Figura 7 - uploaded by Fernanda Schmidt Silveira
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Subfamília Papilionoideae. A. Rhynchosia hauthalii. B. Galactia australis. C. Lathyrus nervosus. D. Collaea stenophylla. E. Centrosema virginianum. F. Lupinus bracteolaris. G. Eriosema tacuaremboense. H. Macropitilium psammodes. I. Vigna longifolia. J. Trifolium polymorphum. K. Stylosanthes leiocarpa. L. Desmodium adscendens. M. Dalbergia frutescens. N. Adesmia ciliata. (Fotos: A,C,E,G,K: F. Schmidt-Silveira; B,D,H: P.P.A. Ferreira; F: H.M. Longhi-Wagner; I,L: R. Lüdtke; J: C. Scherer; G,M: R.L.C. Bortoluzzi; N: J.R.V. Iganci).
Source publication
Os morros graníticos de Porto Alegre ocupam cerca de 24% da área do município e abrigam remanescentes significativos da
vegetação original, dentre os quais o Morro Santana apresenta-se como área prioritária para a conservação. O presente trabalho
objetivou o levantamento da Família Fabaceae deste morro, a elaboração de uma lista de espécies acresci...
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Citations
Grasslands and savannas are dynamic ecosystems, strongly regulated by environmental disturbances such as fire. Maintaining disturbance regimes in these ecosystems are of great conservation concern, and require studies with the use of ecological indicators. Biotic interactions are a major component of biodiversity that are particularly sensitive to environmental changes, and therefore should be considered in ecosystem assessment and monitoring. One of the most common interactions between insects and plants is mediated by extrafloral nectaries (EFNs), where ants use food resources from plants in exchange for protection against herbivores. Here, we explored variations on this ant-plant interaction across a post-fire successional gradient (i.e., few months to more than two years since the last fire) in eleven grassland patches in South Brazil. We evaluated time-since-fire effects on (i) the grassland habitat structure, (ii) an EFN-bearing plant population: Chamaecrista repens, (iii) the EFN-visiting ant communities, and (iv) the ant-plant ecological networks. We expected fire-induced habitat changes to benefit this plant population, and to produce positive cascading effects on interacting ants, thus influencing the structure of ant-plant networks. Freshly-burnt sites presented increased C. repens abundance, and larger individuals with more reproductive structures and EFNs in comparison with sites longer without disturbances. Plant abundance and size were inversely related to the cover of dominant grasses along the habitat gradient. The density of EFN-visiting ants, but not their species richness, increased in freshly-burnt sites, stimulated by the greater resource offer and the habitat openness, which probably facilitated ant activity. Moreover, with increasing time-since-fire, ants interacted with fewer plants, and few species formed the network generalist core. These results could further suggest that the defense service against herbivory provided by ants is also diminished in grasslands longer without disturbances. Overall, by using a series of indicators of habitat change from multiple ecological levels, this study highlights the importance of disturbance for grassland biodiversity and their ecological interactions, helping to improve management decisions.
Battus polystictus (Butler) is a butterfly from the Neotropical region, occurring in the Atlantic Forest and Pampa biomes. It is commonly found in forest fragments surrounded by meadow formations, subjected to marked seasonal changes. Here, we report the population dynamics of B. polystictus at a high latitude environment and provide notes on its natural history. Population parameters were estimated on a 12-month mark-recapture program and the seasonality of resources investigated by exhaustive mapping of host-plants and flowers. The number of butterflies per day was not stable during the year, ranging from zero (winter) to 22 (summer); the sex ratio was always male biased (3M:1F). The age structure was not constant, with an increase of older individuals toward summer. The population density was positively correlated with temperature, relative humidity, and day length. The residence time was lower for males, while the vagility was lower for females; the increment of resources at forest edges seems to increase the likelihood of occurrence of both sexes. The results shown here suggest that South Brazilian populations of B. polystictus have high ecological demands for spring and summer conditions, avoiding winter in diapause.
Passage of a fire can break dormancy of the seeds of many plant species in fire-prone ecosystems. This response to fire is especially well known for the Fabaceae family, but has been poorly studied in Southern Brazil. We collected seeds of four Fabaceae species present in grasslands-forest mosaics of Southern Brazil: Mimosa bimucronata, Desmodium barbatum, Sesbania virgata and Collaea stenophylla. Seeds were exposed to different heat treatments (exposure to 60° and 80 °C for 5 minutes, to 100 °C for 2 minutes, control without heat treatment); not all species were tested in all treatments. After the treatment, the seeds were kept in a germination chamber with a light period of 12/12 hours and temperature of 25 °C. Germinated seeds were counted every 2 days. The results were analyzed by randomization testing. Germination of D. barbatum and S. virgata was increased after exposure to high temperatures (80° and 60 °C, respectively), while M. bimucronata showed reduced germination after temperatures of 80 °C and C. stenophylla no response. This study is the first for Southern Brazil to show a positive response of germination for grassland species exposed to high temperatures, simulating fire effects. As the study presented distinct responses of species to the heat treatment, it seems important to conduct more works with other species from the family, in order to be able to detect more general patterns.
