Biotropica最新文献

Gut passage is an important but understudied component of animal-mediated seed dispersal that can impact germination and survival. Melastomataceae plants are abundant and ecologically important throughout the tropics, but studies have obtained contrasting results regarding effects of avian gut passage on melastome germination. We conducted a paired germination experiment to test how gut passage by four species of manakins—key avian dispersers of melastomes—affects germination of the pioneer melastome shrub Miconia rubescens. Manakin gut passage accelerated M. rubescens germination, with gut-passed seeds germinating an average of 5.1 days earlier than controls, and percent germination of gut-passed seeds was significantly higher at 20 and 40 days post-planting. Interestingly, manakin species varied in their gut passage effects, with L. velutina having stronger overall germination effects than M. manacus. Within species, greater body mass was correlated with higher percent germination and shorter times to first germination. Within M. manacus, seeds passed by females had significantly shorter times to first germination than seeds passed by males. Because control seeds were manually depulped in the experiment, the observed gut passage effects are likely attributable to minor scarification of the seed coat during gut transit. Our results suggest manakin gut passage can have biologically meaningful impacts on melastome germination, and the magnitude of these effects can vary based on manakin species, mass, and sex. This study refines our understanding of the “quality” component of seed disperser effectiveness in an iconic dispersal mutualism, with implications for plant community composition and recovery of deforested neotropical ecosystems.

Abstract in Spanish is available with online material.

Studying plant–herbivore interactions within tropical rain forests is fundamental to understanding their ecology and evolution. An important aspect of plant–herbivore dynamics is the role of temporal and taxonomic variables in determining associations between herbivores and their host. Using the diverse and chemically rich plant family Annonaceae (Magnoliales), we conducted a year-long study in Ecuador's Yasuní National Park in lowland Amazonia. We focused on nine understory tree species across a broad phylogenetic range within Annonaceae. For these species, we investigated patterns of herbivory, identified herbivores through DNA barcoding, and documented unique ant–butterfly associations. In general, leaf damage ranged from 0.09% to 25%, with significant temporal fluctuations for three species. Notably, Anaxagorea brevipes and Unonopsis veneficiorum faced higher herbivore pressure when compared to the other studied species. We document a discreet but diverse herbivore community, with 40 larvae from 12 Lepidoptera families collected throughout the year. Our findings identify, for the first time across a phylogenetically diverse sampling of Annonaceae, the specialization of herbivores on our focal species. Overall, our data provide valuable information on herbivory patterns at the local scale for this important rain forest plant family. Furthermore, these findings contribute to our understanding of the ecological processes that influence plant species diversity in tropical rain forests.

Abstract in Spanish is available with online material.

Present-day Amazonia has an impoverished fauna of large folivorous mammals by comparison with African rainforests, but recent fossil discoveries suggest that late-Quaternary anthropogenic extinctions could account for most size and trophic faunal mismatches. The extent to which modern Amazonian ecology may be an artifact of prehistoric human intervention merits periodic re-evaluation as paleontological evidence of the Pleistocene megafauna continues to emerge.

We observed male euglossines collecting scent at 21 different non-floral sources in Central and South America, strengthening the view that these sources play a central role in euglossine perfume biology. A Protium tree provided over 50% of the perfumes for Eufriesea corusca and was repeatedly revisited. The co-occurrence of females collecting resin suggests an evolutionary link to male perfume-making.

Abstract in Spanish is available with online material.

Seedlings frequently suffer the highest mortality rate, as they have different requirements for growth and survival from their mature life cycle stage. However, the links between functional traits and photosynthetic traits of tree seedlings, especially from dry evergreen forests, remain largely unexplored. Here, we measured eleven functional traits and six photosynthetic traits of thirty species of tree seedlings from the seasonally dry evergreen forest in Southeast Asia. We explored the relationship between traits and photosynthesis, compared them with their canopy layers when mature, and classified growth strategies. The results showed that photosynthetic measurements were highly correlated with seedling growth traits. The measured functional and photosynthetic traits did not correspond with the canopy layers of the mature trees. Through k-mean clustering analyses of the tree seedling trait data, two main groups of growth strategies emerged: (1) the “fast-growing” group, which mainly consists of shade-intolerant or -avoidance species; and (2) the “slow-growing” group, which consists of shade-tolerant species. This finding can be applied by future practitioners to select tree seedlings accurately based on their juvenile physiology, which is fundamental to the success of species selection for forest restoration in the face of global climate change.

Large carnivores play a crucial role in trophic cascades, affecting the population dynamics of both co-predators and prey within an ecosystem. Understanding the significance of these carnivores in trophic interactions is essential for developing effective conservation and management strategies. We examined the effects of occupancy dynamics and patterns of species interactions and coexistence within the carnivore guild in the Panna Tiger Reserve in India. We collected camera trap data (two seasons, 2019) in a presence–absence framework and applied multispecies occupancy models to assess the occupancy, co-occurrence, and interactions among species. We also examined activity overlap to understand the temporal segregation in the carnivore guild. The mean marginal occupancy was highest for leopards in winter (Ψ_winter 0.92 ± 0.02, Ψ_summer 0.63 ± 0.05) and hyenas in summer (Ψ_summer 0.93 ± 0.03, Ψ_winter 0.78 ± 0.03) and was lowest for tigers in both seasons (Ψ_winter 0.62 ± 0.05, Ψ_summer 0.15 ± 0.05). Co-occurrence probability among carnivores was higher in winter than in summer, and conditional occupancy was consistently higher when other species were present. Different environmental factors influenced marginal occupancy and co-occurrence patterns across seasons. Strong temporal overlaps were recorded between tiger–leopard (0.87–0.91) and tiger–hyena (0.78–0.79). We detected a significant spatial segregation between tigers and leopards, as they prefer different habitat types in different seasons, along with high temporal overlap. Resource availability strongly governs the association of carnivores with their habitat selection. Hyenas demonstrated higher dependency on tigers than on leopards for resources. These findings indicate that coexistence with apex-predator species is feasible through strategic adaptation to fulfill resource requisition.

Large old trees (LOTs) are invaluable natural treasures and cultural legacies, holding ecological, historical, social, and economic significance. However, climate change and human impacts threaten their existence. Understanding their species composition, age structure, biomass, and distribution patterns in relation to environmental factors is essential for effective conservation. In Hainan Island, South China, we analyzed 1081 LOTs from 74 species across 35 families, using a combination of field surveys and government data. The dominant families were Moraceae, Sapindaceae, and Fagaceae, with key species including Ficus altissima, Litchi chinensis, and Tamarindus indica. The age distribution followed a reverse J-shape, indicating a prevalence of trees aged 300–399 years. In contrast, diameter at breast height (DBH) and height distributions were unimodal, favoring medium to large-sized trees. Spatial analysis revealed uneven distribution patterns: the western zone exhibited the highest species diversity, the central zone moderate diversity, and the eastern zone low diversity, reflecting uneven urban and agricultural impacts. Most LOTs were concentrated at elevations of 0–50 m. Factors such as GDP, urbanization, and forest cover positively correlated with LOT abundance and diversity, with forest cover and average annual temperature particularly favoring these trees. The findings emphasize the intricate relationship between environmental factors and LOT distribution. They advocate for tailored conservation strategies that address the complex interplay of ecological, socioeconomic, and cultural influences on their preservation.

Abstract in Chinese is available with online material.

Mutualistic interactions between species are widespread and important for community structure and ecosystem function. In a changing environment, the proximate mechanisms that maintain mutualisms affect their stability and susceptibility to perturbation. In ant-plant mutualisms, ants defend their host plants against herbivores or competing plants in exchange for housing or food. While the phenomenon of species exchanging services for resources is well documented, how such arrangements are maintained is not. There are at least four hypothesized mechanisms through which plants use sugar to induce ant defense against herbivores. Three such hypotheses (“deficit”, “fuel for foraging”, “predictable rewards”) predict that the appearance of a new sugar source near the host plant would increase the rate of ant attacks against herbivores, but the fourth hypothesis (“attract and distract”) predicts the opposite. To examine how the mutualism between Triplaris americana and Pseudomyrmex dendroicus would be affected, we simulated the appearance of a novel sugar source at a random half of 34 T. americana trees with P. dendroicus colonies. Compared to control colonies, those with access to the sugar source were less likely to attack herbivorous insects (Nasutitermes sp. termites). Thus, our findings support the “attract and distract” hypothesis. We infer that this ant-plant mutualism could be destabilized by the appearance of an alternative sugar source, such as a nectar-producing plant or honeydew-excreting insect. More broadly, we conclude that the mechanisms responsible for maintaining mutualistic relationships are relevant for understanding how ecological communities are affected by environmental change.

Abstract in Spanish is available with online material.

The ecosystems of The Tropics comprise a majority of the planet's biodiversity, approximately 40% of its terrestrial surface area, and half the human population. Despite this, Tropical Biology has historically been conceptualized as a specialized subdiscipline of the Biological Sciences. I assessed the validity of this assumption and conclude that it depends on the framework and evidence used to evaluate it. I suggest that the way forward as a discipline is not for Tropical Biologists to drop the geographic adjective that unites them, but to recenter The Tropics as the foundation of ecology and evolutionary biology.

Abstract in Spanish is available with online material.

Change in land-use patterns affects a landscape by changing the composition of local flora and fauna. The lateritic plateaus in Konkan are one such example of this rapid land-use change. Although these plateaus are rich in endemic flora and fauna, they are considered as “wastelands” due to lack of woody vegetation and thus, are subjected to various land-uses. Mango cultivation in this region has become a major source of income due to its Alphonso variety of mangoes. Hence, over the last few decades, many plateaus have been converted into mango orchards. However, how the conversion of plateaus to mango orchards has affected species composition of different groups of organisms remains unclear. In the present study, we sampled the lateritic plateaus and plateaus converted into mango orchards in Ratnagiri, Maharashtra, to investigate the response of the reptile communities. We observed more species heterogeneity in the orchards compared to the unaltered sites. Moreover, it appeared that there was a species turnover when the plateaus were converted into orchards. The generalist and widespread species such as agamids and skinks and very few specialist species were comparatively more abundant in the orchards. On the contrary, the plateaus without orchards harbored more specialist species such as Hemidactylus albofasciatus (n = 62, in unaltered sites vs. n = 5 in the orchards), Echis carinatus (n = 15 in unaltered sites and none in the orchards) and Ophisops jerdonii (n = 45 in unaltered site vs. n = 12 in the orchards) compared to the generalist species.