Flowering plants display diverse reproductive systems, including a variety of gender strategies and mechanisms of clonal propagation. Here, I investigate gender strategies, sex-ratio evolution, and sexual dimorphism in the North American clonal aquatic, Sagittaria latifolia (Alismataceae), which exhibits three sex phenotypes (hermaphrodites, females, males) and two modal sexual systems (monoecy, dioecy). This provides an outstanding opportunity to examine the costs and benefits of combined versus separate sexes. My research focused on the northern range limit in eastern N. America, and on disjunct populations in western N. America. I developed microsatellite (SSR) markers to investigate population genetic structure at several spatial scales, including the clonal structure of local populations to continental patterns. These analyses provided insights on the roles of historical, ecological and reproductive factors in the evolution and maintenance of sexual system diversity. Phenotypic sex ratios varied near continuously from monoecy through subdioecy (three sex phenotypes) to dioecy. A comparison of phenotypic and genotypic sex ratios in dioecious populations demonstrated close correspondence. The northern range limit was characterized by a decline in female frequency and an increased incidence of subdioecy. I evaluated two hypotheses to explain this pattern: (1) increased sex inconstancy in dioecious populations; (2) hybridization between monoecious and dioecious populations. I found support for both hypotheses, although hybridization appears to be the more common pathway to subdioecy. I parameterized a model predicting female frequency and hermaphrodite sex allocation; observed and predicted values were correlated suggesting that subdioecious populations are closer to equilibrium than expected for a clonal perennial. A comparison of eastern and western populations indicated genetic differentiation between monoecy and dioecy in the east, but in the west, due to habitat isolation, geography plays a more important role in genetic differentiation. Evidence from cpDNA haplotype variation indicated that the western range was established following long-distance colonization from the east involving a genetic bottleneck. The discovery of gynodioecious populations of S. latifolia in the west, and the absence of ecological and genetic differentiation between monoecious and dioecious populations, raise the possibility that dioecy may have evolved autochthonously in the west, and more recently than in the eastern range.

Flowering plants display diverse reproductive systems, including a variety of gender strategies and mechanisms of clonal propagation. Here, I investigate gender strategies, sex-ratio evolution, and sexual dimorphism in the North American clonal aquatic, Sagittaria latifolia (Alismataceae), which exhibits three sex phenotypes (hermaphrodites, females, males) and two modal sexual systems (monoecy, dioecy). This provides an outstanding opportunity to examine the costs and benefits of combined versus separate sexes. My research focused on the northern range limit in eastern N. America, and on disjunct populations in western N. America. I developed microsatellite (SSR) markers to investigate population genetic structure at several spatial scales, including the clonal structure of local populations to continental patterns. These analyses provided insights on the roles of historical, ecological and reproductive factors in the evolution and maintenance of sexual system diversity. Phenotypic sex ratios varied near continuously from monoecy through subdioecy (three sex phenotypes) to dioecy. A comparison of phenotypic and genotypic sex ratios in dioecious populations demonstrated close correspondence. The northern range limit was characterized by a decline in female frequency and an increased incidence of subdioecy. I evaluated two hypotheses to explain this pattern: (1) increased sex inconstancy in dioecious populations; (2) hybridization between monoecious and dioecious populations. I found support for both hypotheses, although hybridization appears to be the more common pathway to subdioecy. I parameterized a model predicting female frequency and hermaphrodite sex allocation; observed and predicted values were correlated suggesting that subdioecious populations are closer to equilibrium than expected for a clonal perennial. A comparison of eastern and western populations indicated genetic differentiation between monoecy and dioecy in the east, but in the west, due to habitat isolation, geography plays a more important role in genetic differentiation. Evidence from cpDNA haplotype variation indicated that the western range was established following long-distance colonization from the east involving a genetic bottleneck. The discovery of gynodioecious populations of S. latifolia in the west, and the absence of ecological and genetic differentiation between monoecious and dioecious populations, raise the possibility that dioecy may have evolved autochthonously in the west, and more recently than in the eastern range.

Orientador: Simone de Pádua Teixeira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-18T14:54:49Z (GMT). No. of bitstreams: 1 Basso-Alves_JoaoPaulo_M.pdf: 5360673 bytes, checksum: dcedc4cbe8765f92aca350ab0d6cfac5 (MD5) Previous issue date: 2011 / Resumo: A ausência de um dos verticilos reprodutivos em algumas flores pode decorrer da perda ou supressão de primórdios, o que pode ser elucidado por meio de estudos morfológicos do desenvolvimento floral. Ficus L. é um ótimo modelo para estes estudos, uma vez que possui representantes com sistemas sexuais diversos. Assim, o presente trabalho teve por objetivo comparar a morfologia da flor em desenvolvimento em Ficus citrifolia (monóica), F. hispida (ginodióica), F. racemosa (monóica secundária) e F. religiosa (monóica), a fim compreender as vias ontogenéticas que promovem a condição flor imperfeita. Para tal, sicônios em diversos estádios de desenvolvimento foram coletados, fixados em FAA 50, dissecados em lupa e preparados para observações de superfície em microscopia eletrônica de varredura (MEV) e histológicas em microscopia de luz. A organização dos meristemas florais e das flores no interior do sicônio é muito congesta na maioria das espécies estudadas, sendo menos acentuada em F. hispida (ginodióica). Diferenças no tempo de emergência dos meristemas e de alongamento do pedicelo em flores carpeladas foram observadas nas espécies monóicas (F. citrifolia, F. racemosa e F. religiosa) e parecem ser cruciais para a formação da heterostilia incompleta, típica de espécies monóicas deste gênero. As flores carpeladas de todas as espécies exibiram formação de sinestigma ao final do desenvolvimento (exceto aquelas do sicônio produtores de galha em F. hispida). Nossos dados, comparados aos de literatura, indicam que a ausência de estames nas flores carpeladas, tanto em espécies monóicas quanto em ginodióicas de Ficus, deve-se a um processo de perda, ou seja, os primórdios de estames não são iniciados no meristema floral. As flores estaminadas de F. hispida apresentaram supressão carpelar. A perda de primórdios estaminais é difundida no gênero e em Moraceae; já o carpelo pode ser perdido ou suprimido nestes grupos. Aspectos do desenvolvimento floral também são discutidos em relação à reprodução e biologia floral de Ficus / Abstract: The absence of reproductive organs in some flowers may ontogenetically arise by organ loss or suppression. Ficus L. is an interesting model for floral developmental studies, due to its diversity in sexual systems. The aim of this study was to compare the morphology of the floral development in Ficus citrifolia (monoecious), F. hispida (gynodioecious), F. racemosa (secondary monoecious) and F. religiosa (monoecious), to help understanding the ontogenetic pathways that promote the condition "imperfect flower". Thus, figs at various developmental stages were collected, fixed in FAA 50 and prepared for surface (scanning electron microscopy) and histological observations (light microscopy). The organization of the floral meristem and flowers inside the syconium is quite compressed, although F. hispida (gynodioecious) exhibits a less compressed floral arrangement inside the syconium. Variation in meristem inception time and pedicel elongation were observed in carpellate flowers of monoecious species (F. citrifolia, F. racemosa and F. religiosa) and should be crucial for establishment of incomplete heterostyly. The carpellate flowers of all species showed a sinstigma in the later developmental stages (except the gall-producing syconium in F. hispida). The staminate flowers of F. hispida showed carpel suppression. Our data, compared with those in the literature, indicate that the absence of stamens in carpellate flowers is due to loss of stamen primordium, both in gynodioecious and monoecious species. This condition is present in the genus and in Moraceae as a whole, while the carpel primordium may be lost or suppressed in this group. Aspects of floral development observed in Ficus are discussed in relation to their systematic and reproductive biology / Mestrado / Biologia Vegetal / Mestre em Biologia Vegetal

The allocation of resources to male or female progeny, or to male or female reproductive function more generally, is one of the most important life history decisions a sexually reproducing individual must ever make. Sex determination is thus a fundamental process, yet the mechanisms which control it are surprisingly diverse. In this thesis, I examine sex determination in the plant species Mercurialis annua L. (Euphorbiaceae). I assess the mechanism of sex determination operating in dioecious and androdioecious populations of M. annua and also investigate the conservation and evolution of sex-determining mechanisms across the annual mercury clade, the lineages of which display exceptional variation in sexual system. First, using crosses, I establish that sex in dioecious M. annua is controlled by a single-locus genetic mechanism, consistent with recent work that identified a single male-linked DNA marker in the species. My search for new sex-linked genes revealed none, however, suggesting that M. annua possesses at most a small non-recombining region around sex-determining loci. Why many dioecious plants lack heteromorphic sex chromosomes is still poorly understood and I consider explanations for this. I extend my investigation by comparing genetic diversity between loci that differ in their linkage to the sex-determining locus. I find a single male-linked marker to possess significantly lower diversity than autosomal loci, but no difference in the diversity of partially sex-linked and non-sex-linked genes. I also assess the conservation of a sex-linked marker among annual mercury lineages and conduct crosses between lineages to examine the conservation of sex determination. My findings indicate a conserved mechanism of single-locus genetic sex determination and I consider the role polyploidisation and hybridisation have played in sexual system evolution and the modification of sex-determining mechanisms in the clade. Finally, I assess the presence of environmental sex determination in androdioecious M. annua, concluding that although male frequency is not influenced by growing density, a degree of sexual lability exists in the lineage.