Biomedical subjects

Luc F Bussière

Publications and source records attributed to Luc F Bussière.

6 recordsLinked to original sources

PubMed2006

Sexual conflict and cryptic female choice in the black field cricket, Teleogryllus commodus.

The prevalence and evolutionary consequences of cryptic female choice (CFC) remain highly controversial, not least because the processes underlying its expression are often concealed within the female reproductive tract. However, even when female discrimination is relatively easy to observe, as in numerous insect species with externally attached spermatophores, it is often difficult to demonstrate directional CFC for certain male phenotypes over others. Using a biological assay to separate male crickets into attractive or unattractive categories, we demonstrate that females strongly discriminate against unattractive males by removing their spermatophores before insemination can be completed. This results in significantly more sperm being transferred by attractive males than unattractive males. Males respond to CFC by mate guarding females after copulation, which increases the spermatophore retention of both attractive and unattractive males. Interestingly, unattractive males who suffered earlier interruption of sperm transfer benefited more from mate guarding, and they guarded females more vigilantly than attractive males. Our results suggest that postcopulatory mate guarding has evolved via sexual conflict over insemination times rather than through genetic benefits of biasing paternity toward vigorous males, as has been previously suggested.

Animals↗

PubMed2005

Experimental evidence for multivariate stabilizing sexual selection.

Stabilizing selection is a fundamental concept in evolutionary biology. In the presence of a single intermediate optimum phenotype (fitness peak) on the fitness surface, stabilizing selection should cause the population to evolve toward such a peak. This prediction has seldom been tested, particularly for suites of correlated traits. The lack of tests for an evolutionary match between population means and adaptive peaks may be due, at least in part, to problems associated with empirically detecting multivariate stabilizing selection and with testing whether population means are at the peak of multivariate fitness surfaces. Here we show how canonical analysis of the fitness surface, combined with the estimation of confidence regions for stationary points on quadratic response surfaces, may be used to define multivariate stabilizing selection on a suite of traits and to establish whether natural populations reside on the multivariate peak. We manufactured artificial advertisement calls of the male cricket Teleogryllus commodus and played them back to females in laboratory phonotaxis trials to estimate the linear and nonlinear sexual selection that female phonotactic choice imposes on male call structure. Significant nonlinear selection on the major axes of the fitness surface was convex in nature and displayed an intermediate optimum, indicating multivariate stabilizing selection. The mean phenotypes of four independent samples of males, from the same population as the females used in phonotaxis trials, were within the 95% confidence region for the fitness peak. These experiments indicate that stabilizing sexual selection may play an important role in the evolution of male call properties in natural populations of T. commodus.

Analysis of Variance↗

PubMed2004

High-quality male field crickets invest heavily in sexual display but die young.

Only high-quality males can bear the costs of an extreme sexual display. As a consequence, such males are not only more attractive, but they often live longer than average. Recent theory predicts, however, that high-quality males should sometimes invest so heavily in sexual displays that they die sooner than lower quality males. We manipulated the phenotypic quality of field crickets, Teleogryllus commodus, by altering the protein content of their diet. Here we show that nymphs and adult females reared on a high-protein diet lived longer than those on a low-protein diet. In contrast, adult males reared on a high-protein diet died sooner than those on low-protein diets because they invested more energy in calling during early adulthood. Our findings uphold the theoretical prediction that the relationship between longevity and sexual advertisement may be dynamic (that is, either positive or negative), depending on local conditions such as resource availability. Moreover, they caution the use of longevity as a proxy for fitness in sexual selection studies, and suggest avenues for future research on the relationship between sexual attractiveness and ageing.

Aging↗

PubMed2004

Sinister strategies succeed at the cricket World Cup.

Left-handers occur at unexpectedly high frequencies at top levels of many interactive sports. This may occur either because left-handed contestants are innately superior or because they enjoy a negatively frequency-dependent strategic advantage when rare relative to right-handers. We analysed the batting records from the 2003 cricket World Cup and showed that left-handed batsmen were more successful than right-handers, and that the most successful teams had close to 50% left-handed batsmen. We demonstrate that this was because left-handed batsmen have a strategic advantage over bowlers, and that this advantage is greatest over bowlers that are unaccustomed to bowling to left-handers. This provides a clear mechanism for negative frequency-dependent success of left-handed batsmen. Our results may also support a historical role for negative frequency-dependent success in fights and other contests in the maintenance of left-handedness by natural selection.

Functional Laterality↗

PubMed2004

What is genetic quality?

Mate choice is favored by indirect selection if choosy females mate with males of high genetic quality. We believe, however, that testing hypotheses about indirect selection has been constrained by how we conceptualize and therefore empirically measure male genetic quality. Here, we argue that genetic quality is the breeding value of an individual for total fitness. We can therefore learn little about genetic quality from measures of only a few fitness components. We explain breeding value for total fitness, drawing on concepts from life-history theory and quantitative genetics, and suggest how approaches incorporating these insights might result in empirical progress.

Journal Article↗

PubMed2002

A model of the interaction between 'good genes' and direct benefits in courtship-feeding animals: when do males of high genetic quality invest less?

Conflict between mates over the amount of parental investment by each partner is probably the rule except in rare cases of genetic monogamy. In systems with parental care, males may frequently benefit by providing smaller investments than are optimal for individual female partners. Females are therefore expected to choose males that will provide the largest amounts of parental investment. In some species, however, the preferred males provide less care than their rivals. Focusing on species in which males invest by feeding their mates, I use a simple model to demonstrate the conditions under which males preferred by females may have optimal donations that are smaller than those of less-preferred rivals. Pre-mating female choice may sufficiently bias the perception of mate availability of preferred males relative to their rivals such that preferred males gain by conserving resources for future matings. Similarly, 'cryptic' biases in favour of high-quality ejaculates by females can compensate for smaller than average donations received from preferred males. However, post-fertilization cryptic choice should not change the optimal donations of preferred males relative to their rivals. I discuss the implications of this work for understanding sexual selection in courtship-feeding animals, and the relevance of these systems to understanding patterns of investment for animals in general.

Animals↗