Species of Valerianaceae in South America represent one of the best examples of rapid diversification on a continental scale. The phylogeny of Valerianaceae has received a lot of attention within the last 10 years, but relationships among the South American species are fairly unresolved. Results from previous studies have not been well resolved with traditional genetic markers, most likely due to its recent and rapid radiation. Species in this clade exhibit a variety mating systems and inflorescence types. For the first part of this research I used several traditional plastid markers, and 3 new low copy nuclear markers to better resolve the phylogeny and then explore mating system evolution within the clade. For the second part of this research I collected high-throughput “next-generation” genomic sequence data from reduced representation libraries obtained using genotyping-by-sequencing (GBS) protocols, along with several phylogenetic methods, to try to further resolve the phylogeny of this group.

<p> </p> <p>The degree of self-fertilization in a population determines levels of genetic variation and high selfing rates could thus limit future adaptive potential. Theory predicts that intermediate selfing rates should not persist, yet many plants exhibit mixed mating. Cleistogamy is a floral heteromorphism where individuals produce both showy potentially outcrossing chasmogamous flowers and closed obligately selfing cleistogamous flowers. Reproduction via cleistogamous flowers is thought to be beneficial because of their greater energetic economy compared to chasmogamous flowers but can be costly if selfing leads to inbreeding depression or accelerates the fixation of deleterious mutations within populations. Cleistogamy has evolved independently multiple times and can be used to study the maintenance of adaptive mixed mating. To investigate this, I estimated the costs and benefits of selfing in three populations of <em>Ruellia humilis </em>Nutt (Acanthaceae) in greenhouse common garden experiments. To quantify the costs, I performed hand pollinations and quantified fitness components of progeny resulting from selfing and outcrossing within- and between-populations. To quantify the relative energetic advantage of cleistogamous flowers, I measured dry flower mass, fertility, seed number per fruit, and pollen-ovule ratios of both types of flowers. I found negative cumulative inbreeding depression in all populations, indicative of selfed progeny outperforming outcrossed progeny. While the fitness consequences of between population outcrossing ranged from heterosis to outbreeding depression. When looking at the energetic benefits of selfing, I found that the cost of reproduction via cleistogamous flowers was between 3 and 14-fold less than the cost for outcrossing flowers. Finally, I combined data on inbreeding depression and the energetic costs of reproduction and found that chasmogamous flowers of <em>R. humilis </em>must provide between a 3 to a 45-fold fitness advantage to be maintained, the magnitude of which was dependent upon maternal population. Overall, I conclude that none of the existing hypotheses are sufficient enough to provide the selective advantage needed to explain the persistence of chasmogamous flowers in <em>R. humilis</em>. Without any supported explanations for the maintenance of mixed mating, the exploration of genetic constraints on the loss of chasmogamous flowers could solve this long-standing mystery. </p>

Sicyos deppei G. Don (Cucurbitaceae) is an invasive monoic annual tendril-bearing vine; it is endemic to Mexico, adapted to the rainfall cycle (June through the end of September) and produces spiny, single seeded fruits. Under serious infestation conditions, S. deppei grows extensively, covering native plants, crops and tree trunks. This study determined the breeding system and pollinators of S. deppei growing in three study sites at urban gardens and disturbed sites at the Campus of the Universidad de las Américas, Puebla in the city of San Andrés Cholula, Puebla (Mexico). Each female inflorescence had an average of 17 flowers at the three study sites. As a step prior to experiments, the timing for stigma receptiveness and pollen viability was determined with the Peroxtesmo KO test (PKO) and Diaminobenzidine test (DAB),respectively. Stigmas of female flowers reach maximum receptivity when flowers are at anthesis; receptivity decreases as the flower reaches the succeeding floral stages. Viability of pollen grains increases with flower development; viabilitypercentages at early stages of floral development are very low, as opposed to the higher percentages of pollen viability found in flowers at anthesis and following developmental stages. Breeding systems were tested for xenogamy and geitonogamy by hand pollinating female flowers. Breeding systems results demonstrated that S. i deppei has a mixed-mating system, being able to set fruit and seed when pollinated with pollen from different plants and from pollen of the same plants. The pollinators were determined with the single-visit method. The diversity of floral visitors in this study was low; the most effective pollinator for S. deppei in this study was Apis mellifera. Throughout the rainy season, this study also described the phenology of S. deppei at the plant and flower level, as well as total plant length. Each stage of development in male and female flowers lasts one day. At the end of the rainy season (N2010) individual plants measured between 947 and 270 cm. / CONACYT, NSERC-CANPOLIN