Co-occurring species of flowering plants may compete for pollination, which can cause character displacement by altering natural selection on floral traits. In a gynodioecious species, competition for pollination may also affect the evolution of sexual dimorphism of floral traits by influencing sex-specific selection. I demonstrated that Mimulus ringens did not affect seed set of gynodioecious Lobelia siphilitica, indicating that it is not a competitor for pollination. The presence of M. ringens did not alter selection upon most floral traits of L. siphilitica. I detected sex-specific selection upon five floral traits, supporting the hypothesis that sexual dimorphism evolves in response to sex-specific selection, rather than pleiotropic effects. My results also suggest that the presence of a co-flowering species may provide a context for sex-specific selection, and therefore, influence sexual dimorphism. Thus, my results suggest a link between the fields of study of competition for pollination and the evolution of sexual dimorphism. / NSERC, OGS, Ontario Innovation Trust, Canada Fund for Innovation

Perennial warm-season grasses constitute the backbone of many forage production systems, whether for grazing or harvested feed. North American native plants, specifically grasses, forbs and legumes offer unique ecosystem benefits along with forage quality and digestibility that are unmatched by introduced species. The disparity in breeding and research focused on improvement of introduced species as opposed to native genera has led to inflated use of introduced species as forage types in lieu of native options, due to their unimproved nature. Eastern gamagrass [Tripsacum dactyloides (L.) L.] is proven to be a widely adapted, highly productive forage species in the southeast, Great Plains and northeast United States. A major limitation to more widespread use of eastern gamagrass is high seed dormancy, which leads to increased seed cost. Here, research used recurrent phenotypic selection breeding methods to reduce seed dormancy, with the ultimate goal of developing a population of individuals that produce non-dormant eastern gamagrass seed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Phosphorus (P) deficiency and aluminum (Al3+) toxicity are two of the main constraints on achieving high crop yields and, often, those conditions coexist in soils. The selection of more adapted materials through easily assessed phenotype traits has a huge potential in the plant breeding. Thus, this work aimed to evaluate the response of traits of root system architecture to P deficiency and Al3+ toxicity, alone or in interaction, in nutritive solution and the potential of use of them in the plant selection of wheat. It were carried out four experiments, in a greenhouse, with the following treatments combination: [1] bifactorial experiment with four P levels ( 25, 50, 100 and 200 μM) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; [2] bifactorial experiment with four Al3+ levels ( 0, 37.5, 75 and 150 μM) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; [3] bifactorial experiment with four P vs. Al3+ combinations (-P -Al; +P -Al; -P +Al e +P +Al) in the main plot and four cultivars (Anahuac, IAC-5, Onix e Quartzo) in the subplot; and [4] trifactorial experiment with two P levels (25 and 125 μM), two Al3+ levels (0 and 74 μM) and two cultivars (IAC-5 and Onix). The experiment 4 was carried out in pots with sand until the anthesis while the others were carried out in pots with an inert substrate (expanded polystyrene) during 15 days. In all the experiments it was evaluated shoot (length, dry weight, foliar area), root dry weight and root system architecture (dry weight, length, superficial area, volume, diameter) growth, being in the assays 2, 3 and 4 the root variables were evaluated individually for root orders 0, 1 and 2. There was a wide variability among the cultivars for the tested conditions, which allows the use of root system architecture characterization in the selection of more adapted plants to P deficiency and Al3+ toxicity in wheat. P deficiency reduced both root and shoot growth, having the cv. IAC-5 showed the best response. The presence of Al3+ reduced the growth of plants, being cv. IAC-5 to more tolerant. This cultivar had higher growth of lateral roots of first and second order, while the sensitive one (Anahuac) had thickening of these types of root. The experimental system allowed a rapid evaluation of the alterations in the root system architecture in response to P deficiency and Al3+ toxicity, and the responses of short-term experiments are similar to those of the long-term. / A deficiência de fósforo (P) e a toxidez por alumínio (Al3+) são dois dos principais fatores limitantes na obtenção de altas produtividades das culturas agrícolas e, frequentemente, essas duas condições coexistem nos solos. A seleção de materiais mais adaptados através de atributos fenotípicos de fácil mensuração tem um grande potencial de aplicação no melhoramento genético de plantas. Assim, esse trabalho objetivou avaliar as respostas de caracteres da arquitetura do sistema radicular à deficiência de P e toxidez por Al3+, isolados ou em interação, em solução nutritiva e o potencial de utilização deles na seleção de plantas de trigo. Foram realizados quatro experimentos, em casa de vegetação, com as seguintes combinações de tratamentos: [1] experimento bifatorial com quatro níveis de P (25, 50, 100 e 200 μM) na parcela principal e quatro cultivares (Anahuac, IAC-5, Onix e Quartzo) na subparcela; [2] experimento bifatorial com quatro níveis de Al3+ (0, 37,5, 75 e 150 μM) na parcela principal e quatro cultivares (Anahuac, IAC-5, Onix e Quartzo) na subparcela; [3] experimento bifatorial com quatro combinações de P vs. Al3+ (-P -Al; +P -Al; -P +Al e +P +Al) na parcela principal e quatro cultivares (Anahuac, IAC-5, Onix e Quartzo) na subparcela; e [4] experimento trifatorial com dois níveis de P (25 e 125 μM), dois de Al3+ (0 e 74 μM) e duas cultivares (IAC-5 e Onix) constituindo os fatores. O Experimento 4 foi conduzido em vasos com areia até a antese e os demais em vasos contendo substrato inerte (poliestireno expandido) durante 15 dias. Em todos os experimentos foi avaliado o crescimento da parte aérea (comprimento, massa seca e área foliar), massa seca de raízes e arquitetura do sistema radicular (comprimento, área superficial, volume e diâmetro), sendo que nos experimentos 2, 3 e 4 essas variáveis foram avaliadas separadamente para as raízes de ordem 0, 1 e 2. Houve uma ampla variabilidade entre as cultivares para as condições testadas, o que permite a utilização da avaliação de caracteres da arquitetura radicular na seleção de plantas mais adaptadas à deficiência de P e toxidez por Al3+ em trigo. A deficiência de P reduziu o crescimento tanto de raízes quanto parte aérea, sendo a cv. IAC-5 a que apresentou melhor resposta ao nutriente. A presença de Al3+ reduziu o crescimento de plantas, sendo a cv. IAC-5 a mais tolerante. A cultivar tolerante ao Al3+ (IAC-5) teve maior crescimento de raízes laterais de primeira e segunda ordem, enquanto que a sensível (Anahuac) teve engrossamento dessas raízes. O sistema experimental utilizado permitiu uma rápida avaliação das alterações na arquitetura do sistema radicular em resposta à deficiência de P e toxidez por Al3+ , sendo as respostas de experimentos de curto prazo semelhantes ao de longo prazo.

It is well known that animals can exert strong selective pressures on plant traits. However, studies on the evolutionary consequences of plant–animal interactions have mainly focused on understanding how these interactions shape trait means, while overlooking its potential direct effect on the variability among structures within a plant (e.g. flowers and fruits). The degree of within-plant variability can have strong fitness effects but few studies have evaluated its role as a potential target of selection. Here we reanalysed data on Ipomoea wolcottiana stigma–anther distance to test alternate mechanisms driving selection on the mean as well as on intra-individual variance in 2 years. We found strong negative selection acting on intra-individual variation but not on mean stigma–anther distance, suggesting independent direct selection on the latter. Our result suggests that intra-individual variance has the potential to be an important target of selection in nature, and that ignoring it could lead to the wrong characterisation of the selection regime. We highlight the need for future studies to consider patterns of selection on the mean as well as on intra-individual variance if we want to understand the full extent of plant–animal interactions as an evolutionary force in nature.

Natural selection mediated by pollinators has influenced the evolution of floral diversity of the flowering plants (angiosperms). The scope of this thesis was to study: 1) phenotypic selection, 2) mating systems, and 3) floral shifts involved in plant speciation. Model plant species were Platanthera bifolia and P. chlorantha (Orchidaceae). These orchids are moth-pollinated, strictly co-sexual (bisexual flowers), and produce a spike that displays 10-20 white flowers. I explored the influence of characters on plant fitness by using multiple linear regressions. Pollen removal (male fitness) and fruit set (female fitness) increased with more flowers per plant in three P. bifolia populations. There was selection towards longer spurs in a dry year when average spur length was shorter than in normal-wet years. Female function was sensitive to drought, which enabled an application of the male function hypothesis of floral evolution (Bateman's principle). The results show that selection may vary between populations, years, and sex-functions. I examined inbreeding by estimating levels of geitonogamy (self-pollination between flowers of an individual) with an emasculation method in two P. bifolia populations. Geitonogamy did not vary with inflorescence size. Levels of geitonogamy was 20-40% in the smaller, but non-significant in the larger population. This may relate to lower number of possible mates and pollinator activity in the smaller population. Platanthera bifolia exhibits the ancestral character state of tongue-attachment of pollinia on the pollinator. Its close relative P. chlorantha attaches its pollinia onto the pollinator's eyes. To explore the mechanism of a floral shift, pollination efficiency and speed was compared between the two species. The results showed no differences in pollination efficiency, but P. chlorantha had faster pollen export and import. Efficiency of pollination in terms of speed may cause floral shifts, and thus speciation.

<p>Natural selection mediated by pollinators has influenced the evolution of floral diversity of the flowering plants (angiosperms). The scope of this thesis was to study: 1) phenotypic selection, 2) mating systems, and 3) floral shifts involved in plant speciation. Model plant species were <i>Platanthera bifolia</i> and <i>P. chlorantha</i> (Orchidaceae). These orchids are moth-pollinated, strictly co-sexual (bisexual flowers), and produce a spike that displays 10-20 white flowers.</p><p>I explored the influence of characters on plant fitness by using multiple linear regressions. Pollen removal (male fitness) and fruit set (female fitness) increased with more flowers per plant in three <i>P. bifolia</i> populations. There was selection towards longer spurs in a dry year when average spur length was shorter than in normal-wet years. Female function was sensitive to drought, which enabled an application of the male function hypothesis of floral evolution (Bateman's principle). The results show that selection may vary between populations, years, and sex-functions.</p><p>I examined inbreeding by estimating levels of geitonogamy (self-pollination between flowers of an individual) with an emasculation method in two <i>P. bifolia</i> populations. Geitonogamy did not vary with inflorescence size. Levels of geitonogamy was 20-40% in the smaller, but non-significant in the larger population. This may relate to lower number of possible mates and pollinator activity in the smaller population.</p><p><i>Platanthera bifolia</i> exhibits the ancestral character state of tongue-attachment of pollinia on the pollinator. Its close relative <i>P. chlorantha</i> attaches its pollinia onto the pollinator's eyes. To explore the mechanism of a floral shift, pollination efficiency and speed was compared between the two species. The results showed no differences in pollination efficiency, but <i>P. chlorantha</i> had faster pollen export and import. Efficiency of pollination in terms of speed may cause floral shifts, and thus speciation.</p>

Natural selection mediated by pollinators has influenced the evolution of floral diversity of the flowering plants (angiosperms). The scope of this thesis was to study: 1) phenotypic selection, 2) mating systems, and 3) floral shifts involved in plant speciation. Model plant species were Platanthera bifolia and P. chlorantha (Orchidaceae). These orchids are moth-pollinated, strictly co-sexual (bisexual flowers), and produce a spike that displays 10-20 white flowers. I explored the influence of characters on plant fitness by using multiple linear regressions. Pollen removal (male fitness) and fruit set (female fitness) increased with more flowers per plant in three P. bifolia populations. There was selection towards longer spurs in a dry year when average spur length was shorter than in normal-wet years. Female function was sensitive to drought, which enabled an application of the male function hypothesis of floral evolution (Bateman's principle). The results show that selection may vary between populations, years, and sex-functions. I examined inbreeding by estimating levels of geitonogamy (self-pollination between flowers of an individual) with an emasculation method in two P. bifolia populations. Geitonogamy did not vary with inflorescence size. Levels of geitonogamy was 20-40% in the smaller, but non-significant in the larger population. This may relate to lower number of possible mates and pollinator activity in the smaller population. Platanthera bifolia exhibits the ancestral character state of tongue-attachment of pollinia on the pollinator. Its close relative P. chlorantha attaches its pollinia onto the pollinator's eyes. To explore the mechanism of a floral shift, pollination efficiency and speed was compared between the two species. The results showed no differences in pollination efficiency, but P. chlorantha had faster pollen export and import. Efficiency of pollination in terms of speed may cause floral shifts, and thus speciation.

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