Spatial analysis of egg distribution and geographic changes in the spawning habitat of the Brazilian sardine Sardinella brasiliensis

This paper establishes the spawning habitat of the Brazilian sardine Sardinella brasiliensis and investigates the spatial variability of egg density and its relation with oceanographic conditions in the shelf of the south-east Brazil Bight (SBB). The spawning habitats of S. brasiliensis have been defined in terms of spatial models of egg density, temperature-salinity plots, quotient (Q) analysis and remote sensing data. Quotient curves (Q(C)) were constructed using the geographic distribution of egg density, temperature and salinity from samples collected during nine survey cruises between 1976 and 1993. The interannual sea surface temperature (SST) variability was determined using principal component analysis on the SST anomalies (SSTA) estimated from remote sensing data over the period between 1985 and 2007. The spatial pattern of egg occurrences in the SBB indicated that the largest concentration occurred between Paranagua and Sao Sebastiao. Spawning habitat expanded and contracted during the years, fluctuating around Paranagua. In January 1978 and January 1993, eggs were found nearly everywhere along the inner shelf of the SBB, while in January 1988 and 1991 spawning had contracted to their southernmost position. The SSTA maps for the spawning periods showed that in the case of habitat expansion (1993 only) anomalies over the SBB were zero or slightly negative, whereas for the contraction period anomalies were all positive. Sardinella brasiliensis is capable of exploring suitable spawning sites provided by the entrainment of the colder and less-saline South Atlantic Central Water onto the shelf by means of both coastal wind-driven (to the north-east of the SBB) and meander-induced (to the south-west of the SBB) upwelling.

Prey-capture efficiency between juveniles and adults, feeding habitat and abundance of Wattled Jacana foragers in northern Pantanal, Mato Grosso state, Brazil

The choice of foraging strategies implies an attempt at gaining energy by predators. Supposedly, the difference in employing the "sit and wait" or "active foraging" behavior lays in hunter skills, experience and the kind of prey consumed. With the hypothesis that "active foraging" demands no learning, in this study we compared the prey capture efficiency among Wattled Jacana juveniles and adults, and also present descriptive information about feeding habitat and the abundance variation of foragers throughout the day in the northern Pantanal. Prey capture efficiency did not differ significantly among juveniles and adults, corroborating our initial hypothesis that "active foraging" is an instinctive behavior and demands no experience to be effective. However, future work is necessary to compare the energetic quality of consumed items by juveniles and adults, searching for differences explained by adults' experience. Foraging individuals were found at an average distance of 14 m ranging from 2 to 42 m) from the margin of the sampled swamps, however 64% of the foragers were found closer to the margins. The average depth of foraging sites was 17 cm, ranging from 5 to 40 cm, although no preference for specific classes of depth was found (p > 0,05). Despite the accepted general pattern of birds being more active in the early morning, the largest number of individuals foraging was observed between 11:00 and 12:00 AM, but no significant difference was found in the abundance of foraging individuals among different periods of the day. Factors, which were not analyzed, such as food availability and presence of competitors and predators need to be studied to reveal the main factors of the spatial and temporal distribution of the Wattled Jacana.

Habitat use by Sharp-tailed Tyrant (Culicivora caudacuta), and Cock-tailed Tyrant (Alectrurus tricolor) in the Cerrado of Southeastern Brazil

Habitat use by Sharp-tailed Tyrant (Culicivora caudacuta), and Cock-tailed Tyrant (Alectrurus tricolor) in the Cerrado of Southeastern Brazil. Obligatory grassland birds are dependent on a limited set of native habitats that are disappearing almost everywhere. We examined the use of macrohabitat and microhabitat by two threatened species of flycatchers, the Sharp-tailed Tyrant, Culicivora caudacuta and the Cock-tailed Tyrant, Alectrurus tricolor in a preserved area of cerrado. We generated logistic regression models to explain the presence of these species through variables of microhabitat. Both flycatchers occurred mainly in grassland areas and favored areas with a low density of palms (Attalea geraensis) and trees. The Sharp-tailed Tyrant also favored areas with a high density of low shrubs (< 1 m) and less exposed soil. The positive relationship found between the presence of Sharp-tailed Tyrant and soil cover may indicate the importance of litter and understory vegetation for shelter and food. The conservation of both flycatcher species in the study area should benefit from controlling palm density and the maintenance of grasslands with low shrubs.

Egg surface structure of the freshwater toadfish Thalassophryne amazonica (Teleostei: Batrachoididae) with information on its distribution and natural habitat

The egg surface structure of Thalassophryne amazonica, a freshwater toadfish from the Amazon basin is described. Eggs of this species show a remarkable, highly unusual system of parallel ridges and intermittent grooves that originate at the equator of the egg and lead to the micropylar pit, at which they end in a spiralling pattern. A similar egg surface structure has so far been described only from a group of Asian anabantoid percomorphs, obviously not closely related to Thalassophryne. This egg surface pattern may enhance fertilization success by guiding sperm to the micropyle. We review museum records for T amazonica, present an updated map of its occurrence in the Amazon basin, and provide information on its habitat.

Habitat structure and food resources for wildlife across successional stages in a tropical forest

Tropical forests are experiencing an increase in the proportion of secondary forests as a result of the balance between the widespread harvesting of old-growth forests and the regeneration in abandoned areas. The impacts of such a process on biodiversity are poorly known and intensely debated. Recent reviews and multi-taxa studies indicate that species replacement in wildlife assemblages is a consistent pattern, sometimes stronger than changes in diversity, with a replacement from habitat generalists to old-growth specialists being commonly observed during tropical forest regeneration. However, the ecological drivers of such compositional changes are rarely investigated, despite its importance in assessing the conservation value of secondary forests, and to support and guide management techniques for restoration. By sampling 28 sites in a continuous Atlantic forest area in Southeastern Brazil, we assessed how important aspects of habitat structure and food resources for wildlife change across successional stages, and point out hypotheses on the implications of these changes for wildlife recovery. Old-growth areas presented a more complex structure at ground level (deeper leaf litter, and higher woody debris volume) and higher fruit availability from an understorey palm, whereas vegetation connectivity, ground-dwelling arthropod biomass, and total fruit availability were higher in earlier successional stages. From these results we hypothetize that generalist species adapted to fast population growth in resource-rich environments should proliferate and dominate earlier successional stages, while species with higher competitive ability in resource-limited environments, or those that depend on resources such as palm fruits, on higher complexity at the ground level, or on open space for flying, should dominate older-growth forests. Since the identification of the drivers of wildlife recovery is crucial for restoration strategies, it is important that future work test and further develop the proposed hypotheses. We also found structural and functional differences between old-growth forests and secondary forests with more than 80 years of regeneration, suggesting that restoration strategies may be crucial to recover structural and functional aspects expected to be important for wildlife in much altered ecosystems, such as the Brazilian Atlantic forest. (C) 2012 Elsevier B.V. All rights reserved.

The golden lancehead Bothrops insularis (Serpentes: Viperidae) relies on two seasonally plentiful bird species visiting its island habitat

Adult individuals of the island pitviper Bothrops insularis have a diet based on birds. We analysed bird species recorded in the gut of this snake and found that it relies on two out of 41 bird species recorded on the island. When present, these two prey species were among the most abundant passerine birds on the island. A few other migrant birds were very occasionally recorded as prey. A resident bird species (Troglodytes musculus) is the most abundant passerine on the island, but seems able to avoid predation by the viper. Bothrops insularis is most commonly found on the ground. However, during the abundance peak of the tyrannid passerine Elaenia chilensis on the island, more snakes were found on vegetation than on the ground. We suggest that one cause may be that these birds forage mostly on vegetation, and thus cause the snakes to search for prey on this arboreal substratum.

Distribution patterns of a marsh vegetation metacommunity in relation to habitat configuration

The identification of the factors behind the distribution of plant communities in patched habitats may prove useful towards better understanding how ecosystems function. Plant assemblages are especially important for wetland productivity and provide food and habitat to animals. The present study analyses the distribution of a metacommunity of helophytes and phreatophytes in a wetland complex in oder to identify the effects of habitat configuration on the colonisation process. Ponds with wide vegetated shores and a short distance to a big (> 10 ha) wetland, had higher species richness. The average percentage of surface covered by each species in all the wetlands correlated positively with the number of patches occupied by that species. Moreover, the community presented a nested pattern (species-poor patches were subsets of species-rich patches), and this pattern came about by selective extinction and colonisation processes. We also detected the presence of some idiosyncratic species that did not follow nestedness. Conservation managers should attempt to maximise the vegetated shore width and to reduce the degree of isolation to enhance species richness. Furthermore, a single large and poorly isolated reserve may have the highest level of biodiversity in emergent vegetation species in this wetland complex, however, the particular ecological requirements of idiosyncratic species should also be taken into account when managing this type of community.

Habitat alteration and community-level effects of an invasive ecosystem engineer: a case study along the coast of NSW, Australia

We investigated the effects of the habitat-modifying green algae Caulerpa taxifolia on meiobenthic communities along the coast of New South Wales, Australia. Samples were taken from unvegetated sediments, sediments underneath the native seagrass Zostera capricorni, and sediments invaded by C. taxifolia at 3 sites along the coast. Meiofaunal responses to invasion varied in type and magnitude depending on the site, ranging from a slight increase to a substantial reduction in meiofauna and nematode abundances and diversity. The multivariate structure of meiofauna communities and nematode assemblages, in particular, differed significantly in sediments invaded by C. taxifolia when compared to native habitats, but the magnitude of this dissimilarity differed between the sites. These differential responses of meiofauna to C. taxifolia were explained by different sediment redox potentials. Sediments with low redox potential showed significantly lower fauna abundances, lower numbers of meiofaunal taxa and nematode species and more distinct assemblages. The response of meiofauna to C. taxifolia also depended on spatial scale. Whereas significant loss of benthic biodiversity was observed locally at one of the sites, at the larger scale C. taxifolia promoted an overall increase in nematode species richness by favouring species that were absent from the native environments. Finally, we suggest there might be some time-lags associated with the impacts of C. taxifolia and point to the importance of considering the time since invasion when evaluating the impact of invasive species.

Differences in habitat use of two sympatric species of Ameiva in East Costa Rica

Identifying the differences in habitat use for sympatric species is important for understanding the species preferences and the limits of population distribution. We studied the differences in the habitat use of two understudied sympatric species of Ameiva (A. festiva and A. quadrilineata) in a natural reserve of the Caribbean coast of Coast Rica. Ameiva quadrilineata showed a more restrictive habitat use pattern than A. festiva. A. quadrilineata's smaller body size may be one of the factors limiting its habitat range. Both species showed higher density in regenerated forests, while A. quadrilineata was never found in swamp forests. The air temperature and the meteorological condition at the moment of the survey also influenced the occurrence of the A. quadrilineata, while the juveniles of A. festiva were only affected by the meteorological condition. None of the studied variables seemed to affect the occurrence of A. festiva adults. The results of this study can be useful to evaluate possible changes in the species distribution patterns as a consequence of direct (i.e., deforestation) or indirect (i.e., climate change) human activities in the distribution area of these species.

Using AMS combined with mineral shape preferred orientation analysis to understand the emplacement fabrics of the Apiai gabbro-norite (Ribeira Belt, SE Brazil)

The Apiai gabbro-norite is a massive fine-grained Neoproterozoic intrusion emplaced in a core of synformal structure that deforms low-grade marine metasedimentary rocks of the Ribeira Belt of south-eastern Brazil. The lack of visible magmatic layering or any internal fabric has been a major limitation in deciding whether the emplacement occurred before or after the regional folding. To assist in the tectonic interpretations, we combine low-field anisotropy of magnetic susceptibility (AMS) and silicate shape preferred orientation (SPO) to reveal the internal structure of the mafic intrusion. Magnetic data indicate a mean susceptibility of about 10(-2) SI and a mean anisotropy degree (P) of about 1.08, essentially yielded by titanomagnetite. The magnetic and silicate foliations for P >= 1.10 are parallel to each other, while the lineations tend to scatter on the foliation plane, in agreement with the dominant oblate symmetry of the AMS and SPO ellipsoids. For lower P values, the magnetic and silicate fabrics vary from coaxial to oblique, and for P <= 1.05, their shapes and orientations can be quite distinct. The crystal size distribution (CSD) of plagioclase for P > 1.05 is log linear, in agreement with a bulk simple crystallisation history. These results combined show that for a strong SPO, corresponding to a magnetic anisotropy above 1.10, AMS is a reliable indicator of the magmatic fabric. They indicate that the Apiai gabbro-norite consists of sill-like body that was inclined gently to the north by the regional folding.

Habitat Fragmentation Effects on the Orchid Bee Communities in Remnant Forests of Southeastern Brazil

The effect of habitat fragmentation on the structure of orchid bee communities was analyzed by the investigation of the existence of a spatial structure in the richness and abundance of Euglossini species and by determining the relationship between these data and environmental factors. The surveys were carried out in four different forest fragments and one university campus. Richness, abundance, and diversity of species were analyzed in relation to abiotic (size of the area, extent of the perimeter, perimeter/area ratio, and shape index) and biotic characteristics (vegetation index of the fragment and of the matrix of each of the locations studied). We observed a highly significant positive correlation between the diversity index and the vegetation index of the fragment, landscape and shape index. Our analysis demonstrated that the observed variation could be explained mainly by the vegetation index and the size of the fragment. Variations in relative abundance showed a tendency toward an aggregated spatial distribution between the fragments studied, as well as between the sampling stations within the same habitat, demonstrating the existence of a spatial structure on a small scale in the populations of Euglossini. This distribution will determine the composition of species that coexist in the area after fragmentation. These data help in understanding the differences and similarities in the structure of communities of Euglossini resulting from forest fragmentation.

Polyphyly of the hawk genera Leucopternis and Buteogallus (Aves, Accipitridae): multiple habitat shifts during the Neotropical buteonine diversification

Abstract Background The family Accipitridae (hawks, eagles and Old World vultures) represents a large radiation of predatory birds with an almost global distribution, although most species of this family occur in the Neotropics. Despite great morphological and ecological diversity, the evolutionary relationships in the family have been poorly explored at all taxonomic levels. Using sequences from four mitochondrial genes (12S, ATP8, ATP6, and ND6), we reconstructed the phylogeny of the Neotropical forest hawk genus Leucopternis and most of the allied genera of Neotropical buteonines. Our goals were to infer the evolutionary relationships among species of Leucopternis, estimate their relationships to other buteonine genera, evaluate the phylogenetic significance of the white and black plumage patterns common to most Leucopternis species, and assess general patterns of diversification of the group with respect to species' affiliations with Neotropical regions and habitats. Results Our molecular phylogeny for the genus Leucopternis and its allies disagrees sharply with traditional taxonomic arrangements for the group, and we present new hypotheses of relationships for a number of species. The mtDNA phylogenetic trees derived from analysis of the combined data posit a polyphyletic relationship among species of Leucopternis, Buteogallus and Buteo. Three highly supported clades containing Leucopternis species were recovered in our phylogenetic reconstructions. The first clade consisted of the sister pairs L. lacernulatus and Buteogallus meridionalis, and Buteogallus urubitinga and Harpyhaliaetus coronatus, in addition to L. schistaceus and L. plumbeus. The second clade included the sister pair Leucopternis albicollis and L. occidentalis as well as L. polionotus. The third lineage comprised the sister pair L. melanops and L. kuhli, in addition to L. semiplumbeus and Buteo buteo. According to our results, the white and black plumage patterns have evolved at least twice in the group. Furthermore, species found to the east and west of the Andes (cis-Andean and trans-Andean, respectively) are not reciprocally monophyletic, nor are forest and non-forest species. Conclusion The polyphyly of Leucopternis, Buteogallus and Buteo establishes a lack of concordance of current Accipitridae taxonomy with the mtDNA phylogeny for the group, and points to the need for further phylogenetic analysis at all taxonomic levels in the family as also suggested by other recent analyses. Habitat shifts, as well as cis- and trans-Andean disjunctions, took place more than once during buteonine diversification in the Neotropical region. Overemphasis of the black and white plumage patterns has led to questionable conclusions regarding the relationships of Leucopternis species, and suggests more generally that plumage characters should be used with considerable caution in the taxonomic evaluation of the Accipitridae.