Biotropica最新文献

Interspecific interactions play an important role in structuring wildlife communities. On islands, which often have reduced species assemblages, species may expand their niches resulting in unusual patterns of interactions with other members of the ecological community. In this study, we compared spatio-temporal interactions of two food competitors between a site with predators and two predator-free islands in the Coiba archipelago, Panama. Here, capuchin monkeys (Cebus capucinus imitator) exhibit high levels of terrestriality, and some groups engage in stone tool use. This potentially leads to competition with sympatric agoutis (Dasyprocta coibae), which have overlapping diets. We used camera-trap surveys to estimate temporal overlap between both species, distinguishing between arboreal and terrestrial activity of capuchins. We also compared detection rates and intervals between consecutive detections of both species at sites in which the monkeys use stone tools (tool-use area) and sites in which they do not (non-tool-use area). We found high spatio-temporal overlap between agouti and capuchin on the forest floor of both islands. While capuchins visited the tool-use area four times as often as the non-tool-use area, agoutis avoided the tool-use area, capture rates being 25 times as low. Waiting times were shorter for both species at the tool-use area. These results suggest temporal overlap and spatial segregation. Niche expansions on islands thus cause unique interactions that do not occur on the mainland.

Abstract in Spanish is available with online material.

Forest degradation and hunting are two major drivers of species declines in tropical forests, often associated with forest production activities and infrastructure. To assess how the medium-to-large bodied terrestrial vertebrate community varied across these two main gradients of anthropogenic impact, we conducted a camera-trap survey across three production forest reserves in central Sabah, Malaysian Borneo, each with different past and current logging regimes. We analyzed data from a 32-species community using a Bayesian community occupancy model, investigating the response of occurrence, diversity, and composition to forest degradation and accessibility (a proxy for hunting pressure). We found forest degradation to be a strong driver of occurrence of individual species. Such responses led to declines in diversity and shifts in community composition, where forest-dependent species decreased while disturbance-tolerant species increased in occupancy probability with increasing forest degradation. Accessibility had a weaker effect on community diversity and species occupancy, and low-level hunting pressure and management of access to our study sites likely played an important role in mitigating accessibility effects. Nonetheless, our results showed accessibility had compounding effects on a wildlife community already affected negatively by forest degradation. Despite the impacts of forest degradation and accessibility on the terrestrial vertebrate community, our results highlight how the application of more sustainable practices—reducing forest disturbance and managing unauthorized access to logging roads—resulted in more intact wildlife communities. Understanding how both disturbances combined affect the terrestrial vertebrate community is essential for evaluating and developing effective sustainability guidelines.

Abstract in malay is available with online material.

Habitat loss and fragmentation are the greatest threats to reptiles and amphibians (herpetofauna) around the globe, but especially in the Neotropics where high diversity and ongoing land-use change coincide. Persistence of biodiversity in fragmented systems relies both on characteristics of habitat patches, and on the permeability of the landscape that separates the patches (the “matrix”). We sought to understand: (a) how the herpetofauna community differs between forest reserves, patches, corridors, and matrices, and (b) the landscape characteristics that increase suitability of a habitat patch. We conducted herpetofauna surveys in patches, corridors, matrices, and preserves (54 total sites) in a fragmented landscape in Costa Rica for three seasons. We recorded 1663 individuals of 52 species. We found that the herpetofauna community differed, and had lower richness and abundance, in the matrix compared to the other three habitat types. Patches and corridors supported a similar community to the forest preserves, demonstrating the conservation value of small forest remnants. Water body presence was an important predictor of richness and abundance in both patches and matrices. While total richness increased in patches with more edge, this was driven by the response of generalist species, whereas the prime indicator species of forest preserves decreased in patches with complex shapes. The differing response to landscape characteristics between specialist and generalist species demonstrates the importance of considering specific taxa when setting conservation goals, rather than using richness measures alone. Our findings can help guide preservation of forest fragments to optimize biodiversity conservation in mixed forest-pastoral landscapes.

Abstract in Spanish is available with online material.

The presence of invasive species in the environment can be highly detrimental. The success of these species depends on their interaction with native ones. The prey–predator relationship between invasive and native species can result in biodiversity loss or the introduction of new food items for local predators. Due to its tropical and extensive nature, Brazil is vulnerable to the colonization of invasive species. Snakes are a group of animals that can act as both predators and prey for invasive species. The pitviper Bothrops jararaca is an abundant and widely distributed native species on the Brazilian coast. Based on this, we conducted a study on the feeding preferences of naive B. jararaca juveniles regarding invasive and native prey. We found that this species exhibits a greater preference for native anurans compared to Rana catesbeiana, an invasive amphibian associated with significant environmental impacts. Additionally, the gecko Hemidactylus mabouia, a prey that triggered intense predatory responses from the pitviper, reveals that this species, even with a short period of coexistence with B. jararaca, has established an intense prey–predator relationship. The negative correlation between prey size and feeding interest, guided solely by olfactory cues, adds a layer of complexity to understanding the feeding choices of B. jararaca, providing valuable insights for conservation and environmental management strategies.

Abstract in Portuguese is available with online material.

Understanding elevational range size distribution of organisms can provide valuable insights on biogeographic pattern of species and their conservation. Rapoport's rule posits that the elevational range size of species increases with increasing elevation. However, the validity of this rule is often questioned due to variations in methodologies across studies and inconsistencies among different groups of organisms. In this study, we examined the elevational range size distribution of butterflies in the Eastern Himalaya, and assessed the applicability of Rapoport's rule using different approaches, which perhaps is the first of its kind in the Himalaya. We sampled butterflies along the elevational gradient of 16 elevational bands (300–3300 m) using point count method along the transect. The sampled butterflies were grouped into various sub-groups based on family, biogeographic affinity, and larval feeding pattern. We found that the majority of the butterfly species (total as well as sub-groups) had small range sizes, and their elevational range distribution showed support for the Rapoport's rule. Increase in variation in temperature as measured by temperature seasonality and mean annual temperature range were the most important predictors of range size distribution pattern of the overall butterfly community. However, the relationship between range size and climatic variability differed among various sub-groups implying that the perceived pattern may vary even within the species of the same taxon.

Abstract in Nepali is available with online material.

Zoophilous flowering plants have features to attract their pollinators, which may also be used by exploiters like nectar robbers. Nectar robbers access nectar by probing flower corollas (primary robbing) or use existing holes (secondary robbing). Nectar robbing can negatively impact a plant's fitness directly by damaging the reproductive structures of the flower or indirectly by modifying the visitation patterns of pollinators. We tested the hypothesis that the robbed flowers are less visited by legitimate pollinators by comparing floral visitors and visitation frequency in primary-, secondary-, and un-robbed flowers of Tecoma fulva spp. Altoandina, a native shrub species that is an important nectar source for nectarivores in the dry valleys of the Bolivian Andes (Bignoniaceae). The Giant Hummingbird, Patagona gigas (Trochilidae), was the main visitor of T. fulva and visited more frequently un-robbed flowers, followed by secondary robbed and primary robbed flowers. The variation in visitation frequency may result in less pollen transport to robbed flowers, which may have negative consequences for the biological fitness, probably manifested in decreased seed production.

Abstract in Spanish is available with online material.

Degradation and loss of riparian vegetation are some of the main drivers of change in the trophic interactions among aquatic macroconsumers. These changes can often have major consequences for biodiversity and stream ecosystem functioning. Yet, many aspects of food-web dynamics are still not well understood, including how food webs among tropical streams respond to riparian vegetation loss. We examined the role of macroconsumers on community structure of functional feeding groups of benthic macroinvertebrates along a forest cover gradient within the Bodoquena Plateau, Brazil. We compared the effect of excluding macroconsumers (using electric fences) on functional feeding groups to those in controls within seven karst streams along a gradient of riparian vegetation cover. Aquatic insect and gastropod communities were dominated by groups of collector-gatherers, scrapers, and predators across all sites. The exclusion of macroconsumers did not lead to an increase in the abundance of macroinvertebrates and was not affected by the forest cover during the experiment. These findings demonstrated that the experimental exclusion of macroconsumers resulted in a lack of or negligible effect on functional feeding groups along the gradient of forest cover. It is important to consider the specificity of trophic relationships to fully understand the effects of vegetation loss on streams where complex groundwater hydrology can also affect food webs such as in karst terrain.

Abstract in Portuguese is available with online material.

Shifting agriculture and anthropogenic fires are among the main causes of deforestation in the tropics. After fire and land abandonment, vast deforested areas are commonly dominated by the bracken fern Pteridium for long periods. Although forest regeneration in bracken-dominated areas is mainly hindered by dispersal limitation, little is known about the role of seed-disperser communities in slow forest succession. Our objective was to unravel the differences in the properties of the seed-disperser communities between forests and bracken-dominated areas to assess their role in dispersal limitation to foster ecological restoration. We compared species richness, diversity, abundance, and composition of seed-dispersing birds, bats, and medium and large terrestrial mammals between both habitats in a montane forest of Bolivia. The species richness and diversity were similar for bats and higher for birds in bracken-dominated areas than in the forest, but species composition was different between both habitats and groups. Although species composition was similar between both habitats for terrestrial mammals, the abundance was higher in the forest than in bracken-dominated areas. Differences in species composition of seed-dispersing birds and bats could be one of the main causes of dispersal limitation in forest regeneration in tropical bracken-dominated areas. The few shared species between both habitats could explain the low seed rain of animal-dispersed forest tree species in bracken-dominated areas and the consequent hindered forest regeneration. Future studies relevant to natural forest regeneration should focus on analyzing the effects of animal-attractants such as perches, artificial bat-roosts, and seedling transplants on disperser communities, seed dispersal effectiveness, and forest regeneration.

Abstract in Spanish is available with online material.

Global warming is expected to shift the distribution ranges of many species towards higher latitudes and altitudes. This will rewire plant-herbivore food webs as new combinations of herbivore species encounter novel host plants. We investigated the effects of a simulated altitudinal shift in an herbivore-host community of bark and ambrosia beetles on fig trees in a tropical mountain forest on Mt. Wilhelm, Papua New Guinea. We reared beetles from wood baits cut from five local Ficus species in their natural altitudinal ranges, between 200 and 1700 m a. s. l. Further, we transplanted baits from three of these tree species 500 m below the limits of their natural distribution range, to simulate a mean temperature increase of 2.7°C. Beetle species richness declined, and their species composition changed with increasing elevation. Furthermore, while altitude explained a large proportion of variance in beetle composition, host tree species was more important for bark beetles than ambrosia beetles. Beetle communities that assembled on the transplanted baits were similar in diversity and host specificity to those on the fig trees native to the same elevation, but also contained a number of unique species. Overall, these results indicate that saproxylic beetles in this tropical forest are highly resilient and flexible to the potential effects of climate change.

Abstract in Česky is available with online material.

Reasons for geophagy (soil consumption) by herbivorous animals have long been debated. We provide direct evidence of artificial sodium (Na) enrichment driving geophagy by capybaras (Hydrochoerus hydrochaeris), a large herbivore in western Amazonia.

Abstract in Spanish is available with online material.