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Mate competition is a prominent component of sexual selection theory. Typically, males attempt to mate with the most females possible and females attempt to mate with the highest quality males possible. In the polygynous female-defense mating system of Anolis carolinensis, males compete directly for females through territorial behavior. Inter-male competition is intense due to an average polygyny ratio of 1 male to 3 females despite a 1:1 adult sex ratio. Through high levels of territorial behavior (e.g., 100 displays/h, 27 m patrol distances/h, 70% of day in defense-related activities), males attempt to exclude other males from resident females who, in turn, both store sperm and ovulate a single-egg clutch at weekly intervals over a 4-month breeding season. Paternity of hatchlings in 16 naturally occurring breeding groups was analyzed to determine the extent to which the territorial resident male was able to prevent other males from fathering offspring of his resident females. Lizards residing in or neighboring a resident male's territory were collected and RAPD-PCR was used to determine the paternity of hatchlings. Of the 48 hatchlings from 26 females, resident territorial males fathered 52% of hatchlings; 15% were fathered by a male whose territory bordered that of the resident male and 21% were fathered by a smaller male living covertly within the resident male's territory. Paternity for the remaining 12% of hatchlings belonged to an unsampled male. Given that females mated with multiple males, laboratory-based controlled matings were conducted where females were sequentially paired with two males and RAPD-PCR was used to analyze which of the two males fathered the subsequent hatchlings to determine the mechanism of sperm precedence. Regardless of mating order, only one male of the pair fertilized the eggs. Male A. carolinensis have reproductive strategies present in addition to defending resident females and female A. carolinensis have options in addition to simply mating with the resident male. While sperm precedence is present in this species, it is not based on mating order, but may involve both the number of sperm deposited in the female's tract as well as the quality of those sperm. / Ph. D.

Adult green anoles, Anolis carolinensis, exhibit numerous sex differences resulting from divergent strategies for maximizing reproductive success. I focused on the ontogeny of sex differences in behavior in juveniles, in relation to adult sex differences, by documenting the behavior of free-ranging juveniles, examining the structure and use of headbobbing displays, and determining the role of the androgen testosterone (T) in producing behavioral sex differences. Field observations indicated that juvenile males eat and forage actively more often than juvenile females. This divergent feeding behavior may result from sexual selection, given that body size is a major factor in determining the reproductive success of males. Analyses of headbobbing displays, used by adults in aggressive and sexual interactions, revealed that juvenile males and females each give the same three A, B, and C display types described for adults. However, there may be a maturational component to display structure, as juvenile displays differ from those of adults in within-display temporal structure, and are not as stereotyped. Concerning display use, social context affects neither the types of display interactions observed nor the rates of displays and related behaviors. However, size affects nearly every aspect of display behavior. Both juvenile males and females show increased display rates and probabilities of expressing display-related behaviors with increasing body size, although in the largest juveniles, male display rates become higher than those of females. These results, like those from analyses of display structure, suggest a maturational component to display use, perhaps mediated by changes in the underlying motivational states of juveniles. Consistent with the divergence in display rates in large juveniles, males of approximately 30 d of age and older have higher plasma T concentrations than females. Furthermore, juvenile males and females that have been given T implants each respond with increased behavior levels, approaching those of breeding adult males. These analyses indicate that sexual dimorphisms in behavior in adults likely arise through underlying physiological differences between males and females that mediate the expression of behavior, rather than through fundamental sex differences in the ability to perform these behaviors. / Ph. D.

[Truncated abstract] Despite the costs associated with mating, females of many taxa solicit multiple mates during a single reproductive event (polyandry). Polyandry is clearly adaptive when females gain direct benefits from males at mating. However, polyandry has also been shown to increase female fitness in the absence of direct benefits. Thus, a number of genetic benefit hypotheses have been developed to account for the origin of this behaviour. Although not mutually exclusive, a distinction lays between genetic benefits that propose defense against reproductive failure (nonadditive genetic effects), and those that propose benefits from intrinsic sire effects (additive genetic effects). Nonadditive genetic benefits of polyandry have been documented in a number of species; by soliciting multiple mates females can avoid inbreeding and other forms of incompatibility between parental genotypes. Polyandry may also increase female reproductive success when genetically superior males have greater success in sperm competition, and produce better quality offspring. An inevitable consequence of polyandry is that sperm from rival males will overlap in the female reproductive tract and compete to fertilise the ova. The outcome of sperm competition is typically determined by bias in sperm use by the females, interactions between parental genotypes, and ejaculate characteristics that provide a fertilisation advantage. Thus, sperm competition is recognised as a persuasive force in the evolution of male reproductive traits. Comparative analyses across species, and competitive mating trials within species have suggested that sperm competition can influence the evolution of testis size and sperm production, and both sperm form and sperm function. ... After six generations of selection I observed phenotypic divergence in litter size - litter size increased in the polyandrous lines but not in the monandrous lines. This result was not attributable to inbreeding depression, or environmental/maternal effects associated with mating regime. Genetic benefits associated with polyandry could account for this result if increased litter size were attributable to increased embryo survival. However, males from the polyandrous lineages were subject to sperm competition, and evolved ejaculates with more sperm, suggesting that evolutionary increases in litter size may in part be due to improved male fertility. Finally, Chapter Five is an investigation of the natural variation in levels of polyandry in the wild, and the potential for sperm competition to drive macroevolutionary changes in male reproductive traits among geographically isolated island populations of house mice. I sampled seven island populations of house mice along the coast of Western Australia and, by genotyping pregnant females and their offspring, determined the frequency of multiply sired litters within each population. I applied the frequency of multiple paternity as an index of the risk of sperm competition, and looked for selective responses in testis size and ejaculate traits. I found that the risk of sperm competition predicted testis size across the seven island populations. However, variation in sperm traits was not explained by the risk of sperm competition. I discuss these results in relation to sperm competition theory, and extrinsic factors that influence ejaculate quality.

Sexual selection arises via competition for access to mates, and is thus intimately tied to the social environment. For example, individual mating success may depend strongly on how many rivals or mating partners are available. Studies of mate choice and sexual selection may vary the number of mates a subject is presented with during mating experiments, yet it is not clear how this influences the strength and shape of sexual selection acting on traits in either sex. In this thesis I investigate the effect of social environment on sexual selection acting in two closely-related species of lygaeid seed bug: Lygaeus equestris and Lygaeus simulans. Males in both species possess an extremely elongate intromittent organ, which is over two-thirds average male body length. I show that the strength of pre-copulatory selection acting on male processus length in Lygaeus equestris and genital clasper shape in Lygaeus simulans is significantly influenced by the social context. However, selection on male and female body size in Lygaeus equestris is not. Additionally, I use a meta-analysis of 38 published studies to show that mating preferences are significantly stronger when more than one mate option is available, compared to when only a single option is available. I also investigate the functional morphology of male genital traits in Lygaeus simulans, and use formal selection analysis to quantify the strength of selection acting on these traits before, during and after mating. Finally, I use experimental manipulations in Lygaeus simulans to confirm that male processus length directly influences sperm transfer, and that intact genital claspers are required for successful intromission. Overall, my results illustrate that sexual selection in the wild may vary both spatially and temporally depending on the social environment. It is thus especially important that experiments are performed under ecologically relevant conditions.

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. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 729

Thesis (Ph. D.)--Miami University, Dept. of Zoology, 2003. / Title from second page of PDF document. Includes bibliographical references.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Territorial fights between males are frequently observed among insects. However, despite the existence of theoretical models directed at explaining the possible rules adopted to decide the winner, there is little empirical support for these models. The low empirical support may be explained by difficulties in identifying traits that determine the male fighting capacity (RHP- or Resource Holding Potential) and also by the lack of simultaneous tests of different models. In this study we evaluated males traits that may determine RHP in the dragonfly Diastatops obscura. Also, we evaluated the relationship between such characteristics and duration of disputes between pairs of males to test predictions derived from the models War of Attrition (GDA), Sequential Access Information (ASI) and Cumulative Access Information (ACI). Male weight was the main feature related to the winning chances. The dispute duration decreases with increasing weight and presented the opposite pattern for the loser male, rejecting the GDA as the decision rule adopted by males to settle territorial interactions. In addition the duration of the dispute was not related to the loser male weight when we considered only pairs of rivals who presented similar weight differences. This indicates that the rivals make mutual assessment of RHP, as assumed by the model ASI. Since wings are highly melanized, we suggest that males may perform rival assessments of RHP based on wings traits, as occur in odonate species. / Apesar das brigas entre os machos serem frequentes e de existirem modelos teÃricos que postulam possÃveis regras usadas para decisÃo do vencedor, pouco suporte empÃrico direcionado ao entendimento das brigas tem sido encontrado. Provavelmente esse fato ocorre devido à dificuldade em identificar quais caracterÃsticas determinam a capacidade de luta (RHP - Resource Holding Potential) dos indivÃduos e na escassez de testes simultÃneos de diferentes modelos. Neste trabalho, usamos machos da libÃlula Diastatops obscura para identificar caracterÃsticas determinantes do RHP. Posteriormente usamos informaÃÃes sobre a relaÃÃo entre tais caracterÃsticas e a duraÃÃo das disputas entre pares de machos para testar previsÃes derivadas dos modelos Guerra de Atritos (GDA), Acesso Sequencial de InformaÃÃo (ASI) e Acesso Cumulativo de InformaÃÃo (ACI). O peso representou a principal caracterÃstica determinante da chance de vitÃria em uma disputa. A duraÃÃo da disputa diminuiu com o aumento do peso do vencedor e aumentou com o aumento de peso do perdedor, refutando o modelo GDA como explicaÃÃo das regras de resoluÃÃo das brigas. Adicionalmente a duraÃÃo da disputa nÃo esteve relacionada com o peso do macho perdedor quando consideramos apenas pares de rivais que apresentaram diferenÃas semelhantes de peso. Isso indica que os rivais fazem avaliaÃÃo mÃtua do RHP, como presumido pelo modelo ASI. Uma vez que as asas sÃo fortemente melanizadas, sugerimos que eles podem realizar avaliaÃÃes da capacidade de luta ao obter informaÃÃes sobre a coloraÃÃo das asas, como ocorre em outras espÃcies de libÃlulas.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Em muitas espÃcies animais, os machos brigam por territÃrios os quais aumentam as chances de cÃpulas. Os comportamentos de luta dos machos podem variar desde embates sem contato fÃsico atà lutas com injÃrias e possÃveis mortes. Existem pelo menos trÃs modelos propostos para explicar as regras usadas pelos machos para decidirem o vencedor de um confronto territorial: Guerra de Atritos (GDA), Acesso Sequencial de InformaÃÃes (ASI) e Acesso Cumulativo de InformaÃÃes (ACI). PorÃm, para sermos capazes de testar tais modelos à necessÃrio identificar primeiro quais traÃos dos machos determinam funcionalmente sua capacidade de luta (RHP). Para isso, usamos machos da libÃlula Macrothemis imitans para avaliar duas hipÃteses: 1) se as brigas ocorrerem com contato fÃsico, caracterÃsticas ligadas ao tamanho determinarÃo o RHP e 2) se os machos nÃo exibirem contato fÃsico durante as brigas, caracterÃsticas que conferem maior resistÃncia determinarÃo o RHP. Realizamos coletas de campo em campanhas de dois dias seguidos. Nessas campanhas realizamos captura, marcaÃÃo, observaÃÃo comportamental e recaptura de duas categorias de machos: os que possuÃam posse dos territÃrios (machos residentes) e os machos que ocuparam o local apÃs a remoÃÃo experimental dos machos residentes (machos substitutos). ApÃs a recaptura, levamos os machos residentes e substitutos para laboratÃrio para realizar as medidas: Ãrea alar, peso fresco, massa muscular torÃcica e quantidade de gordura. Os resultados indicaram que os machos residentes apresentaram maior quantidade de massa muscular e possivelmente gordura do que os substitutos. Uma vez que as brigas ocorreram com contato fÃsico, a maior quantidade de massa muscular e gordura dos machos residentes indica que a relaÃÃo funcional entre comportamento de luta e traÃos determinantes do RHP deve ser rejeitada. Alternativamente, à possÃvel que a maior quantidade de mÃsculo proporcione maior desempenho para causar injÃrias nos rivais ou evitar acÃmulo acelerado de danos. / In many animal species, males fight for the possession of territories that increase their mating chances. The fighting behavior of males may range from conflicts without physical contact to disputes with injuries and possible deaths. There are three models aiming to explain the rules adopted by males to decide the winner of a contest: war of attrition (WOA), sequential assessment model (SAM) and cumulative assessment model (ACM). However, to be able to test these models it is necessary to identify male traits functionally related to fighting ability (RHP). In this sense, we used males of the dragonfly Macrothemis imitans to evaluate two hypotheses: 1) if contests occur with physical contact, traits related to the size define RHP and 2) if disputes occur without physical contact, traits which confer endurance define male RHP. We did field experiments during campaigns with two consecutive days. In each campaign we captured, marked, made behavioral observations and recaptured males that were defending a territorial site (resident males) and males that stablished territories in this sites after the experimental removal of the resident male (substitute males). After recapturing, we transported all males them to lab to measure total wing area, male fresh weight, muscle mass and fat content.The results indicated that resident males presented higher muscle mass and probably fat content than substitute males. Since disputes occurred with physical contact, these differences in muscle mass and fat content indicate that the functional relationship between fight behavior and traits linked to RHP should be rejected. Alternativelly, it is possible that the higher muscle mass confers higher ability to cause injuries or to avoid damage accrual.

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