Sistema reproductivo de Trichopetalum plumosum (Ruiz & Pav.) J.F. Macbr. (Asparagaceae), geófita endémica de Chile

The breeding system of the geophyte endemic to Chile Trichopetalum plumosum (Ruiz & Pav.) J.F. Macbr. (Asparagaceae) was evaluated with five controlled pollination treatments (agamospermy, autonomous autogamy, self-pollination, crosspollination and natural / control). Emasculated and unpollinated flowers did not produce fruits, therefore, this is a nonapomictic species and needs pollen for seed production. Fruit production via cross and natural pollination treatments were high with 70.0 and 90.9%, respectively. Despite the low production via self-pollination (43.3%), autonomous autogamy (90.0%) achieved high values as cross and natural pollination treatments. The results for the mean number of seeds per flower were similar to fruiting. However, analysis of the mean number of seeds per fruit did not show significant differences. These results indicate that the population of T. plumosum is self-compatible with a high capacity for autonomous autogamy. It could be possible that autonomous autogamy of this species occurs when the stamens of the flowers move toward the stigma while they close and wither at the end of the day, corresponding to a delayed selfing mode.En este estudio se evaluó el sistema reproductivo de Trichopetalum plumosum (Ruiz & Pav.) J.F. Macbr. (Asparagaceae), una geófita endémica de Chile. Se realizaron cinco tratamientos de polinización controlada (agamospermia, autogamia autónoma, autopolinización, polinización cruzada y natural / control). Ninguna de las flores emasculadas y sin polinizar produjo frutos, lo que indica que esta especie no es apomíctica y, por lo tanto, necesita polen para la producción de semillas. La fructificación en el tratamiento de polinización cruzada (70,0%) fue alta y similar al porcentaje alcanzado a través de la polinización natural (90,9%). A pesar del porcentaje menor en la prueba de autopolinización (43,3%), la autogamia autónoma (90,0%) se acercó a los altos valores alcanzados en los dos primeros tratamientos mencionados. Para el promedio de semillas por flor tratada, los resultados concuerdan con los de fructificación. Sin embargo, al evaluar el número promedio de semillas por fruto formado, los tratamientos no mostraron diferencias significativas. Los resultados indican que la población de T. plumosum es autocompatible con una alta capacidad para la autogamia autónoma. Se sugiere que esta última se produce por el movimiento de los estambres hacia el estigma al final del día a medida que las flores se marchitan y cierran, correspondiendo a un modo de autofecundación tardía

Pollinator-mediated selection and experimental manipulation of the flower phenotype in Chloraea bletioides

Artículo de publicación ISI1. While many studies of flower evolution have relied on the assessment of selection coefficients, these estimates represent correlative evidence of selection. Few studies have combined correlative with experimental evidence, and hence the mechanisms underlying selection processes are not well understood. 2. In this study we quantified the magnitude, direction and form of pollinator-mediated selection acting upon morphological traits in the Chilean endemic orchid Chloraea bletioides. Results revealed strong selection differentials for plant height and flower number, and absence of total selection for morphological flower characters. Multivariate analysis of selection revealed a strong and positive directional selection gradient for flower number. 3. The labellar lobe and flower tube were under negative correlational selection, indicating that selection promoted alternative combinations of traits. Plants with long floral tubes and small labellar lobes, and short floral tubes with large labellar lobes were selected for. Interestingly, selection on flower number increased at a higher rate through the female function than through the male function, which suggests that size-dependent resource limitation may be more important than pollinator-mediated selection for fruit set. 4. In addition to estimates of phenotypic selection, we evaluated through phenotype modification the impact of pollinators on the correlation and potential integration of flower traits coming from different whorls. We removed the tip of the lateral sepals and the labellar lobe in a 2 · 2 factorial design. 5. Results revealed that phenotypic modification had no effect on male and female fitness. The absence of effect was consistent with the low and non-significant selection coefficients. Nevertheless, the observation of significant correlational selection for labellar lobe and flower tube suggests that experimental studies performed on these characters may be of interest to evaluate the functional and adaptive integration of flower design in orchids.This study was partially funded by a Master’s fellowship of ICM Project, P05-002 to MCD, and ACT 34 ⁄ 2006 to RM