Orientador: Woodruff Whitman Benson / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-12T18:41:50Z (GMT). No. of bitstreams: 1 Peixoto_PauloEnriqueCardoso_D.pdf: 865304 bytes, checksum: 19540c783ae14daa3ba0b5f8dffc1d86 (MD5) Previous issue date: 2009 / Resumo: Brigas territoriais entre machos de insetos voadores são resolvidas das mais variadas formas. Em borboletas, existem evidencias de que tamanho, idade e motivação são importantes determinantes das chances de vitória. No entanto, as regras utilizadas nas brigas, o contexto biológico que afeta a intensidade dos comportamentos agonisticos e o papel funcional das características dos machos na geração de custos durante os confrontos ainda são pouco conhecidos. Neste trabalho investiguei uma serie de características que podem influenciar os custos e benefícios dos confrontos territoriais utilizando as espécies de satirineos Hermeuptychia hermes (Fabricius, 1775), Moneuptychia soter (Buttler, 1877) e Paryphthimoides phronius (Buttler, 1867) como modelos de estudo. No capitulo 1 investiguei se as disputas intra-especificas pela posse de territórios em machos de H. hermes e de M. soter ocorrem com contato físico e quais podem ser as características funcionalmente relevantes para a distinção entre machos territoriais e não territoriais. Para tanto, documentei as brigas entre machos utilizando filmagens de alta velocidade e realizei comparações morfológicas e fisiológicas entre machos possuidores de territórios (residentes) e machos que ocuparam territórios nos quais os residentes originais foram removidos (intrusos). Machos residentes de H. hermes apresentaram massa corporal e muscular similares as dos seus pares intrusos, porem, possuíram menor desgaste alar e maior quantidade de lipídeos. Machos residentes de M. soter, por outro lado, foram mais pesados que os machos intrusos que ocuparam seus territórios. Machos de H. hermes podem dividir a interação em vôos circulares, espirais ascendentes e perseguições lineares, enquanto machos de M. soter usam vôos circulares mais lentos, os quais são seguidos por perseguições lineares e emissões de som (estalos). Contatos físicos não foram registrados para nenhuma espécie. No capitulo 2 investiguei o papel da residência previa na resolução de conflitos territoriais entre machos de H. hermes. Ao induzir disputas entre dois machos que se comportaram como residentes (um residente original e um residente induzido) e compara-las com disputas naturais entre machos residentes e intrusos, foi possível demonstrar que a residência previa aumenta as chances de vitória em um combate. Massa corporal afetou positivamente as chances de vitória nas brigas induzidas, mas não nas brigas naturais. Finalmente no capitulo 3, investiguei a influencia da presença de recursos alimentares no estabelecimento de territórios de acasalamento por machos de P. phronius. Machos desta espécie defendem sítios de acasalamento localizados em manchas de sol sem recursos evidentes. No entanto, manchas de sol previamente desocupadas passaram a ser defendidas depois de receberem frutas fermentadas. Apesar de machos que se estabeleceram nestes locais aparentemente se alimentarem das frutas, experimentos de escolha de territórios sugerem que eles preferem defender sítios sem recursos e utilizam a defesa de áreas com alimento como tática alternativa de acasalamento. Este estudo representa a primeira investigação deste tipo de variação nas táticas de acasalamento em borboletas. Alem de auxiliar a compreensão da evolução de determinados sistemas de localização de parceiros, esse sistema permite testar qual a implicação da existência de mais de uma tática reprodutiva na intensidade dos confrontos territoriais entre machos / Abstract: Territorial conflicts in flying insects may be resolved through many different ways. In male butterflies, size, age and motivation are often reported as important determinants of the winning chances. However, the rules used when fighting, the biological context that affects the intensity of agonistic behaviors, and the functional role of male traits in the contests costs generation are poorly known. In this study I investigated a series of characteristics that may influence the costs and benefits of territorial conflicts using the satyrine species Hermeuptychia hermes (Fabricius, 1775), Moneuptychia soter (Buttler, 1877), and Paryphthimoides phronius (Buttler, 1867) as study organisms. In chapter 1, I used high-speed video imagery to investigate whether intraspecific disputes between male H. hermes and male M. soter occur with physical contact. Additionally, I removed resident males from their defended sites and the subsequent intruders that established on those areas after the resident removal to assess if wing wear, body mass, fat content and flight muscle ratio are important determinants of male residency status. Resident males of H. hermes were similar in body weight and thoracic muscle mass to their intruder rivals, but had fewer wing wear and higher fat content. Resident males of M. soter, on the other hand, were heavier than intruder males. Male H. hermes divided their interaction in up to three phases consisting of circular flights, ascending spirals and back and forth persecutions, whereas male M. soter used much slower circular flights that were often followed by linear persecutions and clicking sound emissions. Physical contacts were not observed for both species. In chapter 2, I investigated the role of previous residence on contest resolution in the butterfly H. hermes. By inducing territorial interactions between males that behaved as residents (one original resident and another resident-induced one) and comparing them with natural contests between resident and intruder males, it was possible to show that previous residence increases the chances of victory. Body mass positively affected the winning chances in the induced fights, but was unimportant among the natural ones. Finally in chapter 3, I investigated the role of feeding resources in the territory establishment by males of the butterfly P. phronius. Male of this species typically defend sunny clearings on the forest edge which do not contain any evident resource. However, previously undefended sunny clearings were occupied by territorial males after receiving soft fermenting fruit. Although males which established on sites containing feeding resources seem to forage on the fermenting fruit, territory selection experiments shows that males prefer to defend sites without resources. This type of variation in the mate locating tactics has never been previously investigated for butterflies. In addition of helping the understanding of the evolutionary processes leading to different mate-locating strategies, this system allows the testing of the influence of different reproductive behaviors on the intensity of territorial conflicts between males / Doutorado / Doutor em Ecologia

Machos dos opiliões goniosomatíneos Serracutisoma spelaeum e Serracutisoma guaricana, cujas fêmeas copulam com mais de um parceiro em um único período reprodutivo, apresentam uma grande variedade morfológica, especialmente relacionada a caracteres sexuais secundários. Considerando-se que machos menores frequentemente perdem disputas por fêmeas, esta tese objetivou verificar possíveis estratégias reprodutivas alternativas, resultantes de seleção sexual pré e pós-copulatória, adotadas por machos de pequeno porte dessas espécies assim como o papel da fêmea nesses mecanismos. Este trabalho foi, então, dividido em três capítulos, cada um com objetivos específicos. O primeiro deles refere-se à organização do trato reprodutor feminino e caracterização das espermatecas, órgãos de armazenamento de espermatozóides. Imagens de microscopia de luz e de microscopia eletrônica de varredura associadas às obtidas sob estereomicroscópio revelaram a existência de quatro espermatecas inseridas na musculatura da porção distal do ovipositor. Cada uma delas é constituída por quatro sáculos individuais de fundo cego e se comunica com a luz do ovipositor através de um único canal. A complexidade das espermatecas indica que a fêmea pode ser capaz de armazenar separadamente os espermatozóides dos diferentes machos com os quais vier a copular, enquanto a musculatura ao redor dessas estruturas sugere que ela possa determinar a paternidade de sua progênie através de contrações diferenciais. O capítulo 2 abrange observações comportamentais e características morfológicas e morfométricas do trato reprodutor masculino, objetivando identificar possíveis estratégias alternativas utilizadas por machos de pequeno porte na obtenção de sucesso reprodutivo. Para tal, foram efetuados acompanhamento do comportamento sexual e estudos morfométricos de genitália e da gônada. Machos de pequeno porte parecem adotar a estratégia de machos-satélites, copulando com as fêmeas quando machosguardiões estão com a atenção desviada. A ausência de diferenças estatísticas significativas na largura da placa ventral sugere que o pênis de machos grandes e de machos pequenos se ajustam à genitália feminina da mesma maneira e, portanto, sejam vii avaliados pelas fêmeas da mesma forma. Já a semelhança no comprimento da genitália e o menor tamanho corpóreo dos machos pequenos indicam que, durante a cópula, eles poderiam alcançar regiões mais profundas da espermateca, removendo ou deslocando os espermatozóides dos outros machos e, consequentemente, diminuindo o risco de competição espermática. A análise ultraestrutural dos espermatozóides (compostos por núcleo, citoplasma e acrossomo, além de diversas projeções na superfície) mostrou que, provavelmente, todos os machos possuam espermatozóides viáveis, visto que espermatozóides não-férteis, em geral, não possuem acrossomo. As similaridades entre machos de grande e de pequeno porte tanto na morfologia dos gametas como em seu comprimento indicam que tais características possam ter sido objeto de seleção sexual pós-copulatória. O terceiro capítulo propõe uma hipótese para a formação das projeções encontradas nos espermatozóides das duas espécies e que lhes confere uma morfologia peculiar. Para isso foi utilizada a associação de três técnicas de microscopia: microscopia eletrônica de transmissão, de varredura e confocal de varredura a laser. Os resultados obtidos evidenciam que essas estruturas são formadas ao longo do processo de espermatogênese. Uma rede de proteínas situada logo abaixo da membrana plasmática exerceria uma pressão sobre o citoplasma, que extravasaria pelos espaços existentes nessa espécie de malha. Dessa forma, as projeções seriam constituídas de citoplasma envolto por membrana plasmática. Em conclusão, os resultados obtidos na presente tese sugerem que a competição espermática e a escolha críptica da fêmea, componentes da seleção sexual póscopulatória, são pressões seletivas atuantes nessas duas espécies de opilião. / Males of the goniosomatine harvestmen Serracutisoma spelaeum and Serracutisoma guaricana, which females may copulate with more than one partner during the same reproductive season, show a large morphological variation, especially considering secondary sexual features. Since smaller males frequently lose fights against larger males for females, the present thesis aimed at verifying the occurrence of alternative reproductive strategies among these smaller males as a result of pre- and postcopulatory sexual selection, as well as the role of the female in these mechanisms. This study is composed of three chapters, each one with specific objectives, as described as follows. The first chapter describes the general organization of the female reproductive system and the spermathecae, structures for the storage of sperm. Ligth and scanning electronic microscopy images revealed the presence of four spermathecae inserted in the musculature of the distal portion of the ovipositor. Each spermatheca is composed of four individual dead-end sacs and is connected to the ovipositor lumen through a single channel. This complex spermathecae structure indicates that the female is able to store sperm from different males with which she copulates in different places, and that the musculature that involves these structures may be responsible for differential contractions which would result in different paternity for the females descendants. The second chapter includes behavioral observations and morphological and morphometric analysis of the male reproductive system (genitalic and gonadal features), aiming at identifying possible alternative reproductive strategies used by small males to achieve reproductive success. Small males seem to adopt a satellite-male strategy, copulating with females when larger guardian-males are not paying attention. The absence of significant statistic differences in the width of its ventral plate suggests that the penis of both large and small males may adjust to the female genitalia in the same way and, therefore, will be similarly evaluated by the female during copulation. In turn, the smaller length associated to the same sized penis of smaller males in comparison to the larger ones may indicate that they may reach deeper regions of the female genitalia during copulation, possibly removing or displacing the sperm of other males and, in consequence, reducing the risk of sperm competition. The ultrastructure analysis of the spermatozoa (which are composed of a nucleus, cytoplasm and an acrosome, in addition to several surface projections) showed that probably males of different sizes all have viable sperm, since generally non-fertile spermatozoa lack an acrosome. Similarities in the morphology and size of the gametes of both small and large males may indicate that these features have been subjected to postcopulatory sexual selection. The third chapter suggests a new hypothesis for the development of the projections found in the surface of the spermatozoa of the two species here studied. For this study, three microscope techniques were used: transmission electronic microscopy, scanning electronic microscopy, and confocal laser scanning microscopy. The results show that these projections are formed during the spermatogenesis. A net of proteins situated just below the plasmatic membrane restrains the cytoplasm, which flows through the spaces formed in the net, forming the projections, which are externally limited by plasmatic membrane. In conclusion, the results obtained in the present study suggest that sperm competition and female cryptic choice, which are components of the postcopulatory sexual selection process, are selection pressures working on the species studied herein.

De acordo com o modelo de seleção intersexual mediado por parasitas, variações nas condições de ornamentos ou taxa de displays sexuais refletem diferentes graus de resistência ao parasitismo. Em coros naturais de anfíbios, vocalizações mais altas, longas e complexas e/ou emitidas a maiores taxas são, provavelmente, mais facilmente detectadas e atraem mais fêmeas. Entretanto, o esforço vocal está positivamente relacionado aos níveis plasmáticos de esteróides potencialmente imunossupressores, tais como testosterona e corticosterona. O objetivo deste trabalho foi avaliar as relações entre taxa de vocalização, imunocompetência e níveis plasmáticos de corticosterona em Hypsiboas albopunctatus, um anuro de médio porte que ocorre na América do Sul. Tais relações foram estudadas a partir de observação focal do comportamento vocal em coro natural, seguido de coleta de sangue para dosagem de corticosterona e avaliação de alguns parâmetros imunitários. O presente estudo demonstrou uma relação positiva entre a taxa de vocalização com níveis plasmáticos de corticosterona e negativa entre estes dois parâmetros com a imunocompetência mediada por células. Estes resultados apontam para a corticosterona como possível hormônio mediador do compromisso entre esforço vocal e imunidade mediada por células em anuros. / According to the model of intersexual selection mediated by parasites, changes in conditions of sexual ornaments or display rates reflect different degrees of resistance to parasitism. In natural choruses of amphibians, calls that are higher, longer, more complex and / or issued at higher rates are probably more easily detected and attract more females. However, the vocal effort is positively related to plasma levels of potentially immunosuppressive steroids, such as testosterone and corticosterone. The aim of this study was to evaluate the relationship between calling rates, immunocompetence and plasma levels of corticosterone in Hypsiboas albopunctatus, a midsize anuran occurring in South America. Such relationships were studied from focal observations of calling behavior, followed by blood collection for measurements of corticosterone plasma levels and evaluation of some immune parameters. The present study showed a positive relationship between the calling rate with plasma levels of corticosterone, and a negative correlation between these two parameters with cell-mediated immunocompetence. These results highlight the importance of the hormone corticosterone as a possible mediator of trade-off between vocal effort and cell-mediated immunity in anurans.

No description available.

Sex allocation and sexual selection have been heavily studied, but rarely linked. In this thesis I investigated the interface between them in the gregarious parasitoid wasp Nasonia vitripennis, both directly and through their interactions with the mating system and sexual conflict. Chapter 2 investigated sexual selection and mating at the natal site: earlier eclosing males mated more females independently of body size. Nasonia follows Local Mate Competition, which describes how a female laying eggs alone on a patch of resources (a so-called single-foundress) should lay an extremely female-biased brood to minimise competition between her sons, yet ensure all her daughters are fertilised. Based on this I predicted that males with with fewer brothers would be better inseminators. Despite finding significant among-strain variation in (1) single-foundress sex ratio, (2) mate competitiveness when alone and (3) when in competition, (4) sperm resources, but not (5) sperm-depletion (Chapters 3 & 4), I did not find the predicted relationship. Conversely males from strains with more brothers had a higher mating success under competition (Chapter 3) leading to the question: does mating success select on sex ratio or vice versa? Either way it is a result of an interaction between sexual selection and sex allocation. Chapter 5 investigated the role of male post-copulatory courtship on female re-mating, and found that among- strain variation in female re-mating was not associated with variation in the duration of the post-copulatory courtship. Chapter 6 reviewed sexual conflict in the Hymenoptera: their haplodiploid genetics, newly sequenced genomes and varied life- histories provides a base for future research to build on. Finally I highlight the novel links between sexual selection, sex allocation, sexual conflict and the mating system found during my studies that will hopefully prompt future research on this topic.

Abstract Divergence of behavioral traits (e.g. courtship rituals, habitat choice) has had a major impact on species formation and isolation. Species-specific courtship rituals preventing species hybridization may arise as a by-product of natural selection during spatial isolation or through direct action of natural selection to prevent species hybridization after a secondary contact. Coordination leading to the assumption of coevolution of signals and preferences is a prerequisite for effective courtship signaling between a male and a female of the same species. We found a reasonable amount of variation in the mate traits within the Drosophila montana and D. virilis species, but our findings did not reveal evidence of the coevolution between the male courtship signals and female preference for these signals. Variation also did not cause isolation within species. The form of female preference for carrier frequency of male song was found to be stabilizing even in changing environments, when female preference for the carrier frequency and pulse length of the male song was measured at ambient temperature. D. montana females always preferred males with high frequency songs, which probably advertises the male condition. The frequency of male song decreased due to male aging, although males with larger body size were able to maintain frequencies better. Ageing also had a deterioration effect on male reproductive success. The importance of male courtship song was not only highlighted in mate choice, but also in species-recognition. We were able to persuade D. montana females to copulate with alien D. lummei species by playing them simulated song resembling the song of conspecific males. Simulated courtship songs were demonstrated to be a practical tool in studies of preference between sexually isolated Drosophila species. / Tiivistelmä Kosintapiirteiden (esim. kosintarituaalit, habitaatin valinta) vaihtelevuudella on ollut suuri vaikutus lajien muodostumisessa ja eriytymisessä. Lajien välisiä risteytymisiä estäviä lajispesifisiä kosintarituaaleja voi syntyä luonnonvalinnan sivutuotteena spatiaalisen eristäytymisen aikana tai luonnonvalinnan suoralla vaikutuksella estämään lajiristeymät lajien uudelleen kohdatessa. Tehokkaan koiraan ja naaraan välisen kosintaviestinnän edellytyksenä on koordinointi, minkä vuoksi on oletettavaa, että signaalien ja vasteiden välillä on yhteisevoluutiota. Löysimme kohtuullisen määrän vaihtelevuutta kosintapiirteissä Drosophila montana – ja D. virilis – lajeilla, mutta emme löytäneet todisteita koiraan kosintasignaalien ja naaraan näihin signaaleihin kohdistamien vasteiden välisestä yhteisevoluutiosta. Vaihtelu ei myöskään aiheuttanut isolaatiota lajien välille. Naaraan koiraan kosintalaulun kantofrekvenssiin osoittaman vasteen funktion muodon havaittiin olevan tasapainottava jopa vaihtelevissa ympäristöissä, kun naaraan kantotaajuuteen osoittamaa vastetta mitattiin eri lämpötiloissa. D. montana naaraat suosivat koiraita, joilla oli korkeataajuinen kosintalaulu. Laulun korkea taajuus kertoo luultavasti naaraalle koiraan fyysisestä kunnosta. Koiraan laulun frekvenssin havaittiin laskevan koiraan ikääntyessä, mutta isommat koiraat pystyivät paremmin säilyttämään korkean taajuuden laulussaan. Ikääntyminen heikensi myös koiraan lisääntymismenestystä. Koiraan kosintalaulun tärkeys ei korostunut pelkästään parinvalinnassa, vaan myös lajintunnistuksessa. Pystyimme suostuttelemaan D. montana –naaraat parittelemaan vieraan D. lummei –lajin kanssa käyttämällä simuloituja kosintalauluja, jotka osoittautuivat käytännöllisiksi välineiksi tutkittaessa naaraan vasteita seksuaalisesti eriytyneillä Drosophila-lajeilla.

Cuticular hydrocarbons (CHCs) are found on the outer cuticle of all terrestrial arthropods. Although their primary function is in desiccation prevention, these compounds have also been shown to play a variety of roles in insect chemical communication, from species and sex recognition to providing cues of dominance and attractiveness. However, despite growing evidence of their versatility as cues, our knowledge of how CHCs are used in mating interactions is limited to Drosophila and field crickets. In this thesis I investigate the roles CHCs play in interactions at each stage of the mating process in the broad-horned flour beetle Gnatocerus cornutus. I assess the relative importance of CHCs in influencing male reproductive success and examine the complex interplay between different episodes of selection and the mechanisms of sexual selection acting on males. I use a combination of behavioural assays, experimental manipulations and gas chromatography. First, I identify the role of CHCs as cues of sperm competition risk and intensity, demonstrating how the presence of male-derived CHCs on the cuticles of virgin females elicits males to adjust their pre- and post-copulatory investment (chapter 2), by providing information on the state of their competitive environment. I then go on to look at the stability of CHCs as cues of sperm competition over time, finding that they are highly sensitive to environmental degradation (chapter 3) and do not persist in the habitat substrate of this species. Next, I investigate how male CHCs determine fighting and mating success. By estimating and comparing the strength and form of sexual selection imposed by male-male competition and female mate choice, I show that male CHCs are subject to strong antagonistic sexual selection (chapter 4). By experimentally manipulating male CHC profile, I then attempt to verify the selection gradients estimated for female choice 3 (chapter 5). However, my experimental manipulation fails to verify the importance of male CHCs for female mate choice. Finally, I explore the role of same-sex sexual behaviour (SSB) in determining male reproductive success (chapter 6). I find evidence to suggest that SSB may in fact be a form of aggression in its own right, and demonstrate that SSB and fighting may provide equivalent means for males to overcome female choice and secure a mating advantage. My results indicate that CHCs play key roles as chemical cues throughout the mating process and significantly impact male reproductive success. My thesis reveals the intricate nature of the relationships between mechanisms of sexual selection, alongside highlighting the need to consider both the social and physical environment when investigating the importance of chemical cues. I discuss the implications of these results for the evolution of male CHCs and how my findings can be used to further our knowledge of this field.

Abstract Sexual selection results from competition between individuals over access to gametes of the opposite sex. Starting with anisogamy, with females producing larger and fewer gametes than males, females usually invest more in reproduction and thus have lower potential reproductive rates than males. Therefore males are traditionally suggested to compete over females whereas females are choosy. The different evolutionary interests between the sexes result in different selection regimes considering e.g. mating rates. In some species, this conflict is even seen as apparent struggles between males and females over mating decision and/or duration, resulting in antagonistic coevolution with both sexes evolving adaptations to gain more control over the other sex. In this thesis, I studied the role of A. paludum female abdominal spines as an adaptation to reject male mating attempts. I studied both the effect of polyandry and multiple matings on female fecundity to distinguish between the potential material and genetic benefits from mating to females. I also explored the role of various male and female morphological traits on precopulatory sexual selection and the consequent female reproductive output. My results show that female abdominal spines are likely evolved through arms races between the sexes to increase female control over mating decision but according to my studies, female spines are not under active selection. Instead, certain male morphological types were more successful in achieving matings, and mating with these males also increased female fecundity. I found that multiple matings increase female fecundity up to a point, supporting a theory of optimal female mating rate. According to my results, the benefits from multiple mating to A. paludum females result from material origin whereas polyandry per se is even detrimental to female fecundity. / Tiivistelmä Seksuaalivalinta on pohjimmiltaan seurausta yksilöiden välisestä, lisääntymiseen liittyvästä kilpailusta toisen sukupuolen sukusoluista. Seksuaalivalinta on evoluutiomekanismi, joka osaltaan on johtanut sukupuolten välisiin eroihin monissa morfologisissa ja käyttäytymiseen liittyvissä ominaisuuksissa. Sukupuolet eroavat jo siinä, että naaraat tuottavat vähemmän mutta suurempia sukusoluja kuin koiraat. Koska sukupuolet siis investoivat lisääntymiseen jo alkuvaiheessa eri tavalla, niiden välillä on aina jonkin asteinen seksuaalikonflikti. Konfliktin taustalla on sukupuoliin kohdistuva erilainen valintapaine; koiraat saavuttavat usein optimaalisen hedelmällisyytensä suuremmilla parittelujen määrällä kuin naaraat. Joillakin eläinlajeilla seksuaalikonflikti on niin ilmeinen, että se ilmenee koiraan ja naaraan välisinä kamppailutilanteina parittelupäätöksen ja/tai parittelun keston suhteen. Seksuaalikonflikti voi johtaa molemmilla sukupuolilla erilaisiin sopeumiin, jotka lisäävät yksilön kontrollia parittelujen suhteen. Tässä väitöskirjatyössä tutkin naaraan takapäässä sijaitsevien abdominaalisten piikkien merkitystä järvivesimittari A. paludum-naaraiden kyvyssä torjua parittelemaan pyrkiviä koiraita. Tutkin myös polyandrian ja toistuvien parittelujen vaikutusta naaraan hedelmällisyyteen saadakseni selville, lisäävätkö koiraasta johtuvat mahdolliset materiaaliset tai geneettiset tekijät naaraan hedelmällisyyttä. Lisäksi selvitin useiden koiraan ja naaraan morfologisten ominaisuuksien yhteyttä parittelua edeltävään seksuaalivalintaan sekä naaraan hedelmällisyyteen. Tulokseni osoittavat, että naaraan abdominaaliset piikit ovat todennäköisesti kehittyneet seksuaalikonfliktin seurauksena lisäämään naaraan kontrollia parittelupäätöksen suhteen. Niihin ei kuitenkaan nykyisellään näytä kohdistuvan merkittävää valintapainetta. Sen sijaan morfologialtaan tietynlaiset koirastyypit vaikuttavat olevan aktiivisen valinnan kohteena ja parittelu tällaisten koiraiden kanssa lisää myös naaraan hedelmällisyyttä. Toistuvat parittelut saman koiraan kanssa lisäävät naaraan hedelmällisyyttä tiettyyn optimiin asti, mikä tukee teoriaa optimaalisesta parittelujen määrästä. Sen sijaan polyandria itsessään vaikuttaa naaraan hedelmällisyyteen jopa heikentävästi. Niinpä A. paludum-naaraiden saama hyöty useista paritteluista näyttää olevan materiaalista, kun taas polyandriasta saatavia geneettisiä etuja ei tässä tutkimuksessa tullut ilmi.

Sexual reproduction entails complex co-evolution between the sexes, necessary for successful fertilization, ensuring individual and population-level fitness. Interfertility is the main criterion for species definition and understanding speciation requires detailed studies of reproductive barriers. However, many studies on reproductive barriers are constrained to infer evolutionary processes from patterns. In this thesis, I focus on a hybrid zone between collared and pied flycatchers (Ficedula albicollis and hypoleuca) on the island of Öland, and a trait that is essential for fertilization: sperm. Long-term monitoring of these species, combined with recent advances in molecular tools, allow me to study how complex on-going intersexual and interspecific interactions influence reproductive isolation in this young hybrid zone. I start by exploring the links between pre- and postmating sexual selection within collared flycatchers (paper I and II). I show that secondary sexual characters and indirect mate-choice benefits are tightly linked to physiology (paper I), and that a male’s attractiveness and dominance status dictate which sperm traits are optimal, as a male’s fertilization success depends on an interaction between sperm and display traits (paper II). I then report a source of strong postzygotic isolation between recently diverged collared and pied flycatchers: impaired spermatogenesis resulting in absence of mature sperm cells in hybrid males (paper III). I show however that pied flycatcher females, who are most exposed to hybridization, can mitigate these costs through mechanisms of cryptic female choice impairing heterospecific sperm performance, allowing them to bias paternity towards pure-species offspring (paper IV). Finally, by exploring the testes transcriptomes and sperm proteomes of both species, I highlight the importance of gene and protein regulation mechanisms in facilitating phenotypic divergence between these species (paper V). Thus, my thesis reveals complex interactions between primary and secondary sexual characters in a wild bird and suggests that mechanisms of sexual selection are tightly linked to essential physiological functions. I also show that genetic incompatibilities can evolve rapidly despite low genome-wide levels of divergence but that divergence in regulatory regions and proteins potentially allows fast evolution of molecular mechanisms impairing or preventing costly heterospecific fertilization.

Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter ‘T’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5% of males obtaining 87.2% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because < 10% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.