The advent of sexual reproduction in early evolutionary history had profound effects on the evolution of animals. In most sexually reproducing species, males and females have distinct morphological and behavioral differences that are shaped by the evolutionary imperatives of each sex. Underlying the behavioral differences between males and females are distinct and measurable dimorphisms in the nervous system. These dimorphisms can arise in the form of connectivity, neurotransmitter usage, gene expression or combinations of all three. The androdioecious nematode Caenorhabditis elegans, with its stereotyped development and simple nervous system, offers a remarkably powerful system for studying the conserved mechanisms of sex determination that shape neural development. In this thesis, I present my work on the characterization of several genes that regulate the development of sexual dimorphisms in the nervous system. The first part of the thesis concerns the characterization of the gene ham-3, which codes for a subunit of the C. elegans ortholog of the SWI/SNF chromatin remodeling complex. ham-3 is required for the proper terminal differentiation of the HSN, a serotonergic neuron of the sex-specific nervous system, which it manages by regulating the expression of transcription factors required for crucial steps of migration, axon guidance and serotonergic fate adoption. The second part of the thesis concerns the investigation of sexually dimorphic pruning mechanisms. I show that unc-6/Netrin is subject to direct transcriptional repression in hermaphrodites by tra-1, the master transcriptional regulator of sexual fate determination in C. elegans. This regulation is required for the proper timing of the sexually dimorphic pruning of synapses in the tail region in hermaprhodites. In males, where unc-6 is not repressed by tra-1, unc-6 expression perdures into adulthood and the synapse is maintained. Together, these data provide insight into the ways in which conserved genetic and developmental mechanisms manage the generation differentiation, connectivity, and maintenance of sexually dimorphic nervous systems.

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.

Sexual dimorphism is exhibited throughout various organisms and takes an extensive variety of forms, although rarely does it take the form of eye-reduction within a population. This poses the question of whether this dimorphism arises due to sexual selection in order to increase reproductive success or rather from ecological selection as a result of sex-specific niche partitioning. In this case, we study an organism that displays a drastic form of sexual dimorphism, in that the males have large complex lateral eyes whereas the females lack eyes and merely have rudimentary lateral eye-spots. Euphilomedes carcharodonta is a small crustacean native to the coast of California. Studies on the dimorphism between these individuals have mainly been related to genetics and embryology. However, minimal studies have been performed questioning the evolutionary driving force behind their dimorphism. One study suggests that this driving force is ecological selection, more specifically, predator evasion as a result of the reproductive role hypothesis. In this study, we focus on sexual selection as a driving force and ask whether the eyes play a role in the ability of males to find mates. We blinded and mock-blinded male individuals, placed them in tank settings with females in the absence of predators, and observed their behavior. If sexual selection is involved in the eye development of males, we expected to see changes in male and/or female behavior in response to obstructing the vision of the males. We did not see changes in behavior of the males or the females. This leads us to conclude that the development of complex eyes in male Euphilomedes carcharodonta arises from ecological selection rather than sexual selection. With the previous work on predator evasion, these experiments and findings are the first to experimentally test the reproductive role hypothesis and are the beginning steps for further behavioral studies of these organisms and in discovering more about the unique dimorphism exhibited by Euphilomedes carcharodonta.

Harvesting is a human-imposed selective pressure. Harvest-induced mortality is not random and mostly targets heritable traits. Human harvest may impose an artificial selection pressure on life history traits, often opposite to natural selection. Therefore in harvested populations life history strategies will evolve under natural and human imposed selective pressures, favoring individuals with the highest fitness. In ungulate populations hunting is the most common cause of adult mortality. By increasing adult mortality, hunting may have both ecological and evolutionary consequences affecting phenotypic traits and life history strategies. Typically, in sexually dimorphic species large horn and weapon size is the major determinant of success in male-male competition. Large males gain high dominance rank and enjoy high reproductive success. By removing males with large horn and body size, hunters may favor small individuals, opposite to sexual selection. In long lived mammals longevity is the main determinant in female reproductive success. Typically females reproduce once a year, therefore in the energy allocation trade-off they invest more in body maintenance and survival rather than reproduction to increase lifetime reproductive success. By increasing adult female mortality hunting may reduce age and size at maturation, selecting for a strategy of early maturation and great current maternal investment. In this thesis I studied chamois ecology and evolution by comparing hunted and unhunted populations. I tested for possible differences in life history traits and examined the ecological and evolutionary consequence of hunting. In the chamois populations under study phenotypic traits and reproductive strategies were not strongly affected by hunting. There was no evidence of a strong evolutionary effect of sport hunting on horn length or body mass of adult males or yearlings. Although hunters seek long horned males, hunter selectivity is unlikely to lead to an artificial selective pressure on horn size. I found few differences in body and horn size between hunted and protected populations, suggesting the absence of strong effects of hunting on male phenotype. Although yearling body mass declined over time in both hunted populations, environmental factors explained much of the trends. The combination of low variability in adult horn length, weak correlation between horn length and body mass for adult males and strong compensatory horn growth apparently reduced the potential for hunters to selectively remove young adult males with vigorous growth. Although early development in body and horn growth affected reproductive potential in young and senescent females chamois, I found no evidence that female early development affected hunter selectivity. Sport harvest did not appear to have strong impacts on the evolution of phenotypic traits and reproductive strategies of female chamois, likely because of a low harvest rate and weak selection for long-horned females as hunters appeared more concerned with avoiding lactating females. The biology of chamois seems to prevent impact of selective hunting, at least in the case of weak hunting pressure.

The purpose of this study was to determine how two morphs of the acorn barnacle, Chthamalus anisopoma, coexist on rocky intertidal shores in the northern Gulf of California. The test of one of these forms (here called "typical") has the conical, volcano shape which is characteristic of acorn barnacles while the test of the atypical form (here called "bent") grows bent-over so that the plane of the aperture's rim is perpendicular to the substrate. I tested the hypotheses that bents are more resistant than typicals to: (1) desiccation during low tides and (2) attack by a carnivorous snail (Acanthina angelica) involving the use of a labial spine. These two hypotheses (which were suggested from analysis of the distribution patterns of the two morphs) were tested in conjunction with experiments designed to determine whether the bent form is genetically controlled or environmentally induced. The results indicated that the bent-over morph is a developmental response to the presence of A. angelica and that it is more resistant than the typical form to specialized predation by this gastropod. I also tested the hypotheses that: (1) bents are inferior competitors for primary rock space, and (2) the bent-over morphology places constraints on growth and reproduction. I found no evidence to suggest that bents are inferior competitors for space. They were, however, found to grow more slowly than typicals and to brood fewer eggs per unit body size. In summary, the bent-over form of C. anisopoma is a conditional response to the presence of a predator and both the conditional strategy and the dimorphism appear to be maintained by a trade-off between resistance to predation and the ability to convert resources into offspring.

The brown macroalgae Fucus radicans is endemic to the Baltic Sea, but little is known about this newly described species. This thesis investigates the ecology and role of F. radicans within the species poor Baltic Sea ecosystem. The thallus of F. radicans had a more complex structure but was smaller than F. vesiculosus, the other important foundation species with which it grows in sympatry at several sites. The variability of the associated flora and fauna communities of these two Fucus species, however, was explained by the thallus size, not the complexity. Comparisons between the populations of F. radicans in the Bothnian Sea with those in Väinameri Sea on the Estonian coast, showed that the Estonian thalli were smaller, less complex and lacking the numerous adventitious branches which occur extensively in the Bothnian Sea populations. The distribution of F. radicans in Sweden is limited to the Bothnian Sea coast. The low salinity at the northern limit prevented successful fertilization, while increased salinity did not restrict F. radicans but improved its reproductive success. The southern distribution limit was instead shown to be negatively impacted by a combination of grazing and competition. The asexual reproduction through settling of detached fragments was favoured by high light levels and high temperature in laboratory conditions. Re-attachment occurred by basally formed rhizoids but settling also occurred through a calcium-rich substance, seemingly secreted by the fragment. Genetic spatial distribution of F. radicans showed a dominance of a few widespread clones both within and between sites with an intermingled rather than clustered pattern. The extensive female clone, common in most sites, is most likely old and several clonal lineages have derived from her.  Although more clearly expressed in the clonal populations, the macroscopic sexual dimorphism discovered appears to be a species specific trait in F. radicans. This thesis presents further insight in F. radicans role within the Baltic Sea ecosystem and its value as a study species for adaptation, clonality and speciation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p>

Opuntioideae constitui uma das três subfamílias tradicionalmente reconhecidas em Cactaceae, apresentando cerca de 220-350 espécies com hábitos arborescente, arbustivos ou cespitosos, e distribuição no Canadá, América do Norte, Caribe, América Central e do Sul. A subfamília é reconhecida com mais derivadas que não suculentas e folhosas Pereskioideae e menos derivadas que as Cactoideae. No presente estudo são abordados aspectos anatômicos da região areolar, sistema fundamental e de revestimento, bem como dos padrões vasculares, através do desenvolvimento dessas estruturas no segmento caulinar de quatro espécies de Opuntioideae. Os resultados deste estudo, incorporados à literatura disponível serão essenciais para esclarecer importantes paradigmas dos estudos em Cactaceae, como a evolução do lenho e a função das traqueídes vasculares nos diferentes tipos de polimorfismo do lenho e a origem foliar dos espinhos nas aréolas. / Opuntioideae constitui uma das três subfamílias tradicionalmente reconhecidas em Cactaceae, apresentando cerca de 220-350 espécies com hábitos arborescente, arbustivos ou cespitosos, e distribuição no Canadá, América do Norte, Caribe, América Central e do Sul. A subfamília é reconhecida com mais derivadas que não suculentas e folhosas Pereskioideae e menos derivadas que as Cactoideae. No presente estudo são abordados aspectos anatômicos da região areolar, sistema fundamental e de revestimento, bem como dos padrões vasculares, através do desenvolvimento dessas estruturas no segmento caulinar de quatro espécies de Opuntioideae. Os resultados deste estudo, incorporados à literatura disponível serão essenciais para esclarecer importantes paradigmas dos estudos em Cactaceae, como a evolução do lenho e a função das traqueídes vasculares nos diferentes tipos de polimorfismo do lenho e a origem foliar dos espinhos nas aréolas. Palavras chave: Cactaceae, Opuntioideae, anatomia, aréolas, dimorfismo. ABSTRACT Opuntioideae constitutes one of the three recognized subfamilies traditionally in Cactaceae, with 220-350 species with habits arborescent, shrub or caespitose and distribution in Canada, North America, Caribbean, Central and South America. The subfamily is viewed as more derived than the leafy, nonsucculent Pereskioideae and less derived than Cactoideae. In the present research are showed anatomical characters on the areoles, skin and growth system and vascular patterns, through the development of these structures on the stem segments of four Opuntioideae species. The results this study, incorporated to available literature will be essential for important paradigms of the studies in Cactaceae, as the wood evolution and function of the vascular tracheids in the different types of polymorphism of the wood and foliar origin of the spines in the areoles.

Interconnected freshwater habitats are essential for many fish populations, which allow fish to migrate between areas to fulfil their life-cycle and maximize their fitness. Currently, such populations are negatively affected by human habitat exploitation. As a result, the biodiversity in freshwater ecosystems is decreasing. In this study, I use data from surveys of two Asp (Leuciscus aspius) populations in Uppland to see how a representation of day length, water temperature and water current influence their spawning migrations. I also determine the difference in timing of migration between males and females, and if the individual body size matters. I found that day length, water temperature and water current affect the migratory behavior of Asp. I also found a significant difference in migratory timing between males and females, where males on average arrive 5-6 days earlier than females to spawning areas.

Capítulo 1: Dimorfismo sexual em aberturas glandulares das pernas de três subfamílias de Gonyleptidae (Arachnida: Opiliones: Laniatores) Glândulas sexualmente dimórficas podem não apenas ser informativas taxonomicamente como podem ainda trazer informações importantes sobre a comunicação entre os sexos. Nesse trabalho estudamos a evolução de aberturas glandulares sexualmente dimórficas nas pernas I (basitarso) e pernas IV (presença/ausência de intumescimento e quantidade de poros no metatarso) em uma linhagem monofilética pertencente ao clado K92 composta pelas subfamílias Progonyleptoidellinae, Sodreaninae e parte de Gonyleptinae. Utilizamos Microscopia Eletrônica de Varredura para descrever as aberturas glandulares e compará-las entre exemplares das três subfamílias analisadas. Encontramos aberturas glandulares sexualmente dimórficas na perna I de uma espécie em Progonyleptoidellinae (de seis analisadas), de uma espécie de Gonyleptinae (de quatro analisadas) e em três espécies de Sodreaninae (de seis analisadas). Com relação às aberturas da perna IV, todos os machos estudados possuem maiores quantidades de poros na perna IV do que as fêmeas exceto uma espécie de Gonyleptinae e uma de Sodreaninae. Os machos de todas as espécies estudadas possuem o astrágalo das pernas IV intumescidos, exceto uma espécie em Progonyleptoidellinae. Portanto as aberturas glandulares sexualmente dimórficas na perna I nos machos mostram-se variáveis na linhagem interna ao clado K92 estudada nesse trabalho. Por outro lado, o intumescimento e quantidade de poros na perna IV dos machos parecem ser conservados na linhagem estudada. Capítulo 2: Morfologia interna das glândulas sexualmente dimórficas de Progonyleptoidellus striatus Roewer 1913 (Opiliones: Laniatores: Gonyleptidae) Apesar de diversos trabalhos sugerirem a presença de glândulas sexualmente dimórficas nas quatro subordens de Opiliones, há poucos trabalhos que investigam essas glândulas histologicamente. Morfologia interna fornece importantes informações sobre o funcionamento e composição das secreções. Para isso, utilizamos técnicas histológicas e ultraestruturais para estudar a morfologia interna de duas glândulas de Progonyleptoidellus striatus (Progonyleptoidellinae): uma no basitarso das pernas I e a outra no metatarso das pernas IV. Adicionalmente, investigamos a composição histológica e ultraestrutural da área glandular no metatarso IV. Encontramos diferenças entre os sexos, tanto na morfologia interna como externa: machos possuem intumescimentos das áreas glandulares e internamente possuem células glandulares ausentes nas fêmeas. Encontramos abundantes retículos endoplasmáticos rugosos, lisos e mitocôndrias, além de Complexo de Golgi bem desenvolvido na perna I dos machos. Diferentemente da perna I, não encontramos retículos endoplasmáticos lisos na perna IV, o que pode implicar em composições de produtos secretórios diferentes para as pernas. Nas duas pernas encontramos abundância de vesículas secretoras / Sexually dimorphic glands may not only be taxonomically informative but can also bring important information about communication between the sexes. In this work we studied the evolution of sexually dimorphic glandular openings on legs I (basitarsus) and legs IV (presence/absence of swollen area and quantity of pores on metatarsus) in a monophyletic lineage belonging to clade K92 that include the subfamilies Progonyleptoidellinae, Sodreaninae and part of Gonyleptinae. We used Scanning Electron Microscopy to describe the glandular openings and compare them among specimens of the three subfamilies analyzed. We found sexually dimorphic glandular openings on legs I of one species in Progonyleptoidellinae (out of six analyzed), one specie of Gonyleptinae (out of four analyzed) and three species of Sodreaninae (out of six analyzed). Concerning glandular openings on legs IV, all males studied have more pores than females except for one species in Gonyleptinae and another in Sodreaninae. Males of all species studied have a swollen astragalus IV, except for one species in Progonyleptoidellinae. Therefore, the glandular openings in leg I in males are shown to be variable for the internal lineage to the Clade K92 studied in this work. On the other hand, the swollen area and the greater quantity of pores on legs IV of males seem to be conserved in the lineage studied. Although several studies suggest the presence of sexually dimorphic glands in the four suborders of Opiliones, there are few studies that investigate these glands histologically. Internal morphology provides important information about the functioning of the glands and the composition of secretions. Here we used histological and ultrastructural techniques to study the internal morphology of two glands of Progonyleptoidellus striatus (Progonyleptoidellinae): one in the basitarsus of legs I and another in the metatarsus of legs IV. We found differences between the sexes, both in internal and external morphology, in which males have swollen of the glandular areas and internally the males have glandular cells, absent in females. We found abundant rough, smooth endoplasmic reticulum and mitochondria, as well as Golgi Complex well developed in legs I of males. In contrast, we did not find smooth endoplasmic reticulum in legs IV, which may result in different compositions of glandular products in each leg. In both legs we found abundance great number of secretory vesicles

O órgão vomeronasal de 10 machos e 10 fêmeas de ratos Wistar adultos, com 120 dias de idade, com pesos entre 210 e 318 gramas, foram utilizados para o presente estudo com objetivo de determinar a estrutura histológica e as dimensões deste órgão para verificar a existência de dimorfismo sexual. Após perfusão, os órgãos foram imersos em solução de glutaraldeído 2,5% em tampão fosfato para fixação, isolado juntamente com o septo nasal, imerso em solução de Perenyi para descalcificação e, em seguida cortados segundo técnicas clássicas de estudos morfométricos e estereológicos. As secções foram colocadas sobre lâminas, coradas com azul de toluidina e analisadas em microscopia de luz. Também foi feita diafanização do órgão com posterior coloração com hematoxilina ácida. Foram descritas e quantificadas a constituição e distribuição dos tecidos que compõem o órgão vomeronasal de ratos machos e fêmeas, maduros sexualmente, e estabelecidas a área total de vasos, o volume do órgão, a proporção de volume ocupada pelos vasos no volume total do órgão, área total do lúmen, do epitélio sensorial e não sensorial em ratos que já atingiram a maturidade. Apesar de não existir diferenças significativas no volume do órgão vomeronasal entre machos e fêmeas de ratos Wistar adultos, os componentes deste complexo órgão, apresentam notáveis diferenças. / The vomeronasal organ of 10 male and 10 female Wistar rats, adults, 120 days weighting between 210 and 318g, were used for this study to determine the histological structure and to verify the existence of sexual dimorphism. After perfusion, the organs were fixed by immersion in 2,5 glutaraldehyde in phosphate-buffered solution; isolated with the nasal septum, immersed in Perenyi solution for decalcification and then sectioned using classic morphometric and stereologic techniques. The sections qere placed on slides and stained with toluidina blue and analysed in light microscope. Diafanization of the organ was done and this sample was stained with acid hematoxilin. The constitution and distribution of the VNO tissue of male and female rats, sexually mature were described and quantified. We also established the vessel total area, total volume organ, the volume ratio occupied by the vessels in the total volume organ, total lumen area and total sensorial and no sensorial area. However there are no significative differences in the organ volume between male and female Wistar rats, the structures of this complex organ show remarkable differences.