Browsing by Author "Bustamante, Ramiro O."

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    Effect of a native tree on seedling establishment of two exotic invasive species in a semiarid ecosystem
    (2011) Becerra, Pablo I.; Bustamante, Ramiro O.
    Theory predicts that in more stressful environments, positive plant-plant interactions should be more important than negative ones. For instance, in arid and semiarid regions, amelioration of soil drought produced by the shade of established plants could facilitate establishment of other species, in spite of light reduction. However, this theory has not been tested widely in the context of plant invasion. In this paper we evaluated the hypothesis that in a semiarid ecosystem of central Chile, the native tree, Lithrea caustica, should facilitate through positive shading effects, the seedling establishment of two widely planted and invasive forestry species, Pinus radiata and Eucalyptus globulus. We assessed the seedling establishment examining two processes: seedling recruitment (including germination) and subsequent seedling survival. We sowed seeds to assess recruitment) and planted 8 months old seedlings (to assess seedling survival) of each exotic species under Lithrea patches, open sites and under an artificial shade mimicking Lithrea shading. The study was repeated in a north-facing and a southfacing slope in the study area located in a xeric zone within the distribution range of plantations of these species in central Chile. Our results show that in a north-facing slope Lithrea had positive effects on recruitment of both species, which was produced by shading. These effects were counteracted by negative effects on seedling survival but through a different mechanism, which suggests that Lithrea would have no significant effect on the whole seedling establishment process of Pinus radiata nor Eucalyptus globulus in this habitat. In turn, in a south-facing slope Lithrea had no significant effect on recruitment but had a negative effect on seedling survival, which was not produced by shading. This suggests that in this habitat Lithrea has a negative effect on the seedling establishment of these exotic species. Our results suggest that the effect of the native Lithrea caustica on the seedling establishment of these exotic species is dependent upon the life-cycle phase (recruitment or seedling survival) and habitat even within the same semiarid ecosystem. In contrast to the expected positive effects Lithrea is unlikely to facilitate seedling establishment of these exotic species in this area, and in fact in some habitats this effect could be negative. However, our results also suggest that a common mechanism proposed to resist invasion in forest ecosystems such as shading, probably is not sufficient to inhibit invasion in a semiarid region.
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    Effect of the invasive exotic herb Centaurea solstitialis on plant communities of a semiarid ecosystem
    (2020) Becerra, Pablo I.; Cavieres, Lohengrin; Bustamante, Ramiro O.
    Background
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    Genetic Diversity and Population Structure of Jubaea chilensis, an Endemic and Monotype Gender from Chile, Based on SNP Markers
    (2022) Jara-Arancio, Paola; da Silva Carvalho, Carolina; Carmona-Ortiz, Martin R.; Bustamante, Ramiro O.; Schmidt Villela, Priscilla M.; da Silva Andrade, Sonia C.; Pena-Gomez, Francisco T.; Gonzalez, Luis A.; Fleury, Marina
    Jubaea chilensis (Molina) Baill., also named Chilean palm, is an endemic species found in the coastal area of Mediterranean sclerophyllous forest in Chile. It has a highly restricted and fragmented distribution along the coast, being under intense exploitation and anthropogenic impact. Based on 1038 SNP markers, we evaluated the genetic diversity and population structure among six J. chilensis natural groups encompassing 96% of the species distribution. We observed low levels of genetic diversity, a deficit of heterozygotes (mean H-E = 0.024; H-O = 0.014), and high levels of inbreeding (mean F-IS = 0.424). The fixation index (F-ST) and Nei's genetic distance pairwise comparisons indicated low to moderate structuring among populations. There was no evidence of isolation by distance (r = -0.214, p = 0.799). In the cluster analysis, we observed a closer relationship among Culimo, Cocalan, and Candelaria populations. Migration rates among populations were low, except for some populations with moderate values. The K value that best represented the spatial distribution of genetic diversity was Delta K = 3. Habitat fragmentation, deterioration of the sclerophyllous forest, lack of long-distance dispersers, and a natural regeneration deficit may have driven inbreeding and low levels of genetic diversity in the palm groves of J. chilensis. Although extant populations are not at imminent risk of extinction, the rate of inbreeding could increase and migration could decrease if the effects of climate change and human impact become more acute.
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    Niche models as a tool to inform restoration and conservation strategies: the case of Jubaea chilensis (palm, Arecaceae) and its seed disperser Octodon degus (rodent, Octodontidae)
    (2023) Nunez-Hidalgo, Ignacio; Fleury, Marina; Bustamante, Ramiro O.
    IntroductionBiotic interactions are a crucial component of the plant regeneration process, which has been traditionally studied at more local scales, providing the tools for planning and decision-making. Studies showing the signature of species interactions at coarser spatial scales contrasting with animal-plant interactions at fine scales have been scarce. This study aimed at integrating an approach, over both biogeographic and local scales, by testing two endemic species of Mediterranean central Chile: the relict and southernmost threatened Chilean palm Jubaea chilensis (Chilean palm; Molina; Baillon) and the caviomorph scatter-hoarding rodent Octodon degus (Degu; Molina), on which this palm currently relies for seed dispersal. MethodsIntegrating Geographic Information Systems and Ecological Niche Modeling, the intensity of seed-rodent interactions from a territorial perspective was evaluated in the range of the palm, at a biogeographic scale, identifying areas with greater or lesser potential for seed-rodent interactions; and in local populations, incorporating a variety of environmental factors that might affect palm regeneration. ResultsThe present results show that the rodent (Octodon degus) may play a role in Chilean palm (Jubaea chilensis) seed dispersal and seed establishment, since; Chilean palm regeneration is higher in areas where both species co-occur. At a local scale, a prominent overlap between palm seedlings and degu burrows was also found, which, allied with other abiotic variables such as altitude and topographic humidity, are crucial for successful palm regeneration. DiscussionUnderstanding the full extent of animal-plant interactions and how they are affected by habitat perturbation in a wide range will provide essential information for the design of effective conservation and management strategies, such as rewilding based on plant species.