Biotropica最新文献

The Amazonian primate Chiropotes albinasus (red-nosed cuxiu) is a specialist on seeds of hard-husked unripe fruit. These are accessed with specialized processing behavior, involving highly modified canines and incisors. This is energetically demanding and carries a high dental damage risk. Hypothesizing that red-nosed cuxiu process foods in ways that minimize both energetic expenditure and maximize dental safety, we predicted that individuals would selectively bite fruit husks at locations that were easiest to penetrate. Sutures were the easiest area to penetrate for all the 11 analyzed red-nosed cuxiu diet species with functioning (non-fused) sutures. Quantification of bite mark locations on these fruits showed significant clustering along the lower-penetrability areas (sutures) in 8 of 11 species (72.7%). This pattern did not exist for another 10 species that lacked sutures; bites did not cluster on the thinnest (and most easily penetrated) parts of the husk for 9 of these 10 species (90%). For four species that were functionally indehiscent due to fused or thick sutures, penetrability was lowest at the face (2 species) and suture (2 species). Thus, despite robust crania, mandibles, and dentition that appear highly suited for resisting forces generated by powerful biting action, red-nosed cuxiu deploy a more refined technique and often select the weakest areas of fruits for their seed-accessing bite sites, especially when the fruits are dehiscent with unfused sutures.

Anthropogenic activities such as livestock grazing and agriculture drive the conversion and homogenization of ecosystems. These impacts lead to local extirpations and changes in native species abundance and distribution, particularly in biodiversity-rich tropical regions where agricultural frontiers expand. The giant anteater (Myrmecophaga tridactyla), a large mammal species, has been affected by land use changes. However, little is known about the role of landscape features in predicting its mean relative abundance in agricultural landscapes. To address this gap, we evaluated the influence of landscape composition and configuration on mean relative abundance. We sampled 55 landscapes in a transition zone between two hotspots, the Atlantic Forest and Cerrado biomes, where most of Brazil's agricultural commodities are produced. The giant anteater occupied most of the study area, and its mean relative abundance varied little among sampled landscapes. Mean relative abundance was positively related to the proportion of remaining native forest. In landscapes with < 50% native forest, the predominant scenario in our region, mean relative abundance increases slightly with edge density and decreases slightly with distance between native vegetation patches. Vast monocultures with little native forest may force the giant anteater to explore edges for resources, affecting thermoregulation and increasing human conflict. Our findings support the assertion that small patches of native forest play an important role in wildlife conservation. Native forest and connectivity between vegetation patches are crucial for the persistence of this charismatic and endangered mammal in landscapes heavily modified by agricultural activity.

Environmental filtering and ecological interactions can shape the phylogenetic structure of coexisting species. Given the high mortality rates early in plant development, studying the relative roles of these processes in structuring seedling communities across habitats highlights the importance of specialization in the regeneration niche. Additionally, because seedlings interact at fine spatial scales, focusing on smaller assemblages and source pools is essential. We analyzed the phylogenetic structure of seedling communities in a white-sand tropical forest mosaic on the southeastern coast of Brazil, influenced by seasonal flooding and varying soil conditions. We tested whether the occurrence- and abundance-based mean phylogenetic distance of seedling assemblages in three forest types differed from null expectation at both habitat and neighborhood scales and evaluated the influence of dispersal limitation by quantifying the proportion of seedling species also present as adults nearby. At the habitat scale, poorer sandy soils filtered closely related species, while the flooded habitat favored distantly related species, likely due to the effects of natural enemies. However, we cannot rule out the role of neutral processes and dispersal limitation, given the random phylogenetic patterns when species abundance was considered. At the neighborhood scale, assemblages with very closely related species were rarer than expected in all three forest types, emphasizing the role of ecological interactions at short distances. As seedling species occurrence within neighborhoods was not strongly associated with the presence of adults nearby, we argue that seedling phylogenetic structure results from processes acting on the regeneration niche rather than merely reflecting adult patterns.

Understanding the factors influencing the dynamics of natural populations is essential for mitigating the impacts of anthropogenic changes. Here, we investigate the effects of climate, microclimate, and ecophysiology on the demography of Tropidurus oreadicus, an endemic lizard found in the Brazilian Cerrado savannas. In a vegetation gradient, we monitored the lizards monthly for 4 years using a mark-recapture protocol with pitfall traps. We conducted ecophysiological experiments with 20 individuals and used microclimatic temperatures to estimate hours of activity and locomotor performance for each trap and month. Throughout this period, we made 598 captures and recaptures of 372 individuals. Environmental variables could not explain the determinants of population growth, such as survival and recruitment. Instead, these demographic parameters appear to fluctuate due to the size-structured seasonal variation of the population each year and negative density dependence relationships. We identified a strong correlation between recruitment and the rainy months, with peaks occurring in December and January. Precipitation and locomotor performance were good predictors of capture probability and abundance of T. oreadicus. We captured more lizards in the driest months, while abundance increased in the rainy season when locomotor performance was at its highest. Thus, our results suggest that the seasonal availability of microhabitats that optimize locomotor performance is a key selective pressure that has shaped the reproductive timing of T. oreadicus, a mechanism likely crucial for other ectotherms. Stochastic and anthropogenic changes in precipitation and microclimatic temperatures may hinder T. oreadicus abundance, jeopardizing the local population's persistence.

Aquatic hyphomycetes species traits are critical for organic matter processing in low-order streams. This study evaluated the functional diversity of hyphomycetes associated with Nectandra angustifolia leaves in tropical and subtropical streams, presenting data on sporulation rates, species abundance, and decomposition rates. We examined Functional Richness (FRic), Divergence (FDiv), Dispersion (FDis), and Evenness (FEve) in aquatic hyphomycete assemblages, relating these to environmental variables such as temperature, pH, dissolved oxygen, and electrical conductivity. In tropical streams, poor leaf quality promoted wood saprotroph and foliar endophyte dominance. Moreover, our findings indicated increased functional diversity (FRic and FDis) in subtropical streams compared to tropical streams, reflecting larger conidiophores, diverse conidia shapes, and the prevalence of litter saprotrophs. We also linked colder waters to an increase in trait diversification. Additionally, environmental fluctuations, such as cooler temperature, more dissolved oxygen, and neutral pH, increased FRic, which reflects greater dissimilarity among co-occurring taxa. Our results underscore the significant role of water properties in shaping aquatic hyphomycete assemblage functional diversity.