Browsing by Author "Torres-Morales, Patricio"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Extremely Long-Lived Stigmas Allow Extended Cross-Pollination Opportunities in a High Andean Plant
    (2011) Torres-Diaz, Cristian; Gomez-Gonzalez, Susana; Stotz, Gisela C.; Torres-Morales, Patricio; Paredes, Brayam; Perez-Millaqueo, Matias; Gianoli, Ernesto
    High-elevation ecosystems are traditionally viewed as environments in which predominantly autogamous breeding systems should be selected because of the limited pollinator availability. Chaetanthera renifolia (Asteraceae) is an endemic monocarpic triennial herb restricted to a narrow altitudinal range within the high Andes of central Chile (3300-3500 m a.s.l.), just below the vegetation limit. This species displays one of the larger capitulum within the genus. Under the reproductive assurance hypothesis, and considering its short longevity (monocarpic triennial), an autogamous breeding system and low levels of pollen limitation would be predicted for C. renifolia. In contrast, considering its large floral size, a xenogamous breeding system, and significant levels of pollen limitation could be expected. In addition, the increased pollination probability hypothesis predicts prolonged stigma longevity for high alpine plants. We tested these alternative predictions by performing experimental crossings in the field to establish the breeding system and to measure the magnitude of pollen limitation in two populations of C. renifolia. In addition, we measured the stigma longevity in unpollinated and open pollinated capitula, and pollinator visitation rates in the field. We found low levels of self-compatibility and significant levels of pollen limitation in C. renifolia. Pollinator visitation rates were moderate (0.047-0.079 visits per capitulum per 30 min). Although pollinator visitation rate significantly differed between populations, they were not translated into differences in achene output. Finally, C. renifolia stigma longevity of unpollinated plants was extremely long and significantly higher than that of open pollinated plants (26.3 +/- 2.8 days vs. 10.1 +/- 2.2, respectively), which gives support to the increased pollination probability hypothesis for high-elevation flowering plants. Our results add to a growing number of studies that show that xenogamous breeding systems and mechanisms to increase pollination opportunities can be selected in high-elevation ecosystems.
  • No Thumbnail Available
    Item
    Soil disturbance by a native rodent drives microhabitat expansion of an alien plant
    (2012) Torres-Diaz, Cristian; Gomez-Gonzalez, Susana; Torres-Morales, Patricio; Gianoli, Ernesto
    The "niche opportunity'' hypothesis proposes that alien plant establishment is generally driven by the integrated effects of environmental conditions, changes in resource availability and reduced herbivory pressure, but there is yet little evidence supporting such a complex interaction in nature. We evaluated the interactive effects of soil disturbance by the native fossorial mammal Spalacopus cyanus, microhabitat (beneath shrubs and open areas), and introduced herbivores (rabbit, Oryctolagus cuniculus) on the establishment (seedling emergence, adult abundance, aboveground biomass, and reproductive effort) of the alien annual plant Fumaria capreolata in a coastal matorral of central Chile. In the absence of disturbance, seedling emergence and plant establishment of F. capreolata was largely restricted to understory microhabitats. Soil disturbance by S. cyanus significantly increased seedling emergence and establishment, both beneath shrubs and in open areas. There was no effect of herbivore exclusion on the abundance, biomass and reproductive effort of F. capreolata, although the biomass of other co-existing species was reduced. Overall, these results suggest that native fossorial mammals may favor the invasion of F. capreolata by allowing microhabitat expansion into open areas and by increasing its performance in those microhabitats already occupied. We show how the interplay between soil disturbance, microhabitat, and reduced herbivory may explain invasion patterns at the local scale in natural communities.