Biotropica最新文献

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.

This study explores the relationship observed between ‘guests’—foreign inhabitants of social colonies—and the density and fecundity of eusocial-like staghorn ferns (Platycerium bifurcatum, Polypodiaceae). Our observations suggest that guests in staghorn colonies have a range of commensal and negative relationships, paralleling those seen in eusocial animal species.

In seasonally dry tropical forests (SDTF's) drought risk driven by topography-related factors determines vegetation structure, functional composition, and species diversity; however, the effect of slope aspect and topographic position on tree community dynamics are still poorly explored. In this paper, we studied the dynamics and structural attributes of the tree community of a Mexican SDTF. Plots were established in a combination of two topographic conditions: slope aspect (north/south) and topographic position (upper/middle/lower). Differences among these conditions were assessed through (i) community dynamics´ parameters, (ii) species dynamics, (iii) vegetation structure, and (iv) species diversity. We analyzed community attributes for each of our study years (2012–2020) and rates of change between this period for the entire community (DBH ≥1 cm), small-sized trees (DBH ≤3 cm), and large-sized trees (DBH >3 cm). Multivariate analyses were also used to examine the relationship between vegetation and topography. In upper positions, trees showed higher mortality (mean mr ± SE = 3.1 ± 0.2% yr − 1) and lower recruitment rates (mean rr ± SE = 6.3 ± 0.9% yr − 1) than those from the lower positions (mean mr ± SE = 1.7 ± 0.1% yr − 1; mean rr ± SE = 7.7 ± 0.7% yr − 1). The relative change (%) in the number of individuals for the entire community and small-sized trees increased towards the lower positions. The entire community showed a temporary loss of stems on south-facing slopes, but temporary gains in number of stems in lower positions for the small-sized trees. We did not find any temporary changes in species diversity attributes. The drought risk gradient imposed by topographic position influences the tree dynamics with a higher mortality of stems/individuals towards upper positions, but species diversity was maintained.

When a root-climber Ficus pumila and an epiphyte Peperomia quadrangularis were exposed to a light gradient, over 90% of the shoots grew away from light. This is the first demonstration of negative phototropism in these species. Whereas negative phototropism may help climbers locate support, its function in epiphytes remains uncertain.

In caves, the absence of natural light in deeper regions starkly contrasts with the entrance areas, which still exhibit a light gradient extending into the cave interior. This interplay with the structural gradient of the environment potentially exerts distinct influences on invertebrate communities residing in different cave light zones. To investigate this, we formulated a hypothesis positing that communities within distinct cave light zones respond differently to habitat structure and microclimatic conditions. Our approach involved a spatial multi-scale sampling of invertebrates and the application of statistical analyses to contrast the responses of communities inhabiting photic and aphotic zones. Photic zone richness is influenced by factors such as air moisture, resource availability, root presence, and shelter diversity. In contrast, the richness of communities in aphotic zones is shaped by resource availability, the presence of roots, branches, and distance from the cave entrance. As expected, the richness in the photic zone surpasses that of the deeper regions, highlighting the challenges faced by invertebrates attempting to establish themselves in the aphotic zone. The species composition of faunal communities varied predictably from the entrance to the aphotic zone, and the three most important factors driving this variation were geographic distance, humidity, and distance from the entrance. The composition between these cave zones differs significantly, primarily due to the high number of obligate cave species predominantly inhabiting the aphotic region. Indeed, communities associated with different cave zones exhibit distinct responses to resource, microclimatic, and structural variables.

Abstract in Portuguese is available with online material.

Marine nutrients underpin productivity and functioning of oceanic island ecosystems. On islands where they nest, seabirds represent a primary source of marine nutrients. In tropical regions, some of the largest seabird populations nest on atolls, yet there is limited information available on seabird contributions to atoll ecosystem nutrient dynamics. To investigate the spatial and seasonal dynamics of seabird contributions, we assessed seabird colonies of different taxa, including red-footed boobies and terns, nesting on separate islands of Farquhar Atoll, Seychelles. We assessed nutrient concentrations of guano, soil, coastal plants, and nearby seagrass in seabird colonies and at a control island with no seabirds, during the wet and dry seasons. Sooty terns contributed the highest quantities of nutrients, estimated at 71.2 N tonne/year and 52.2 P tonne/year. Seabird-derived nutrient transfer occurred year-round from seabird colonies to soil, coastal plants and seagrass. Soil macro- and inorganic nutrients were higher in the high-density tern colony and during the dry season, coinciding with the breeding period of sooty terns. Both red-footed booby and tern colonies maintained high nitrogen levels in coastal plants year-round, while phosphorus levels did not differ between islands or seasons. Seabird-derived nitrogen reversed nitrogen limitation of seagrass during the dry season. We provide the first insights into seabird nutrient contributions to atoll ecosystems in Seychelles, with recommendations for seabird conservation to boost and support atoll and island ecosystem resilience. Our results from a relatively undisturbed atoll serve as a baseline with which more impacted atolls and future changes can be assessed.

We provide the first conclusive evidence that at least one leech species (Chtonobdella sp. from Madagascar) can jump. For each jump, the leech coils back before taking off. Visually, this appears somewhat like a backbending cobra or a spring being pulled back to maximize potential energy.

Abstract in Malagasy is available with online material.

We documented new records of Choloepus didactylus extending up to 820 km south of its current geographic distribution. These records, and others found in literature for the central-southern Amazon, evidence a southern expansion of about 30% of the known species' area of occurrence and help shedding light on decades of uncertainties about its real distribution.

Abstract in Portuguese is available with online material.

Several ecological filters in deforested and degraded areas reduce seedling emergence and establishment and hinder ecological restoration by direct seeding. Understanding whether functional traits are related to a species' capacity to overcome these filters and predict their field performance might improve the success of direct seeding techniques for ecological restoration. We assessed eight seed functional traits of tropical tree species, seeking those that best explained their establishment success in direct seeding restoration projects. We analyzed a dataset from 52 studies that tested direct seeding techniques with tree species in Brazil. From each study, we collected the mean establishment percentage for all tree species. Seed mass, cotyledon function, and germination speed were the only functional traits that significantly affected the species establishment percentage in direct seeding restoration projects. Species with larger seeds, storage cotyledons, and faster germination had higher establishment percentages. Choosing species with these functional traits for seed mixes will provide higher establishment percentages and, consequently, improve restoration success by direct seeding techniques.