Interações Planta-polinizador Em Vegetação De Altitude Na Mata Atlântica

Tropical high-altitude vegetation is unique due to susceptibility to severe weather conditions in relation to lower formations, and by the peculiarity of its flora with many relictual components. Studies on plant-pollinator interactions in high-altitude rocky outcrops and forests of the Atlantic Forest are scarce, but compilation of information allows us to identify some patterns: low frequency of visits, high floral longevity and generalized pollination system. In tropical mountain ecosystems, the degree of generalization of pollination systems in functional (pollinator groups) and ecological (number of species) terms tends to be high, mainly due to the over-representation of certain plant taxa (e.g., Asteraceae in rocky outcrops and Fabaceae, Myrtaceae, Rubiaceae and Sapindaceae in montane forests). Generalized pollination systems and autogamy may be advantageous for tropical high-altitude plants due to the more severe weather conditions (e.g., low temperature), which decrease abundance and limit the activity of pollinators, resulting in lower visitation frequency. Nevertheless, some well represented groups in forests, such as orchids and plants pollinated by hummingbirds and bats, exemplify cases of higher functional specialization, as well as plants with poricidal anthers pollinated by bees in the high-altitude grasslands. However, in rocky outcrops, for some functional groups of pollinators (e.g., hummingbirds, bats, beetles and hawkmoths), the availability of resources does not allow the maintenance of all species throughout the year, favoring possible local or altitudinal migrations. Thus, rocky outcrops and high-altitude forests constitute a unit in the sense of sustaining the pollinator community. Indeed rocky outcrops and high-altitude forests share an evolutionary history at the regional scale since they passed through similar events of expansion and retraction in response to climate changes in the Quaternary. This could explain the complementarity between the two types of vegetation in the use of floral resources by pollinators. Besides the associations identified here, the ecology and evolution of plant-pollinator interactions in high-altitude vegetation of the Atlantic Forest remain poorly understood, making urgent the development of an integrative research program, as well as projects on issues related to climate change and biodiversity conservation. © 2016, Universidade Federal do Rio de Janeiro (UFRJ). All rights reserved.20272

Two Orchids, One Scent? Floral Volatiles Of Catasetum Cernuum And Gongora Bufonia Suggest Convergent Evolution To A Unique Pollination Niche

Floral volatile organic compounds (VOCs) are important signals in plant-pollinator communication and thus subjected to olfactory-mediated selection. Occasionally, phylogenetically unrelated plant species will converge towards similar patterns of floral scent signalling to harness pollinators, representing a common adaptive pollination niche. Catasetum cernuum and Gongora bufonia, epiphytic orchids that are native to the Atlantic Forest of southeastern South America, are exclusively pollinated by male Eufriesea violacea orchid-bees; we hypothesised that the two species have converged towards similar floral scent compositions to effectively attract these particular fragrance-seeking floral visitors. The similarity of the chemical composition of floral scent samples obtained through headspace collection was tested using multiple approaches of multivariate analyses (Multiple Response Permutation Procedure-MRPP). According to MRPP, floral scents of C. cernuum and G. bufonia are significantly different. Additionally, the floral scents of C. cernuum and G. bufonia present (E)-β-ocimene and (E)-epoxyocimene as their major compounds, respectively. (E)-β-ocimene is a common constituent of floral scents from euglossine-pollinated orchids, while (E)-epoxyocimene is quite rare in orchids' floral scents and it is found in only a few other species which occur outside the distribution range of C. cernuum, G. bufonia and E. violacea. However, 12 out of the 34 identified VOCs, including (E)-β-ocimene and (E)-epoxyocimene, are shared between both species. Therefore, we assume that both (E)-β-ocimene and (E)-epoxyocimene, either alone or mixed with other floral VOCs, play a major role in the specific association between these two orchids and their exclusive euglossine pollinator. © 2016 Elsevier GmbH.23220721

Linking land-use and land-cover transitions to their ecological impact in the Amazon

Human activities pose a major threat to tropical forest biodiversity and ecosystem services. Although the impacts of deforestation are well studied, multiple land-use and land-cover transitions (LULCTs) occur in tropical landscapes, and we do not know how LULCTs differ in their rates or impacts on key ecosystem components. Here, we quantified the impacts of 18 LULCTs on three ecosystem components (biodiversity, carbon, and soil), based on 18 variables collected from 310 sites in the Brazilian Amazon. Across all LULCTs, biodiversity was the most affected ecosystem component, followed by carbon stocks, but the magnitude of change differed widely among LULCTs and individual variables. Forest clearance for pasture was the most prevalent and high-impact transition, but we also identified other LULCTs with high impact but lower prevalence (e.g., forest to agriculture). Our study demonstrates the importance of considering multiple ecosystem components and LULCTs to understand the consequences of human activities in tropical landscapes