Nitrogen-tixing and vesicular-arbuscular mycorrhizal symbioses in some tropical legume trees of tribe Mimoseae

Response to mineral fertilization and inoculation with rhizobia and/or arbuscular mycorrhiza fungi (AMF) of the Anadenanthera colubrina, Mimosa bimucronata and Parapiptadenia rigida (Leguminosae-Mimosoideae) native trees from Brazilian riparian forests, were studied in nursery conditions. Each species was submitted to seven treatments, varying nitrogen and phosphorous fertilization and inoculation with rhizobia (r), mycorrhiza (m) or both (rm): NP, P, P + r, P + rm, N, N + m and N + rm. Results showed that AMF inoculations did not enhance the mycorrhizal colonization, and P uptake was not sufficient to sustain good growth of plants. The level of P mineral added affected negatively the AMF colonization in A. colubrina and M. bimucronata, but not in P. rigida. Native fungi infected the three legume hosts. The absence of mineral N limited growth of A. colubrina and P. rigida, but in M. bimucronata the lack of N was corrected by biological nitrogen fixation. N mineral added inhibited the nodulation, although spontaneous nodulation had occurred in A. colubrina and M. bimucronata. Rhizobia inoculation enhanced the number of nodules, nitrogenase activity and leghemoglobin content of these two species. Thus, the extent of rhizobial and mycorrhizal symbiosis in these species under nursery conditions can affect growth and consequently the post-planting success. (C) 2004 Elsevier B.V. All rights reserved.

Tree population and community dynamics in a Brazilian tropical semideciduous forest

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Using network connectance and autonomy analyses to uncover patterns of photosynthetic responses in tropical woody species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reduction of a native fish fauna by alien species: an example from Brazilian freshwater tropical lakes

The consequences of introducing Cichla cf. monoculus Spix & Agassiz, Astronotus ocellatus (Agassiz) and Pygocentrus nattereri Kner into lakes in the River Doce basin, Brazil, on richness, diversity and efficiency of aquatic macrophytes as natural refugia to native fishes was investigated. Samples were taken from lakes with and without alien fishes in areas with and without aquatic macrophytes. The presence of alien fishes reduced richness and diversity of the native fish community. The refugia function, which could be attributed to the clustering of aquatic macrophytes, does not exist in these lakes probably because the alien fishes exploit such habitats for reproduction. Since introductions threaten the native fish diversity of the region, studies on regional dispersion and factors that minimise the spread of alien fishes are needed.

Genetic structure in a tropical lek-breeding bird, the blue manakin (Chiroxiphia caudata) in the Brazilian Atlantic Forest

Determining the genetic structure of tropical bird populations is important for assessing potential genetic effects of future habitat fragmentation and for testing hypotheses about evolutionary mechanisms promoting diversification. Here we used 10 microsatellite DNA loci to describe levels of genetic differentiation for five populations of the lek-mating blue manakin (Chiroxiphia caudata), sampled along a 414-km transect within the largest remaining continuous tract of the highly endangered Atlantic Forest habitat in southeast Brazil. We found small but significant levels of differentiation between most populations. F-ST values varied from 0.0 to 0.023 (overall F-ST = 0.012) that conformed to a strong isolation by distance relationship, suggesting that observed levels of differentiation are a result of migration-drift equilibrium. N(e)m values estimated using a coalescent-based method were small (<= 2 migrants per generation) and close to the minimum level required to maintain genetic similarity between populations. An implication of these results is that if future habitat fragmentation reduces dispersal between populations to even a small extent, then individual populations may undergo a loss of genetic diversity due to an increase in the relative importance of drift, since inbreeding effective population sizes are relatively small (N-e similar to 1000). Our findings also demonstrate that population structuring can occur in a tropical bird in continuous habitat in the absence of geographical barriers possibly due to behavioural features of the species.

Health variables and gill morphology in the tropical fish Astyanax fasciatus from a sewage-contaminated river

The relative condition factor (Kn), gonadosomatic index (GSI), selected hematological variables and gill morphology of the fish Astyanax fasciatus were analyzed in two sites (site I was unpolluted and site 2 was polluted with untreated domestic sewage) of a tropical river (Camanducaia river, São Paulo State, Brazil). The relationship between the body mass (M-B) and the standard length (L-S) of A. fasciatus from both sites was M-B = 0.00799 L-S(3.51843). Tyhe Kn values from both the males and females were significantly higher in site 2. The mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were higher in females from site 2. Gill tissue anomalies and gill parasites were rare in fish from both sites; however, the number of chloride cells was significantly higher in fish from site 1. A. fasciatus presents high capacity to live in ion-poor and soft water and is able to compensate for environmental changes caused by untreated domestic sewage discharges. (c) 2004 Elsevier B.V. All rights reserved.

The goatfish Pseudupeneus maculatus and its follower fishes at an oceanic island in the tropical west Atlantic

The influence of a substratum-disturbing forager, the spotted goatfish Pseudupeneus maculatus on the assemblage of its escorting, opportunistic-feeding fishes was examined at Fernando de Noronha Archipelago (tropical west Atlantic). Followers attracted to spotted goatfish foraging singly differed from followers of spotted goatfish foraging in groups in several characteristics. The larger the nuclear fish group, the greater the species richness and number of individuals of followers. Moreover, groups of foraging spotted goatfish attracted herbivores, not recorded for spotted goatfish foraging singly. The size of follower individuals increased with the size and the number of foraging spotted goatfish. The zoobenthivorous habits of the spotted goatfish and its ability to disturb a variety of soft substrata render it an important nuclear fish for several follower species of the reef fish assemblage at Fernando de Noronha. (c) 2006 the Authors Journal compilation (c) 2006 the Fisheries Society of the British Isles.

Foraging activity and resource use by three parrotfish species at Fernando de Noronha Archipelago, tropical West Atlantic

Parrotfishes are important components of the herbivore and detritivore guilds of tropical and subtropical reefs. Most of parrotfish species are protogynous hermaphrodites that change colour and sex, from initial phase females or males (IP) to terminal phase males (TP). We studied the foraging behaviour of Sparisoma amplum, S. axillare and S. frondosum, three syntopic scarids on the rocky reefs of Fernando de Noronha Archipelago, Tropical West Atlantic. The three parrotfish species differed in food selection and preference, but IP and TP individuals of the same species preferred the same food types, except for S. amplum. Feeding rates of IP individuals were higher than those of TP individuals, but the distribution of feeding frequencies throughout the day of IP and TP individuals of the same species was similar. IP individuals had higher feeding rates than TP ones, which seems related to the fact that TP individuals spend a large amount of time patrolling their territories and chasing away conspecific individuals at the study site. The general foraging pattern we found for S. amplum, S. axillare and S. frondosum is similar to patterns found for other parrotfish species in the Western Atlantic.

Anurans of a seasonally dry tropical forest: Morro do Diabo State Park, São Paulo state, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Spatial and temporal distribution of tadpole assemblages (Amphibia, Anura) in a seasonal dry tropical forest of southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Seasonal variation in body size of tropical anuran amphibians.

Most anurans are considered short lived reproducing only once, with adult size being an important factor contributing to mating success. We sampled anurans with 30 pitfall traps in three forest patches of the northwestern São Paulo State, Brazil, throughout one year. Our objective was to analyze the variation in anuran body size between the dry and rainy season. Our hypothesis is that anurans registered during the rainy season will be larger than conspecifics registered during dry season, since there is a selective advantage in having a larger body size during reproduction activity. The most abundant species registered in the patches were Eupemphix nattereri, Physalaemus cuvieri and Leptodactylus podicipinus. Males and females of E. nattereri and P. cuvieri recorded in the rainy season were larger than of those captured in the dry one. In contrast, males of L. podicipinus were larger in the dry season than in the rainy season. Besides, the operational sex ratio (OSR) in the breeding season was biased towards males in these three species with, respectively, 4.66, 3.2 and 1.87 males per female. Our results suggest that probably body size variation between different seasons is a consequence of individuals' turnover between rainy seasons. Lower individuals captured in the dry season, would be reproductively active adults in the next breeding season.

Three exopolysaccharides of the beta-(1 -> 6)-D-glucan type and a beta-(1 -> 3;1 -> 6)-D-glucan produced by strains of Botryosphaeria rhodina isolated from rotting tropical fruit

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mesocosm experiment on the impact of invertebrate predation on zooplankton of a tropical lake

Invertebrate predation on zooplankton was investigated in mesocosms in the shallow tropical Lake Monte Alegre, Sauo Paulo State, Brazil, in the summer of 1999. Two treatments were applied: one with natural densities of prey and the predators Chaoborus brasiliensis and the water mite Krendowskia sp. (Pr+), and another without predators (Pr-). Three enclosures (volume: 6.6 m(3) of water per enclosure) per treatment were installed in the sediment of the deepest area of the lake (5.0 m). At the beginning, Chaoborus larvae were present in Pr- enclosures, because of technical difficulties in preventing their entrance, but they virtually disappeared in the course of the experiment. Water mites were almost absent in Pr- enclosures. Chaoborus predation negatively influenced the Daphnia gessneri population, but not the populations of the copepods Tropocyclops prasinus and Thermocyclops decipiens and the rotifers Keratella spp. Death rates of Daphnia were generally significantly higher in the Pr+ treatment; Daphnia densities increased after the disappearance of Chaoborus in Pr-. Copepod losses to predation in the experiment may be compensated by higher fecundity, shorter egg development time, and lower pressure on egg-bearing females, resulting in a lower susceptibility to Chaoborus predation. The predation impact of water mite on microcrustaceans and rotifers in the experiment was negligible.

Evaluation of seasonal dynamics and bioindication potential of macroalgal communities in a polluted tropical stream

Macroalgal communities and environmental variables were analyzed seasonally along a polluted tropical stream in São Paulo State, Brazil, We aimed to improve the knowledge of tropical macroalgal communities, to study the longitudinal and seasonal dynamics of these communities in influenced environments, to evaluate the relationship of algal frequency and abundance with selected environmental variables, and to look for potential macroalgal species indicators. The seasonal abundance pattern was similar to natural or low influenced systems and was mainly determined by rainfall regime. However, community composition was closely related to some chemical water pollution indicators, such as phosphorus and nitrogen compounds. Some species are suggested as potential indicators of organic pollution (e.g. Oscillatoria ornata, Stigeoclonium helveticum and Schizomeris leibleinii), but more detailed studies have to be developed to determine the tolerance limits of these species. on the basis of our results and literature data, the use of occurrence of Oscillatoriales in relation to other orders of Cyanoprokaryota is suggested to be a good indicator of organic pollution in tropical lotic ecosystems.