and Hawaiian sword‐tail crickets, Laupala cerasina (Oh & Shaw, ).…”

“…Females exert directional sexual selection for increased male calling effort (French & Cade, ; Hunt et al ., ; Bentsen et al ., ). Evidence of stabilizing selection has been found for call structure (Brooks et al ., ; Bentsen et al ., ; Hunt et al ., ) and dominant frequency (Oh & Shaw, ; Ower et al ., ), both of which may be important in species recognition.…”

Reproductive isolation between two populations ofAglaoctenus lagotis, a funnel-web wolf spider

“…Behaviour evolves quickly in response to environmental changes, which is why it may be the most easily detected feature in speciation events (Barlow, ). Indeed, several studies suggest the emergence of new species as a result of differences in behaviour between populations during sexual interactions (Pillay & Rymer, ; Oh & Shaw, ), although not all cases with intraspecific differences of this kind could reflect individual variation or personalities (Claridge & Morgan, ). As sexual interactions usually involve a rich communicatory exchange (Coyne & Orr, ), in some scenarios multiple signals are used to recognize conspecifics, whereas in others a single signal can give information about more than one individual trait, such as sexual identity and mate quality (Candolin, ; Hebets & Papaj, ; Rypstra et al ., ).…”

Vocal imitation of mother's calls by begging Red-backed Fairywren nestlings increases parental provisioning

“…277-1008C; RadioShack, Fort Worth, Texas, USA) connected to an Apple iPod Nano via a 20 m cable. The RadioShack speaker has been used in other published playback experiments successfully without distortion (see Hauber et al 2001, Uy et al 2009, Benedict 2010, Oh and Shaw 2013. In addition, the use of the 2 speakers was balanced in terms of which track was used with which speaker (with 50% of the trials in the low similarity range and 50% in the high similarity range) and so any difference in responses observed would not have resulted from differences in speaker quality.…”