Ramiro O. Bustamante

The decline of an endangered temperate ecosystem: the ruil (Nothofagus alessandrii) forest in central Chile

We describe the current state of the ruil (Nothofagus alessandrii) forest, a rare and endemic temperate forest in central Chile. Because of a long history of land-use, the ruil forest has suffered intense deforestation and fragmentation. By 1991, there remained 352.2 ha of forest in 183 fragments, most of them small and regular and a few large and irregular. From 1981 to 1991 the forest disappeared at a rate of 8.15% per year, to our knowledge, the highest value reported in forest fragmentation. Fragments are surrounded by a matrix of Pinus radiata plantations. Only 42 ha of forest (12% of the total area) are protected in a public reserve. An analysis of the composition of the forest shows that 13.8% of the total species are introduced. Pinus radiata is the only tree that has invaded this forest successfully. The 45.4% of native tree species are shade-tolerant and dependent on biotic pollinators and dispersers. These species should be the targets for future conservation efforts as they are particularly sensitive to fragmentation. We conclude that the current situation of the ruil forest is critical, and it will disappear in the next decade unless we conduct an active strategy of conservation, including integrated efforts both inside and outside protected areas and between landowners and public agencies.

Is Pinus radiata invading the native vegetation in Central Chile? Demographic responses in a fragmented forest

Forest fragmentation facilitates the invasion of exotic species. This threat may be especially severe if forest fragments are surrounded by plantations of exotic species like Pinus radiata, an aggressive colonizer and shade-intolerant tree that has invaded successfully several native ecosystems of the southern hemisphere. In this study, we experimentally tested if the conditions of a successful seedling establishment P. radiata are fulfilled at the Coastal Maulino forest, an endemic fragmented forest of central Chile. Results demonstrated that seeds are dispersed into the native forests, however seedling establishment occurs only at the edges. We conclude that this exotic species is not invading native forests up to date. However, we suggest to conduct evaluations of seed rain and seedling establishment in the long term, in order to monitor the fate of this exotic species in fragmented native forest of Central Chile.

Effects of sampling completeness on the structure of plant—pollinator networks

Plant-animal interaction networks provide important information on community organization. One of the most critical assumptions of network analysis is that the observed interaction patterns constitute an adequate sample of the set of interactions present in plant-animal communities. In spite of its importance, few studies have evaluated this assumption, and in consequence, there is no consensus on the sensitivity of network metrics to sampling methodological shortcomings. In this study we examined how variation in sampling completeness influences the estimation of six network metrics frequently used in the literature (connectance, nestedness, modularity, robustness to species loss, path length, and centralization). We analyzed data of 186 flowering plants and 336 pollinator species in 10 networks from a forest-fragmented system in central Chile. Using species-based accumulation curves, we estimated the deviation of network metrics in undersampled communities with respect to exhaustively sampled communities and the effect of network size and sampling evenness on network metrics. Our results indicate that: (1) most metrics were affected by sampling completeness but differed in their sensitivity to sampling effort; (2) nestedness, modularity, and robustness to species loss were less influenced by insufficient sampling than connectance, path length, and centralization; (3) robustness was mildly influenced by sampling evenness. These results caution studies that summarize information from databases with high, or unknown, heterogeneity in sampling effort per species and should stimulate researchers to report sampling intensity to standardize its effects in the search for broad patterns in plant-pollinator networks.

The effects of seed size and pericarp on seedling recruitment and biomass in Cryptocarya alba (Lauraceae) under two contrasting moisture regimes

Establishment success of plants derived from large seeds has been proposed to be greater than that of those derived from smaller ones, particularly under unfavourable conditions of moisture. Therefore, the advantages conferred by large seeds in terms of seedling performance may be modulated by abiotic conditions. The effect of seed size on Cryptocarya alba seedling performance (as determined by seedling recruitment and seedling size) was evaluated under two contrasting rainfall regimes (wet and dry year regime), simulated in the laboratory. It was also determined whether the presence of a pericarp, which had been shown to reduce germination, decreases desiccation and if this counterbalances the greater recruitment of seeds without a pericarp, especially under unfavourable conditions of moisture. Large seeds had a greater probability of recruitment and their seedlings attained a greater biomass, independently of the amount of water applied. In the simulated wet year regime, seeds with a pericarp showed a greater probability of recruitment than those lacking a pericarp. However, seedlings derived from both seed types attained a similar biomass. Under the dry year regime, seeds with and without a pericarp showed similar recruitment probabilities and their seedlings had similar biomasses. These results do not support the assumption that under favourable conditions of moisture, individual differences in seed size would not matter in term of seedling performance. A possible explanation in this case, is the presence of recalcitrant seeds in C. alba, which determines a very short time period for germination following dispersal. Therefore, any attribute that increases germination (e.g., large seeds) would be advantageous, independently of the prevailing abiotic conditions.

Increasing the understanding of plant invasions in southern South America: first symposium on Alien Plant Invasions in Chile

The first symposium on Alien Plant Invasions in Chile was held in southern Chile in November of 2002. Chile represents an interesting setting to study biological invasions because of its long history of introductions, and its high rate of endemisms that makes it more prone to invasions. However, little is known about plant invasions in Chile and the country lacks a clear policy on alien species. The speakers at the symposium discussed their research on several aspects of alien plant invasions in southern Chile and Argentina. They also elaborated a list of future challenges of plant invasion ecology for the area. The package of recommendations may be useful for other developing countries with similar state of knowledge of their flora and similar environmental and economic issues. We expect that this type of meeting will help to stimulate the scientific debate about invasion ecology and the development of coordinated research to answer local questions, while contributing to find generalities in plant invasion patterns and processes.

Seed predation and seedling recruitment in plants: the effect of the distance between parents

We present a graphic model that explores the effect of distance between parent plants on seed predation and seedling recruitment. Based on the assumption that distance between parents may affect the shape of the seed shadow, the model predicts that seed predators may affect seedling recruitment curves under isolated plants but they are unable to affect these curves under close parent plants. The predictions of the model are tested experimentally in Cryptocarya alba (Lauraceae), a common tree of the Mediterranean forest, Central Chile. Results show that predictions are not met under isolated parent plants. Although seed density decreases significantly away from parent plants, this effect is not relevant for seed predation and seedling recruitment. The biotic/abiotic contrast existing under the canopy vs outside the canopy, plus the shade-tolerance of this tree, better explains the seedling recruitment observed under isolated parent plants. Nevertheless, the predictions of the model are corroborated under close parent plants. Seed shadows overlap to the extent that they generate a homogeneous seed distribution, homogeneous seed predation and homogeneous seedling recruitment as well. We discuss the implications of the model in terms of the spatial pattern of seedlings and the benefits of dispersal from isolated and close parent plants.

Water Deficit as a Driver of the Mutualistic Relationship between the Fungus Trichoderma harzianum and Two Wheat Genotypes

ABSTRACT The aim of this study was to assess the occurrence of mutualistic interactions between the fungus Trichoderma harzianum and two wheat genotypes, Triticum aestivum cv. Talhuén and T. turgidum subsp. durum cv. Alifén, and the extent to which water deficit affected these interactions. Two wheat genotypes were cultivated in the presence or absence of T. harzianum and in the presence or absence of water deficit. T. harzianum was in turn cultivated in the presence or absence of wheat plants and in the presence or absence of water deficit. To evaluate the plant-fungus interactions, the root volume, dry biomass, and fecundity of wheat were determined, as was the population growth rate of the fungus. Trichoderma harzianum exerted a positive effect only on plants subjected to water deficit. The population growth rate of T. harzianum was negative in the absence of wheat plants and reached its highest level in the presence of plants under conditions of water deficit. These results confirm the occurrence of a mutualistic interaction between wheat and T. harzianum and show that it is asymmetric and context dependent.

Global invasion of Lantana camara: has the climatic niche been conserved across continents?

Lantana camara, a native plant from tropical America, is considered one of the most harmful invasive species worldwide. Several studies have identified potentially invasible areas under scenarios of global change, on the assumption that niche is conserved during the invasion process. Recent studies, however, suggest that many invasive plants do not conserve their niches. Using Principal Components Analyses (PCA), we tested the hypothesis of niche conservatism for L. camara by comparing its native niche in South America with its expressed niche in Africa, Australia and India. Using MaxEnt, the estimated niche for the native region was projected onto each invaded region to generate potential distributions there. Our results demonstrate that while L. camara occupied subsets of its original native niche in Africa and Australia, in India its niche shifted significantly. There, 34% of the occurrences were detected in warmer habitats nonexistent in its native range. The estimated niche for India was also projected onto Africa and Australia to identify other vulnerable areas predicted from the observed niche shift detected in India. As a result, new potentially invasible areas were identified in central Africa and southern Australia. Our findings do not support the hypothesis of niche conservatism for the invasion of L. camara. The mechanisms that allow this species to expand its niche need to be investigated in order to improve our capacity to predict long-term geographic changes in the face of global climatic changes.

Patterns of chemical defences in plants: an analysis of the vascular flora of Chile

Summary.The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs, shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and stress hypotheses are sustained.

Plant invasions research in Latin America: fast track to a more focused agenda.

While many developed countries have invested heavily in research on plant invasions over the last 50 years, the immense region of Latin America has made little progress. Recognising this, a group of scientists working on plant invasions in Latin America met in Chile in late 2010 to develop a research agenda for the region based on lessons learned elsewhere. Our three main findings are as follows. (1) Globalisation is inevitable, but the resultant plant introductions can be slowed or prevented by effective quarantine and early intervention. Development of spatially explicit inventories, research on the invasion process and weed risk assessments can help prioritise and streamline action. (2) Eradication has limited application for plants and control is expensive and requires strict prioritisation and careful planning and evaluation. (3) Accepting the concept of novel ecosystems, new combinations of native and introduced species that no longer depend on human intervention, may help optimise invasive species management. Our vision of novel ecosystem management is through actions that: (a) maintain as much native biodiversity and ecosystem functionality as possible, (b) minimise management intervention to invasives with known impact, and (c) maximise the area of intervention. We propose the creation of a Latin American Invasive Plants Network to help focus the new research agenda for member countries. The network would coordinate research and training and establish funding priorities, develop and strengthen tools to share knowledge, and raise awareness at the community, governmental and intergovernmental levels about the social, economic and environmental costs of plant invasions.