Common Morning Glory Ipomoea Purpurea Research Articles

Maternal environmental effects on the phenotypic responses of the twining vine Ipomoea purpurea to support availability

The presence of physical support elicits a number of morphological changes in the shoot of the common morning glory Ipomoea purpurea, including a shortening of internodes and petioles and a thickening of the main stem. Working with experimentally supported and non‐supported plants of I. purpurea, I tested the existence of maternal environmental effects of physical support in this twining vine. I evaluated whether the offspring of supported plants differed from the offspring of non‐supported plants in a number of morphological and reproductive characters. Stem diameter was the only shoot trait that showed a significant effect of the maternal environment (support). The stems of the progeny of supported mother plants were thicker than the stems of the progeny of non‐supported mother plants. This was true for both supported and non‐supported progeny. Stem diameter, however, was not significantly related to plant fitness (seed number) in supported or non‐supported progeny plants. The maternal environment did not affect the magnitude of the phenotypic responses to support of shoot traits in the progeny plants. There were no maternal environmental effects of physical support on the proportion of flowering plants at week 10 in both non‐supported and supported progeny. Likewise, the presence of physical support in the maternal environment did not affect reproductive traits (seed number, seed size, percentage of reproductive biomass) in supported and non‐supported progeny plants. Finally, the relationship between seed size and seed number was affected by the maternal support environment. The progeny of supported mother plants showed a significantly negative association (trade‐off) between seed size and number, whereas such a trade‐off was not observed in the progeny of non‐supported plants. This was true for both supported and non‐supported progeny.

Stabilization of Mixed-Mating Systems by Differences in the Magnitude of Inbreeding Depression for Male and Female Fitness Components

Stabilization of Mixed-Mating Systems by Differences in the Magnitude of Inbreeding Depression for Male and Female Fitness Components

Frequency‐Dependent Pollen Discounting Contributes to Maintenance of a Mixed Mating System in the Common Morning GloryIpomoea purpurea

Pollen discounting, a reduction in outcross success associated with increased selfing, was evaluated in the common morning glory Ipomoea purpurea. A field experiment was conducted to estimate selfing rates and outcross success using small arrays of plants with large or small anther-stigma distance (ASD). To evaluate the effect of genotypic composition on the mating-system parameters, arrays were composed of five different frequencies of small- and large-ASD genotypes. While the selfing rates of genotypes with small ASD were consistently higher than genotypes with large ASD regardless of the genotypic frequency, outcross success was negatively frequency dependent. The genotype that was at lower frequency in the array had higher outcrossing success in three out of the four array types with unequal frequencies. This advantage-when-rare phenomenon can contribute to preventing the fixation of either extreme ASD-morph and maintaining a mixed mating system in I. purpurea.

Natural Selection on Two Seed‐Size Traits in the Common Morning GloryIpomoea purpurea(Convolvulaceae): Patterns and Evolutionary Consequences

Plants may express two separate seed-size characters during their lifetimes: the size of the seeds from which they germinate (initial seed size) and the mean size of seed they produce as adults (maternal seed size). Many empirical studies indicate that selection often favors a larger initial seed size. In contrast, patterns of natural selection on maternal seed size have not been measured, although theory often predicts stabilizing selection. Here, I report on a field study of the common morning glory Ipomoea purpurea, which provided measurements of natural selection on both initial and maternal seed size. For initial seed size, selection favored larger seeds, but a greenhouse study indicated no genetic variation for this trait. For maternal seed size, there was no evidence of either directional or stabilizing selection, but there was significant additive genetic variation. The genetic correlation between the number and size of seeds was not significant, indicating no trade-off between these traits, but a negative genetic correlation was found between maternal seed size and the probability of surviving to reproduce. The absence of the predicted pattern of stabilizing selection on maternal seed size in the study population highlights the need for more empirical work on the evolution of seed size.

Frequency-Dependent Pollen Discounting Contributes to Maintenance of a Mixed Mating System in the Common Morning Glory Ipomoea purpurea

Pollen discounting, a reduction in outcross success associated with increased selfing, was evaluated in the common morning glory Ipomoea purpurea. A field experiment was conducted to estimate selfing rates and outcross success using small arrays of plants with large or small anther‐stigma distance (ASD). To evaluate the effect of genotypic composition on the mating‐system parameters, arrays were composed of five different frequencies of small‐ and large‐ASD genotypes. While the selfing rates of genotypes with small ASD were consistently higher than genotypes with large ASD regardless of the genotypic frequency, outcross success was negatively frequency dependent. The genotype that was at lower frequency in the array had higher outcrossing success in three out of the four array types with unequal frequencies. This advantage‐when‐rare phenomenon can contribute to preventing the fixation of either extreme ASD‐morph and maintaining a mixed mating system in I. purpurea.

Nucleotide polymorphism in the chalcone synthase‐A locus and evolution of the chalcone synthase multigene family of common morning glory Ipomoea purpurea

Chalcone synthase (CHS) is a small multigene family with at least four members (CHS‐A, B, C and PS) in common morning glory Ipomoea purpurea ROTH. The chalcone synthase enzyme performs the initial condensation reaction that results in the 15‐carbon three‐ring structure that is the backbone of flavonoid biosynthesis. The biochemical pathway that commences with CHS is important in plant disease defence, pigment biosynthesis and UV protection. Accordingly, it is of substantial interest to characterize levels and patterns of molecular diversity for genes that encode this important enzyme. We report the sequence of 19 CHS‐A alleles from Mexican and American populations of common morning glory. American populations of this annual self‐compatible vine are believed to have been introduced from Mexico, where the species is native. Individual plants were sampled from populations of common morning glory throughout Mexico and the south‐eastern USA. Four American alleles were sequenced and these, together with one allele from Mexico City, were identical in primary nucleotide sequence. These data suggest a restricted origin for the American population, probably as a consequence of selection for domestication by pre‐Columbian peoples. Additionally the Mitontic (Chiapas, Mexico) population is significantly more homogeneous than expected by chance indicating that this population may also have experienced a recent population bottleneck. Estimates of nucleotide diversity from the Mexican CHS‐A alleles were high. We present evidence that these estimates may, in part, result from low to moderate levels of interlocus recombination/gene conversion. We also present evidence that the ancient duplication of the CHS gene family, preceding the origin of the genus Ipomoea, was associated with heterogeneity in the rate of substitution between the resulting gene family members. The group of gene family members whose sequences possess a signature amino acid of the closely related Stilbene synthase exhibit a significantly faster proportional rate of nonsynonymous substitution.

FREQUENCY-DEPENDENT VARIATION FOR OUTCROSSING RATE AMONG FLOWER-COLOR MORPHS OF IPOMOEA PURPUREA.

In a series of previous studies, it has been shown that populations of the common morning glory Ipomoea purpurea are typically polymorphic for flower-color genes that bias pollinator service and, hence, the rate of outcrossing. In this study, we show that the rate of outcrossing for the white flower-color morph depends on its frequency in experimental populations of the morning glory. White flowers are visited less often by the primary pollinator, bumblebees, and have lower outcrossing rates than colored flowers when they are in the minority. In contrast, blue or pink flower morphs are not undervisited and do not have lowered outcrossing rates when they are rare. In plant populations where genes that increase selling are selectively favored due to their transmission bias, undervisitation of rare morphs may act to stabilize genetic variation for outcrossing rates.