Sonja Sbilordo

Sexual selection promotes traits that enhance mating or fertilization success, but these traits can be very costly under harsh environmental conditions. The extent to which differential investment in costly traits under varying intensities of sexual selection is related to their susceptibility to environmental stress remains unclear. This study exp...

Biodiversity is increasingly threatened by unpredictable, frequent, and intense climatic events like heatwaves that pose harmful impacts on ectotherms. Beyond the health and survival of organisms, reduced reproductive performance has emerged as a critical fitness consequence of thermal stress induced by high temperatures. Many studies on these effe...

Frequent and extreme temperatures associated with climate change pose a major threat to biodiversity, particularly for organisms whose metabolism is strictly linked to ambient temperatures. Many studies have explored thermal effects on survival, but heat-induced fertility loss is emerging as a greater threat to population persistence. However, whil...

The processes underlying mate choice profoundly influence the dynamics of sexual selection and the evolution of male sexual traits. Consistent preference for certain phenotypes may erode genetic variation in populations through directional selection, whereas divergent preferences (e.g., genetically compatible mates) provide one mechanism to maintai...

Nongenetic parental effects can contribute to the adaptation of species to changing environments by circumventing some of the limitations of genetic inheritance. A clearer understanding of the influence of nongenetic inheritance and its potentially sex-specific responses in daughters and sons is needed to better predict the evolutionary trajectorie...

Dietary restriction during development can affect adult body size and condition. In many species, larger (high‐condition) males gain higher mating success through male‐male competition and female choice, and female condition can affect the extent of both female mate choice and male investment in courtship or ejaculates. However, few studies have ex...

The additive genetic variation (VA) of fitness in a population is of particular importance to quantify its adaptive potential and predict its response to rapid environmental change. Recent statistical advances in quantitative genetics and the use of new molecular tools have fostered great interest in estimating fitness VA in wild populations. Howev...

In presence of rapid environmental changes it is of particular importance to assess the potential of populations to adapt to new conditions. For rapid evolution to occur, standing genetic variation within a population is essential. Additive genetic variance (V A ) in fitness is therefore a key parameter for evaluating adaptive capacity. In this stu...

Polyandrous mating is extremely common, yet for many species the evolutionary significance is not fully resolved. In order to understand the evolution of mating systems, it is crucial that we investigate the adaptive consequences across many facets of reproduction. We performed experimental evolution with the naturally polygamous flour beetle Tribo...

Cold tolerance is an important trait directly related to survival and hence fitness. In the present study, the link is addressed between cold tolerance and body size, which is associated with many key fitness traits, at both the intra- and interspecific levels. Specifically, chill coma recovery time, as a metric of cold tolerance, is examined in fi...

To capture how sexual selection shapes male reproductive success across different stages of reproduction in Tribolium castaneum (Coleoptera, Tenebrionidae), we combined sequential sperm defence (P1) and sperm offence (P2) trials with additional trials where both males were added simultaneously to the female. We found a positive correlation between...

Hybridization must be followed by repeated backcrossing of the subsequent hybrid generations to the parental species for gene exchange between species to occur. Due to meiotic failures, first-generation hybrids of some species produce unreduced gametes. Their progeny in backcrosses with a diploid parental species are polyploid and functionally ster...

Background: Starvation is known to decrease male reproductive success in Tribolium castaneum. Starved males transfer less sperm, but we do not know whether reduced reproductive success is caused by lower oviposition rates of females or more frequent deposition of unfertilized eggs. Study organism: The red flour beetle Tribolium castaneum (Coleopter...

Knowledge of karyotypical characteristics of a species is essential for understanding how sexually selected and sexually antagonistic traits evolve. The yellow dung fly Scathophaga stercoraria L. (Diptera: Scathophagidae) is an established model system for studies of sexual selection and sexual conflict, but karyotypical data are lacking to date. H...

This dissertation comprises the results of five microscopical studies addressing issues related to sexual reproduction. The main focus of the first two studies (Chapters 1-2) on water snail hybrids lies on chromosomal differences and their potential involvement in isolation mechanisms between these hybridizing species. The two studies on the yellow...

Females of many species mate multiple times and store transferred sperm in storage organs. The mechanisms underlying sperm release from the stores at fertilization remain poorly understood, although they are central to an understanding of the female influence on post-copulatory male competition. Using double-mated females of the yellow dung fly, we...

Female yellow dung flies, Scathophaga stercoraria, can influence the traffic of sperm stored in their spermathecae to the site of fertilization in the bursa copulatrix. However, the anatomical mechanisms employed are largely unknown. We investigated the anatomy of the female genital tract, seeking structures involved in sperm transfer and egg ferti...