When Love Comes Calling: Measuring Sexual Selection on Sagebrush Crickets

Abstract

Male sagebrush crickets exhibit differential mating success based on their previous mating experience: virgin males have a higher probability of obtaining a mating than do non-virgin males. Measures of lifetime mating success in male sagebrush crickets have revealed that the median mating frequency is one, with many males failing to secure a mate at all and a small minority obtaining two to four mates. The purpose of this study was to investigate the acoustic and morphological characteristics that make male sagebrush crickets attractive to females. Male crickets were captured from Deadman’s Bar in Grand Teton National Park and their songs were recorded on subsequent evenings. Five song characteristics were measured including pulse duration, interpulse duration, dominant frequency, train duration, and intertrain duration. Multivariate selection analysis revealed significant linear and nonlinear selection on male song, with each of the five measured song characters contributing to male attractiveness. There was significant directional selection favoring longer pulse durations and shorter interpulse durations, which could be an honest indicator of male quality because these song characters likely impose high energetic costs. Significant stabilizing selection favored males with ~ 13.2 kHz calls and intermediate intertrain durations, which may be imposed by the auditory sensitivity of females.