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The Evolution of Sexually Homologous Ornaments: Selection via Male Mate Choice Coinciding with Male-Male Competition in a Neotropical Mosquito
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The evolution of elaborate male ornaments via sexual selection is well-understood while the selective pressures acting on female ornaments remains unresolved. Female ornaments in species with strong sexual selection on the male homologue of the ornament were originally thought to result from an intersexual genetic correlation. My thesis explores the evolution of ornaments in females due to direct selection by developing theoretical models and examining the biology of a neotropical mosquito (Sabethes cyaneus) with sexually homologous ornaments coinciding with male-male competition.

I began by exploring the morphology of the ornaments in both sexes of S. cyaneus. Sexual dimorphism in the size and shape of the ornaments was slight and both male and female ornaments showed classic hallmarks of sexually selected traits. I then tested for direct selection on S. cyaneus male and female ornaments via mutual mate choice. I found evidence of male, but surprisingly not female, preferences for ornaments.

I then further considered the evolution of male mate choice in polygynous species. First, I investigated whether male investment in courtship by S. cyaneus may result in a lower operational sex ratio and thereby reduce the costs associated with male mate choice. Male courtship did pose a significant longevity cost to male S. cyaneus. Second, I explored the possibility that a female preference for male courtship effort may contribute to the benefits of male mate choice in a series of population genetic models. The spread of a male preference gene can be driven by female preferences for male courtship when males court preferred females more.

Finally, I found that female S. cyaneus are not benefitting from signalling to increase their mating rate as they are monandrous. My thesis therefore challenges standing sexual selection theory and suggests that sexual selection on females may be more widespread than previously thought.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2011. , p. 52
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 799
Keywords [en]
sexual selection, Sabethes cyaneus, Diptera, Culicidae, mosquito, mutual ornamentation, sexual selection, mutual mate choice, male mate choice, female ornament, ecology, animal behaviour
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:uu:diva-141936ISBN: 978-91-554-7985-5 (print)OAI: oai:DiVA.org:uu-141936DiVA, id: diva2:386603
Public defence
2011-02-25, Zootissalen, EBC, Villavägen 9, Uppsala, 09:30 (English)
Opponent
Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 729Available from: 2011-02-03 Created: 2011-01-12 Last updated: 2011-03-21Bibliographically approved
List of papers
1. Morphological variation of an ornament expressed in both sexes of the mosquito Sabethes cyaneus
Open this publication in new window or tab >>Morphological variation of an ornament expressed in both sexes of the mosquito Sabethes cyaneus
2009 (English)In: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 11, no 1, p. 1-21Article, review/survey (Refereed) Published
Abstract [en]

Question: Do elaborate ornaments expressed in both sexes show patterns of phenotypic variation consistent with selection via mutual mate choice? Data description: Detailed morphometric data on the striking leg 'paddle' ornament of the sabethine mosquito Sabethes cyaneus: ornament size and shape and size of general morphological traits. Data derive from 80 males and 80 females from a wild-type laboratory colony established with individuals collected in Panama. Search method: Shape variation was analysed using geometric morphometric methods (elliptic Fourier analyses). We investigated sex differences in the relationships between body size on the one hand and leg length, ornament size, and ornament shape on the other, using general linear models. We also explored morphological variation in asymmetry, allometry, and in the magnitude of phenotypic variation across traits. Conclusions: These ornaments showed many of the classic hallmarks of a sexually selected and condition-dependent ornament: (i) phenotypic variation in size was much greater than for any other trait; (ii) the size of the major part of the paddle showed positive allometry; and (iii) the degree of fluctuating asymmetry in one component of the shape of the leg paddles decreased with body size. Remarkably, these patterns were more pronounced in females and sexual dimorphism in size and shape of the leg paddle ornament was slight. Although data on the current pattern of morphological variation alone does not allow firm conclusions about past selection, our results are consistent with the maintenance of these ornaments in both sexes by sexual selection via mutual mate choice.

Keywords
allometry, Diptera, elliptic Fourier analysis, sexual selection, signal, variation
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-135151 (URN)000263624900001 ()
Available from: 2010-12-06 Created: 2010-12-05 Last updated: 2017-12-12Bibliographically approved
2.
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3. Male mating costs in a polygynous mosquito with ornaments expressed in both sexes
Open this publication in new window or tab >>Male mating costs in a polygynous mosquito with ornaments expressed in both sexes
2009 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 276, no 1673, p. 3671-3678Article in journal (Refereed) Published
Abstract [en]

Male mate choice in species with conventional sex roles is difficult to explain and has, therefore, been the focus of many recent theoretical models. These models have focused on variance in female quality and, to a lesser extent, male investments/costs associated with mating. In this study, we investigate the costs of courtship and copulation in the polygynous mosquito Sabethes cyaneus. In this species, both males and females possess elaborate ornaments. Previous studies suggest that the most likely explanation for the presence of these ornaments is mutual mate choice. Thus, this system provides an excellent model for exploring the evolution of mutual mate choice in polygynous species. We disentangle the costs of courtship and copulation by monitoring male survival in three groups of males: housed alone (group 1); able only to court females (group 2); or able to court and copulate with females (group 3). We show that males incur a cost of courtship and copulation and that courtship intensity is negatively related to male longevity. Our results suggest that courtship and copulation carry additive costs to males. We discuss the implications of these results in the context of current mutual mate choice theory and suggest that courtship costs may be an unappreciated key factor in the evolution of male mate choice.

Keywords
Culicidae, Diptera, mutual mate choice, sex roles, sexual selection
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-127511 (URN)10.1098/rspb.2009.0991 (DOI)000270172200013 ()
Available from: 2010-12-06 Created: 2010-07-13 Last updated: 2017-12-12Bibliographically approved
4. Female preference for male courtship effort drives the evolution of male mate choice
Open this publication in new window or tab >>Female preference for male courtship effort drives the evolution of male mate choice
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The evolution of male mate choice is constrained by costs of choice in species with a male-biasedoperational sex ratio. Previous theoretical studies have shown that significant male benefits ofmale choice are required, e.g., by mating with more fecund females, in order for these costs to beoffset and the male preference to spread. We consider the possibility that another type of effectmay favour the evolution of male mate choice by exploring a series of population genetic models.We find that a male mating preference can spread when males court preferred females more andfemales prefer, and thus are more likely to mate with, males who court more. Further, viability orfecundity selection on the preferred female trait is a much more powerful determinant of the fateof the female trait than is the presence of the male preference. We confirm that indirect selectionon the male preference due to linkage disequilibrium between the female trait and malepreference alleles can affect the evolution of the male trait, however, these effects are slight incomparison to direct selection on the male trait.

National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-141925 (URN)
Available from: 2011-01-12 Created: 2011-01-12 Last updated: 2011-03-11
5. Evidence of monandry in a mosquito (Sabethes cyaneus) with elaborate ornaments in both sexes
Open this publication in new window or tab >>Evidence of monandry in a mosquito (Sabethes cyaneus) with elaborate ornaments in both sexes
2008 (English)In: Journal of insect behavior, ISSN 0892-7553, E-ISSN 1572-8889, Vol. 21, no 6, p. 451-459Article in journal (Refereed) Published
Abstract [en]

Despite the benefits of multiple mating to females many mosquitoes appear to be monandrous. Members of the mosquito tribe Sabethini are unique among the mosquitoes for they possess iridescent scales and elaborate ornaments in both sexes. Additionally, this tribe boasts the only reported cases of courtship display within the mosquitoes. Due to these singular traits and behaviors, we predicted that members of this tribe have a different mating system with relatively high female mating rate. We tested this prediction in the ornamented mosquito Sabethes cyaneus. Contrary to our prediction, however, females were monandrous throughout their lifetime and multiple gonotrophic cycles. We discuss the possible implications of monandry on the evolution of sexually homologous ornaments, with particular consideration of mutual mate choice.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-107854 (URN)10.1007/s10905-008-9137-0 (DOI)000259733300001 ()
Available from: 2009-08-31 Created: 2009-08-31 Last updated: 2017-12-13Bibliographically approved

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