Biotropica最新文献

Formation of forest islands in West Africa has been linked to anthropogenic soil improvement resulting in luxuriant tree growth in otherwise open savanna landscapes. However, there is limited understanding of how such unique ecosystems modulate soil carbon (C) dynamics and nutrient cycling. In this study, we report soil nutrient characteristics and two distinct soil organic carbon pools of Anogeissus grove (forest island) associated with abandoned village sites of the Mole National Park in the Guinea savanna or tropical continental climatic zone of Ghana, taking opportunity of a previously published study in Biotropica in 1978. We compared present-day differences in soil characteristics between the previously studied forest grove and adjoining open savanna in the Park and evaluated vegetation dynamics since first measurement in 1974. Overall, we see changes related to self-thinning and expansion of the grove on a decadal timescale. Soil organic matter and available phosphorus contents were greater in the grove and increased by 19.6% and 18.7%, respectively over time, showing persistence after four decades. Mineral-associated organic carbon (MAOC) differed significantly (p < .05) between the vegetation types, being 3.44% in the grove and 2.34% in the savanna. The grove was ca. 25% greater in particulate organic carbon (POC) content than the savanna. In both vegetation types, >55% of carbon was stabilized in the mineral fraction. Our study demonstrates long-term human impacts on soil and vegetation and offers a clear nature-based solution for climate change mitigation through sustainable land management by indigenous people toward achievement of the “4p1000” initiative.

Human activities and biological invasions have caused unprecedented biodiversity loss over the past 500 years. Proximity to humans drives the spatial distribution of species toward less disturbed habitats. Invasive species can competitively exclude native species, but species may coexist due to different habitat preferences. Here, we investigated how proximity to farms and the presence of the non-native European hare (Lepus europaeus) influence the habitat use by the Brazilian cottontail (Sylvilagus minensis) in southeastern Brazil. We found that the probability of cottontail site use increased with native forest cover and decreased with farmhouse proximity, ranging from 0.05 (SE = 0.02) at sites close to farmhouses (≅900 m) with no native forest to 0.70 (SE = 0.15) at sites far from farmhouses (≅2500 m) dominated by native forest. Higher risk of harassment and predation by free-roaming dogs and cats may explain the negative effect of farmhouse proximity on cottontail habitat use. We found little evidence for competitive exclusion by the European hare. Instead, our results suggest that the two species spatially segregate due to different habitat preferences. While the European hare more likely uses farmland in its native and non-native range, our results suggest that the Brazilian cottontail is a forest dweller. Although we found only weak evidence of competitive exclusion, we advise caution because invasive species may delay the onset of detrimental effects due to initial low population densities in newly invaded areas as is the case of the European hare in southeastern Brazil.

Abstract in Portuguese is available with online material.

Tropical forests play a major role in the global carbon cycle but their diversity and structural complexity challenge our ability to accurately estimate carbon stocks and dynamics. Palms, in particular, are prominent components of many tropical forests that have unique anatomical, physiological, and allometric differences from dicot trees, which impede accurate estimates of their aboveground biomass (AGB) and population dynamics. We focused on improving height estimates and, ultimately, AGB estimates for a highly abundant palm in Puerto Rico, Prestoea acuminata. Based on field measurements of 1003 individuals, we found a strong relationship between stem height and diameter. We also found some evidence that height–diameter allometry of P. acuminata is mediated by various sources of environmental heterogeneity including slope and neighborhood crowding. We then examined variability in AGB estimates derived from three models developed to estimate palm AGB. Finally, we applied our novel height:diameter allometric model to hindcast dynamics of P. acuminata in the Luquillo Forest Dynamics Plot during a 27-year period (1989–2016) of post-hurricane recovery. Overall, our study provides improved estimates of AGB in wet forests of Puerto Rico and will facilitate novel insights to the dynamics of palms in tropical forests.

Abstract in Spanish is available with online material.

Insect–plant interactions are less well studied than other types of herbivory on islands, precluding a comprehensive understanding of the evolutionary ecology of these interactions. Declines in native island plants and insects call for urgent attention to characterize these species' interactions for their conservation and to better understand evolution in these unique, insular ecosystems. In Hawai‘i, the Kamehameha butterfly (Vanessa tameamea) is one of only two native butterflies, and larvae are specialists on native urticaceous plants. Using a no-choice bioassay, we investigated performance of V. tameamea reared from egg hatching through eclosion on four native urticaceous host plants, Boehmeria grandis, Pipturus albidus, Touchardia latifolia, and Touchardia oahuensis, and one exotic urticaceous species, Cecropia obtusifolia. Performance varied significantly among the plant diets, with V. tameamea performing best on P. albidus and T. oahuensis among the performance metrics of survival, pupal and adult body mass, and development time. Larval responses to the exotic host plant C. obtusifolia varied among populations, with O‘ahu caterpillars successfully completing development on it, but Hawai‘i Island caterpillars rejecting it completely, suggesting a geographic mosaic for this novel species interaction. Characterization of a suite of nutritive and defensive plant traits revealed significant variability among plant species, but patterns did not align well with V. tameamea performance rankings, making it difficult to identify key drivers of host plant quality. Future work examining additional plant traits under natural conditions would provide new insights, contributing critical ecological information to conserve this charismatic island species.

The evolution of extremely long (>10 cm) floral tubes in angiosperms is closely linked with adaptation for pollination by long-proboscid hawkmoths. In most cases, pollen is placed on the head or body of these moths, selecting for floral tubes that match or slightly exceed their proboscis length as this ensures contact with reproductive parts of the flower. However, in the case of Chamaepentas nobilis (Rubiaceae), anthers are inserted inside the c. 12-cm floral tubes and coat the proboscis of visiting hawkmoths with sticky pollen, meaning that insects with proboscides longer than the floral tube can be effective pollinators, despite trait mismatching. Direct observations and camera trapping on granite outcrops in central Zambia showed that C. nobilis was visited both by Agrius convolvuli (proboscis length c. 13 cm) and Xanthopan morganii (proboscis length c. 17 cm), which are the only moth species in Africa that can access the small amounts of dilute nectar at the base of the floral tube. Pollen on the proboscides of captured hawkmoths was confirmed to originate from C. nobilis. Key floral advertising traits of C. nobilis include early evening anthesis, the highly reflective white limbus, and the evening production of scent dominated by oxygenated aromatic and terpenoid compounds known to elicit antennal responses of A. convolvuli. This study shows that that A. convolvuli and X. morganii share floral resources and jointly pollinate C. nobilis, despite their proboscides differing in length and being mismatched with the corolla tube length.

We studied communities of leaf litter weevils along a 2000 m elevation gradient in El Cielo Biosphere Reserve, northeastern Mexico, an area where Nearctic and Neotropical biotas overlap. After achieving high inventory completeness (0.922 site sample coverage), we encountered 81 weevil morphospecies, of which 55 were known to be leaf litter specialists. The diversity of leaf litter weevils increased with elevation. Beta diversity across the elevational gradient was mostly explained by species turnover rather than nestedness. The interaction between forest structure (measured as median DBH of trees) and precipitation seasonality explained more than 20% of the variation in weevil species richness: weevil richness showed a negative relationship with tree DBH and was positively associated with low climate seasonality variation, characteristics of tropical montane cloud forests. In contrast with insect taxa such as ants and dung beetles, which attain their highest richness at lower elevations, leaf litter weevil richness peaked at 1600 m. These results suggest that most litter weevil species are highly associated with a particular elevation range and the overall pattern of richness increasing with elevation is probably the result of an association of many weevil species with tropical montane cloud forest habitats, which occur close to the top of the mountain.

Abstract in Spanish is available with online material.

In urban ecosystems, bats play an essential role in seed dispersal, which is facilitated by their use of feeding roosts. However, there are several knowledge gaps in this ecosystem service that bats provide in urban areas. We aimed to describe the fruits consumed by bats in an urban area, the selection and use of feeding roosts, and the patterns of seed dispersal by fruit bats in a Brazilian city. We collected and identified the seeds deposited under feeding roosts and tested for differences in the size of the seed of fruits consumed by bats and the seeds of fruits available in the study area. We also captured and identified bats feeding near roosts using mist nets and assessed the vegetation structure and urban variables that might influence the bats' tree choice for roosts. We found that Artibeus lituratus, Artibeus planirostris, and Platyrrhinus lineatus potentially used feeding roosts and preferred the tallest trees, which were located further away from artificial light. The average distance of seed dispersal was 105.5 meters, and the average size of the dispersed seeds did not differ from the seeds of the fruits available in the area, suggesting that bats are not limited to dispersing only tiny seeds. However, the prevalence of exotic seeds raises concerns that bats may spread exotic species, especially in surrounding protected areas. These results highlight the importance of frugivorous bats as significant seed dispersers in urban areas and emphasize the need for further research to understand their role in shaping urban ecosystems.

Abstract in Portuguese is available with online material.

The reproductive phenology of plants has profound influence on ecosystem dynamics including plant–animal interactions. Broad phenological patterns, especially the timing of reproduction, may result from long-term climate trends and co-evolution between plants and their pollinators, dispersers, and predators. Yet, interannual climate variation and local abiotic conditions may also affect the timing and magnitude of plant reproduction. Understanding the patterns of and controls on plant reproduction are crucial for conservation efforts under a changing global climate and rapidly expanding human development. However, phenology studies from the Neotropics are sparse. Here, we examine the relative timing and magnitude of fleshy-fruited plant reproduction during the winter dry season in subtropical dry forest on Eleuthera, The Bahamas over a nine-year period. At least 47 species were observed with some dry season reproductive activity, but only 17% showed evidence of a fruiting peak or continuous reproduction. Overall fruit abundance generally declined through the dry season, but flower production increased between mid and late dry season. Variation in fruit and flower abundance among years was related to temperature and rainfall, but local site conditions—particularly successional stage and groundwater availability—explained more variability in reproductive activity than climate variation. Groundwater availability had a particularly strong positive influence on flower and fruit abundance at the end of the dry season, a critical time for migrant frugivores preparing to return to their breeding grounds. This emphasizes the importance of protecting sites with accessible groundwater to conserve biodiversity in the archipelago and elsewhere.

Global change is impacting forests worldwide, leading to shifts in forest dynamics and functional composition. We evaluated the changes in the liana community and trait composition over a five-year period (2014–2019) in a Chinese tropical rainforest and assessed the underlying putative mechanisms. We monitored >20,000 lianas in a 20-ha plot, and analyzed community changes for each of the 20 1-ha plots. To identify the putative drivers underlying community change, we used community-weighted mean (CWM) trait values of 18 functional traits that are important for liana performance. During the 5-year period, liana density decreased by 12.6% because of the high mortality of small lianas, whereas liana basal area increased by 5.8% because of the high growth of large lianas. After 5 years, liana communities showed a shift in trait values indicating that they changed towards more large, acquisitive lianas with rapid water use. The temporal shift from slow to fast community trait spectra in carbon, nutrient, and water use was also supported by shifts in the individual CWM traits, from conservative tough leaves towards more acquisitive and water-spending leaves with higher K concentration, leaf thickness, and vessel diameter. Overall, we found no support for a role of disturbances or drought as drivers of the observed changes in the studied liana community. Instead, our study implies that CO₂ fertilization should be considered to better understand dynamics in liana communities in tropical forests.

Abstract in Chinese is available with online material.

The drivers behind plant-pollinator interactions still need to be fully understood. Previous research has suggested that observed interactions result from either neutral interaction between species based on their abundance or from niche-based processes, which are reflected in the adaptations of both plants and pollinators. Furthermore, the importance of both scenarios can differ depending on seasonal dynamics translated into differences in resource availability. Extensive research has been conducted on New-World hummingbirds (Trochilidae), whereas much less is known about Old World nectar-feeding sunbirds (Nectariniidae). Our study aimed to explore whether sunbird-plant interactions are explained by neutral and/or niche-based processes. Thus, we tested the effects of abundance, morphology, and nectar sugar content on the observed interactions and the link between sunbirds and plant traits. Moreover, we explored the effects of robbing on these mechanisms. Finally, we investigated the partitioning of bird pollination niches, based on floral traits. We used a dataset of sunbird-plant interactions collected at Mount Cameroon during two seasons (dry and wet seasons). Our study shows that sunbird-plant interactions are influenced by both neutral and niche-based processes. Neutral processes and nectar reward were the main mechanisms underlaying the observed interactions in the dry season. However, as more ornithophilous plants bloom during the rainy season, morphological trait-matching becomes more important. We found a correlation between bill length and floral tube dimensions and observed niche overlap among the sunbird species. Considering this and other research, we suggest that plant-pollinator interactions are influenced by a combination of both neutral and niche-based processes.