Evolution of individual variation in a competitive trait: a theoretical analysis.

When competitive traits are costly, negative frequency dependence can maintain genetic variance. Most theoretical studies examining this problem assume binary polymorphisms, yet most trait variation in wild populations is continuous. We propose that continuous trait variation can result from continuous variation in resource quality and that, specifically, the shape of the resource distribution determines trait maintenance.

Variation in claw morphology among the digits of Bent-toed geckos (Cyrtodactylus: Gekkota: Gekkonidae).

Background: Ecomorphological studies of lizards have increasingly employed comparison of claw morphology among species in relation to spatial niche use. Typically, such studies focus on digit IV of the autopodia, especially the pes. Uniformity of claw morphology among digits is more often implicitly assumed than tested.

On the use of antibiotics in plasticity research: Gastropod shells unveil a tale of caution.

Through phenotypic plasticity, individual genotypes can produce multiple phenotypes dependent on the environment. In the modern world, anthropogenic influences such as man-made pharmaceuticals are increasingly prevalent. They might alter observable patterns of plasticity and distort our conclusions regarding the adaptive potential of natural populations.

Sperm competition in yellow dung flies: No consistent effect of sperm size.

The male competition for fertilization that results from female multiple mating promotes the evolution of increased sperm numbers and can impact sperm morphology, with theory predicting that longer sperm can at times be advantageous during sperm competition. If so, males with longer sperm should sire more offspring than competitors with shorter sperm. Few studies have directly tested this prediction, and findings are inconsistent.

Vegetation Height as the Primary Driver of Functional Changes in Orthopteran Assemblages in a Roadside Habitat.

Exhibiting manifold ecological impacts on terrestrial biota, roads have become a major driver of environmental change nowadays. However, many insect groups with high indication potential, such as grasshoppers and crickets (Orthoptera), have been largely neglected in road ecology research from a functional perspective. Using two complementary sampling methods, we have investigated the spatial dynamics of functional diversity and six functional traits in orthopteran assemblages, with respect to motorway proximity and the associated environmental factors, in a grassland habitat in the Lika region, Croatia.

Male size and reproductive performance in three species of livebearing fishes (Gambusia spp.): A systematic review and meta-analysis.

The genus Gambusia represents approximately 45 species of polyandrous livebearing fishes with reversed sexual size dimorphism (i.e. males smaller than females) and with copulation predominantly via male coercion.

Material heterogeneity of male genitalia reduces genital damage in a bushcricket during sperm removal behaviour.

Sperm removal behaviour (SRB) is known in many animals, and male genital structures are often involved in the SRB, e.g. rubbing female genitalia vigorously.

Poor nutritional condition promotes high-risk behaviours: a systematic review and meta-analysis.

Animal behaviour can lead to varying levels of risk, and an individual's physical condition can alter the potential costs and benefits of undertaking risky behaviours. How risk-taking behaviour depends on condition is subject to contrasting hypotheses. The asset protection principle proposes that individuals in better condition should be more risk averse, as they have higher future reproductive potential (i.

The jury is still out regarding the generality of adaptive 'transgenerational' effects.

A recent meta-analysis concluded, 'transgenerational effects are widespread, strong and persistent'. We identify biases in the literature search, data and analyses, questioning that conclusion. Re-analyses indicate few studies actually tested transgenerational effects - making it challenging to disentangle condition-transfer from anticipatory parental effects, and providing little insight into the underlying mechanisms.

Impact of low sperm competition on male reproductive trait allometries in a bush-cricket.

Background: Studying reproductive trait allometries can help to understand optimal male investment strategies under sexual selection. In promiscuous mating systems, studies across several taxa suggest that testes allometry is usually positive, presumably due to strong selection on sperm numbers through intense sperm competition. Here, we investigated testes allometry in a bush-cricket species, Metaplastes ornatus, in which females mate promiscuously, but where sperm removal behaviour by males likely drastically reduces realised sperm competition level.

Sex-specific repeatabilities and effects of relatedness and mating status on copulation duration in an acridid grasshopper.

In species with direct sperm transfer, copulation duration is a crucial trait that may affect male and female reproductive success and that may vary with the quality of the mating partner. Furthermore, traits such as copulation duration represent the outcome of behavioral interactions between the sexes, for which it is important-but often difficult-to determine which sex is in phenotypic control. Using a double-mating protocol, we compared copulation durations between (1) virgin and nonvirgin and (2) sibling and nonsibling mating pairs in rufous grasshoppers .

Strong cryptic prezygotic isolation despite lack of behavioral isolation between sympatric host races of the leaf beetle Lochmaea capreae.

One of the major goals in speciation research is to understand which isolation mechanisms form the first barriers to gene flow. This requires examining lineages that are still in the process of divergence or incipient species. Here, we investigate the presence of behavioral and several cryptic barriers between the sympatric willow and birch host races of Lochmaea capreae.

A Paradox of Genetic Variance in Epigamic Traits: Beyond "Good Genes" View of Sexual Selection.

Maintenance of genetic variance in secondary sexual traits, including bizarre ornaments and elaborated courtship displays, is a central problem of sexual selection theory. Despite theoretical arguments predicting that strong sexual selection leads to a depletion of additive genetic variance, traits associated with mating success show relatively high heritability. Here we argue that because of trade-offs associated with the production of costly epigamic traits, sexual selection is likely to lead to an increase, rather than a depletion, of genetic variance in those traits.

Ecologically dependent and intrinsic genetic signatures of postzygotic isolation between sympatric host races of the leaf beetle Lochmaea capreae.

The fitness of hybrids might be compromised as a result of intrinsic isolation and/or because they fall between ecological niches due to their intermediate phenotypes ("extrinsic isolation"). Here, we present data from several crosses (parental crosses, F1, F2, and backcrosses) between the two host races of Lochmaea capreae on willow and birch to test for extrinsic isolation, intrinsic isolation, and environmentally dependent genetic incompatibilities. We employed a reciprocal transplant design in which offspring were raised on either host plant and their survival was recorded until adulthood.

Genetic architecture underlying host choice differentiation in the sympatric host races of Lochmaea capreae leaf beetles.

Speciation in herbivorous insects has received considerable attention during the last few decades. Much of this group's diversity originates from adaptive population divergence onto different host plants, which often involves the evolution of specialized patterns of host choice behaviour. Differences in host choice often translates directly into divergence in mating sites, and therefore positive assortative mating will be created which will act as a strong barrier to gene flow.

Speciation Progress: A Case Study on the Bushcricket Poecilimon veluchianus.

Different mechanisms such as selection or genetic drift permitted e.g. by geographical isolation can lead to differentiation of populations and could cause subsequent speciation.

Evolution of risk-taking during conspicuous mating displays.

In many species, males possess conspicuous characteristics to attract females. These traits often attract predators as well, and males thus may have to balance the conspicuousness of their signals in relation to the prevailing predation risk. Here we develop a theoretical model of optimal signaling and risk-taking behavior for males differing in the attractiveness of their signals.

Choosiness, a neglected aspect of preference functions: a review of methods, challenges and statistical approaches.

Animals are faced with many choices and a very important one is the choice of a mating partner. Inter-individual differences in mating preferences have been studied for some time, but most studies focus on the location of the peak preference rather than on other aspects of preference functions. In this review, we discuss the role of variation in choosiness in inter-sexual selection.

Genome size variation affects song attractiveness in grasshoppers: evidence for sexual selection against large genomes.

Genome size is largely uncorrelated to organismal complexity and adaptive scenarios. Genetic drift as well as intragenomic conflict have been put forward to explain this observation. We here study the impact of genome size on sexual attractiveness in the bow-winged grasshopper Chorthippus biguttulus.

The variability is in the sex chromosomes.

Sex differences in the mean trait expression are well documented, not only for traits that are directly associated with reproduction. Less is known about how the variability of traits differs between males and females. In species with sex chromosomes and dosage compensation, the heterogametic sex is expected to show larger trait variability ("sex-chromosome hypothesis"), yet this central prediction, based on fundamental genetic principles, has never been evaluated in detail.

Comment on "Bateman in nature: predation on offspring reduces the potential for sexual selection".

Byers and Dunn's (Reports, 9 November 2012, p.802) conclusion that predation constrains sexual selection is problematic for three reasons: their nonstandard calculation of Bateman slopes; their assertion that random processes do not influence reproductive success; and the statistically unjustifiable use of 6 variables to explain just 10 observations.

Limited condition dependence of male acoustic signals in the grasshopper Chorthippus biguttulus.

In many animal species, male acoustic signals serve to attract a mate and therefore often play a major role for male mating success. Male body condition is likely to be correlated with male acoustic signal traits, which signal male quality and provide choosy females indirect benefits. Environmental factors such as food quantity or quality can influence male body condition and therefore possibly lead to condition-dependent changes in the attractiveness of acoustic signals.

A neural network-based analysis of acoustic courtship signals and female responses in Chorthippus biguttulus grasshoppers.

In many animal species, male acoustic courtship signals are evaluated by females for mate choice. At the behavioural level, this phenomenon has been well studied. However, although several song characteristics have been determined to affect the attractiveness of a given song, the mechanisms of the evaluation process remain largely unclear.