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Secondary Sexual Characters (secondary + sexual_character)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

RAPID ANTAGONISTIC COEVOLUTION BETWEEN PRIMARY AND SECONDARY SEXUAL CHARACTERS IN HORNED BEETLES

EVOLUTION, Issue 9 2008
Harald F. Parzer
Different structures may compete during development for a shared and limited pool of resources to sustain growth and differentiation. The resulting resource allocation trade-offs have the potential to alter both ontogenetic outcomes and evolutionary trajectories. However, little is known about the evolutionary causes and consequences of resource allocation trade-offs in natural populations. Here, we explore the significance of resource allocation trade-offs between primary and secondary sexual traits in shaping early morphological divergences between four recently separated populations of the horned beetle Onthophagus taurus as well as macroevolutionary divergence patterns across 10 Onthophagus species. We show that resource allocation trade-offs leave a strong signature in morphological divergence patterns both within and between species. Furthermore, our results suggest that genital divergence may, under certain circumstances, occur as a byproduct of evolutionary changes in secondary sexual traits. Given the importance of copulatory organ morphology for reproductive isolation our findings begin to raise the possibility that secondary sexual trait evolution may promote speciation as a byproduct. We discuss the implications of our results on the causes and consequences of resource allocation trade-offs in insects. [source]

CLIMATIC AND TEMPORAL EFFECTS ON THE EXPRESSION OF SECONDARY SEXUAL CHARACTERS: GENETIC AND ENVIRONMENTAL COMPONENTS

EVOLUTION, Issue 3 2004
Dany Garant
Abstract Despite great interest in sexual selection, relatively little is known in detail about the genetic and environmental determinants of secondary sexual characters in natural populations. Such information is important for determining the way in which populations may respond to sexual selection. We report analyses of genetic and large-scale environmental components of phenotypic variation of two secondary sexual plumage characters (forehead and wing patch size) in the collared flycatcher Ficedula albicollis over a 22-year period. We found significant heritability for both characters but little genetic covariance between the two. We found a positive association between forehead patch size and a large-scale climatic index, the North Atlantic Oscillation (NAO) index, but not for wing patch. This pattern was observed in both cross-sectional and longitudinal data suggesting that the population response to NAO index can be explained as the result of phenotypic plasticity. Heritability of forehead patch size for old males, calculated under favorable conditions (NAO index median), was greater than that under unfavorable conditions (NAO index < median). These changes occurred because there were opposing changes in additive genetic variance (VA) and residual variance (VR) under favorable and unfavorable conditions, with VA increasing and VR decreasing in good environments. However, no such effect was detected for young birds, or for wing patch size in either age class. In addition to these environmental effects on both phenotypic and genetic variances, we found evidence for a significant decrease of forehead patch size over time in older birds. This change appears to be caused by a change in the sign of viability selection on forehead patch size, which is associated with a decline in the breeding value of multiple breeders. Our data thus reveal complex patterns of environmental influence on the expression of secondary sexual characters, which may have important implications for understanding selection and evolution of these characters. [source]

A morphometric approach to the geographic variation of the terrestrial isopod species Armadillo tuberculatus (Isopoda: Oniscidea)

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2009
M. Kamilari
Abstract The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs. Resumen El isópodo terrestre Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) es una especie extensamente polimórfica distribuida por la región sur-central del piélago Egéo (Grecia), con una forma distinta en cada isla. Se trata de variaciones en la coloración, el tamaño de los tubérculos cuticulares y en la forma del primer exopodio masculino del pleopodo (carácter sexual secundario de importancia taxonómica). Estudiamos el crecimiento alométrico del tubérculo cuticular en 17 poblaciones (en individuos de ambos sexos) y la variación de la forma del primer exopodio masculino del pleopodo en 10 poblaciones según el análisis de Fourier elíptico (Elliptic Fourier Analysis) para detectar patrones de variación intraespecifica y relaciones posibles entre las formas de la especie. Además, el análisis Thin Plate Spline fue utilizado para el cálculo de la Energía de Flexión Mínima (Minimum Bending Energy) entre diversas formas del exopodio, que entonces fue utilizada para estimar la Mínima Red de Distancias (Minimum Spanning Network, MSN) que las conectaba. Detectamos una correlación significativa entre las diversas tasas de crecimiento alométrico del tubérculo entre los grupos de islas y la latitud de la isla. Por otro lado, la agrupación de las islas y la MSN, basada en las diferencias de la forma del exopodio, no fueron relacionados con la paleogeografía de la región del piélago Egéo ni con las actuales distancias geográficas de las islas. Estos resultados se interpretan como evidencia para la radiación non-adaptativa de las diversas formas de la especie. [source]

CLIMATIC AND TEMPORAL EFFECTS ON THE EXPRESSION OF SECONDARY SEXUAL CHARACTERS: GENETIC AND ENVIRONMENTAL COMPONENTS

Territorial behaviour and immunity are mediated by juvenile hormone: the physiological basis of honest signalling?

FUNCTIONAL ECOLOGY, Issue 1 2009
Jorge Contreras-Garduño
Summary 1The role of the juvenile hormone (JH) as a potential mediator in the trade-off between male,male competition and immune response has not been tested, but its study could reveal a potential mechanism that mediates resource allocation between these two traits. 2Controlling for body size, we tested whether males of the territorial damselfly Calopteryx virgo administrated with methoprene acid, an analog of the JH (JHa), compared to control males, increased their aggression and occupation time on territories but decreased their phenoloxidase (PO) activity (a key enzyme used during immune response after a bacterial challenge). We found an increase in aggression in JHa treated males compared to control males, but the opposite was found for PO activity. 3As fat load and muscle mass are also important traits during a contest, we tested whether JHa males compared to control males showed more fat and muscle content 2 h after JHa administration. Our results did not show a significant difference between both male groups, suggesting that JHa only increased aggression. 4These results and a review of other published articles, which have documented an effect of JH on a variety of functions in insects, suggest that JH may be a target of sexual selection: this hormone not only promotes the expression of secondary sexual characters but also seems condition-dependent and so its titers may indicate male condition. [source]

Fat stores in birds: an overlooked sink for carotenoid pigments?

FUNCTIONAL ECOLOGY, Issue 3 2001
J. J. Negro
Summary 1,Carotenoids are responsible for the most striking colours in birds, but also play an important role as enhancers of the immune system. Consequently, a trade-off between the ornamental and health functions of carotenoids in birds has been proposed. 2,Although it is well known that birds can store carotenoids in different organs and tissues, including the fat stores, until now all field studies of the regulation of carotenoid stores have focused on plasma carotenoids. 3,Carotenoids in the fat of 44 wild Greylag Geese (Anser anser L.) wintering in south-western Spain were identified and quantified. In addition, the relationships between carotenoids and the size of the fat stores, as well as the sex and age of the geese, were analysed. 4,The major carotenoid in goose fat was lutein. This and related carotenoids are also the most prevalent pigments in bird plasma and secondary sexual characters. We also detected ,-cryptoxanthin, ,-carotene, neochrome and neoxanthin. Total carotenoid concentration was negatively correlated with the size of the fat stores. Males had higher concentrations of carotenoids than females. 5A possible explanation for these patterns is that male birds tend to have higher plasma carotenoids than females, a difference that could be transposed to fat if carotenoids diffused passively from the blood into adipose tissues. Carotenoids, however, may tend to remain in the fat stores. If this were true, fat would not be a reservoir of carotenoids, but a sink where a significant amount of these pigments would be sequestered, being no longer available for other functions. [source]

Can the limited marsupium space be a limiting factor for Syngnathus abaster females?

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2008
Insights from a population with size-assortative mating
Summary 1Some syngnathid species show varying degrees of sex role reversal aside from male pregnancy, with females competing for access to mates and sometimes presenting conspicuous secondary sexual characters. Among other variables, brooding space constraints are usually considered a key element in female reproductive success, contributing strongly to the observed morphological and behavioural sexual differences. Nevertheless, a close relationship between sex role reversal and male brooding space limitation has not yet been accurately demonstrated in field studies. 2The present work, conducted over two consecutive breeding seasons in a wild population of the sex role-reversed pipefish Syngnathus abaster, simultaneously analysed egg number and occupied space, as well as the free area in the male's marsupium. The number of eggs that would fit in the observed unoccupied space was estimated. 3Contrary to what would be expected, given the marked sexual dimorphism observed in the population studied, where females were larger and more colourful, male brooding space did not appear to limit female reproduction as neither large nor small individuals presented a fully occupied pouch. Interestingly, the largest unoccupied areas of marsupium were found in the larger individuals, although they received more and larger eggs. Laboratory data also showed that larger females lay larger eggs. 4Together, these results suggest the existence of assortative mating, which may result from: (i) the reluctance of larger males (which tend not to receive small eggs usually laid by small females) to mate with lower quality females, even at the expense of a smaller number of offspring; or (ii) female,female competition, which might strongly reduce the hypothesis of a small female mating with a large male. The potential impact of temperature on reproduction and population dynamics is also discussed in the light of ongoing climatic changes. [source]

The allometric pattern of sexually size dimorphic feather ornaments and factors affecting allometry

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 7 2009
J. J. CUERVO
Abstract The static allometry of secondary sexual characters is currently subject to debate. While some studies suggest an almost universal positive allometry for such traits, but isometry or negative allometry for nonornamental traits, other studies maintain that any kind of allometric pattern is possible. Therefore, we investigated the allometry of sexually size dimorphic feather ornaments in 67 species of birds. We also studied the allometry of female feathers homologous to male ornaments (female ornaments in the following) and ordinary nonsexual traits. Allometries were estimated as reduced major axis slopes of trait length on tarsus length. Ornamental feathers showed positive allometric slopes in both sexes, although that was not a peculiarity for ornamental feathers, because nonsexual tail feathers also showed positive allometry. Migration distance (in males) and relative size of the tail ornament (in females) tended to be negatively related to the allometric slope of tail feather ornaments, although these results were not conclusive. Finally, we found an association between mating system and allometry of tail feather ornaments, with species with more intense sexual selection showing a smaller degree of allometry of tail ornaments. This study is consistent with theoretical models that predict no specific kind of allometric pattern for sexual and nonsexual characters. [source]

The Genus Chelipoda Macquart (Diptera, Empididae, Hemerodromiinae) in Chile

MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 1 2009
Adrian R. Plant
Abstract Chilean species of Chelipoda Macquart, 1823 (Diptera, Empididae, Hemerodromiinae) are reviewed and a key provided to all known species. Six new species are described; Chelipoda ceraphoron sp. n., C. deletrix sp. n., C. interfectrix sp. n., C. kolua sp. n., C. lentiginosa sp. n. and C. perditrix sp. n. Lectotypes and paralectotypes are designated for C. fimbriata Collin, 1933, C. obtusipennis Collin, 1933 and C. remissa Collin, 1933 and a lectotype is designated for C. subflava Collin, 1933. Cladistic analysis resolved two distinct clades defined largely on male genitalic characters. Habitat, biogeography and occurrence of secondary sexual characters are briefly discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Repeatability of size and fluctuating asymmetry of antler characteristics in red deer (Cervus elaphus) during ontogeny

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2007
L. BARTO
Fluctuating asymmetry (FA) has been suggested as a measure of the sensitivity of development to a wide array of genetic and environmental stresses. It has been also suggested that antlers in red deer could be important during social and rutting displays. We used antler measurements of 51 males that were measured over subsequent seasons, from 3,8 years of age, and analysed three antler traits: antler weight, length, and the number of antler tines (antler size). We calculated absolute and relative FA. All three size traits were highly significantly intercorrelated. By contrast to this, the FA of the three traits, did not show such relationships. With increasing age, antler size and FA also increased. When testing the repeatability of FA and antler size, there was a principal difference in the pattern between FA and antler size, with the latter being much more consistent than the former. This suggests that antler size, not FA, may be a good predictor of the bearer's quality in mate selection. This fits well with the good-genes hypothesis that the development of extravagant secondary sexual characters can be an honest advertisement of heritable male quality. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 215,226. [source]

Publication bias in ecology and evolution: an empirical assessment using the ,trim and fill' method

BIOLOGICAL REVIEWS, Issue 2 2002
MICHAEL D. JENNIONS
ABSTRACT Recent reviews of specific topics, such as the relationship between male attractiveness to females and fluctuating asymmetry or attractiveness and the expression of secondary sexual characters, suggest that publication bias might be a problem in ecology and evolution. In these cases, there is a significant negative correlation between the sample size of published studies and the magnitude or strength of the research findings (formally the ,effect size'). If all studies that are conducted are equally likely to be published, irrespective of their findings, there should not be a directional relationship between effect size and sample size; only a decrease in the variance in effect size as sample size increases due to a reduction in sampling error. One interpretation of these reports of negative correlations is that studies with small sample sizes and weaker findings (smaller effect sizes) are less likely to be published. If the biological literature is systematically biased this could undermine the attempts of reviewers to summarise actual biology relationships by inflating estimates of average effect sizes. But how common is this problem? And does it really effect the general conclusions of literature reviews? Here, we examine data sets of effect sizes extracted from 40 peer-reviewed, published meta-analyses. We estimate how many studies are missing using the newly developed ,trim and fill' method. This method uses asymmetry in plots of effect size against sample size (,funnel plots') to detect ,missing' studies. For random-effect models of meta-analysis 38% (15/40) of data sets had a significant number of ,missing' studies. After correcting for potential publication bias, 21% (8/38) of weighted mean effects were no longer significantly greater than zero, and 15% (5/34) were no longer statistically robust when we used random-effects models in a weighted meta-analysis. The mean correlation between sample size and the magnitude of standardised effect size was also significantly negative (rs=-0.20, P < 0-0001). Individual correlations were significantly negative (P < 0.10) in 35% (14/40) of cases. Publication bias may therefore effect the main conclusions of at least 15,21% of meta-analyses. We suggest that future literature reviews assess the robustness of their main conclusions by correcting for potential publication bias using the ,trim and fill' method. [source]