Evolutionary transitions between the two major predator avoidance strategies aposematism and crypsis are expected to be associated with changes in many important traits of animals. However, empirical studies on populations experiencing ongoing or recent transitions between these strategies are rare. This thesis investigates the co-evolution of traits among populations of the Strawberry poison frog D.pumilio in Bocas del Toro, Panama. I found that all investigated populations were genetically distinct but that colour and pattern did not correlate with genetic or geographic distance, which suggests that selection needs to be invoked to explain the observed variation. Based on the chromatic contrast between frog dorsal colour and the natural habitat substrates used by the frogs, the populations were defined as bright or dull coloured. I found that frogs from bright coloured populations were larger. This is expected if aposematism is enhanced by large signals while crypsis is enhanced by small size. Further, individuals from bright coloured populations had a coarser black dorsal pattern, which is expected if crypsis is impaired by a bold pattern. The importance of pattern coarseness was confirmed by an avian detection experiment showing that coarse patterned dark green prey were more easily detected than dark green prey without pattern or with fine pattern. I put forward the hypothesis that enhanced protection, gained by aposematism, may affect behaviours that influence dispersal and pairing patterns. Indeed, males from bright coloured populations displayed at more exposed sites and showed a tendency to be more explorative and aggressive. In summary, my results show that the bright and dull coloured populations most likely represent an aposematic and a cryptic strategy, respectively. Furthermore, I show that evolutionary changes between aposematism and crypsis can be associated with coevolution of both morphology and behaviour. I argue that this coevolution may increase the likelihood of both pre- and post-zygotic reproductive isolation. This is because greater phenotypic differences between populations increase the likelihood of selection against badly adapted migrants and hybrids with intermediate traits.

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Inbreeding can have profound negative effects on individuals by reducing fertility and viability. In populations, inbreeding depression can reduce growth rates and increases extinction risk. The aims of this thesis are to investigate inbreeding depression in male guppies (Poecilia reticulata) and to study the evolution of mechanisms for inbreeding avoidance in females, using guppies from a feral population in Queensland, Australia. Male guppies are highly polymorphic in their sexual ornamentation, indeed they show one of the most extreme polymorphisms observed in nature. Female guppies exhibit complex mate choice based on preferences for ornamentation, as well as social context. I aim is to examine how these factors of inbreeding avoidance alter sexual selection. In male guppies I found strong inbreeding depression in male sperm numbers, which is amplified under semi-natural compared to laboratory conditions (Chapter 2). Moreover, inbreeding depression results in low fertility under sperm competition: an experiment using artificial insemination techniques reveals that highly inbred males are heavily disadvantaged in gaining paternity (Chapter 3). On population level, inbreeding depression is manifest in reduced growth rates, predominantly in the early stages of inbreeding (Chapter 4). Population growth at inbreeding coefficients f=0.375-0.59 did not seem to lead to inbreeding depression, whereas lower levels of inbreeding reduced population growth. Although the growth rates in inbred populations appear normal, severe inbreeding depression is uncovered after outbred immigrants are added. Specifically, male immigrants are most efficient in short-term genetic rescue, probably due to insemination of large numbers of females whereas females are limited in the number of eggs they can produce (Chapter 4). Male ornamental traits show significant inbreeding depression in semi-natural conditions only (Chapters 2 & 3). Inbreeding avoidance mechanisms seem to have evolved in females: they prefer courtship displays of non-inbred males (Chapter 2), unfamiliar males (Chapter 5) and males with rare patterns (Chapter 6). This preference might increase the mating success of immigrants, and may have evolved to facilitate the avoidance of inbreeding. Together with context-independent preferences for ornament combinations (Chapter 6), it also offers an explanation for the maintenance of polymorphism in this species.

Inbreeding can have profound negative effects on individuals by reducing fertility and viability. In populations, inbreeding depression can reduce growth rates and increases extinction risk. The aims of this thesis are to investigate inbreeding depression in male guppies (Poecilia reticulata) and to study the evolution of mechanisms for inbreeding avoidance in females, using guppies from a feral population in Queensland, Australia. Male guppies are highly polymorphic in their sexual ornamentation, indeed they show one of the most extreme polymorphisms observed in nature. Female guppies exhibit complex mate choice based on preferences for ornamentation, as well as social context. I aim is to examine how these factors of inbreeding avoidance alter sexual selection. In male guppies I found strong inbreeding depression in male sperm numbers, which is amplified under semi-natural compared to laboratory conditions (Chapter 2). Moreover, inbreeding depression results in low fertility under sperm competition: an experiment using artificial insemination techniques reveals that highly inbred males are heavily disadvantaged in gaining paternity (Chapter 3). On population level, inbreeding depression is manifest in reduced growth rates, predominantly in the early stages of inbreeding (Chapter 4). Population growth at inbreeding coefficients f=0.375-0.59 did not seem to lead to inbreeding depression, whereas lower levels of inbreeding reduced population growth. Although the growth rates in inbred populations appear normal, severe inbreeding depression is uncovered after outbred immigrants are added. Specifically, male immigrants are most efficient in short-term genetic rescue, probably due to insemination of large numbers of females whereas females are limited in the number of eggs they can produce (Chapter 4). Male ornamental traits show significant inbreeding depression in semi-natural conditions only (Chapters 2 & 3). Inbreeding avoidance mechanisms seem to have evolved in females: they prefer courtship displays of non-inbred males (Chapter 2), unfamiliar males (Chapter 5) and males with rare patterns (Chapter 6). This preference might increase the mating success of immigrants, and may have evolved to facilitate the avoidance of inbreeding. Together with context-independent preferences for ornament combinations (Chapter 6), it also offers an explanation for the maintenance of polymorphism in this species.

Inbreeding can have profound negative effects on individuals by reducing fertility and viability. In populations, inbreeding depression can reduce growth rates and increases extinction risk. The aims of this thesis are to investigate inbreeding depression in male guppies (Poecilia reticulata) and to study the evolution of mechanisms for inbreeding avoidance in females, using guppies from a feral population in Queensland, Australia. Male guppies are highly polymorphic in their sexual ornamentation, indeed they show one of the most extreme polymorphisms observed in nature. Female guppies exhibit complex mate choice based on preferences for ornamentation, as well as social context. I aim is to examine how these factors of inbreeding avoidance alter sexual selection. In male guppies I found strong inbreeding depression in male sperm numbers, which is amplified under semi-natural compared to laboratory conditions (Chapter 2). Moreover, inbreeding depression results in low fertility under sperm competition: an experiment using artificial insemination techniques reveals that highly inbred males are heavily disadvantaged in gaining paternity (Chapter 3). On population level, inbreeding depression is manifest in reduced growth rates, predominantly in the early stages of inbreeding (Chapter 4). Population growth at inbreeding coefficients f=0.375-0.59 did not seem to lead to inbreeding depression, whereas lower levels of inbreeding reduced population growth. Although the growth rates in inbred populations appear normal, severe inbreeding depression is uncovered after outbred immigrants are added. Specifically, male immigrants are most efficient in short-term genetic rescue, probably due to insemination of large numbers of females whereas females are limited in the number of eggs they can produce (Chapter 4). Male ornamental traits show significant inbreeding depression in semi-natural conditions only (Chapters 2 & 3). Inbreeding avoidance mechanisms seem to have evolved in females: they prefer courtship displays of non-inbred males (Chapter 2), unfamiliar males (Chapter 5) and males with rare patterns (Chapter 6). This preference might increase the mating success of immigrants, and may have evolved to facilitate the avoidance of inbreeding. Together with context-independent preferences for ornament combinations (Chapter 6), it also offers an explanation for the maintenance of polymorphism in this species.

Made available in DSpace on 2014-06-11T19:30:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-03Bitstream added on 2014-06-13T20:00:48Z : No. of bitstreams: 1 castro_als_dr_jabo.pdf: 338540 bytes, checksum: 2873a81aaff2ff97d28c2182b3255c16 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O comportamento reprodutivo dos teleósteos envolve a seleção de parceiros para acasalamento por meio de escolha da fêmea e da disputa entre machos. A disputa pode levar à formação de hierarquia de dominância, na qual os machos dominantes têm vantagem no acasalamento por impedir que outros machos se aproximem da fêmea. Por outro lado, é possível que a fêmea prefira machos com maior habilidade competitiva, antes da formação da hierarquia. Assim, para compreender os fatores que afetam a preferência da fêmea e se a presença da fêmea durante as competições fornece vantagem na luta dos machos, realizamos dois estudos com a tilápia-do-Nilo (Oreochromis niloticus). O primeiro estudo testou a preferência das fêmeas em relação à características indicadoras da habilidade competitiva dos machos, sem a interferência da competição entre eles. Para isso, uma fêmea foi submetida ao contato visual com dois machos isolados e a preferência por um deles foi testada. Posteriormente os mesmos machos interagiram e estabeleceram a dominância. O macho preferido não se tornou dominante. Assim, não houve associação entre a preferência da fêmea e características indicadoras da habilidade competitiva dos machos. No segundo estudo testamos o efeito do contato visual de um macho com uma fêmea sobre a disputa hierárquica entre machos, uma vez que as interações macho-fêmea podem modular a reprodução e agressão dos peixes. Para isso, um macho em contato visual prévio com uma fêmea interagiu com um macho previamente isolado até o estabelecimento hierárquico. Porém, o macho em contato visual com a fêmea não se tornou dominante nem emitiu maior freqüência de ataques ao oponente. A presença da fêmea causou aumento do Índice Gonadossomático do... / Reproductive behavior of many fish species is performed by sexual selection and mate choice based on male-male contests. In such situation, selection is related to individual male competitive ability. Competition causes a social hierarchy, and dominant fish takes advantages for mating by avoid subordinate approach of females. Thus, it is possible that female prefer highest competitive ability males. To understand factors affecting female preference and, whether female presence can affect reproductive male ability, we performed two studies with Nile tilapia (Oreochromis niloticus) to understand the factors involved in dominance and female choice. In the first study we tested the female preference for highest competitive ability male. For this purpose, a female was kept in a visual contact with two males and the preference was tested by recording time female spent near to them. After that, both males were put together to fight, and we analyzed the chosen male was the winner. There was no association between female choice and male competitive ability. In the second study, we tested the effect of male visual contact with female and we supposed this could guarantee victories in a contest. Thus, a male was kept seeing a female during 6 days, and after that it was paired with a 6-days isolated male until hierarchical settlement. Female presence causes gonadosomatic index rise, but did not enhance chances for male victory in the social contest. This means that males that have more developed gonads do not take advantage in social interactions. Finally, we concluded that: i) females showed preference for one male; ii) female preference is not associated to male competitive ability; iii) visual stimulated males by female (with better gonadal condition) have not advantage in the hierarchy settlement.

What processes contribute to the evolution of reproductive isolation and the coexistence of interfertile species in the same habitat? This thesis investigates the relative roles of species interactions and intraspecific processes in contributing to reproductive isolation. I combine behavioural and genomic approaches to test hypotheses about what mechanisms maintain the general species boundary between two closely related field cricket species: Teleogryllus oceanicus and T. commodus. These species are a classic study system for sexual communication and readily hybridize in the laboratory, however little is known about species interactions in sympatric populations. I examine patterns of geographic variation in two key sexual traits: calling song and cuticular hydrocarbons (CHCs), and the geographic distribution of genetic variation across a broad sample of allopatric and sympatric populations. I test whether X chromosomes play a pronounced role in population divergence and reproductive isolation. Using close range mating trials and hybridization experiments I identify numerous pre-mating and post-mating barriers between the species. The results indicate that the species are currently reproductively isolated and the pattern of population differentiation does not strongly support contemporary species interactions contributing to phenotypic diversity. Numerous barriers exist between the species, in particular hybrid females are sterile in both cross directions, while hybrid males are relatively fertile. This provides a rare exception to Haldane's rule which is central to many genetic theories of speciation. Established theory predicts that X chromosomes should play a pronounced role in the evolution of both pre- and postzygotic barriers. Contrary to this, I found no evidence that X chromosomes contribute to hybrid female sterility. Moreover, X-linked loci exhibited an unexpected pattern of reduced population differentiation within species, but increased species divergence compared to autosomal loci, which may indicate selective sweeps or sex-biased processes. Taken together, the results suggest that the causes and consequences of X chromosome evolution, in particular among XO taxa, may contradict some of the established theories.

Le processus de sélection intersexuelle peut impliquer plusieurs mécanismes différents dans le choix du partenaire. Chez la pyrale Achroia grisella, les femelles choisissent les mâles en se basant sur des caractères de leur chant d'avertissement ultrasonique, et de précédentes études ont montré que ce choix peut procurer, à une femelle discriminante, certains bénéfices génétiques indirects. Dans cette thèse, j'ai continué à explorer le mécanisme de bénéfices indirects chez cette espèce en 1) déterminant avec plus de précision un paramètre acoustique, l‟amplitude du chant, qui influence le choix des femelles et en 2) examinant la covariance génétique entre les traits du chant mâle et ceux de la préférence femelle. J'ai constaté qu'en plus de préférer des chants mâles émis avec une plus grande amplitude et une plus grande puissance acoustique, les femelles font également une discrimination en faveur des chants comprenant des forts « pics d'amplitude ». Cependant, mes analyses génétiques moléculaires de la relation entre les traits du signal mâle et ceux de la préférence femelle, n'ont révélé aucune covariance significative, comme prédit par la théorie de la sélection sexuelle. Ces derniers résultats fournissent un aperçu important concernant l‟existence d‟un tempo réduit de la sélection sexuelle, dans les populations naturelles. / The process of inter-sexual selection may involve several different mechanisms of mate choice. In the pyralid moth Achroia grisella, females choose males based on characters of their ultrasonic advertisement song, and previous work has indicated that such choice may afford a discriminating female certain indirect genetic benefits. In this thesis I continued to probe the indirect benefits mechanism in this species by 1) determining with more precision one acoustic character, song amplitude, that influences female choice and by 2) examining the genetic covariance between the male song trait and the female preference trait. I found that in addition to preferring male songs delivered at greater amplitude and with greater acoustic power, females also discriminate in favor of songs including higher 'amplitude peaks'. However, my molecular genetic analyses of the relationships between the male signal and female preference traits did not reveal any significant covariance, as predicted by sexual selection theory. These latter findings provide important insight on the reduced tempo of sexual selection that may exist in natural populations.

Chez les insectes où les males chantent en chorus, l’interférence locale de signaux impose des contraintes majeures à des femelles qui doivent évaluer les mâles individuellement. Les mâles subis des difficultés pour évaluer la compétitivité de leurs voisins et pour montrer clairement aux femelles les caractéristiques de leurs propres chants. J’ai analysé différents aspects de cette problématique chez deux espèces acoustiques : chez la sauterelle ephippiger et une pyrale nocturne qui émettent leurs signaux au sein de regroupements. Nos expériences ont mis en évidence certains mécanismes comportementaux permettant aux femelles de localiser les meuliers males et d’autres permettant aux mâles de se communiquer efficacement et percevoir leur environnement acoustique. / In acoustic insects where males sing in choruses, local signal interference may present major difficulties for females evaluating and individual males. Males too may be prevented from assessing the competitivity of their neighbors as well as from advertising the characteristics of their own signals to females in a clear manner. Moreover, the background noise from local signals may prevent both sexes from perceiving other sounds in the environment, e.g. predator cues. I studied these problems at several levels in two acoustic insect species: in which males broadcast their advertisement songs while remaining in dense clusters. The experiments revealed behavioral mechanisms with which females can identify favored males and others with which males can communicate effectively.

[pt] Diversos fatores são considerados no julgamento da atratividade de possíveis parceiros amorosos. Esses fatores abrangem características físicas, traços psicológicos, status social e demonstração de recursos. Homens que ostentam posse de recursos são considerados mais atraentes por mulheres que preferem relacionamentos de longo prazo. Pesquisas recentes vêm mostrando que o consumo conspícuo pode ter importante papel como critério de atratividade. Por outro lado, o consumo conspícuo parece aumentar a atratividade dos homens perante mulheres interessadas em relações de curto prazo. Desse modo, o primeiro capítulo consiste numa revisão de literatura sobre recursos como sinais de atratividade em relacionamentos de longo prazo. O segundo capítulo consiste numa análise dos resultados de quatro experimentos que tiveram como objetivo investigar a influência do consumo conspícuo como critério de atratividade de mulheres interessadas em relacionamentos de curto prazo. O segundo objetivo desse estudo foi verificar se o consumo conspícuo influenciaria a atratividade de indivíduos não-heterossexuais em relacionamentos de curto prazo. Os resultados não mostraram influência do consumo conspícuo sobre a atratividade, independente da orientação sexual. Surpreendentemente, alguns resultados sugeriram que as mulheres acharam mais atraentes os indivíduos na condição sem consumo conspícuo. Isso pode ter ocorrido devido a um viés amostral. A maioria dos participantes tinha alto grau educacional, o que pode estar associado maior preferência por relacionamentos de longo prazo. O objeto usado como consumo conspícuo (carro popular e carro luxuoso) pode, ainda, não ser de especial interesse dessa amostra com alto grau de escolaridade. / [en] Several factors are essential in judging the attractions of your mating partners. These encompassing physical factors, psychological traits, social status and demonstration of resources/wealth. Men who possess resources are considered more attractive by women who prefer long-term relationships. Recent research showing conspicuous consumption may play an important role as a criterion of attractiveness. On the other hand, conspicuous consumption seems to increase the attractiveness of men to women interested in short-term relationships. Thus, the first chapter consists of a literature review of resources as signs of attractiveness in long-term relationships. The second method is an analysis of the results of four experiments that attempt to corroborate an influence of conspicuous consumption as a criterion of attractiveness of women interested in short-term relationships. Considering the scarcity of studies with non-heterosexual participants, the second objective of this study was to verify if conspicuous consumption would influence the attractiveness of non-heterosexual individuals in short-term relationships. The results did not showed influence of conspicuous consumption on attractiveness, regardless of sexual orientation. Surprisingly, some results suggested that women found individuals more attractive in the condition without conspicuous consumption. This may have occurred due to sample bias. Most participants had a high educational level, which may be associated with higher preference for long-term relationships. The object used as conspicuous consumption (popular car and luxury car) may still not be of special interest to the sample with a high degree of schooling.