Browsing by Autor "Gerardo R. Camilo"

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    Evaluating the fitness effects of seed size and maternal tree size on<i>Polylepis tomentella</i>(Rosaceae) seed germination and seedling performance
    (Cambridge University Press, 2020) Alejandra I. Domic; José M. Capriles; Gerardo R. Camilo
    Abstract In vascular plants, larger seeds are generally associated with higher germination potential, healthier seedlings and overall higher rates of survivorship. How this relationship holds or what other physiological tradeoffs evolved in plants adapted to high-altitude environments, such as the tropical and subtropical highland Polylepis tree, remain unclear. In this study, we evaluated the relationship between seed mass and seedling performance by testing the reserve effect, the metabolic effect, and the seedling-size effect hypotheses in Polylepis tomentella Weddell (Rosaceae). Since the relationship between fitness and seed size can often depend on maternal plant size, we additionally investigated the association between germination success, seedling performance (survival, relative growth rate (RGR) and height), and size of bearing-seed trees under controlled greenhouse conditions. Our results showed that heavier seeds are more likely to germinate, but we did not find evidence that could support the reserve effect, metabolic effect or seedling-size effect. As seedlings from larger and medium seeds exhibited comparatively similar RGR, survival percentages and final size, maternal plant size was positively associated with improved seed quality and seedling performance. These results demonstrate that seed mass and maternal size during early seedling establishment are critical for Polylepis persistence, demography and conservation.
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    Pollination Ecology of<i>Polylepis tomentella</i>(Rosaceae), an Andean Anemophilous Tree Presenting a Potential Floral Fungal Infection
    (University of Chicago Press, 2017) Alejandra I. Domic; Peter Bernhardt; Retha Edens-Meier; Gerardo R. Camilo; José M. Capriles
    Premise of research. Anemophily is considered to be a mechanism that evolved to promote pollination success. However, reproductive output can decrease if pollen loads are scarce due to low abundance of compatible mates or floral infections. Here we analyze the effects of breeding system, pollen limitation, and a potential floral fungal infection on the reproductive output of the Andean tree Polylepis tomentella (Rosaceae).Methodology. We performed pollen supplementation experiments in the field to assess the extent of the effect of pollen limitation on fruit and seed set and to identify any pre- or postzygotic self-incompatibility responses within receptive pistils. Supplementary scanning electron microscopy and epifluorescence microscopy were used to observe the possible effects of a potential floral fungal infection on sexual reproduction.Pivotal results. Pollen supplementation did not increase fruit and seed set, suggesting weak evidence of pollen limitation. Most stigmas from self- and cross-pollinated flowers showed germinated pollen grains and pollen tubes in the style, indicating that the species exhibits prezygotic self-compatibility. The presence of three Ascomycota genera in stigmas and styles appears to have negatively affected the germination of pollen grains by inhibiting pollen tube growth, but we did not find evidence suggesting that hyphae are able to penetrate the ovary.Conclusions. This study showed that P. tomentella possesses a prezygotic self-compatible system and that fruit and seed set are not affected by pollen limitation. Therefore, reproductive assurance is achieved through pollen transfer between plants by wind and the role played by self-compatibility that allows selfing in the species. However, it is possible that the potential fungal infection could reduce the fecundity of its tree host, as hyphae are able to penetrate pollen grains.
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    Small‐scale Farming and Grazing Reduce Regeneration of <i>Polylepis tomentella</i> (Rosaceae) in the Semiarid Andes of Bolivia
    (Wiley, 2013) Alejandra I. Domic; Gerardo R. Camilo; José M. Capriles
    Abstract In the Andean highlands, Polylepis woodlands are a rare and unique ecosystem of the treeline. Although human activities have caused the loss of extensive forested areas and decreased woodland regeneration, few systematic and quantitative assessments have been carried out in Polylepis forests. This study compares differences in habitat characteristics, population structure, and reproductive output in populations of Polylepis tomentella subject to different levels of human disturbance in the south‐central Andes of Bolivia. We selected P. tomentella because the species still covers large extensions in the form of fragmented forest patches. Results show that human activities affected all the studied populations. Moderately disturbed populations exhibited a lower percentage of farmed area (0.6%) and browsed plants (4%) than strongly disturbed populations (5% and 12%, respectively). All populations exhibited similar proportion of plants with logging scars. Potassium content and canopy closure were 1.5 and 2.5 higher, respectively, in strongly disturbed populations. The density of saplings and seedlings were 75 percent and 80 percent lower in strongly disturbed populations than in moderately disturbed population, even though reproductive individuals produced twice more flowers and fruits. Our results suggest that fruit production does not limit regeneration of P. tomentella and post‐dispersal mechanisms may decrease seed germination and increase seedling mortality. Overall, strongly disturbed populations will be less likely to regenerate, leading to population decline. Conservation programs should facilitate forest recovery by promoting seedling establishment, reducing overharvesting and over‐browsing, and protecting remaining adult plants.