Biotropica最新文献

Urban ecology and tropical biology have both developed rapidly in recent decades and matured into important interdisciplinary fields, with significant implications for biodiversity and human communities globally. However, urban ecosystems within the tropics remain understudied and poorly characterized despite these systems representing major hotspots for both biodiversity and human population growth. Here we review the state of the field of “tropical urban ecology.” We first evaluated and propose ecological hypotheses about how tropical versus extratropical species and ecosystems might differ from one another in how they respond to urbanization pressures. While data remain limited, we expect that tropical biodiversity should be at least as vulnerable to urbanization (and potentially more vulnerable) than extratropical biodiversity. We also examined the importance of ecosystem services in tropical cities and demonstrate the challenges in quantifying, managing, and sustaining these across diverse socioeconomic and environmental contexts. Finally, we propose an agenda for moving the field of tropical urban ecology forward through an interdisciplinary lens that synthesizes recent advances in both urban ecology and tropical biology. Specifically, advances and development in community science, Earth observation, environmental justice, One Health, and land sparing/sharing strategies could lead to major steps forward in the conservation of biodiversity in tropical cities. As the world urbanizes increasingly in biodiverse-rich tropical ecosystems, we must have strong conceptual frameworks and increased data/attention on both the ecological and human communities most impacted by these significant global changes.

Understanding how diversity responds to habitat heterogeneity in a landscape is a central issue for implementing effective conservation plans. In this study, we analyzed how the composition and abundance of neotropical bird assemblages vary among habitats in the Ñeembucú Wetlands Complex, the largest wetland system in Paraguay. Bird surveys were conducted during 1 year within dominant habitats in the landscape: riparian forests, natural grasslands, savannas, and anthropized sites. The Ñeembucú Wetlands Complex showed a high bird richness (209 species) that contrasted with a pattern of dominance by a small set of 16 species that comprised half of the abundance. This set of oligarchic species consists of generalist species that exploited a wide variety of habitats and were well adapted to human disturbance, contributing to an important overlap in the composition of assemblages. However, despite this overall similarity, there is still significant differentiation in bird assemblages, especially between habitats with the most contrasting vegetation physiognomy. Riparian forests and savannas showed higher diversity values than the more structurally homogeneous grasslands. Also, all natural habitats showed, in general, higher diversity values than anthropized sites. Oligarchic species had higher importance in anthropized environments, which also had the most uneven distribution of abundance between species, indicating the dominance by a smaller number of species and the loss of ecological diversity as farmland and urban development increase.

Abstract in Spanish is available with online material.

While variation in temperature appears to be the main environmental cue for plasticity in adult traits in many species of Mycalesina, relying on temperature would result in a mismatch between adult phenotype and environment in some regions. We measured phenotypes of six species of Bicyclus butterflies (Nymphalidae: Satyrinae: Mycalesina) in a humid tropical forest with two rainy seasons per year and modest unimodal seasonal temperature variation, such that temperature does not predict rainfall and butterflies can reproduce year-round. The butterflies showed subtle temporal variation in body size and relative eyespot size, while relative androconia length was robust to temporal environmental variation. After higher temperatures, body size tended be smaller, and relative eyespot size was larger for some species-eyespot combinations. This indicates that these butterflies follow the “hotter is smaller” rule, and show developmental plasticity in eyespot size that is typical in this clade. Eyespot sizes tended to be correlated with each other, except Cu1 in B. auricruda and some eyespots that always remained very small. Androconia length was not related to eyespot size. This pattern of correlations suggests conserved cue-use and shared mechanisms for eyespot size using both temperature and rainfall-related cues, with some exceptions.

Habitat degradation, a common consequence of land-use changes, reduces termite species richness. However, the impact of these changes on functional diversity remains poorly understood. This research aimed to assess the response of the taxonomic and functional diversity of termites in different land uses within the Colombian Amazon. Termites were surveyed in three habitat types (secondary forest, silvopastoral system, and agroforestry system) using a structured sampling design with 36 sampling points. Seven functional traits were measured from 30 individuals (worker caste) per species. We collected 23,140 individuals distributed in 2 families, 7 subfamilies, 50 genera, and 95 species. Results showed higher taxonomic diversity in the secondary forest compared to silvopastoral and agroforestry systems, which were similar. Likewise, the secondary forest presented higher functional species differentiation than the agricultural systems. Furthermore, land-use intensification led to changes in functional traits, with body size increasing in degraded habitats. This research provides significant evidence of the consequences of land use changes on the taxonomic diversity and functional traits of termites, emphasizing the importance of considering functional diversity responses in future research.

Research on impacts of subsistence hunting on habitat use and species communities of forest wildlife is limited. Subsistence hunting of mammals in one of the world's most biodiverse region, Manu National Park, Peru, is considered sustainable, but this is based on sparse evidence. We analyzed change in species relative abundance and functional composition of mammal communities, including non-hunted species along a hunting pressure gradient. We used camera trap data and tested for confounding effects of environmental and disturbance gradients (distances to rivers, lakes, settlements, and trails; NDVI at survey point). We found that sites with no hunting or at further distances from settlements harbor relatively more species with a larger body mass, long generation lengths, and small litters (primarily carnivores: 36% at non-hunted site vs. 13%–29% at hunted sites), indicating selective impacts of hunting pressure on mammal communities. However, all carnivore species still occurred at all sites. Species with a smaller body mass, short generation lengths, and large litters were more prevalent at the hunted sites (mostly rodents: 23%–31% at hunted sites vs. 20% at non-hunted site). Surprisingly, large herbivores appeared unaffected by hunting despite being one of the most hunted mammals in Manu (25% at non-hunted site vs. 23%–27% at hunted sites). Our findings suggest that current hunting pressure is largely sustainable with only local depletion of a few sensitive species. Habitat is more important for some species than hunting pressure (e.g., distance to lake), further emphasizing the importance of local forest management.

Lianas are important to rainforest ecosystems but often impede tree growth and increase tree mortality and stem damage after disturbances that favor their growth. Understanding how lianas affect biomass recovery and rates of carbon sequestration following disturbance is therefore of crucial importance. In this study, we determine how a tropical forest recovers biomass following a large-scale disturbance, and test how this varies with liana dominance and stem damage. We use remote sensing methods to develop a model, validated by field data from 40 20 × 20 m vegetation plots, to measure the change in tree aboveground biomass 8 years after Tropical Cyclone Yasi damaged logged forests in the Australian Wet Tropics. We related tree biomass changes to field measures of current liana dominance over trees, expressed as liana: tree basal area ratio, and assessed how these measures related to tree stem damage. Biomass declined in 34 of the 40 plots during the 8 years post-disturbance, with loss rates and proportions of damaged tree stems increasing with the liana: tree ratio. From spatial upscaling, we found a net loss in biomass across the study landscape over the same period. Our results show that, following disturbances, lianas not only limit tree biomass recovery but also are associated with further biomass declines, most likely through their contribution to stem damage and delayed mortality. Furthermore, our finding of net biomass loss across the landscape since the cyclone shows that, post-disturbance, rainforests can act as a carbon source with consequences for the global carbon sink.

Leaf shelters function as microclimatic refuges, reducing arthropod exposure to climatic fluctuations of surrounding habitats. Although facilitation is expected to increase under stressful conditions, empirical studies investigating the patterns of variation and magnitude of effects of ecosystem engineering (EE) at different spatial and temporal scales are still scarce. In this study, we evaluated the facilitation consequences of leaf shelter created by gall-inducers on arthropod communities of Miconia ligustroides (DC.) Naudin (Melastomataceae). We evaluated how such effects change at the leaf and plant levels in a habitat subject to strong climatic seasonality. The presence of leaf shelters on M. ligustroides increased arthropod diversity and biomass, modified the species composition at both the leaf and plant levels, during wet and dry seasons. However, the addition of artificial leaf shelters during the dry season showed greater abundance, richness, and biomass of arthropods when compared to shelters added during the wet season. Regarding the global effects of artificial leaf shelters on the diversity of arthropods associated with M. ligustroides, the dry season showed strong and positive effects, increasing the abundance, richness, and biomass of arthropods by an average of 65% for both years. Our study contributes to a better understanding of the patterns of variation and magnitude of EE at different spatial and temporal scales and provides new insights into the importance of shelters for aridity-sensitive species.

The structure and dynamics of forest ecosystems are the outcome of differential performance playing out at the individual level. Interactions between the traits of an organism and its environment determine performance. Thus, our ability to understand and, ultimately, model forest dynamics critically relies on knowledge regarding the functional biology of the organisms. In tropical forests, this is a daunting challenge due to the diversity of the systems. This has driven ecologists to focus on identifying a handful of fundamentally important trade-offs and a few traits that may indicate where a species falls along that trade-off axis. In other cases, some ecologists have argued that species can be roughly binned into a handful of functional groups or guilds that capture most of the information needed to generate realistic models of forest dynamics. Here, we discuss the functional biology of tropical forest dynamics. We identify a series of key trade-offs that should underpin forest dynamics and the traits ecologists have attempted to link to these trade-offs. We then explore how far we can get by using functional groups or guilds to model tropical forest dynamics, the conceptual frameworks used for promoting such approaches, and what this modeling framework does not capture. We then use this to identify key gaps that should motivate the future of tropical tree functional ecology.

Natural history provides an important basis for observing interactions between organisms in their environments. Biotropica recently inaugurated a new paper category called “Natural History Field Notes” to provide an outlet for such studies. Depicted here are drawings and observations by the author from research trips.

Already threatened by deforestation, the Brazilian Cerrado—a complex and biodiverse tropical savannah that provides important ecosystem services—could experience climate warming of 1–5°C by 2100. This could negatively impact sexual reproduction (considered particularly sensitive to temperature stress) in native plant species, potentially limiting the production of viable pollen, fruits, and seeds; however, such impacts are largely unstudied in wild tropical species. To investigate the potential effects of higher temperatures on Cerrado species reproduction, developing inflorescences of common and widespread tree Byrsonima pachyphylla (Malpighiaceae) were passively heated in situ from an early bud stage (by 3–4°C during the daytime). Viability of pollen samples (analyzed through in vitro pollen germination and differential pollen staining) and fruit set (the proportion of hand-pollinated flowers that developed into mature fruit) were compared between heated and control (ambient temperature) inflorescences, hypothesizing that both would be lower in heated inflorescences. However, higher daytime temperatures had no impact on viable pollen production, suggesting a strong resilience to warming. Nevertheless, fruit set was significantly reduced, which could have serious implications for future species recruitment and potentially Cerrado community structure, insect and animal food chains, and human populations, especially if representative of other Cerrado species. To the best of our knowledge, this experiment is the first manipulative warming of Cerrado vegetation in situ. It provides initial insights into the effects that increasing temperatures could have on future reproductive success and demonstrates the importance of considering reproduction when evaluating the possible impacts of climate change on tropical ecosystems.

Abstract in Portuguese is available with online material.