Body temperature, size, nuptial colouration and mating success in male Moor Frogs (Rana arvalis)

AbstractVariation in colouration has rarely been related to sexual selection in anuran amphibians, even though such a relationship has been proven for many other vertebrate taxa. Male and female Moor Frogs (Rana arvalis) have a cryptic brown colour pattern, but males develop a conspicuous blue nuptial colouration during the reproductive season. To investigate the possibility that colouration plays a role in sexual selection in this species, we studied the temporal variation in blue colouration, determined if body size or body temperature affected blueness and investigated if blueness of males could be related to their mating success. Results confirmed previous observations that males develop and maintain blue colouration for only a very few nights during peak reproductive activity. Colouration of males was unrelated to body size, but males exhibiting higher body temperatures were somewhat bluer than males with lower body temperatures. Further, males in amplexus had higher body temperatures than non-mated males. Finally, mating success was positively related to blueness in small males, whereas in large males no such relationship was detected. While our results align with the hypothesis that the bright blue colouration of males may be a target of sexual selection, alternative explanations are also discussed.

Download Full-text

Colour pattern predicts outcome of female contest competition in a sexually monomorphic fish

Biology Letters ◽

10.1098/rsbl.2018.0480 ◽

2018 ◽

Vol 14 (11) ◽

pp. 20180480 ◽

Cited By ~ 1

Author(s):

Angelika Ziegelbecker ◽

Florian Richter ◽

Kristina M. Sefc

Keyword(s):

Sexual Selection ◽

Mating Success ◽

Cichlid Fish ◽

Black Body ◽

Colour Pattern ◽

Contest Competition ◽

Social Competition ◽

Female Territoriality ◽

Males And Females ◽

Male Contests

Selection arising from social competition over non-mating resources, i.e. resources that do not directly and immediately affect mating success, offers a powerful alternative to sexual selection to explain the evolution of conspicuous ornaments, particularly in females. Here, we address the hypothesis that competition associated with the territoriality exhibited by both males and females in the cichlid fish Tropheus selects for the display of a conspicuous colour pattern in both sexes. The investigated pattern consists of a vertical carotenoid-coloured bar on a black body. Bar width affected the probability of winning in size-matched female–female, but not male–male, contests for territory possession. Our results support the idea that the emergence of female territoriality contributed to the evolution of sexual monomorphism from a dimorphic ancestor, in that females acquired the same conspicuous coloration as males to communicate in contest competition.

Download Full-text

Sexual selection on size and shape in Japanese beetles (Popillia japonica)

Behavioral Ecology ◽

10.1093/beheco/araa054 ◽

2020 ◽

Vol 31 (4) ◽

pp. 1073-1083 ◽

Cited By ~ 1

Author(s):

Clint D Kelly

Keyword(s):

Sexual Selection ◽

Body Size ◽

Mating Success ◽

Insect Pest ◽

Popillia Japonica ◽

Female Size ◽

Male Body ◽

Japanese Beetle ◽

Size Dimorphism ◽

Selection For

Abstract The mobility hypothesis argues that species in which males compete for mates in scrambles often exhibit female-biased size dimorphism because smaller male body size should increase male mobility and success in searching for mates. Sexual dimorphism can be further exaggerated if fecundity or sexual selection concurrently selects for larger female size. Scramble competition can select for trait characteristics that optimize locomotion; for example, long and slender wings should be favored if aerial speed is important to mating success. I tested these predictions in the scrambling Japanese beetle (Popillia japonica), a female-biased size dimorphic insect pest that is invasive to North America. Multivariate selection analyses support the prediction that smaller body size and larger wings in males benefit their mating success. My analyses also revealed significant selection for larger wings in females but, contrary to prediction, direct sexual selection favors smaller body size in females. These results support the mobility hypothesis and partially explain the evolution of female-biased size dimorphism in this species. Sexual selection favored rounder bodies in females and more tapered bodies in males, whereas, in both sexes, the effect of wing shape appears less important to fitness than wing size.

Download Full-text

How influential are squamate reptile traits in explaining population responses to environmental disturbances?

Wildlife Research ◽

10.1071/wr19064 ◽

2020 ◽

Vol 47 (3) ◽

pp. 249

Author(s):

Yang Hu ◽

Tim S. Doherty ◽

Tim S. Jessop

Keyword(s):

Body Size ◽

Body Temperature ◽

Clutch Size ◽

Random Effects ◽

Animal Species ◽

Species Traits ◽

Body Temperatures ◽

Mean Body Temperature ◽

Squamate Reptiles ◽

Ecological Disturbances

Abstract Context Understanding how organismal attributes influence sensitivity to environmental perturbations is a central theme in ecology and conservation. Certain traits, such as body size, habitat use, dietary preference and reproductive output are considered important determinants of animal species’ responses to the impacts of ecological disturbances. However, the general relationships between functional traits and post-disturbance responses by animals are not fully understood. AimsOur primary aim was to use a meta-analysis to evaluate the influence of species traits on variation in population abundances of squamate reptiles (i.e. lizards and snakes). MethodsWe extracted data from 107 original published studies, from which 1027 mean effect sizes of post-disturbance responses by 298 species were estimated. We examined short-term responses only (i.e. within 3 years since the most recent disturbance). A comprehensive range of disturbances was examined, such as habitat destruction, fragmentation, fire, and exotic-species invasions. We used Bayesian linear mixed-effect modelling (BLMM), utilising the Markov-chain Monte Carlo algorithm (MCMC) for the meta-regression. Specifically, we tested the influence of eight species traits (body size, diet, temporal activity pattern, sociality, reproductive mode, clutch size, habitat selection, and mean body temperature), along with disturbance type, in explaining variation in species-specific abundance responses of squamate reptiles post-disturbance. Key resultsPost-disturbance abundance responses of squamate species were significantly influenced by two parameters, namely, mean body temperature and clutch size. In general, significant positive responses post-disturbance were observed for species with higher mean body temperatures and a greater clutch size. The type of disturbance had no detectable influence on squamate abundances. The influence of random effects (heterogeneity among studies and species, and broad taxonomic identity) accounted for more of the model variation than did the fixed effects (species traits and disturbance type). ConclusionsCertain species traits exerted some influence on the sensitivities of lizards and snakes to ecological disturbances, although the influence of random effects was very strong. Our findings are likely to be a result of the complexity and idiosyncratic nature of natural abundance patterns among animal species, in addition to the potential confounding effect of methodological differences among studies. ImplicationsThe present study is the first major quantitative synthesis of how species traits influence population-level responses of squamate reptiles to ecological disturbances. The findings can be used to guide conservation efforts and ecological management, such as by prioritising the efforts of mitigation on species that reproduce more slowly, and those with lower body temperatures.

Download Full-text

Disruptive sexual selection on male body size in the polyphenic black scavenger fly Sepsis thoracica

Behavioral Ecology ◽

10.1093/beheco/ary038 ◽

2018 ◽

Vol 29 (3) ◽

pp. 769-777 ◽

Cited By ~ 1

Author(s):

Juan Pablo Busso ◽

Wolf U Blanckenhorn

Keyword(s):

Sexual Selection ◽

Body Size ◽

Reproductive Success ◽

Mating Success ◽

Directional Selection ◽

Disruptive Selection ◽

Simultaneous Occurrence ◽

Male Body ◽

Male Body Size ◽

Starting Point

Abstract Sexual selection has 2 main components, female preference and male–male competition, which can lead males to adopt alternative reproductive tactics to optimize their reproductive success. Two traits that significantly influence reproductive success are body size and coloration, as they can facilitate access to females through male contests or as female attractors. We investigated whether, and if so which mechanism of sexual selection contributes to the maintenance, and possibly even the establishment, of 2 almost discrete male morphs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae): small and black, or large and amber. We performed 2 complementary laboratory experiments to evaluate the mating success of the different male morphs and the behaviors (of both males and females) presumably mediating their mating success. We found evidence for intraspecific disruptive sexual selection on male body size that is mediated by male–male interactions, and significant positive directional selection on body size that interacted with (directional) selection on coloration, likely contributing to the origin and/or maintenance of the threshold relationship between the 2 traits in this species. The simultaneous occurrence of disruptive selection and polyphenism in S. thoracica supports the role of sexual selection in the intraspecific diversification of coupled traits (here body size and coloration), which could be a speciation starting point.

Download Full-text

Sexual dimorphism and evidence for intrasexual selection from quill impalements, injuries, and mate guarding in porcupines (Erethizon dorsatum)

Canadian Journal of Zoology ◽

10.1139/z97-107 ◽

1997 ◽

Vol 75 (6) ◽

pp. 847-854 ◽

Cited By ~ 6

Author(s):

Richard Alan Sweitzer ◽

Joel Berger

Keyword(s):

Sexual Selection ◽

Body Size ◽

Sexual Dimorphism ◽

Mate Guarding ◽

Reproductive Activity ◽

Erethizon Dorsatum ◽

Threshold Size ◽

Guarding Behavior ◽

Mating Opportunities ◽

Foot Pad

Sexual selection is a commonly cited explanation for sexual size dimorphism. We examined patterns of sexual dimorphism in North American porcupines (Erethizon dorsatum) and used data on quill impalements, injuries, and guarding behavior to examine the intrasexual component of sexual selection among male porcupines. Results indicated that porcupines were sexually dimorphic for foot-pad length, body length, and body mass because males grew more rapidly and for longer periods than females. Quill impalements, injuries, and guarding episodes were restricted predominantly to older, larger males, intimating that only the largest porcupines were reproductively active. Regression analyses suggested that size was more important than age in predicting reproductive activity among males. Also, relatively few quill impalements and guarding episodes among younger, smaller animals suggest that there is a threshold size below which male porcupines do not attempt to compete for mate access. Although our data do not directly link larger body size in males with relatively high reproductive success, they suggest that sexual dimorphism in this species is at least partly the result of the intrasexual component of sexual selection. It is also possible that females select males on the basis of quill morphology or some other indicator of male quality. Thus, our understanding of sexual dimorphism in porcupines would benefit from additional research investigating the extent to which body size and patterns of quill number or size are advantageous to male porcupines in garnering mating opportunities and enhancing fitness.

Download Full-text

Preprint "The relative importance of intra- and intersexual selection on human male sexually dimorphic traits"

10.31234/osf.io/edw4f ◽

2017 ◽

Author(s):

Tobias Kordsmeyer ◽

John Hunt ◽

David Puts ◽

Julia Ostner ◽

Lars Penke

Keyword(s):

Sexual Selection ◽

Body Size ◽

Female Choice ◽

Mating Success ◽

Upper Body ◽

Sexual Attractiveness ◽

Sexually Dimorphic ◽

Physical Strength ◽

Human Male ◽

Physical Dominance

Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a larger role than female choice. In a sample of men (N = 164), we sought to provide further evidence on the effects of men’s physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits purportedly under sexual selection (height, vocal and facial masculinity, upper body size from3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness based on self-presentation video recordings were assessed and associated with mating success (sociosexual behaviour and number of potential conceptions) in a partly longitudinal design. Results from structural equation models and selection analyses revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection.

Download Full-text

With our powers combined: integrating behavioral and genetic data to estimate mating success and sexual selection

10.1101/129346 ◽

2017 ◽

Author(s):

Zoé Gauthey ◽

Cédric Tentelier ◽

Olivier Lepais ◽

Arturo Elosegi ◽

Laura Royer ◽

...

Keyword(s):

Sexual Selection ◽

Body Size ◽

Reproductive Success ◽

Mating Success ◽

Genetic Data ◽

Male Body ◽

Gamete Release ◽

Sexual Interaction ◽

Reproductive Process ◽

Behavioral Observations

AbstractThe analysis of sexual selection classically relies on the regression of individual phenotypes against the marginal sums of a males × females matrix of pairwise reproductive success, assessed by genetic parentage analysis. When the matrix is binarized, the marginal sums give the individual mating success. Because such analysis treats male and female mating/reproductive success independently, it ignores that the success of a male × female sexual interaction can be attributable to the phenotype of both individuals. Also, because it is based on genetic data only, it is oblivious to costly yet unproductive matings, which may be documented by behavioral observations. To solve these problems, we propose a statistical model which combines matrices of offspring numbers and behavioral observations. It models reproduction on each mating occasion of a mating season as three stochastic and interdependent pairwise processes, each potentially affected by the phenotype of both individuals and by random individual effect: encounter (Bernoulli), concomitant gamete emission (Bernoulli), and offspring production (Poisson). Applied to data from a mating experiment on brown trout, the model yielded different results from the classical regression analysis, with only a limited effect of male body size on the probability of gamete release and a negative effect of female body size on the probability of encounter and gamete release. Because the general structure of the model can be adapted to other partitioning of the reproductive process, it can be used for a variety of biological systems where behavioral and genetic data are available.

Download Full-text