Search

Fruit availability experienced by different primate species is likely to vary due to species‐specific fruit use, even within the same habitat and timeframe. Pitheciines, primates of the subfamily Pitheciinae, particularly favor the seeds of unripe fruits. Researchers consider this dietary characteristic an adaptation to increase access to fruit resources. However, the relative advantages of pitheciines over sympatric non‐pitheciine non‐seed‐eating primates regarding species‐specific fruit availability is not well studied. In a 26‐ha forest within the city of Manaus, Amazonian Brazil, we assessed the wild‐food feeding behavior of free‐ranging groups of golden‐faced sakis (Pithecia chrysocephala) and sympatric common squirrel monkeys (Saimiri sciureus). We hypothesized that sakis would have greater and more consistent access to wild fruit due to (1) a wider variety of fruit species in their diet, and (2) longer consumption periods per fruit species. We recorded the plant species, part (pulp or seed), and developmental stage (ripe or unripe) of wild fruit consumed by both species. We also conducted monthly fruit censuses of 1000 trees and vines to estimate overall wild fruit abundance. As an indicator of fruit availability, we calculated the proportion of available fruiting trees and vines for each primate species separately based on their observed diet. Throughout the year, the proportion of available trees and vines was significantly higher and more temporally stable for sakis than for squirrel monkeys. This was because sakis used shared fruit species longer than squirrel monkeys by consuming both ripe and unripe fruit. Although sakis had a broader fruit repertoire than squirrel monkeys, it did not contribute to the higher fruit availability. Thus, the fruit feeding system of sakis identifies aspects of a niche that is less restricted in the timing of fruit consumption, which led to a relative advantage in fruit availability. Research Highlights: We examined the advantages of saki feeding system in fruit availability by direct comparison with sympatric squirrel monkeys.Sakis consumed fruits earlier and for longer periods than squirrel monkeys.The proportion of available fruiting trees/vines was considerably higher and more temporally stable for sakis than for squirrel monkeys. [ABSTRACT FROM AUTHOR]

Nonsessile animals could partition the use of resources in different axes, reducing the effects of competition and allowing coexistence. Here, we investigated the spatial and trophic niche dimensions in four lizard assemblages in the Neotropical semiarid Caatinga to investigate the determinants of resource use and the extent to which lizards partition their niches. We sampled each lizard assemblage once, for 10 days, in the dry season of 2017 and 2018. In two lizard assemblages, we detected nonrandom niche overlap patterns that were higher or lower than expected by chance. The high niche overlap patterns suggest that either there is intense current competition for available microhabitats or an abundance of microhabitats. The lower niche overlap may be influenced by the presence of species adapted to sandy habitats (psammophilous), suggesting that spatial partitioning detected has historical basis, which is supported by the pPCA results and by the lack of patterns in the realized niche distribution of species across niche space. We detected trophic niche partitioning in three lizard assemblages. In one assemblage, we discovered random spatial and trophic niche overlap patterns, revealing that competition is not a determining factor in the structure of that assemblage. In fact, phylogenetic effects were predominantly the main determinants of resource use in the four studied lizard assemblages. Arid and semiarid habitats cover about one third of land surface of the world. Comparisons between our findings and those from other regions of the world may aid identify general trends in the lizard ecology of dry environments. [ABSTRACT FROM AUTHOR]

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches. [ABSTRACT FROM AUTHOR]

Secondary forests and human-made forest gaps are conspicuous features of tropical landscapes. Yet, behavioral responses to these aspects of anthropogenically modified forests remain poorly investigated. Here, we analyze the effects of small human-made clearings and secondary forests on tropical bats by examining the guild- and species-level activity patterns of phyllostomids sampled in the Central Amazon, Brazil. Specifically, we contrast the temporal activity patterns and degree of temporal overlap of 6 frugivorous and 4 gleaning animalivorous species in old-growth forest and second-growth forest and of 4 frugivores in old-growth forest and forest clearings. The activity patterns of frugivores and gleaning animalivores did not change between old-growth forest and second-growth, nor did the activity patterns of frugivores between old-growth forest and clearings. However, at the species level, we detected significant differences for Artibeus obscurus (old-growth forest vs. second-growth) and A. concolor (old-growth forest vs. clearings). The degree of temporal overlap was greater than random in all sampled habitats. However, for frugivorous species, the degree of temporal overlap was similar between old-growth forest and second-growth; whereas for gleaning animalivores, it was lower in second-growth than in old-growth forest. On the contrary, forest clearings were characterized by increased temporal overlap between frugivores. Changes in activity patterns and temporal overlap may result from differential foraging opportunities and dissimilar predation risks. Yet, our analyses suggest that activity patterns of bats in second-growth and small forest clearings, 2 of the most prominent habitats in humanized tropical landscapes, varies little from the activity patterns in old-growth forest. [ABSTRACT FROM AUTHOR]

The present work aims to characterize a fish assemblage from a northeastern Brazilian estuary according to its diet and trophic organization along the estuarine-reef gradient. Sampling was performed at the Mamanguape Estuary and fishes were collected using three types of nets at seventeen sites, grouped into four regions according to salinity range: reefs and the lower, middle and upper estuary. The most abundant species were Atherinella brasiliensis, Mugil curema and Sphoeroides testudineus. The highest species abundance and richness was observed for the lower estuary. Zooplankton was the most consumed category, recorded for fortytwo species. Among the guilds, piscivores were the most abundant, followed by crab eaters. Herbivores, mostly represented by Abudefduf saxatilis, had a higher abundance in reefs, being correlated according to ANOSIM analysis to this region, while piscivores and crab eaters showed a high contribution to inner regions of the Mamanguape Estuary. [ABSTRACT FROM AUTHOR]

Aims The coastal Brazilian rainforest on white-sand (restinga) ranks among the most fragmented forest types in the tropics, owing to both the patchy distribution of sandy soils and widespread coastal development activities. Here we study the environmental and evolutionary determinants of a forest tree assemblage at a single restinga forest in Southeastern Brazil. We also explore the ability of competing hypotheses to explain the maintenance of species diversity in this forest type, which includes contrasting extremes of edaphic conditions associated with flooding stress. Methods The study was conducted in a white-sand forest permanent plot of 10.24 ha on the coastal plain of Southeastern Brazil. This plot was divided into 256 quadrats of 20×20 m, which were classified into two main edaphic habitats (flooded and drained). Trees with a diameter ≥1cm at breast height were identified. We assembled DNA sequence data for each of the 116 morphospecies recognized using two chloroplast markers (rbcL and matK). A phylogenetic tree was obtained using the maximum likelihood method, and a phylogenetic distance matrix was produced from an ultrametric tree. We analyzed similarity in floristic composition and structure between habitats and related them to cross-plot distances using permutation procedures. Null model torus shift simulations were performed to obtain a statistical significance level for habitat association for each species. The phylogenetic structure for the two habitats and for each 20×20 m quadrat was calculated using the mean phylogenetic distance weighted by species abundance and checked for significance using the standardized effect size generated by 5000 randomizations of phylogenetic tip labels. Important Findings Our results indicate that partitioning among edaphic habitats is important for explaining species distributions and coexistence in restinga forests. Species distributions within the plot were found to be non-random: there was greater floristic similarity within than between habitats, and >40% of the more abundant species were positively or negatively associated with at least one habitat. Patterns of habitat association were not independent of phylogenetic relatedness: the community was overdispersed with respect to space and habitat type. Closely related species tended to occur in different habitats, while neighboring trees tended to belong to more distantly related species. We conclude that habitat specialization is important for the coexistence of species in restinga forests and that habitat heterogeneity is therefore an essential factor in explaining the maintenance of diversity of this unique but fragile and threatened type of forest. [ABSTRACT FROM AUTHOR]

Competition plays a central role in the maintenance of biodiversity. A backbone of classic niche theory is that local coexistence of competitors is favoured by the contraction or divergence of species' niches. However, this effect should depend on the diversity of resources available in the local environment, particularly when resources vary in multiple ecological dimensions. Here, we investigated how available resource breadth (i.e. prey diversity) and competition together shape multidimensional niche variation (between and within individuals) and interspecific niche overlap in 42 populations of congeneric tropical frog species. We modelled realized niches in two key trophic dimensions (prey size and carbon stable isotopes) and sampled available food resources to quantify two-dimensional resource breadth. We found a 14-fold variation in multidimensional population niche width across populations, most of which was accounted for by within-individual diet variation. This striking variation was predicted by an interaction whereby individual niche breadth increased with resource breadth and decreased with the number of congeneric competitors. These ecological gradients also interact to influence the degree of niche overlap between species, which surprisingly decreased with population total niche width, providing novel insights on how similar species can coexist in local communities. Together, our results emphasize that patterns of exploitation of resources in multiple dimensions are driven by both competitive interactions and extrinsic factors such as local resource breadth.

The occurrence of treefall gaps has been hypothesized to maintain tree species diversity in tropical forests. To analyze this hypothesis for the Brazilian Atlantic montane rainforest, 558 tree and shrub individuals were sampled in 23 natural treefall gaps (29 to 256 m2) in two different sites of the forest. In both sites, the smallgaps were more abundant, occuping the majority of the area with gap disturbance. There was no evidence of regeneration niche partitioningamong species related to gap size; consequently gap size is not the best parameter to predict gap floristic and ecological composition. The gaps were preferentially colonized by typical understory species, which represented 50 to 60.5% of the total species sampled. Accordingto our results, the Atlantic montane forest has a low richness of shade-intolerant species (9.8 to 12.5% of the total sampled), particularly considering the large pioneers. Most of the shade-intolerant species sampled seems to regenerate successfully in other habitats. [ABSTRACT FROM AUTHOR]