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

Abstract

Although the strength and form of sexual selection on song in male crickets have been studied extensively, few studies have examined selection on the morphological structures that underlie variation in males' song, particularly in wild populations. Geometric morphometric techniques were used to measure sexual selection on the shape, size and symmetry of both top and bottom tegmina in wild populations of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males. The size of the tegmina negatively covaried with song dominant frequency and positively covaried with song pulse duration. Sexual selection was more intense on the bottom tegmen, conceivably because it interacts more freely with the subtegminal airspace, which may play a role in song amplification. An expanded coastal/subcostal region was one of the phenotypes strongly favoured by disruptive selection on the bottom tegmen, an adaptation that may form a more effective seal with the thorax to prevent noise cancellation. Directional selection also favoured increased symmetry in tegminal shape. Assuming more symmetrical males are better able to buffer against developmental noise, the song produced by these males may make them more attractive to females. Despite the strong stabilizing selection documented previously on the dominant frequency of the song, stabilizing selection on the resonator that regulates dominant frequency was surprisingly absent. Nonetheless, wing morphology had an important influence on song structure and appears to be subject to significant linear and nonlinear sexual selection through female mate choice.

Immediate predation risk alters the relationship between potential and realised selection on male traits in the Trinidad guppyPoecilia reticulata

“…In agreement with previous work on the same population of guppies in conditions similar to our control treatment [19,52], we found that sexual selection was largely nonlinear. Such pattern of disruptive selection, with multiple phenotypes being similarly advantaged, has been described in multiple taxa including insects [73], birds [74] and fish [75]. While we found no significant linear β regression coefficients or θ coefficients on the M vectors in either treatment (table 1; electronic supplementary material, table S5), comparisons between treatments revealed that selection on GTs and boldness was more strongly linear in the predation treatment, and opposite in direction, compared with control (electronic supplementary material, table S6).…”

Sexual selection and population divergence II. Divergence in different sexual traits and signal modalities in field crickets (Teleogryllus oceanicus )

“…A recent study tested the relationship between acoustic signals in a sister species of field cricket, Teleogryllus commodus, and morphological features of male forewings that contribute to their resonant properties (Pitchers et al 2014). Such a pattern may be influenced by a greater degree of lability in behavioral traits compared to morphological traits that are fixed during development (Pitchers et al 2014;Ower et al 2016). Such a pattern may be influenced by a greater degree of lability in behavioral traits compared to morphological traits that are fixed during development (Pitchers et al 2014;Ower et al 2016).…”

“…Pitchers et al (2014) found that wing morphology and acoustic signal properties covaried with differing strength in different populations of this species, but that overall covariance was minimal and appeared unrelated to patterns of population divergence. Such a pattern may be influenced by a greater degree of lability in behavioral traits compared to morphological traits that are fixed during development (Pitchers et al 2014;Ower et al 2016).…”

Functional morphology of tegmina-based stridulation in the relict speciesCyphoderris monstrosa(Orthoptera: Ensifera: Prophalangopsidae)

“…Consideration of just one of these aspects, while being robust in the chosen field, may lead to unreliable interpretation of data (e.g. Ower et al, 2016). Some attempts have been made to infer basic singing parameters from Jurassic cricket species (Gu et al, 2012), but inferences are currently limited by a lack of knowledge on the characteristics of weakly delimited vibration-compliant areas.…”