Gymnotus, the banded electric knifefish, is a diverse genus with a range that extends from Argentina to southern Mexico and includes species distributed both east (cis-Andean) and west (trans-Andean) of the Andes. Each Gymnotus species exhibits a distinctive electric organ discharge (EOD), used for communication and navigation. Here, I present a new molecular phylogenetic hypothesis for 35 Gymnotus species based on two mitochondrial (cyt b and 16S) and two nuclear genes (RAG2 and Zic1). I found that the trans-Andean species are distributed in four distinct lineages with varying amounts of divergence from their closest cis-Andean sister taxa. I suggest that not all trans-Andean species evolved as a result of the orogeny of the Andes. I evaluate EOD phase number evolution in Gymnotus and find a trend for reduced phase numbers in both cis- and trans-Andean regions. Finally, I suggest hypotheses to account for the patterns of EOD phase number diversification.

Gymnotus, the banded electric knifefish, is a diverse genus with a range that extends from Argentina to southern Mexico and includes species distributed both east (cis-Andean) and west (trans-Andean) of the Andes. Each Gymnotus species exhibits a distinctive electric organ discharge (EOD), used for communication and navigation. Here, I present a new molecular phylogenetic hypothesis for 35 Gymnotus species based on two mitochondrial (cyt b and 16S) and two nuclear genes (RAG2 and Zic1). I found that the trans-Andean species are distributed in four distinct lineages with varying amounts of divergence from their closest cis-Andean sister taxa. I suggest that not all trans-Andean species evolved as a result of the orogeny of the Andes. I evaluate EOD phase number evolution in Gymnotus and find a trend for reduced phase numbers in both cis- and trans-Andean regions. Finally, I suggest hypotheses to account for the patterns of EOD phase number diversification.

La communication est essentielle à de nombreuses fonctions vitales en permettant le transfert d’information entre les individus via des signaux. Alors que les fonctions de ces signaux ainsi que les contraintes à leur propagation ont été intensivement étudiées, leur évolution a majoritairement été envisagée à travers le prisme de la dyade constituée par l’émetteur du signal et le récepteur du signal. Pourtant les signaux sont toujours émis au sein de communautés sensorielles et de nombreuses interactions interspécifiques conditionnent les pressions de sélections qui les affectent. Dans cette thèse je me suis intéressé aux liens entre différentes composantes de la composition des communautés et l'évolution du chant et de la couleur chez les oiseaux. Tirant partie des conditions particulières retrouvées dans les îles océaniques, j'ai étudié comment les changements de richesse spécifique, densité de conspécifique et présence de prédateur étaient susceptibles de modifier les comportements de communication et les caractéristiques des signaux émis. Cette approche écologique de l'évolution des signaux est nécessaire pour comprendre leur évolution au sein de communautés sensorielles. Elle m’a permis de mettre en évidence le rôle potentiellement majeur des interférences acoustiques sur la niche sensorielle des espèces ainsi que celui de la prédation sur les changements de coloration en milieu insulaire. Dans le dernier chapitre de cette thèse, je me suis intéressé à un phénomène complémentaire en étudiant les liens entre l’extravagance des signaux et la dynamique des populations au sein des communautés aviaires. Cette thèse produit des éléments forts pour affirmer que la composition des communautés détermine une part des pressions évolutives conditionnant la communication mais qu’à l'inverse, les liens entre caractéristiques des signaux et la composition des communautés sont complexes et difficile à déterminer. / Communication efficiency is related with many essential functions determining the fitness of individuals. Mating signals leads to reproductive isolation, and hence to speciation and a huge amount of studies focused on their evolution. However signals are shaped by environmental properties including the composition of signalling community but this have been understudied. Here, I examined the link between different components of communities’ composition and the evolution of two mating signals: song and coloration in birds. Taking advantage of the particular conditions found in oceanic islands, I studied how species richness, conspecific density, and predator presence were likely to alter communication behaviors and the peculiarities of the transmitted signal. In doing so, I adopted an ecological approach of communication study which I believed to be necessary to understand the evolution of signal within sensory spaces. In the last chapter of this thesis, I focused on a complementary phenomenon by studying how such signals can be deleterious for species decreasing the life expectancy of populations. Overall, this thesis produces additional evidence that the composition of communities partly determines evolutionary pressures conditioning the communication and that conversely, signal characteristic can affect the composition of the communities by determining the viability of certain populations.

In aposematism a prey species use bright colours, often combined with a black contrasting pattern, to signal unprofitability as prey to potential predators. Although there are several different hypotheses about the presence of these internally contrasting patterns, there is little experimental evidence of any beneficial effects. In this thesis I have used bird predators and artificial prey signals to investigate if the contrasting internal patterns in warning displays may have evolved to increase signal efficacy, especially regarding the speed of avoidance learning. In paper I the relative importance of colour and pattern in avoidance learning was studied. The conclusion was that birds primarily attend to colour, not pattern, when learning the discrimination, which was further supported by the results in paper II-IV, all suggesting a secondary role of patterns. In paper II I show that predators may to some degree use patterns for discrimination, if they convey important information about prey quality. The predators showed a hierarchical way of learning warning colour components, where colour is learned to a higher degree than pattern. In paper III I investigate if internal contrasting patterns promote avoidance learning by increasing conspicuousness as prey-to-background contrast does. The study did not support this idea, as the presence of internal black patterns did not improve avoidance learning on a colour matching background. In paper IV, however, I show that the presence of many internal colour boundaries resulted in faster avoidance learning on a multi-coloured background, and predator generalization favoured more internal boundaries, while there was no effect of pattern regularity. From these studies I conclude that internal pattern contrasts may function to increase the efficacy of the warning colour, its salience, and as a means for aposematic prey to be discriminated from harmful mimics. However, the major finding is the importance of colour over pattern. / <strong><em></em></strong><em></em><em></em>At  the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 2: Manuscript; Paper 4: Manuscript<strong><em> </em></strong>

No description available.

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.

Flamboyant colors are widespread throughout the animal kingdom. While many of these traits arise through sexual selection, bright coloration can also evolve through natural selection. Many aposematic species, for example, use conspicuous warning coloration to communicate their noxiousness to predators. Recent research suggests these signals can also function in the context of mate choice. Studies of warning color evolution can therefore provide new insights into how the interplay of natural and sexual selection impact the trajectory of conspicuous signal evolution. For my dissertation, I investigated the potential for male-male competition to impact the warning color evolution of a species of poison frog. I focused my work on an exceptionally bright and toxic population of the strawberry poison frog (Oophaga pumilio) where males are brighter than females, a classic signature of sexual selection. In Chapter 1, I used theoretical models of predator and frog visual systems to determine which can see the variation in bright warning coloration within this population. I found that birds, the presumed major predator, likely cannot see this variation, indicating that sexual selection can work under the radar of predators in this species. In Chapter 2, I tested the aggressive responses of males using a two-way choice paradigm that manipulated the perceived brightness of stimulus males. I found that males directed more of their behaviors to bright stimulus frogs, and brighter focal frogs more readily approached stimuli and directed more of their attention to the brighter rival. In Chapter 3, I tested the outcomes of dyadic interactions between males of varying brightness and observed male reactions to simulated intruders in their territories. I found that brighter males initiated aggressive interactions with rivals more readily, and brightness asymmetries between males settled interactions in a way that is consistent with classic hypotheses about male sexual signals. In Chapter 4 I sought to describe physiological correlates of male warning color brightness. While male brightness did not co-vary with classic measures of body condition (circulating testosterone and skin carotenoids), it did correlate with toxins sequestered from the diet and thus appears to be a reliable signal of toxicity in this population. / text

Aposematic species have evolved conspicuous warning signals, such as bright colors and striking patterns, to deter predators. Some edible and harmless species take advantage of this deterrent effect by mimicking their appearance. Mimicry is a great example of how natural selection produces remarkable adaptations. However, while some species evolve a very close similarity to their models to effectively avoid attacks, others are successful in doing so despite an incomplete similarity, i.e. imperfect mimicry. In some cases, it is surprising how such a crude disguise can fool predators. Why and how imperfect mimicry can persist has been much discussed and considered as a problem for the theory of natural selection. It is therefore of great interest to understand what makes it possible. Predator psychology is an important factor in the evolution of aposematism and mimicry. In the past decades it has been suggested that certain components of prey appearance are more important to predators than others during prey assessment. We developed this idea by incorporating concepts from associative learning, and presented a new approach to explain imperfect mimicry. Our general hypothesis is that prey traits have different salience to predators. Certain traits are perceived as highly salient and are thus used primarily in the discrimination and generalization of prey, while traits with low salience are overshadowed and not used in the assessment. The salience of a trait can depend on how conspicuous or discriminable it is in the particular context, and can vary due to for example previous predator experience. We tested our ideas with wild blue tits and domestic chickens as predators, and artificial and semi-natural prey stimuli. In paper I we found that the trait that was perceived as most salient (color) was the one used to discriminate and generalize between prey. Mimics of that specific trait were highly avoided, despite differences in the other traits. We also found that salience is relative and context dependent (paper II). In a context where two traits were perceived as similarly salient, mimicry of a single trait offered intermediate protection, while mimicry of both offered high protection. In another context, the traits were perceived differently salient, and mimicry of one trait was enough for high protection. In paper III we tested a proposed scenario for the initiation of mimicry evolution in the edible butterfly mimic Papilio polyxenes asterius to its noxious model Battus philenor. The results showed that a partial similarity with the model in the salient black wing color offered intermediate protection from attacks, despite a general dissimilarity. This thesis investigates the major questions of imperfect mimicry: the initial step of mimicry evolution, the persistence of imperfect mimicry, and variation in mimic-model similarity. We conclude that mimicry evolution can begin in a non-mimetic species that acquires similarity to a model species in a high-salience trait. When multiple traits have similar salience, multi-trait mimicry is needed for higher protection. Mimicry can remain imperfect if the differences are in traits with low salience, and therefore under low or no selection pressure to change. To complete the picture, we showed that predators can have a biased generalization toward a more pronounced version of a salient trait (paper IV). The evolution of aposematism could therefore be explained by gradual enhancement of salient traits. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Accepted. Paper 4: Manuscript.</p>