Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of the mineral content of the seston on tropical cladocerans of a marginal lake.

Bioassays were carried out seasonally to evaluate individual growth and reproduction of cladocerans, from a marginal lake, with the addition of nitrogen (N), phosphorus (P), and both N and P to natural seston; Methods: Cohorts originated from cultivated females were submitted to the following treatments: 1) lake seston, 2) lake seston + P, 3) lake seston + N, and 4) lake seston + NP; Results: The sestonic C:P and C:N molar ratios were always high and limiting, according to threshold ratios estimated for temperate lakes. P addition to seston enhanced the growth rates of one species, D. birgei. A significant higher growth rate of B. longirostris was found in the seston enriched with N compared to natural seston, as well as a higher fecundity of M. minuta. The fecundity of D. birgei was significantly higher in the seston enriched with both N and P. C, N, and P body content of cladocerans was similar to that of temperate counterparts; Conclusion: Energy limitation related to carbon content or food quality seems to be most important in controlling cladocerans' populations in the lake than food mineral content.

Plankton richness and abundance in several different hydrological situations in lakes lateral to a river: a case study in the mouth zone of a tributary into a tropical reservoir.

A descriptive analysis of the responses of plankton from lakes lateral to a river in its mouth zone into a tropical reservoir to water level variations is presented. Three situations were reported: 1) a comparison of species richness and diversity and of algae population abundance in prolonged drought and in periods of connection of lakes to the river, 2) the spatial distribution of abundance and richness of Rotifera species in four isolated water bodies formed by fragmentation of a lateral lake during a period of prolonged drought and in the same areas during a period of integrity as an ecosystem, 3) the variability of total zooplankton and Cladocera densities at the end of the isolation period of a lateral lake and after the recovery of connection with the river and in a year of continuous connection with the lotic ecosystem. Various idiosyncrasies were observed in connected lateral lakes, like the surface hydrologic connectivity, a primary factor in species richness modifcations and a secondary controlling factor of plankton abundance. Underground hydrologic connectivity, through the river[forward arrow] lake water fux during the high-water period and lake [forward arrow] river during drought period, appears to have an important role in richness and abundance variations of planktonic populations in the lake isolated from the river.

Effects of temperature, sestonic algae features, and seston mineral content on cladocerans of a tropical lake

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

Relative growth and morphological sexual maturity of Uca Cumulanta (Crustacea : Decapoda : Ocypodidae) from a tropical Brazilian mangrove population

The relative growth of the fiddler crab Uca cumulanta was studied, primarily to determine the size at the onset of sexual maturity for a mangrove population in the estuary of the Patitiba River, Paraty, Rio de Janeiro state, Brazil. The evaluation of the morphological sexual maturity of U. cumulanta was performed using the allometric technique. The relationships that most precisely indicated the size at onset of sexual maturity were carapace length (CL) vs propodus length for males and CL vs abdomen width for females. Males and females are mature at 5.25 and 4.75 mm CL, respectively. The remarkable ontogenetic changes observed in the allometric growth of the male major cheliped and the female abdomen, indicate that growth of these structures is closely connected to the timing of sexual maturity. The relative size at onset maturity obtained for this species was 0.68 and this index was compared to that seen in other species in the genus.

Occurrence of sibling species of Lutzomyia longipalpis (Diptera : Psychodidae) in Venezuela: First evidence from reproductively isolated sympatric populations

The delimitation of cryptic species within the main vector of the American visceral leishmaniasis, Lutzomyia longipalpis, remains a topic of controversy. An analysis of generic variability based on 8 enzymatic loci revealed fixed differences in 2 diagnostic loci, adenylate kinase (Ak) and hexokinase (Hk), between sympatric and allopatric populations at 4 localities in Venezuela. The absence of heterozygotes for these 2 loci within 1 locality indicates, for the first time, the presence of 2 sympatric reproductively isolated populations or cryptic species within L. longipalpis. Significant differences were also detected between these cryptic species in the allele frequencies of glucose-6-phosphate isomerase (Gpi) and malate dehydrogenase, decarboxylating (Me). One species showed mean heterozygosities that ranged between 6.6% and 6.7%, with 1.6-1.9 alleles detected per locus, while the other had mean heterozygosities that ranged from 4.3% to 6.3%, with 1.3-1.6 alleles per locus. Comparisons of isozyme profiles with published data suggests that 1 species is similar to the L. longipalpis described in Colombian and Brazilian populations, whereas the other has not been previously reported.

Seed predation and fruit damage of Solanum lycocarpum (Solanaceae) by rodents in the cerrado of central Brazil

Although neotropical savannas and grasslands, collectively referred to as cerrado, are rich in seed-eating species of rodents, little is known about seed predation and its determinants in this habitat. In this study, we investigated seed predation and damage to fruits of the widespread shrub Solarium lycocarpurn. In addition, the influence of two possible determinants (distance from the parental plant and total crop size) on the feeding behaviour of Oryzorrys scotti (Rodentia, Sigmodontinae) was also examined. O. scotti were captured more frequently close to the shrubs or on shrub crops, indicating that these rodents were attracted to the shrubs and that seed predation was probably distance-dependent. Moreover, the proportion of damaged fruit on the plant decreased as the total crop size increased; consequently, more productive plants were attacked proportionally less by rodents. This pattern of fruit damage may reflect predator satiation caused by the consumption of a large amount of pulp. Alternatively, secondary metabolites in S. lycocarpum fruits may reduce the pulp consumption per feeding event, thereby limiting the number of fruits damaged. (c) 2006 Elsevier Masson SAS. All rights reserved.

The Effects of Nectar-Robbing on Fruit Production in Sparattosperma leucanthum (Bignoniaceae)

Many animals behave as robbers or thieves of floral resources, causing damage to floral tissues or consuming resources used to attract pollinators, or producing effects similar to emasculation by reducing the pollen load in the anthers (which generally results in losses in terms of sexual reproduction). The present work examined the direct and indirect impacts caused by nectar-robbing on the reproductive success of Sparattosperma leucanthum. Different manipulations of the flowers were tested to determine if fruit production was influenced by the perforations made in the floral tissues (direct damage), and if there were changes in visitation frequencies or in the behaviors of effective pollinators (indirect damage). Perforations made by nectar robbers did not lower the reproductive success of the plant species studied. The bee Trigona spinipes was the most frequent visitor and caused the largest perforations in the calyx and corolla of S. leucanthum. Additionally, we noted the occurrence of pollen theft by this same bee in flowers that had been protected against nectar-robbing. These results suggest that if S. leucanthum had developed a mechanism of resistance to robbery by T spinipes it would probably have experienced even lower pollination levels as a result of reductions in the quantities of pollen available for transfer by effective pollinators. We were not able to evaluate if nectar depletion through robbery modified the behavior of the effective pollinators (bumblebees of the genus Bombus).

The invasion of five alien species in the Delta do Parnaiba Environmental Protection Area, Northeastern Brazil

Marine biological invasions have been regarded as one of the major causes of native biodiversity loss, with shipping and aquaculture being the leading contributors for the introductions of alien species in aquatic ecosystems. In the present study, five aquatic alien species (one mollusk, three crustaceans and one fish species) were detected during dives, shore searches and from the fisheries on the coast of the Delta do Parnaiba Environmental Protection Area, in the States of Piaui and Maranhao, Northeastern Brazil. The species were the bicolor purse-oyster Isognomon bicolor, the whiteleg shrimp Litopenaeus vannamei, the giant river prawn Macrobrachium rosenbergii, the Indo-Pacific swimming crab Charybdis hellerii and, the muzzled blenny Omobranchus punctatus. Ballast water (I. bicolor, C. hellerii, and O. punctatus) and aquaculture activities (L. vannamei and M. rosenbergii) in adjacent areas are the most likely vectors of introduction. All exotic species found have potential impact risks to the environment because they are able to compete against native species for resources (food and habitat). Isognomon bicolor share the same habitat and food items with the native bivalve species of mussels and barnacles. Litopenaeus vannamei share the same habitat and food items with the native penaeids such as the pinkspot shrimp Farfantepenaeus brasiliensis, the Southern brown shrimp Farfantepenaeus subtilis, and the Southern white shrimp Litopenaeus schmitti, and in the past few years L. vannamei was responsible for a viral epidemics in the cultivation tanks that could be transmitted to native penaeid shrimps. Charybdis hellerii is also able to cause impacts on the local fisheries as the species can decrease the populations of native portunid crabs which are commercialized in the studied region. Macrobrachium rosenbergii may be sharing natural resources with the Amazon River prawn Macrobrachium amazonicum. Omobranchus punctatus shares habit with the native redlip blenny Ophioblennius atlanticus and other fishes, such as the frillfin goby Bathigobius soporator. Some immediate remedial measures to prevent further introductions from ballast water and shrimp farm ponds should be: (i) to prevent the release of ballast water by ship/vessels in the region; (ii) to reroute all effluent waters from shrimp rearing facilities through an underground or above-ground dry well; (iii) to install adequate sand and gravel filter which will allow passage of water but not livestock; (iv) outdoor shrimp pounds located on floodable land should be diked, and; (v) to promote environmental awareness of those directly involved with ballast water (crews of ship/vessels) and shrimp farms in the region. Rev. Biol. Trop. 58 (3): 909-923. Epub 2010 September 01.

Effects of flooding regime and woody bamboos on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil

The influence of a population of the understorey woody bamboo Merostachys riedeliana and different flooding regimes on tree community dynamics in a section of tropical semideciduous forest in South-Eastern Brazil was examined. A forest section with an area of 1.6 ha composed of 71 adjacent plots was located on a slope ending at the river margin. The section was divided into five topographical sectors according to the mean duration of river floods. In 1991 and 1998 all trees with a diameter at the base of the trunk greater than or equal to 5 cm were measured, identified and tagged, and all live bamboo culms were counted. Annualised estimates of the rates of tree mortality and recruitment, gain and loss of tree basal area, and change in bamboo density were calculated for each of the 71 plots and five topographical sectors as well as for diameter classes and tree species. To segregate patterns arising from spatially autocorrelated events, geostatistical analyses were used prior to statistical comparisons and correlations. In general, mortality rates were not compensated by recruitment rates but there was a net increase in basal area in all sectors, suggesting that the tree community as a whole was in a building phase. Tree community dynamics of the point bar forest (Depression and Levee sectors) differed from that of the upland forest (Ridgetop, Middle Slope and Lower Slope sectors) in the extremely high rates of gain in basal area. The predominant and specialised species, Inga vera and Salix humboldtiana, are probably favoured by relaxed competition in an environment stressed by long-lasting floods. In the upland forest, mortality rates were highest at the Middle Slope, particularly for smaller trees, while recruitment rates were lowest. As bamboo clumps were concentrated in this sector, the locally higher instability in the tree community probably resulted from the direct interference of bamboos. The density of bamboo culms in the upland forest was negatively correlated with the rates of tree recruitment and gain in basal area, and positively correlated with tree mortality rates. Bamboos therefore seemed to restrict the recruitment, growth and survival of trees.

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.

Variações interanuais na fenologia de uma comunidade arbórea de floresta semidecídua no sudeste do Brasil

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

Tree population and community dynamics in a Brazilian tropical semideciduous forest

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Germination performance of congeneric Styrax species from the Cerrado sensu lato areas and their distribution pattern in different physiognomies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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)