scholarly journals Sex ratio and sexual selection in wormshrimps (Crustacea, Amphipoda, Ingolfiellidea)

2006 ◽  
Vol 75 (03-04) ◽  
pp. 189-194 ◽  
Author(s):  
Ronald Vonk ◽  
Vincent Nijman
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Habitat Use ◽  
Individual Species ◽  
Small Populations ◽  
Secondary Sexual Characters ◽  
Elusive Species ◽  
The Individual ◽  
Secondary Sexual

Small populations of several species of the groundwater dwelling amphipod genus Ingolfiella are found in caves, wells, seabottoms, beaches and riverbed interstitial habitats. To gain insight in the socio-ecology of these elusive species, we used data from collected specimens to explore the relationships between sexratios, display of secondary sexual characters and other morphological features, and habitat use. We extracted data on the sex ratios and the presence-absence of secondary sexual characters of 13 species from the literature and through examination of museum material. We found a clearly skewed sex ratio with a preponderance of females, both in the individual species as in the genus as a whole. However, sex ratio and the display of secondary sexual characters were not correlated, nor did these characters correlate with the amount of sexual dimorphism. It remains unknown why so many ingolfiellids have evolved these costly features.

Do secondary sexual dimorphism and female intolerance to drought influence the sex ratio and extinction risk of Taxus baccata?

Plant Ecology ◽  
2008 ◽  
Vol 200 (2) ◽  
pp. 229-240 ◽  
Author(s):  
Grzegorz Iszkuło ◽  
Anna K. Jasińska ◽  
Marian J. Giertych ◽  
Adam Boratyński
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Extinction Risk ◽  
Taxus Baccata ◽  
Secondary Sexual Dimorphism ◽  
Secondary Sexual

Sexual dimorphism of the major chela and sex ratio as indicators of the mating system in the estuarine snapping shrimp Alpheus colombiensis Wicksten, 1988 (Decapoda: Caridea: Alpheidae)

2020 ◽  
Vol 40 (6) ◽  
pp. 649-656
Author(s):  
Juan C Azofeifa-Solano ◽  
Jeffrey A Sibaja-Cordero ◽  
Ingo S Wehrtmann
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Mating System ◽  
Mate Guarding ◽  
Female Size ◽  
Monogamous Species ◽  
Low Degree ◽  
Adult Sex Ratio ◽  
Snapping Shrimps

Abstract The sexual selection over traits that favor access to mating partners could promote the emergence of sexual dimorphism when the pressure is different between sexes. Monogamous species are considered to have a low degree of sexual dimorphism. The highly diverse snapping shrimps are usually regarded as monogamous, but the mating system has been studied only in few species. We aimed to provide insights into the mating system and sexual dimorphism of Alpheus colombiensisWicksten, 1988. The adult sex ratio was female biased, and solitary ovigerous females were found, suggesting a temporary mate guarding type of mating system. Our results also revealed sexual dimorphism on the snapping claw, which is larger in males than in females. The male’s snapping claw is probably under sexual selection, which can be mediated by male-male competition or female choice. We also estimated the A. colombiensis female size at maturity at 5.2 ± 0.76 mm. Our results contradict the common idea that snapping shrimps are monogamous species, and support that A. colombiensis probably have a temporary mate guarding (e.g., males can sexually interact with more than one female, in opposition to sexual monogamy). This study also sustains the growing evidence that alpheid shrimps display snapping claw sexual dimorphism.

A new fossil Eurypinae genus and sexual dimorphism in the representatives of Omineus (Coleoptera: Mycteridae) from Tertiary amber of Europe

Zootaxa ◽  
2020 ◽  
Vol 4820 (3) ◽  
pp. 551-562
Author(s):  
VITALII IGOREVICH ALEKSEEV ◽  
ANDRIS BUKEJS ◽  
DARREN ANDREW POLLOCK
Keyword(s):  
Computed Tomography ◽  
Sexual Dimorphism ◽  
Baltic Amber ◽  
Micro Computed Tomography ◽  
Fossil Species ◽  
X Ray ◽  
Secondary Sexual Characters ◽  
Kaliningrad Region ◽  
First Time ◽  
Secondary Sexual

Europoeurypus inglaeso gen. et sp. nov. is described from Eocene Baltic amber found on the Sambian Peninsula, Kaliningrad Region, Russia. Four additional specimens of mycterid beetles from collections of Baltic amber are reported. The secondary sexual characters and sexual dimorphism in the Eocene representatives of the genus Omineus Lewis, 1895 are documented for the first time and examined using X-ray micro-computed tomography (μCT). The studied Omineus male specimens were attributed to the fossil species Omineus febribilis Alekseev, Pollock & Bukejs, 2019. A key to fossil species of Eurypinae from Eocene ambers is provided and several aspects of the biogeography of the subfamily Eurypinae are discussed.

scholarly journals Reproductive competition and sexual selection

2017 ◽  
Vol 372 (1729) ◽  
pp. 20160310 ◽  
Author(s):  
Tim Clutton-Brock
Keyword(s):  
Sex Differences ◽  
Sexual Selection ◽  
Operational Sex Ratio ◽  
Reproductive Decisions ◽  
Comprehensive Understanding ◽  
Reproductive Competition ◽  
Selection Gradients ◽  
Secondary Sexual Characters ◽  
Animal Societies ◽  
Secondary Sexual

This paper traces the development of our understanding of the development of different approaches to estimating the strength of reproductive competition and sexual selection in the two sexes, based on measures of the operational sex ratio, the opportunity for sexual selection and contrasts in selection gradients between the sexes. It argues that different approaches provide complementary insights into the causes of sex differences in reproductive competition, the operation of sexual selection and the evolution of secondary sexual characters and that improvements in our understanding of the evolution of secondary sexual characters will require a more comprehensive understanding of the ways in which social and ecological conditions modify reproductive competition and development in females and males. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

Sexual dimorphism and condition dependence in the anal pad of the small Indian mongoose (Herpestes auropunctatus)

2015 ◽  
Vol 93 (5) ◽  
pp. 397-402
Author(s):  
M.A. Owen ◽  
D.C. Lahti
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Indirect Evidence ◽  
Condition Dependence ◽  
Secondary Sexual Traits ◽  
Herpestes Auropunctatus ◽  
Sexual Traits ◽  
Indian Mongoose ◽  
Small Indian Mongoose ◽  
Secondary Sexual

Secondary sexual traits tend to be sexually dimorphic, and theory predicts that such traits should also be condition-dependent in a sex-specific manner. We investigate these phenomena in a field study of the small Indian mongoose (Herpestes auropunctatus (Hodgson, 1836); formerly Herpestes javanicus (É. Geoffroy Saint-Hillaire, 1818)), in the first attempt at understanding secondary sexual traits and sexual selection in this species. Small Indian mongooses are solitary and nonterritorial, and they likely depend on chemical (scent) rather than visual or acoustic signals for communication. Additionally, they possess a fleshy projection around their anus, the anal pad, thought to aid in scent-marking. Our results revealed strong male-biased sexual dimorphism in mass, skull and body lengths, canine diameters, and anal pad area. After controlling for the influence of body length, males were 31% heavier and possessed anal pads that were 68% larger than females’. Additionally, anal pad size was positively related to body size in males but not in females and was condition-dependent in males but not in females. Taken together, our findings provide indirect evidence that the anal pad might have evolved, at least in part, via sexual selection.

scholarly journals Models of sex-ratio meiotic drive and sexual selection in stalk-eyed flies

1999 ◽  
Vol 74 (3) ◽  
pp. 245-253 ◽  
Author(s):  
RUSSELL LANDE ◽  
GERALD S. WILKINSON
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Sex Ratios ◽  
Meiotic Drive ◽  
Total Body Length ◽  
Complete Suppression ◽  
Male Character ◽  
Female Mating ◽  
Female Mating Preferences

Hypertrophied sexually dimorphic eye stalks have evolved independently in several families of Diptera, with the eyespan of males exceeding their total body length in some species. These structures function in intermale contests for territories and in mate attraction, the classical mechanisms of sexual selection. In the family Diopsidae, species with extremely exaggerated eye stalks and marked sexual dimorphism in relative eyespan also usually have strongly female-biased sex ratios in nature caused by X-linked meiotic drive, whereas species with relatively small eye stalks have little or no sexual dimorphism, often lack meiotic drive and have even sex ratios. We investigate the possible connection between sexual selection and sex-ratio meiotic drive by analysing a three-locus model for the evolution of female choice for a male character associated with meiotic drive. Both meiotic drive and the male character are X-linked and the female preference is autosomal. Our model shows that suppressed recombination between meiotic drive and the male character, e.g. by inversion of the X chromosome, is necessary for sex-ratio selection to promote the origin of female mating preferences and exaggerated secondary sexual characters. With complete suppression of recombination, sexual selection reduces the frequency of meiotic drive, and may eliminate it. Very rare recombination, gene conversion or mutation, at rates characteristic of chromosome inversions in Drosophila, restores the meiotic drive polymorphism to its original equilibrium. Sex-ratio meiotic drive may thus act as a catalyst accelerating the origin of female mating preference and exaggerated male traits.

Selection on size and secondary sexual characters of the damselfly Calopteryx splendens when sympatric with the congener Calopteryx virgo

2011 ◽  
Vol 89 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Katja Kuitunen ◽  
Janne S. Kotiaho ◽  
Mari Luojumäki ◽  
Jukka Suhonen
Keyword(s):  
Sexual Selection ◽  
Positive Selection ◽  
Relative Abundance ◽  
Interspecific Interactions ◽  
Spot Size ◽  
Male Mating ◽  
Intraspecific Interactions ◽  
Secondary Sexual Characters ◽  
Calopteryx Splendens ◽  
Secondary Sexual

Male mating success is often determined by body size or secondary sexual characters because of female mate choice or competition for females. In addition to intraspecific interactions, interspecific interactions may interfere with intraspecific selection. In this study, we investigated sexual selection on size and sexual characters of male banded demoiselle ( Calopteryx splendens (Harris, 1780)) in wild populations sympatric with the beautiful demoiselle ( Calopteryx virgo (L., 1758)). As secondary sexual characters, male C. splendens have pigmented wing spots whose size appears to be under positive selection. Male C. virgo resemble male C. splendens that have the largest wing spots, leading to interspecific male–male aggression and possibly also to heterospecific matings via mistaken species recognition. If interspecific interactions interfere with intraspecific sexual selection on wing-spot size of C. splendens, their effects should increase with the increasing relative abundance of C. virgo. Our results did not show the expected positive selection on wing-spot size in C. splendens, suggesting that interspecific interactions might interfere with sexual selection. Also, we observed no relationship between the strength of interspecific sexual selection and the relative abundance of C. virgo. However, there was a positive intraspecific density-dependent sexual selection for larger size. Although the present results are tentative, we suggest that interspecific interactions should be considered along with intraspecific selection when studies of sexual selection are performed in the wild.

scholarly journals Sexual selection on body size and secondary sexual characters in 2 closely related, sympatric chameleons in Madagascar

2009 ◽  
Vol 20 (5) ◽  
pp. 1079-1088 ◽  
Author(s):  
Kristopher B. Karsten ◽  
Laza N. Andriamandimbiarisoa ◽  
Stanley F. Fox ◽  
Christopher J. Raxworthy
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Secondary Sexual Characters ◽  
Secondary Sexual

Two Seira Lubbock 1869 (Collembola, Arthropleona, Entomobryidae) new to science, with remarkable secondary sexual characters

Zootaxa ◽  
2006 ◽  
Vol 1185 (1) ◽  
pp. 21 ◽  
Author(s):  
DOUGLAS ZEPPELINI ◽  
BRUNO CAVALCANTE BELLINI
Keyword(s):  
New Species ◽  
Sexual Dimorphism ◽  
Mating Behavior ◽  
Secondary Sexual Characters ◽  
Two New Species ◽  
Secondary Sexual

Two new species of Seira Lubbock 1869 are described and illustrated. The males of these species show modifications in the fore legs, probably associated with sexual courtship and/or mating behavior. Despite the similarity of the modifications of the two species, they are not otherwise similar. Thus the similarity is due to convergence rather than homology. These are the first records of sexual dimorphism other than genital openings in Entomobryidae.

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