Female ornamentation inMalurusfairy-wrens: a hidden evolutionary gem for understanding female perspectives on social and sexual selection

In this final chapter I want to briefly recap what I presented in the previous chapters and provide a few ideas on what might be done in the future to move the field forward. All three factors I discussed as relevant in male mate choice—male investment in reproduction, sex ratios, and variability in partner quality—are still emerging fields in sexual selection research and need more theoretical and empirical work. I suggest that variability in female quality is more important and more complex than currently known. The same is true for sex ratios. On the other hand, I suggest that sheer investment in gametes may be a little less important than currently assumed. Most importantly we need to explore the interactions of these three pathways to male mate choice. Female competition and also female ornamentation are still somewhat enigmatic and both topics are likely to grow in importance for our understanding of sexual selection. I think considering male and female choice together, as well as female and male competition will ultimately provide a more complete picture of Darwinian sexual selection.

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Experimental evidence that female ornamentation increases the acquisition of sperm and signals fecundity

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2006.3757 ◽

2006 ◽

Vol 274 (1609) ◽

pp. 583-590 ◽

Cited By ~ 48

Author(s):

Charlie K Cornwallis ◽

Tim R Birkhead

Keyword(s):

Sexual Selection ◽

Mate Choice ◽

Sexual Partners ◽

Male Mating ◽

Female Ornamentation ◽

Female Ornament ◽

Female Ornaments ◽

Sexual Ornamentation ◽

Gain Access

Mate choice can lead to the evolution of sexual ornamentation. This idea rests on the assumption that individuals with more elaborate ornaments than competitors have higher reproductive success due to gaining greater control over mating decisions and resources provided by partners. Nevertheless, how the resources and quality of sexual partners that individuals gain access to are influenced by the ornamentation of rival individuals remains unclear. By experimentally concealing and subsequently revealing female ornaments to males, we confirm in the fowl, Gallus gallus , that female ornamentation influences male mating decisions. We further show, by manipulating the relative ornament size of females, that when females had larger ornaments than competitors they were more often preferred by males and obtained more sperm, especially from higher quality males, as measured by social status. Males may benefit by investing more sperm in females with larger ornaments as they were in better condition and produced heavier eggs. Female ornament size also decreased during incubation, providing a cue for males to avoid sexually unreceptive females. This study reveals how inter-sexual selection can lead to the evolution of female ornaments and highlights how the reproductive benefits gained from mate choice and bearing ornaments can be dependent upon social context.

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Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.0375 ◽

2015 ◽

Vol 282 (1809) ◽

pp. 20150375 ◽

Cited By ~ 25

Author(s):

Richard K. Simpson ◽

Michele A. Johnson ◽

Troy G. Murphy

Keyword(s):

Sexual Selection ◽

Sexual Dichromatism ◽

Ancestral State ◽

Migration Distance ◽

Female Ornamentation ◽

Wood Warblers ◽

Selection For ◽

Evolution Of Migration ◽

And Migration ◽

Female Coloration

The mechanisms underlying evolutionary changes in sexual dimorphism have long been of interest to biologists. A striking gradient in sexual dichromatism exists among songbirds in North America, including the wood-warblers (Parulidae): males are generally more colourful than females at northern latitudes, while the sexes are similarly ornamented at lower latitudes. We use phylogenetically controlled comparative analysis to test three non-mutually exclusive hypotheses for the evolution of sexual dichromatism among wood-warblers. The first two hypotheses focus on the loss of female coloration with the evolution of migration, either owing to the costs imposed by visual predators during migration, or owing to the relaxation of selection for female social signalling at higher latitudes. The third hypothesis focuses on whether sexual dichromatism evolved owing to changes in male ornamentation as the strength of sexual selection increases with breeding latitude. To test these hypotheses, we compared sexual dichromatism to three variables: the presence of migration, migration distance, and breeding latitude. We found that the presence of migration and migration distance were both positively correlated with sexual dichromatism, but models including breeding latitude alone were not strongly supported. Ancestral state reconstruction supports the hypothesis that the ancestral wood-warblers were monochromatic, with both colourful males and females. Combined, these results are consistent with the hypotheses that the evolution of migration is associated with the relaxation of selection for social signalling among females and that there are increased predatory costs along longer migratory routes for colourful females. These results suggest that loss of female ornamentation can be a driver of sexual dichromatism and that social or natural selection may be a stronger contributor to variation in dichromatism than sexual selection.

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Does reproductive mode affect sexually-selected coloration? Evaluating UV–blue spots in parthenogenetic and bisexual lizards of the genus Darevskia

Current Zoology ◽

10.1093/cz/zoaa039 ◽

2020 ◽

Author(s):

Andran Abramjan ◽

Marine Arakelyan ◽

Daniel Frynta

Keyword(s):

Sexual Selection ◽

Reproductive Mode ◽

General Tendency ◽

Selective Pressures ◽

Female Ornamentation ◽

Lacertid Lizards ◽

Selective Forces ◽

And Bisexual ◽

Parthenogenetic Reproduction ◽

Chromatic Properties

Abstract Sexual selection often leads to evolution of conspicuous signals, raising the chances of attracting not only potential mates, but also predators. In lacertid lizards, ultraviolet (UV)–blue spots on flanks and shoulders represent such a trait. Some level of correlation between male and female ornamentation is also known to exist. Therefore, the phenotype of females may change in the absence of sexual selection. We tested this hypothesis on a complex of parthenogenetic and bisexual lizards of the genus Darevskia. We evaluated area, counts, and chromatic properties (UV opponency, saturation) of UV–blue spots and compared the values between the clones and their bisexual progenitor species. We found a fair heterogeneity between the parthenogenetic species, but no general tendency toward higher crypsis or conspicuousness. Values of the parthenogens were not significantly different from the values of sexual females. A possible explanation is that the changes in selective forces associated with parthenogenetic reproduction are too small to affect the resulting pattern of selective pressures on the studied traits, or that the phenotypes of the parthenogens result from the unique combination of parental genomes and are conserved by clonal reproduction.

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Competition for access to mates predicts female-specific ornamentation and polyandry

10.1101/2019.12.21.885996 ◽

2019 ◽

Author(s):

Rosalind L. Murray ◽

Elizabeth J. Herridge ◽

Rob W. Ness ◽

R. Axel W. Wiberg ◽

Luc F. Bussière

Keyword(s):

Sexual Selection ◽

Selection Intensity ◽

Nuptial Gifts ◽

Female Receptivity ◽

Female Ornamentation ◽

Trade Offs ◽

Ornament Evolution ◽

Female Specific ◽

Operational Sex Ratios ◽

Dance Fly

AbstractSexually selected ornaments are highly variable and the factors that drive variation in ornament expression are not always clear. Rare instances of female-specific ornament evolution (such as in some dance fly species) are particularly puzzling. While some evidence suggests that such rare instances represent straightforward reversals of sexual selection intensity, the distinct nature of trade-offs between ornaments and offspring pose special constraints in females. To examine whether competition for access to mates generally favours heightened ornament expression, we built a phylogeny and conducted a comparative analysis of Empidinae dance fly taxa that display ornate female-specific ornaments. We show that species with more female-biased operational sex ratios in lek-like mating swarms have greater female ornamentation, and in taxa with more ornate females, polyandry is increased. These findings support the hypothesis that ornament diversity in dance flies depends on female receptivity, which is associated with contests for nutritious nuptial gifts provided by males. Moreover, our results suggest that increases in female receptivity lead to higher levels of polyandry and sperm competition among males. The incidence of both heightened pre-mating sexual selection on females and post-mating selection on males contradicts assertions that sex-roles are straightforwardly reversed in dance flies.

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