Biotropica最新文献

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.

Thermal variation over space and time shapes global patterns of biodiversity and responses of species to climate change. Vertical microclimate gradients from the understory to the canopy mediate biogeographic patterns of arboreal species across larger spatial scales. Yet, the magnitude to which microhabitats in the canopy, such as large epiphytes, alter the exposure of arboreal species to hot and variable canopy conditions across biogeographic gradients is not well known. We first examine the extent to which maximum temperatures and temperature variation in epiphytic bird's nest ferns (BNFs) and the understory are lower than those in the canopy across an elevation gradient in the Philippines and the environmental factors influencing these differences. We find that differences in maximum temperatures (i.e., offset) and temperature variation (i.e., buffering) between the canopy and BNFs are greater than differences between the canopy and understory. Offset and buffering are largest when canopy temperatures are high and are positively impacted by precipitation. Furthermore, we address the theory that exposure to higher thermal variation in the canopy may increase the range sizes of arboreal species. We find that lower thermal variation over time in BNFs reduces the thermal overlap between low and high elevations relative to canopy temperatures. Arboreal species that shelter in BNFs during the day may therefore have narrow physiological tolerances and consequently smaller elevational ranges. By providing thermal regimes more similar to the understory than the canopy, BNFs may therefore effectively function as “arboreal soil”, mediating impacts of arboreality on patterns of biodiversity and trait variation.

Unsustainable harvesting of orchid species is a critical, global threat to orchid diversity and abundance, fueled by domestic and global demand. However, drivers of demand continue to be under-explored, despite opportunities for proactive engagement and/or behavior change strategies with and/or directed at orchid collectors. In this study, we surveyed self-identified Vietnamese orchid collectors, some of whom were also known to engage in wild harvesting of endangered species, to understand sociological dimensions including motivations, knowledge, attitudes, behaviors, and conservation ethos. We found that knowledge about domestic and international regulations was low, and that orchid collectors were likely to believe that Vietnam has plenty of orchids left in the wild. Orchid collectors were highly willing to share their expertise and collections with international NGOs, and receive advice on propagation of orchid species. Through Bayesian logistic regression, we found no statistically significant influence of demographic attributes on the behavior of harvesting from the wild; however, having access to propagation equipment and supplies increased the likelihood of wild harvest. Accurate knowledge (awareness) is a key first step in the behavior change process. We suggest the implementation of awareness-raising campaigns targeted at Vietnamese orchid collectors, which communicate domestic and international restrictions about orchid harvest and trade, as well as the known status of orchid species in the wild. Additionally, we suggest that an opportunity exists to recruit Vietnamese orchid collectors into a formal network for knowledge-sharing and the co-creation of sustainable guidelines around keeping and propagating orchids.

Abstract in Vietnamese is available with online material.

Madagascar is acclaimed for its floral and faunal endemism and biodiversity. Among the island nation's most emblematic fauna are its native mammalian carnivores; they are members of the threatened and endemic Eupleridae family. The Corridor of Marojejy, Anjanaharibe-Sud Special Reserve, Tsaratanana (COMATSA) is a newly protected corridor system that faces deforestation and lacks detailed assessments of its native carnivore community. We deployed 44 motion-activated trail cameras to identify which terrestrial carnivores are found within the rainforest corridor landscape of COMATSA-Sud and Marojejy National Park, and to examine carnivore occupancy, relative activity and the impacts of habitat edge. Our sampling array operated from October 20, 2021, to February 10, 2022 (113 days) and confirmed the presence of four species in Eupleridae: Cryptoprocta ferox, Fossa fossana, Galidia elegans, and Galidictis fasciata, as well as a non-native carnivore species: Canis familiaris. We show that carnivore occurrences significantly increase with distance to forest edges. We discuss the negative impacts of forest loss on native carnivores and highlight the threats posed by the non-native carnivore C. familiaris. Our findings spotlight faunal detections across the corridor and indicate that fewer native carnivores are found in the corridor compared to nearby protected areas, suggesting that deforestation correlates with a skewed distribution of carnivore detections. Based on our data, we provide management recommendations for the protection of the forest corridor and its endemic faunal community.

Tropical cyclones are stochastic—sometimes catastrophic—weather events that can shape the ecology of impacted regions and have long-lasting effects on ecosystems. These destructive events are concerning for species persistence in areas with high endemism. Madagascar is among the world's most biodiverse hotspots and given the island's location within the southwest Indian Ocean, it is frequently impacted by cyclones. In March 2018, Cyclone Eliakim made landfall in northeast Madagascar, passing the species range of the predominantly frugivorous red ruffed lemur (Varecia rubra), allowing us to document their response. In addition to characterizing the forest damage, we conducted behavioral and feeding ecology data collection over 57 months from March 2018 to November 2022. We evaluated temporal adjustments in lemur behavioral and dietary strategies over a nearly five-year period, during which there were no recorded tropical storms or cyclones over the Masoala Peninsula despite landfall elsewhere. Cyclone destruction was concentrated on large trees, which subsequently reduced fruit availability. Our results showed lemurs consumed a greater proportion of leaves and utilized more canopy strata following the cyclone, representing an immediate ecological response. Red ruffed lemurs' broad dietary and microhabitat diversity gradually returned to their more typical ecological niche as their habitat recovered. Our research highlights the ecological flexibility of a dietary specialist in response to a destructive cyclone, a behavioral adjustment that is likely to have evolved under Madagascar's highly variable weather and aids this species' persistence following stochastic weather events.

Abstract in Malagasy is available with online material.

The expansion of agriculture and forest plantations over tropical biomes has caused significant species loss, while others persist in remnant native areas and anthropogenic lands. Penelope superciliaris, a large seed disperser bird, inhabits human-modified landscapes; however, its habitat use is poorly known. We investigated how native land covers, distance to water sources, and anthropogenic landscape features affect the species' ground habitat use in disturbed and undisturbed areas of three landscapes in Southeastern Brazil. We expected the species to use the ground more in native areas and near water sources because of the higher habitat quality. We collected presence-absence data during two dry seasons at 205 sampling stations with camera traps. Using occupancy models, we calculated the cumulative AICc weights of covariates for occupancy (interpreted as probability of use, Ψ) and detection (interpreted as frequency of use, p) parameters. The proportion of managed forests negatively influenced the species' frequency of use. The probability of use was higher when camera trap stations were located on unpaved roads. Model averaged prediction showed that the species uses about 56% of the landscapes. Our results suggest that intensively managed forests are not favorable or attractive habitats for the species. Unpaved roads associated with native vegetation edges may provide valuable habitats for the species during the dry season, possibly associated with movement and resource tracking. These findings may help guide conservation strategies in such modified landscapes, with caution in considering unpaved roads as secure habitats until further data on population abundance are available.

Abstract in Portuguese is available with online material.

The effects of vertebrate seed predation on the regeneration of restored forests are not well understood because most past studies have focused on seed predation within the first few years after restoration and have measured seed removal without quantifying subsequent seedling establishment of seeds that avoid predation. Quantifying the establishment of seeds that escape predation in restored forests at later stages of regrowth is crucial for anticipating longer-term recovery trajectories. Here, we evaluated the potential role of vertebrate seed predators in limiting recruitment of later-successional tree species in nine forests actively restored ≥15 years prior and in four paired remnant forest fragments embedded in an agricultural landscape in southern Costa Rica. We conducted seed addition experiments with four tree species inside and outside vertebrate exclosures and used camera trapping to detect seed predators. To determine the fate of seeds that avoided predation, we also measured seedling establishment after 1 year, given that other mortality factors may compensate in the absence of vertebrate seed predation. We detected two species of birds and five species of granivorous mammals removing seeds. Seed tagging indicated that most removal resulted in predation. For three of the four tree species tested, vertebrate seed predation reduced seedling establishment. The magnitude of this effect depended on species' susceptibility to other causes of mortality during the seed-to-seedling transition. Our study demonstrates that vertebrate seed predators can substantially reduce later-successional seedling recruitment in restored forests and should be considered alongside dispersal limitation and microsite conditions as factors slowing forest recovery.

Abstract in Spanish is available with online material.