Tactical adjustment of signaling leads to increased mating success and survival

Most sexually reproducing animals overcome the challenge of searching for and attracting mates by utilizing signals that are broadcast through a spatially and temporally varying environment. A diverse suite of behavioral solutions exist for overcoming such environmental variability, including the adjustment of signaling behavior based upon receiver feedback. Few studies have directly examined the relationship between such tactical signaling adjustments and proxies of male fitness; the few that have, failed to find a relationship. Using the wolf spider, Schizocosa rovneri, we set out to first quantify among-male variation in the form and degree of responsiveness to female feedback. Following exposure to female receptivity cues, some males increased their signaling on an effective signaling substrate (filter paper) while others decreased signaling on the effective substrate. These groups of males were then run through mating trials, conducted in a heterogeneous environment, to examine the relationship between male signaling adjustments and subsequent mating success. Males that adaptively adjusted their signaling (i.e. increased signaling on a more effective substrate) were (1) more likely to copulate, (2) achieved a copulation more quickly and (3) were less likely to be attacked; thus establishing a positive relationship between tactical adjustments of courtship signaling and male fitness

Tactical adjustment of signaling leads to increased mating success and survival

Most sexually reproducing animals overcome the challenge of searching for and attracting mates by utilizing signals that are broadcast through a spatially and temporally varying environment. A diverse suite of behavioral solutions exist for overcoming such environmental variability, including the adjustment of signaling behavior based upon receiver feedback. Few studies have directly examined the relationship between such tactical signaling adjustments and proxies of male fitness; the few that have, failed to find a relationship. Using the wolf spider, Schizocosa rovneri, we set out to first quantify among-male variation in the form and degree of responsiveness to female feedback. Following exposure to female receptivity cues, some males increased their signaling on an effective signaling substrate (filter paper) while others decreased signaling on the effective substrate. These groups of males were then run through mating trials, conducted in a heterogeneous environment, to examine the relationship between male signaling adjustments and subsequent mating success. Males that adaptively adjusted their signaling (i.e. increased signaling on a more effective substrate) were (1) more likely to copulate, (2) achieved a copulation more quickly and (3) were less likely to be attacked; thus establishing a positive relationship between tactical adjustments of courtship signaling and male fitness

The complexities of female mate choice and male polymorphisms: Elucidating the role of genetics, age, and mate-choice copying

Genetic, life history, and environmental factors dictate patterns of variation in sexual traits within and across populations, and thus the action and outcome of sexual selection. This study explores patterns of inheritance, diet, age, and mate-choice copying on the expression of male sexual signals and associated female mate choice in a phenotypically diverse group of Schizocosa wolf spiders. Focal spiders exhibit one of two male phenotypes: ‘ornamented’ males possess large black brushes on their forelegs, and ‘non-ornamented’ males possess no brushes. Using a quantitative genetics breeding design in a mixed population of ornamented/non-ornamented males, we found a strong genetic basis to male phenotype and female choice. We also found that some ornamented males produced some sons with large brushes and others with barely visible brushes. Results of diet manipulations and behavioral mating trials showed no influence of diet on male phenotype or female mate choice. Age post maturation, however, influenced mate choice, with younger females being more likely to mate with ornamented males. A mate-choice copying experiment found that, following observations of another female’s mate choice/copulation, virgin mature females tended to match the mate choice (ornamented vs. non-ornamented males) of the females they observed. Finally, analyses of genetic variation across phenotypically pure (only one male phenotype present) vs. mixed (both phenotypes present) populations revealed genetic distinction between phenotypes in phenotypically-pure populations, but no distinction in phenotypically-mixed populations. The difference in patterns of genetic differentiation and mating across geographic locations suggests a complex network of factors contributing to the outcome of sexual selection

The complexities of female mate choice and male polymorphisms: Elucidating the role of genetics, age, and mate-choice copying

Genetic, life history, and environmental factors dictate patterns of variation in sexual traits within and across populations, and thus the action and outcome of sexual selection. This study explores patterns of inheritance, diet, age, and mate-choice copying on the expression of male sexual signals and associated female mate choice in a phenotypically diverse group of Schizocosa wolf spiders. Focal spiders exhibit one of two male phenotypes: ‘ornamented’ males possess large black brushes on their forelegs, and ‘non-ornamented’ males possess no brushes. Using a quantitative genetics breeding design in a mixed population of ornamented/non-ornamented males, we found a strong genetic basis to male phenotype and female choice. We also found that some ornamented males produced some sons with large brushes and others with barely visible brushes. Results of diet manipulations and behavioral mating trials showed no influence of diet on male phenotype or female mate choice. Age post maturation, however, influenced mate choice, with younger females being more likely to mate with ornamented males. A mate-choice copying experiment found that, following observations of another female’s mate choice/copulation, virgin mature females tended to match the mate choice (ornamented vs. non-ornamented males) of the females they observed. Finally, analyses of genetic variation across phenotypically pure (only one male phenotype present) vs. mixed (both phenotypes present) populations revealed genetic distinction between phenotypes in phenotypically-pure populations, but no distinction in phenotypically-mixed populations. The difference in patterns of genetic differentiation and mating across geographic locations suggests a complex network of factors contributing to the outcome of sexual selection

Females Are Choosier in the Dark: Environment-Dependent Reliance on Courtship Components and Its Impact on Fitness

A broad understanding of multimodal courtship function necessitates knowledge of the potential information content of signal components, the efficacy of signal components in eliciting the appropriate receiver response, and the fitness consequences of mating decisions based upon various signal components. We present data addressing each of these requirements for the multimodal-signaling wolf spider, Schizocosa floridana Bryant. Using diet manipulations, we first demonstrate that both visual and seismic courtship signals are condition-dependent. Next, using high- and low-quantity diet individuals in mate choice trials across manipulated signaling environments, we demonstrate that the seismic signal is crucial for mating success and further show that female choosiness is environment-dependent. Females mated more with high diet males only in the absence of visual signals, showing no discrimination in the presence of visual signals. Finally, by quantifying the number of offspring produced by our mated females, we reveal that a female’s mating environment, in conjunction with her potential resource availability, influences her fitness—in environments in which females exerted choice, heavier females produced more offspring. Together, this comprehensive set of experiments demonstrates that female choosiness varies across environments, leading to direct fitness consequences

Modeling complex phenotypes: generalized linear models using spectrogram predictors of animal communication signals

Summary. A major goal of evolutionary biology is to understand the dynamics of natural selection within populations. The strength and direction of selection can be described by regressing relative fitness measurements on organismal traits of ecological significance. However, many important evolutionary characteristics of organisms are complex, and have correspondingly complex relationships to fitness. Secondary sexual characteristics such as mating displays are prime examples of complex traits with important consequences for reproductive success. Typically, researchers atomize sexual traits such as mating signals into a set of measurements including pitch and duration, in order to include them in a statistical analysis. However, these researcher-defined measurements are unlikely to capture all of the relevant phenotypic variation, especially when the sources of selection are incompletely known. In order to accommodate this complexity we propose a Bayesian dimension-reduced spectrogram generalized linear model that directly incorporates representations of the entire phenotype (one-dimensional acoustic signal) into the model as a predictor while accounting for multiple sources of uncertainty. The first stage of dimension reduction is achieved by treating the spectrogram as an "image" and finding its corresponding empirical orthogonal functions. Subsequently, further dimension reduction is accomplished through model selection using stochastic search variable selection. Thus, the model we develop characterizes key aspects of the acoustic signal that influence sexual selection while alleviating the need to extract higher-level signal traits a priori. This facet of our approach is fundamental and has the potential to provide additional biological insight, as is illustrated in our analysis

A simple two species ecological model exhibiting chaotic behaviour

The classical prey-predator model of Lotka-Volterra is revisited. Instead of constant growth rates, a modulated growth rate for the prey is used. It is shown that in this very simple case, the resulting system's evolution may become nonlinearly resonant. This shows that complex behaviour is not necessarily related to complex systems