Biotropica最新文献

Strawberry guava (waiawī, Psidium cattleyanum Sabine, Myrtaceae) is a small tree invasive on oceanic islands where it may alter forest ecosystem processes and community structure. To better understand the dynamics of its invasion in Hawaiian rainforests in anticipation of the release of a biocontrol agent, we measured growth and abundance of vertical stems ≥0.5 cm DBH for 16 years (2005–2020) in Metrosideros-Cibotium rainforest on windward Hawai'i Island. Specifically, we compared the growth and abundance of both shoots (originating from seed or from the root mat) and sprouts (originating above ground from established stems) in four replicate study sites. Mean stem density increased from 9562 stems/ha in 2005 to 26,595 stems/ha in 2020, the majority of which were stems <2 cm DBH. Early in the invasion, both density and per capita recruitment of shoots was greater than that of sprouts, but as overall stem density increased, sprout abundance and recruitment came to surpass that of shoots. Relative growth rates among small stems <2 cm DBH declined over time for both shoots and sprouts, but relative growth rates of sprouts were consistently greater than that of shoots after the first 3 years. The capacity of strawberry guava to recruit from both shoots and sprouts facilitates its invasion of rainforest, its persistence in the forest understory, and its response to canopy opening. Strawberry guava thus poses a considerable risk of stand replacement for Hawaiian rainforests. Stand management will require perpetual efforts to control both seed production and sprouting.

The composition and biodiversity of insect community assemblages are mediated by a complex set of biotic and abiotic factors. Among these factors are forest structure and atmospheric variables (like temperature and humidity), which are heavily influenced by frequent hurricane activity in the Caribbean. Despite this, changes in Caribbean insect assemblages as forests recover from hurricane disturbance are poorly documented. Butterflies represent a charismatic model taxon in biodiversity and conservation, and are thus an ideal subject for exemplifying these shifts in insect abundances and diversity across ecological succession. Here, we monitored butterfly communities in two Puerto Rican forests differing in structure (i.e., canopy height, tree size) to assess butterfly diversity, abundances, and community level wing traits (size and color) over 1 year, beginning 6 months after Hurricane Maria. Monthly sampling over the course of 1 year revealed no relationships between abundances and canopy openness or humidity; instead, species abundances fluctuated seasonally and were nonlinearly correlated with temperature. In contrast, wing size and color were linearly correlated with abiotic variables. Specifically, wings were larger in cooler and more open conditions. Wing color saturation and brightness were negatively correlated with humidity. Our results suggest that, first, a functional approach may provide better insight into the factors mediating species responses to disturbances. Second, further disentangling abundance seasonality from impacts of extreme disturbances necessitates long-term monitoring.

Abstract in Spanish is available with online material.

Conversion of lands to agroecosystems has resulted in a decline in bird biodiversity. Analyzing functional diversity is a central tool for detecting changes in the ecological functions performed by birds in these landscapes. This paper aims to investigate the responses of bird taxonomic and functional diversity to landscape heterogeneity and native forest cover in Neotropical vineyards. We sampled 19 vineyard landscapes in southeastern Brazil. These landscapes covered a gradient of forest cover and heterogeneity resulting from various land-uses. To assess bird diversity, we considered both taxonomic diversity and functional diversity (i.e., functional richness, evenness, and divergence). To examine the potential interactions between landscapes and bird assemblages, we employed generalized linear models (GLM). Taxonomic diversity showed no correlation with any landscape metrics. On the other hand, variation in the three metrics of functional diversity was related to landscape heterogeneity. However, in heterogeneous landscapes, these communities can be structured by limiting similarity processes. We highlight the negative impact of landscape homogenization on the ecological functions performed by birds in vineyards, while finding no significant effect on species diversity. These findings can provide valuable support for the formulation of public policies aimed at striking a balance between agricultural production and biodiversity conservation.

Abstract in Portuguese is available with online material.

Various factors may mediate the visitation of frugivores to fruiting plants, which can dictate the quantum of seeds removed (dispersed) away from the parent plant. Past studies have laid emphasis on species-specific factors and environmental contexts that frugivores may use as cues to make foraging decisions and differentially visit various plant species. However, differences in plant traits (intrinsic factors) and local environmental contexts (extrinsic factors) can influence the diversity and abundance of frugivores that visit individual plants of the same species, resulting in intraspecific variation in seed dispersal. We observed individuals of two co-fruiting plant species with morphologically similar fruits—Naringi crenulata and Ziziphus oenopolia—for 134 h and examined the influence of fruit crop size, plant height, and fruiting neighborhood on the diversity of visiting avian frugivores and quantum of fruit removal for individual plants. We found that despite their similarity in fruits and sharing of a similar set of frugivore species, the two plant species differed in how they attracted frugivores, with consequences for fruit removal rates. Fruit crop size was an important determinant of fruit removal for N. crenulata¸ while plant height led to greater visitation and fruit removal for Z. oenopolia. We discuss potential reasons for the difference in frugivore visitation and fruit removal for the two plant species. Our results support a growing body of evidence that intraspecific variation in seed dispersal is pervasive and highly context-dependent, and describe frugivore interactions of two plant species from an understudied tropical savanna.

Razanamaro, O. H. M., Ravelomanana, A., Andriantsaralaza, S., Rafalinirina, A. H., Razanaparany, T. P., Ratsimbazafy, J., Rabakonandrianina, E., & Goodman, S. M. (2024). ATBC 2019 in Madagascar: Its impact on the National Scientific Community. Biotropica, 56, 50–57. https://doi.org/10.1111/btp.13277

In the originally published version of this article, the partner name World Resources Institute wrongly appeared as World Research Institute in Table 1 and the first paragraph of Section 3.1.

We apologize for this error.

Functional lateralization in directional preference for predator evasion was examined in 45 Pointed-belly frogs (Leptodactylus podicipinus). T-maze trials revealed a preference for rightward escape, though individual bias was minimal, at only 33%, to evade predictability. Sex and size didn't influence escape decisions, aligning with predator avoidance strategies.

Abstract in Portuguese is available with online material.

Monitoring biodiversity changes associated with ecological restoration is crucial in the current UN Decade on Restoration. Although several studies highlight the impacts of restoration on ecosystems, it is also important to understand how restoration alters species' behavior, including vocalization. Advances in conservation technology, such as passive acoustic monitoring, facilitate rapid and noninvasive monitoring. In this study, we quantified changes in the vocal behavior of a bird species in response to small-scale restoration carried out by removing the invasive shrub, Lantana camara (lantana), in a Central Indian tropical dry forest. We examined associations between sites of varying lantana densities and the vocalization of one of its primary dispersers, red-vented bulbul (RVBU). We found statistically significant differences in note-length and bandwidth of RVBU vocalizations across sites. A random forest classification model showed that Lantana density was not an important predictor of RVBU vocalizations. Apart from the percentage of forest area and farms in our sites, total human population was the most important predictor for RVBU vocalizations suggesting RVBU's use of human habitations as possible resource hubs. Our findings suggest that lantana removal is not associated with significant changes in RVBU vocalization. This study provides empirical evidence that ecological restoration may not alter species' vocalization in the short term and highlights the importance of moving beyond species presence and understanding the impact of restoration on species behavior.

Passive acoustic monitoring (PAM) is increasingly popular in ecological research, but recording and analyzing large amounts of data is still a critical bottleneck for the long-term monitoring of multiple species. We evaluated how temporal and spatial sampling effort affects species diversity estimates using a set of 14,045 1-min recordings from various neotropical birds and anuran communities. Our goals were to evaluate (i) the daily vocal activity cycle of birds and anurans, (ii) the effect of temporal structure (e.g., number of minutes listened each hour; continuous versus intermittent recordings) on determining the species composition, and (iii) the species–area relationship, and how the number of recorders affects species richness estimates. Based on sampling coverage and completeness, we (iv) evaluate manual inspection schedules for birds and anurans across four biomes of Brazil. We found marked diel variation in vocal activity between taxonomic groups, indicating that birds and anurans are more efficiently detected during early periods of the day and night, respectively. For proper diversity estimates, biomes with higher biodiversity required longer inspecting periods and a larger number of replicates, irrespective of taxa. Although fewer recordings per hour are less informative than full-hour sampling, species diversity is better estimated when inspected minutes are interspersed over longer periods than inspecting minutes recorded over shorter timespans. Based on our findings, we recommend how to set PAM programs over highly diverse ecosystems.

Abstract in Portuguese is available with online material.

Seed dispersal is a key process that influences the recruitment of plant species, yielding profound consequences on vegetation structure. This process can be affected by environmental disturbances, such as fires, leading to varied impacts on the agents involved, both dispersers and plants. We investigated the potential role of small mammals (rodents and marsupials) as seed dispersers in a Neotropical savanna (Brazilian Cerrado). We also evaluated the impact of fire severity on the seed dispersal services provided by these animals in gallery forests, 3 years after a major fire event. We live-trapped small mammals in 14 sites, 7 of which were located in forests classified in three categories of fire severity (“unburned”, “low severity”, or “moderate severity”). We captured 13 mammal species, finding a total of 11,688 seeds in their feces (collected inside traps or handling bags). These seeds encompassed 28 plant species from at least 8 families. A multivariate analysis (NMDS) revealed differences among small mammal species in terms of potentially dispersed plants, with seeds of 18 plant species being consumed by no more than one small mammal species. An increase in fire severity affected the composition of plant species potentially dispersed, changed the relative role of forest small mammals as seed dispersers, and decreased observed richness of defecated seeds. We conclude that high-severity wildfires affect highly relevant ecological processes, such as seed dispersal by animals. These effects could impact the recruitment dynamics of plant species and, consequently, the vegetation recovery and plant community composition in fire-affected areas.

Abstract in Portuguese is available with online material.

Interspecific interactions play an important role in structuring wildlife communities. On islands, which often have reduced species assemblages, species may expand their niches resulting in unusual patterns of interactions with other members of the ecological community. In this study, we compared spatio-temporal interactions of two food competitors between a site with predators and two predator-free islands in the Coiba archipelago, Panama. Here, capuchin monkeys (Cebus capucinus imitator) exhibit high levels of terrestriality, and some groups engage in stone tool use. This potentially leads to competition with sympatric agoutis (Dasyprocta coibae), which have overlapping diets. We used camera-trap surveys to estimate temporal overlap between both species, distinguishing between arboreal and terrestrial activity of capuchins. We also compared detection rates and intervals between consecutive detections of both species at sites in which the monkeys use stone tools (tool-use area) and sites in which they do not (non-tool-use area). We found high spatio-temporal overlap between agouti and capuchin on the forest floor of both islands. While capuchins visited the tool-use area four times as often as the non-tool-use area, agoutis avoided the tool-use area, capture rates being 25 times as low. Waiting times were shorter for both species at the tool-use area. These results suggest temporal overlap and spatial segregation. Niche expansions on islands thus cause unique interactions that do not occur on the mainland.

Abstract in Spanish is available with online material.