Στόχος της παρούσας εργασίας αποτελεί η διερεύνηση της προσυζευκτικής συμπεριφορικής απομόνωσης στο ερμαφρόδιτο χερσαίο σαλιγκάρι Albinaria caerulea (Pulmonata, Clausiliidae), η πολυπλοκότητα της οποίας, μπορεί να αντανακλά δράση εξελικτικών μηχανισμών επιλογής συντρόφου και κατ' επέκταση ειδογενετικών διεργασιών. Η ποικιλότητα κελυφικής ποίκιλσης είναι έντονη στο είδος αυτό (δύο μορφές, λεία και γραμμωτή, που συνιστούν δυο υποείδη), αλλά δε φαίνεται να συσχετίζεται με αντίστοιχη οικολογική και γενετική διαφοροποίηση. Η συλλογή των ατόμων πραγματοποιήθηκε στη Φολέγανδρο, όπου παρατηρούνται αλλοπάτριοι πληθυσμοί αλλά και ζώνες επαφής μεταξύ των λείων και των γραμμωτών μορφών. Στο εργαστήριο πραγματοποιήθηκαν πειράματα αναπαραγωγικής συμπεριφοράς, όπου καταγράφονταν ο αριθμός κι ο τύπος (ετεροτυπικά-ομοτυπικά) των σχηματιζόμενων ζευγών, καθώς και οι αντίστοιχες ερωτοτροπικές προσπάθειες (φλερτ). Βάσει των συχνοτήτων των σχηματιζόμενων ζευγών υπολογίστηκε ο βαθμός προσυζευκτικής συμπεριφορικής απομόνωσης με τον αμερόληπτο δείκτη ΙPSI. Καταγράφηκαν επίσης και άλλες συμπεριφορικές παράμετροι (αριθμός και τύπος φλερτ, χρόνος ως το πρώτο ενεργητικό φλερτ, χρόνος από την αφύπνιση ως την έναρξη της σύζευξης, διάρκεια σύζευξης), με σκοπό την ανίχνευση λοιπών προσυζευκτικών συμπεριφορικών διαφορών μεταξύ των δυο μορφών. Τέλος, ελέγχθηκε αν τυχόν μορφομετρικές διαφορές (σχήμα/μέγεθος κελύφους) μεταξύ των δύο μορφών, χρησιμοποιούνται στις στρατηγικές επιλογής συντρόφου. Ο βαθμός προσυζευκτικής συμπεριφορικής απομόνωσης βρέθηκε μικρός, καθώς τα άτομα, ως επί το πλείστον, επέλεγαν ετεροτυπικό σύντροφο. Επίσης βρέθηκε μεγαλύτερη προσυζευκτική και συζευκτική δραστηριότητα στις ζώνες επαφής, κάτι που απορρίπτει την υπόθεση περί μηχανισμού ενίσχυσης, .καθώς εάν υπήρχε απομόνωση θα ανιχνεύονταν πρώτα σε αυτές. Όσον αφορά τις μορφομετρικές διαφορές, παρά το ότι τα άτομα διακρίνονται βάσει σχήματος και μεγέθους κελύφους, δεν φαίνεται να χρησιμοποιούν τις διαφορές αυτές στους μηχανισμούς επιλογής συντρόφου. Εντούτοις, οι διαφορές στο μέγεθος κελύφους των δυο μορφών εξομαλύνονται στις ζώνες επαφής, και επομένως δεν υπάρχει απόκλιση χαρακτήρα. Έτσι λοιπόν, ενώ δεν φαίνεται να υπάρχουν ισχυρά προσυζευκτικά φράγματα στο είδος αυτό, περισσότερο φως στις αντίστοιχες εξελικτικές διεργασίες, θα ρίξει η μελέτη μετασυζευκτικών μηχανισμών απομόνωσης, αλλά και παραμέτρων της οικολογίας και της πληθυσμιακής γενετικής τους. / The aim of this study was the investigation of premating behavioural isolation in the hermaphrodite land snail Albinaria caerulea (Pulmonata, Clausiliidae). The snails of this genus exhibit a really complicated premating behaviour, a fact that may reflect evolutionary mechanisms of mate choice, or even speciation forces acting. Shell differentiation is intense, with two patterns (smooth and ribbed) constituting two subspecies, which don’t seem to differ ecologically or genetically. The animals were collected from the island of Folegandros, where they can form contact zones –between animals with smooth and ribbed shell- or the two forms can be isolated. Mate choice experiments were conducted, with variable number of possible mates and the premating behaviour was reported (mating attempts, successful copulations, copulation duration, mating activity), between populations exhibiting the same or different ribbing pattern. To reveal other behavioural differences between the two morphs, we also reported the number and type of courtships, the time from the awakening till the beginning of copulation, the time untill the first active courtship and the duration of copulation. Finally, we examined if possible morphometric differences (shell shape and size) between the two morphs, can be used in the mate choice strategies. The unbiased isolation index IPSI, which based on mate frequencies, suggested that there aren’t strong premating barriers. The intense observed activity (copulations and courtships) in the contact zones agrees with the above results and consequently does not support the initial hypothesis of reinforcement of behavioural barriers in these sites. As far as it concerns the morphometric differences, despite the fact that the morphs are being distinguished, they don’t seem to use them as criterion in the mate choice. Nevertheless, such differences in size, seem to be eliminated in the contact zones, suggesting that there is no character displacement. In conclusion, further investigation of the reproduction of the genus in the basis of postmating isolation mechanisms, the ecology and population genetics of the genus, will reveal the possible action of evolutionary forces.

<p>Sexual selection has long been accepted as a widespread force of evolution shaping male traits across taxa. In recent years, biologists have begun to investigate the extent to which sexual selection may also shape traits among females. However, current models of sexual selection have largely been developed using assumptions that--while generally met in males--often do not apply to females. Thus, attempts to apply these contemporary models to the study of sexual selection in females reveal weaknesses in the theoretical framework for sexual selection research. One consequence of this for empirical research is that researchers often infer the action of sexual selection upon evidence of male mate choice. Although male mate choice is increasingly common, it is much less likely to exert selection pressure than its female counterpart. I begin by proposing a conceptual framework that explicitly accounts for ...Next, I investigate a female trait that has recently become an iconic example of sexual selection in females; that is the exaggerated estrous swellings of cercopithecine primates. By combining morphological data collected with a non-invasive photographic method and observational behavioral data with longitudinal ecological and demographic data from the ongoing Amboseli Baboon Research Project, I examine the sources of variance in this exaggerated signal of fertility. Finally, I test the hypothesis that male baboons prefer females with larger sexual swellings because those females have higher fitness. I find no evidence to support this hypothesis. Instead, my results suggest that mate choice among male baboons has evolved to detect, not the intrinsic quality of the female as has typically been proposed, but the quality of a reproductive opportunity.</p> / Dissertation

Sexual selection is usually invoked to explain the evolution of elaborate epigamic characters in animals. However, the mechanism by which female choice operates is poorly understood, and it is not clear whether female choice is purely aesthetic or related to male genotypic quality. It has been suggested that Moller's fluctuating asymmetry (FA) hypothesis may resolve the 'arbitrary trait'-'good gene' debate. However, tests of this controversial hypothesis have yielded equivocal results. I examined the allometric patterns of FA in the redcollared widow in order to test the FA hypothesis. In addition, I documented intrapopulation variation in trait size to determine whether females could distinguish between males on the basis of ornament size and/or symmetry. Male tail length was found to be more variable in size than other traits, suggesting that sufficient variation exists in ornament size for females to distinguish between males on this basis. In addition, the prediction of the FA hypothesis that ornaments would display higher degrees of asymmetry than non-ornamental traits was supported. However, no significant linear or second-order polynomial relationship was found between trait size and asymmetry for tail, wing and tarsus length. Furthermore, neither tail length or symmetry was correlated with indices of body condition. Although this might suggest that the FA hypothesis is invalid, I argue that the assumptions of the hypothesis are too simplistic for it to hold true for all species without taking the basic biology of the species into account. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.

Evolution is not always straight-forward, as selection pressures may differ between different generations of the same species. This thesis focuses on the evolution of life history of the model species, the Green-veined White butterfly Pieris napi. In central Sweden P. napi has two generations per year. The directly developing summer generation is short-lived and time stressed, compared to the diapausing generation. In paper I polyandry, defined as female mating rate, was shown to differ between generations but was unaffected by environmental factors. In paper II both males and females of the direct developing generation were shown to eclose more immature than the diapausing generation, indicating larval time constraints. Consistent with this, diapausing males mated sooner than direct developers. Directly developing females, however, mated sooner after eclosion than diapausing females, even though they are more immature. This was shown to negatively affect fecundity, but can pay off when the season is short. Paper III shows that directly developing males have less sex pheromones at eclosion than diapausers, and the differences in sex pheromone production is consistent with developmental time constraints and the differences in mating system. In P. napi and other polyandrous butterflies, males transfer a large, nutritious ejaculate at mating. Large ejaculates confer advantages under sperm competition, but as they are costly, males should adjust ejaculate size to the risk of sperm competition. In paper IV we found that males transfer on average 20% larger spermatophores under high male competition than at low competition. The same effect could be observed if we added male sex pheromone to the air in a mating cage without male-male competition. Paper V shows that males of the two generations respond differently to an increase in male-male competition, with diapausing males transferring larger spermatophores than direct developers at high male competition risk. / <p>At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 5: Submitted manuscript.</p>

Mate choice among males is relatively understudied, despite recent evidence supporting its ubiquity. Theory predicts male mate choice in response to variation in female quality, and male mating strategies that limit polygyny. However empirical research investigating these connections, particularly under natural conditions, is generally lacking. Using the Western black widow spider, Latrodectus hesperus, I investigated male mate choice, male investment, and the advantage of mating with females that differ in their potential to deliver fitness benefits to males via higher fecundity and/or reduced risk of sperm competition. Males were found to be preferentially attracted to larger, high-diet virgin females over females that were smaller due to a lower diet, or having been previously mated, or both. Through a three-year field study on females I found that males likely benefit from selectivity, as smaller, low-diet females often failed to deposit any egg sacs throughout the breeding season, likely due to their shortened web-site tenure and/or lack of bodily resources. I investigated the costs and benefits to male genital breakage in L. hesperus, a strategy typically assumed to result in male sterility while providing paternity protection. I found that genital mutilation in L. hesperus did not cause sterility and that males were capable of inseminating multiple females, likely because of the comparatively low amount of genital damage and the likelihood of the efficient placement of genital fragments. Evidence from double mating trials supported the efficacy of broken genital fragments as plugs, but first male sperm precedence was often maintained in cases where male genital breakage failed or fragments were positioned incorrectly, which occurred frequently. Together, these laboratory and field experiments contribute to a more complete view of mate choice.

While there has long been interest in the form of sexual selection in males, studies characterizing this selection in females remain sparse. Sexual selection on females is predicted for sex-role reversed Mormon crickets, where males are choosy of mates and nutrient-deprived females compete for matings to gain nutritious nuptial gifts. I used selection analyses to describe the strength and form of sexual selection on female morphology. There was no positive sexual selection on the female body size traits predicted to be associated with male preferences and female competition. Instead, I detected selection for decreasing head width and mandible length. Additionally, I tested the validity of a commonly-used instantaneous measure of mating success (mated vs. unmated) by comparing selection results with those determined using a more detailed fitness measure (cumulative mating rate). The two fitness measures yielded similar patterns of selection, supporting the common sampling method comparing mated and unmated fractions.

Mate choice among males is relatively understudied, despite recent evidence supporting its ubiquity. Theory predicts male mate choice in response to variation in female quality, and male mating strategies that limit polygyny. However empirical research investigating these connections, particularly under natural conditions, is generally lacking. Using the Western black widow spider, Latrodectus hesperus, I investigated male mate choice, male investment, and the advantage of mating with females that differ in their potential to deliver fitness benefits to males via higher fecundity and/or reduced risk of sperm competition. Males were found to be preferentially attracted to larger, high-diet virgin females over females that were smaller due to a lower diet, or having been previously mated, or both. Through a three-year field study on females I found that males likely benefit from selectivity, as smaller, low-diet females often failed to deposit any egg sacs throughout the breeding season, likely due to their shortened web-site tenure and/or lack of bodily resources. I investigated the costs and benefits to male genital breakage in L. hesperus, a strategy typically assumed to result in male sterility while providing paternity protection. I found that genital mutilation in L. hesperus did not cause sterility and that males were capable of inseminating multiple females, likely because of the comparatively low amount of genital damage and the likelihood of the efficient placement of genital fragments. Evidence from double mating trials supported the efficacy of broken genital fragments as plugs, but first male sperm precedence was often maintained in cases where male genital breakage failed or fragments were positioned incorrectly, which occurred frequently. Together, these laboratory and field experiments contribute to a more complete view of mate choice.

While there has long been interest in the form of sexual selection in males, studies characterizing this selection in females remain sparse. Sexual selection on females is predicted for sex-role reversed Mormon crickets, where males are choosy of mates and nutrient-deprived females compete for matings to gain nutritious nuptial gifts. I used selection analyses to describe the strength and form of sexual selection on female morphology. There was no positive sexual selection on the female body size traits predicted to be associated with male preferences and female competition. Instead, I detected selection for decreasing head width and mandible length. Additionally, I tested the validity of a commonly-used instantaneous measure of mating success (mated vs. unmated) by comparing selection results with those determined using a more detailed fitness measure (cumulative mating rate). The two fitness measures yielded similar patterns of selection, supporting the common sampling method comparing mated and unmated fractions.

Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.

The Fence Lizard (Sceloporus undulatus complex) is a wide ranging North American species complex occurring from the eastern seaboard westward through the great plains and central Rocky Mountains and into the American Southwest. A recent phylogeny suggests four species lineages occur within S. undulatus. Traits within an interbreeding species that are influenced by sexual selection are under different selection pressures and may evolve independently from the selective forces of habitat. Sceloporus lizards have several characters that are influenced by sexual selection. I investigated sexual size dimorphism and allometric relationships of body size (snout vent length), torso length, rear leg length and three measurements of head size in 12 populations from the four species in the S. undulatus complex (N=352) specifically looking for variation among the 4 species. Additionally I investigated the size of signal patches between males and females in three species (N=339 specimens of S. consobrinus, S. cowlesi, S. tristichus) of the S. undulatus complex. Sexual confusion, was recently described in a population of the Sceloporus undulatus complex occurring in White Sands, New Mexico and the behavior is correlated with variation in badge size between male and female lizards. To make inferences about sexual confusion at the species level I investigated the presence and absence of signal patches in female lizards, and compare the sizes of signal patches between males and females. My analyses suggest that torso length and head size are significant sources of sexual size dimorphism but the findings differ from earlier published investigations of sexually dimorphic characters in the species complex. I also find support for the S. undulatus complex being generally a female larger species complex. However two of the 12 populations I investigated displayed male biased sexual size dimorphism. Analysis of signal patches across three species of the S. undulatus complex suggests that sexual dimorphism in signal patch size for S. cowlesi and S. tristichus may not prevent sexual confusion. While the near total absence of signal patches in female S. consobrinus is evidence that sexual confusion is not possible with regards to signal patches.