Frugivore Community Research Articles

Assembly, Persistence, and Disassembly Dynamics of Quaternary Caribbean Frugivore Communities.

AbstractHow communities assemble and restructure is of critical importance to ecological theory, evolutionary theory, and conservation, but long-term perspectives on the patterns and processes of community assembly are rarely integrated into traditional community ecology, and the utility of communities as an ecological concept has been repeatedly questioned in part because of a lack of temporal perspective. Through a synthesis of paleontological and neontological data, I reconstruct Caribbean frugivore communities over the Quaternary (2.58 million years ago to present). Numerous Caribbean frugivore lineages arise during periods coincident with the global origins of plant-frugivore mutualisms. The persistence of many of these lineages into the Quaternary is indicative of long-term community stability, but an analysis of Quaternary extinctions reveals a nonrandom loss of large-bodied mammalian and reptilian frugivores. Anthropogenic impacts, including human niche construction, underlie the recent reorganization of frugivore communities, setting the stage for continued declines and evolutionary responses in plants that have lost mutualistic partners. These impacts also support ongoing and future introductions of invader complexes: introduced plants and frugivores that further exacerbate native biodiversity loss by interacting more strongly with one another than with native plants or frugivores. This work illustrates the importance of paleontological data and perspectives in conceptualizing ecological communities, which are dynamic and important entities.

Frugivore-mediated seed dispersal in fragmented landscapes: Compositional and functional turnover from forest to matrix.

Seed dispersal by frugivores is a fundamental function for plant community dynamics in fragmented landscapes, where forest remnants are typically embedded in a matrix of anthropogenic habitats. Frugivores can mediate both connectivity among forest remnants and plant colonization of the matrix. However, it remains poorly understood how frugivore communities change from forest to matrix due to the loss or replacement of species with traits that are less advantageous in open habitats and whether such changes ultimately influence the composition and traits of dispersed plants via species interactions. Here, we close this gap by using a unique dataset of seed-dispersal networks that were sampled in forest patches and adjacent matrix habitats of seven fragmented landscapes across Europe. We found a similar diversity of frugivores, plants, and interactions contributing to seed dispersal in forest and matrix, but a high turnover (replacement) in all these components. The turnover of dispersed seeds was smaller than that of frugivore communities because different frugivore species provided complementary seed dispersal in forest and matrix. Importantly, the turnover involved functional changes toward larger and more mobile frugivores in the matrix, which dispersed taller, larger-seeded plants with later fruiting periods. Our study provides a trait-based understanding of frugivore-mediated seed dispersal through fragmented landscapes, uncovering nonrandom shifts that can have cascading consequences for the composition of regenerating plant communities. Our findings also highlight the importance of forest remnants and frugivore faunas for ecosystem resilience, demonstrating a high potential for passive forest restoration of unmanaged lands in the matrix.

Structural but not functional resistance of frugivore-plant interaction networks to the defaunation process

Defaunation is the process of sequential loss of larger animal species caused by anthropogenic activities such as deforestation and hunting. This phenomenon has potential to disrupt the ecosystem stability, as well as their functional performance through the disruption of trophic interactions. We evaluated the effect of defaunation on structure and function in frugivore-plant interaction networks. We characterized interaction networks in two areas in northern Colombia and used a simulation model of species extinction in three different scenarios. The first scenario eliminated species based on body size, measured by body mass, according to the progressive effect of non-random species loss (defaunation); the second scenario eliminated species according to their contribution to network structure (CNS); and finally, the third scenario eliminated species according to their seed dispersal potential (SDP). Based on these simulations we evaluated the effect of species loss on the structural patterns (nestedness and modularity) and the functional diversity of the frugivore community, through the indexes of functional richness (FRic) and functional evenness (FEve). The loss of species with larger body sizes increased nestedness and did not affect modularity, whereas in the CNS scenario both patterns were affected. The FRic index decreased in the first stages of extinction by defaunation and by SDP, while the FEve index did not suffer significant variations in any scenario. The combination of interaction network analysis with functional diversity indices allows direct quantification of the robustness of network structural patterns and the vulnerability of the functional capacity of frugivore communities in the face of defaunation.

Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

AbstractVertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant‐frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under‐ and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant‐frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning.Abstract in Spanish is available with online material.

Novel plant–frugivore network on Mauritius is unlikely to compensate for the extinction of seed dispersers

Insular communities are particularly vulnerable to anthropogenic extinctions and introductions. Changes in composition of island frugivore communities may affect seed dispersal within the native plant community, risking ecological shifts and ultimately co-extinction cascades. Introduced species could potentially mitigate these risks by replacing ecological functions of extinct species, but conclusive evidence is lacking. Here, we investigate changes in plant–frugivore interactions involving frugivorous birds, mammals and reptiles in Mauritius, an oceanic island with an exceptionally well-specified frugivore community and well-described species introduction history. We demonstrate substantial losses of binary interaction partnerships (at the species level) resulting from native species extinctions, but also gains of equal numbers of novel interactions with introduced species, potentially supporting the idea that non-native species might compensate for lost seed dispersal. However, closer investigation of animal seed handling behaviour reveals that most interactions with seed dispersers are replaced by ecologically different interactions with seed predators. Therefore, restoration of seed dispersal functionality in this novel plant–frugivore community is unlikely.

Plant–frugivore interactions across the Caribbean islands: Modularity, invader complexes and the importance of generalist species

AbstractAimMutualistic interactions between plants and animals are fundamental for the maintenance of natural communities and the ecosystem services they provide. However, particularly in human‐dominated island ecosystems, introduced species may alter mutualistic interactions. Based on an extensive dataset of plant–frugivore interactions, we mapped and analysed a meta‐network across the Caribbean archipelago. Specifically, we searched for subcommunity structure (modularity) and identified the types of species facilitating the integration of introduced species in the Caribbean meta‐network.LocationCaribbean archipelago (Lucayan archipelago, Greater Antilles, Lesser Antilles).MethodsWe reviewed published scientific literature, unpublished theses and other nonpeer‐reviewed sources to compile an extensive dataset of plant–frugivore interactions. We visualized spatial patterns and conducted a modularity analysis of the cross‐island meta‐network. We also examined which species were most likely to interact with introduced species: (1) endemic, nonendemic native or introduced species, and (2) generalized or specialized species.ResultsWe reported 3060 records of interactions between 486 plant and 178 frugivore species. The Caribbean meta‐network was organized in 13 modules, driven by a combination of functional or taxonomic (modules dominated by certain groups of frugivores) and biogeographical (island‐specific modules) mechanisms. Few introduced species or interaction pairs were shared across islands, suggesting little homogenization of the plant–frugivore meta‐network at the regional scale. However, we found evidence of “invader complexes,” as introduced frugivores were more likely to interact with introduced plants than expected at random. Moreover, we found generalist species more likely to interact with introduced species than were specialized species.Main conclusionsThese results demonstrate that generalist species and “invader complexes” may facilitate the incorporation of introduced species into plant–frugivore communities. Despite the influx of introduced species, the meta‐network was structured into modules related to biogeographical and functional or taxonomic affinities. These findings reveal how introduced species become an integral part of mutualistic systems on tropical islands.

Tree visitation and potential seed dispersal of keystone Ficus species by vertebrates in an urban mosaic landscape in eastern South Africa

Globally with the human population increase, urban expansion has increased, impacting biodiversity and ecosystem functions. Visitation of fruiting trees by vertebrate frugivores can influence the persistence of fleshy fruited trees and so further maintain frugivore communities in transformed landscapes. Figs (Ficus spp.) have been recognised as keystone plant resources that support diverse frugivorous vertebrate communities. Our main objective was to identify the frugivorous vertebrates visiting fruiting Ficus trees in an urban mosaic landscape of Durban, Ethekwini Municipality, KwaZulu-Natal, South Africa, using camera traps focused on focal fig trees. We quantified the diurnal and nocturnal frugivore visitation rates and levels of interactions. We analysed frugivore visits to 12 individual trees of five Ficus species between 2019 and 2020. During 3888 h, we recorded a total of 4,071 videos from camera traps with 10,016 visits and levels of interactions of three main vertebrate taxa (8958 fruit bat visits, 808 bird visits and 250 monkey visits). These were in five Ficus species (F. burkei, F. lutea, F. natalensis, F. sur and F. sycomorus). Of the bird species visiting, we identified a total of 34 species, but some species were unidentified. We recorded a total of 8958 visits by Wahlberg's epauletted fruit bats Epomophorus wahlbergi, and 250 visits by vervet monkeys Chlorocebus pygerythrus. The latter tended to stay for prolonged periods in the trees feeding. Our data showed the importance of fruiting fig trees for vertebrate frugivores in the urban mosaic landscape. This highlights the conservation implications of figs as keystone resources in the urban mosaic landscape. Our findings support the planting and conservation of native Ficus tree species in transformed urban mosaic landscapes for the persistence of forest species biodiversity.

Frugivore community composition and interaction frequency are vertically stratified in a liana species fruiting across forest strata

Frugivore community composition and interaction frequency are vertically stratified in a liana species fruiting across forest strata

Frugivore distributions are associated with plant dispersal syndrome diversity in the Caribbean archipelagos

AbstractAimMany plants rely on interactions with frugivores for dispersal, suggesting that animal communities may affect plant occupancy and diversity. However, the contribution of these interaction‐led biotic variables on plant diversity is poorly understood, especially in archipelagic hotspots such as the Caribbean. In island ecosystems, biogeographic theories suggest that island configurations drive colonization‐extinction dynamics, while macroecology argues for the importance of climatic drivers of biodiversity. Within this context, we examine how frugivore‐driven biotic factors are associated with fruiting plant species richness in relation to abiotic (climatic and geologic) and island configuration characteristics.LocationCaribbean archipelagos.MethodsWe compiled a review of the diversity and distributions of 6039 plants and 326 vertebrate frugivores across 105 islands within the Caribbean. We then identified characteristics related to plant‐frugivore interactions and assigned each species as having either abiotic (wind, water, etc.) or zoochoric (frugivory‐dependent) dispersal syndromes. We related plant richness and dispersal syndromes to the regional diversity and characteristics of frugivorous animals, abiotic environments and island configuration characteristics through stepwise multivariate regression with generalized linear models and model selection.ResultsWe found that 44.6% of Caribbean plants are dispersed through frugivory (endozoochory). Frugivore‐related characteristics, namely accumulated body mass of island bird assemblages, were the best predictors of the diversity of seed dispersal syndromes. To a lesser degree, reptile richness and soil variety were also considered important predictors for zoochoric plant distribution, while island areas affected abiotically‐dispersed plants.Main conclusionWe found that biotic characteristics of frugivore communities are important predictors of plant diversity in the Caribbean archipelagos. However, this may also be influenced by climate and colonization history. Given the importance of biotic metrics in explaining plant diversity, we suggest that fruit‐frugivore interactions are important components of island biogeography and that frugivorous communities should be accounted for plant biodiversity predictions and forecast models.

Assessing short and long‐term variations in diversity, timing and body condition of frugivorous birds

Seed dispersal by frugivorous bird species involves a fine temporal tuning between fruiting plants and birds. However, this interaction may be severely threatened by anthropogenic climate and land‐use change, which may result in phenological mismatches and pervasive ecological consequences for avian communities. In this study, we evaluate changes at long (~40 years) and short‐time (seasonal) spans in an avian frugivore community using a snapshot resampling. Particularly, we focus on changes in composition, abundance, migratory timing (i.e. phenology) and physical condition in relation to variations in fruit supply. We used bird and fruit data collected during 1981–1983 and 2019–2021 in a Mediterranean scrubland site in Doñana Natural Area, SW Spain. Our findings indicate a profound transformation of species composition, bird phenology and body condition: in ~40 years, the avian community showed a 66% and 18.4% decrease of the abundance of wintering and seed‐disperser species, respectively. Seasonal abundance peaks were advanced for at least one month in the 9 out of 11 frugivorous bird species included in the analyses. Avian body condition during the migratory passage has worsened, with fewer individuals showing a high‐fat percentage now than in the past. Finally, we report a fruit production decrease of almost half in 2019–2021 compared to 1981–1983, probably linked to habitat encroachment by pine trees and replacement of fleshy‐fruited shrubs. Vegetation encroachment and climate change are the most plausible explanations for the observed changes in the avian community, but the relative importance of these factors is yet unknown. Our results at a local scale mirror the dramatic consequences of global change affecting the diversity, phenology and physical condition of frugivorous bird species reported in multiple studies across the globe. The loss of frugivores may trigger feedback mechanisms in which seed dispersal is disrupted, leading to impaired recruitment of fruiting plants and hence less food availability for the avian community.

Simplified Communities of Seed-Dispersers Limit the Composition and Flow of Seeds in Edge Habitats

Edge effects, driven by human modification of landscapes, can have critical impacts on ecological processes such as species interactions, with cascading impacts on biodiversity as a whole. Characterizing how edges affect vital biotic interactions such as seed dispersal by frugivores is important for better understanding potential mechanisms that drive species coexistence and diversity within a plant community. Here, we investigated how differences between frugivore communities at the forest edge and interior habitats of a diverse tropical rainforest relate to patterns of animal-mediated seed dispersal and early seedling recruitment. We found that the lemur communities across the forest edge-interior gradient in this system showed the highest species richness and variability in body sizes at intermediate distances; the community of birds showed the opposite pattern for species richness. Three large-bodied frugivores, known to be effective dispersers of large seeds, tended to avoid the forest edge. As result, the forest edges received a lower rate of animal-mediated seed dispersal compared to the interior habitats. In addition, we also found that the seeds that were actively dispersed by animals in forest edge habitats were smaller in size than seeds dispersed in the forest interior. This pattern was found despite a similarity in seed size of seasonally fruiting adult trees and shrubs between the two habitats. Despite these differences in dispersal patterns, we did not observe any differences in the rates of seedling recruitment or seed-size distribution of successful recruit species. Our results suggest that a small number of frugivores may act as a potential biotic filter, acting on seed size, for the arrival of certain plant species to edge habitats, but other factors may be more important for driving recruitment patterns, at least in the short term. Further research is needed to better understand the potential long-term impacts of altered dispersal regimes relative to other environmental factors on the successional dynamics of edge communities. Our findings are important for understanding potential ecological drivers of tree community changes in forest edges and have implications for conservation management and restoration of large-seeded tree species in disturbed habitats.

Frugivore diversity increases evenness in the seed rain on deforested tropical landscapes

The diversity of tropical forests is strongly shaped by mutualistic interactions involving plants and frugivores that disperse their seeds. However, it is little known how decreases in the diversity of frugivores can affect seed dispersal patterns, plant community composition and species' coexistence in tropical forest landscapes. Here, we investigated the effects of bird frugivore diversity on seed dispersal of rare plant species and on the magnitude of equalizing effects on the seed rain in open areas within 12 fragmented landscapes in the Brazilian Atlantic Forest. We monitored the production of bird‐dispersed seeds and bird abundance in forest fragments, and sampled the seed rain and the activity of birds attracted to experimental tree nuclei established in neighboring pastures. The activity of frugivores in tree nuclei was positively correlated with the diversity of birds recorded in nearby forest fragments, and the seed rain diversity increased with frugivore activity. The proportion of seeds dispersed more frequently than expected by chance in tree nuclei increased linearly with the species' richness of birds. The richness and abundance of active frugivores in deforested areas promoted a seed rain with evenness and diversity up to five times greater than the seed pool available in forest fragments due to the proportional increase in the dispersal of rare plant species and a concomitant proportional decrease in the dispersal of dominant fruiting plants. Furthermore, every additional bird species detected in a site was associated with a 10% increase in the equalizing effect on dispersed seeds' relative abundance. Our results show that the aggregated behavior of avian frugivore communities on deforested areas results in higher species richness in the seed rain of plant communities and underscore the urgency to reduce bird species' loss and the simplification of their communities in tropical landscapes.

Ecological drivers of intraspecific variation in seed dispersal services of a common neotropical palm

AbstractThrough frugivory and seed dispersal, vertebrates influence plant demography and forest regeneration. Variation in local habitat surrounding fruiting plants can influence frugivore foraging decisions, thereby creating intraspecific variation in seed dispersal services. However, we have little knowledge of drivers of local variation in frugivory. Here, we investigate factors that may influence frugivore diversity and fruit removal at the level of individual plants. We focus on a common understory palm within a continuous Chocó forest with mixed land‐use histories in Ecuador. The density of pioneer tree species in the genus Cecropia around focal palms was negatively related to fruit removal and the diversity of frugivores visiting palms. This may relate to the fact that the presence and abundance of Cecropia species often indicate the existence and severity of past disturbances. Local Cecropia density was also related to an overall shift in the frugivore community that corresponded with an increase in fruit removal by lower‐quality seed dispersers (rodents). We also found that the local density of fruiting conspecifics was positively related to frugivore diversity, but not fruit removal. Our results provide information on drivers of intraspecific inequalities in plant populations across tropical forest landscapes. The reduction in fruit removal and frugivore diversity associated with local Cecropia abundance suggests that seed dispersal services can be sensitive to fine‐scale variation in habitat structure. Furthermore, because Cecropia are often indicative of past disturbances, this indicates that even small‐scale habitat degradation by humans can have lasting effects by creating localized pockets of forest unfavored by frugivores.Abstract in Spanish is available with online material.

Fruit and seed traits of native and invasive plant species in Hawai‘i: implications for seed dispersal by non-native birds

For alien invasive plant species dependent on frugivores for seed dispersal, traits that influence consumption can be important determinants of invasion and spread. However, trait comparisons between native and invasive species have documented mixed results. In Hawai‘i, one of the most invaded systems in the world, nearly all frugivory, and thus seed dispersal, is dependent on non-native birds. Moreover, the majority of dispersal events also involve invasive plants, suggesting the potential for an “invasional meltdown”. Here we compare fruit and seed traits between native and invasive plants and evaluate how those traits influence consumption by non-native avian frugivores. Although we found that most traits examined were similar between native and invasive fruiting species, invasive species tended to have higher fruit protein content, longer fruiting duration, were less likely to have orange fruits, and have less variable seed length. Longer fruiting duration and smaller seed size were important predictors for avian frugivore consumption. In combination, these results suggest that traits that increase probability of encounter (fruiting duration) and ability to be consumed (seed size) are more important for dispersal by frugivores than traits associated with fruit preferences and, thus, are driving the spread of invasive species and limiting dispersal of some native species. Further, we document an apparent seed size threshold for avian consumption (~ 7.0 mm), supporting previous work suggesting that large seeded species, particularly native plant species adapted for extinct large-bodied frugivores, are likely dispersal limited based on gape size limitation of the current non-native frugivore community.

Climate change reshapes the eco‐evolutionary dynamics of a Neotropical seed dispersal system

AbstractAimGlobal changes will redistribute biodiversity, reshaping ecological interactions and ecosystem processes. The decoupling in the distribution of plants and their mutualistic seed dispersers, for instance, may have overlooked eco‐evolutionary effects. How animal‐dispersed plants will respond to changes in the distribution of their seed dispersers remains largely an open question. Here, we forecast the consequences of climate change and frugivory interactions for the spatial distribution and seed size evolution of a Neotropical palm species.LocationAtlantic forests of South America.Time periodPresent day, end of 21st century.Major taxa studiedThirty‐two species of frugivorous birds, and a palm (Euterpe edulis).MethodsFuture patterns of animal–plant co‐occurrence were derived from ecological niche models, climate forecasts, projections of future forest loss, and seed dispersal simulations. We further explored the evolutionary effect of the spatial reorganization of interactions by modelling palm seed sizes as a function of changes in the distribution of frugivore traits.ResultsOur models indicate that future climate change and deforestation may reduce the palm’s suitable distribution by 20%–50%. However, our simulations suggest that 66% of all remaining future suitable distribution (76,200 km2) would still be inaccessible to the palm without the active dispersal of seeds by frugivores. In addition, novel frugivore communities are projected to have smaller mean body mass and gape size (−23% and −10%, respectively), due to the loss of large frugivores, which may translate into a 6%–17% reduction of seed sizes across the palm’s remaining distribution.Main conclusionsOur projections indicate that frugivore seed dispersal may be critical to allow occupancy of future habitat by animal‐dispersed plants. However, loss of large frugivores may affect trait selection regimes, creating hotspots of plant evolution towards smaller seeds. We argue that such complex dynamics emerging from species‐specific responses to global change may reshape the distribution and evolution of several interacting partners worldwide.

Large frugivores matter more on an island: Insights from island-mainland comparison of plant-frugivore communities.

Endozoochory, a mutualistic interaction between plants and frugivores, is one of the key processes responsible for maintenance of tropical biodiversity. Islands, which have a smaller subset of plants and frugivores when compared with mainland communities, offer an interesting setting to understand the organization of plant–frugivore communities vis‐a‐vis the mainland sites. We examined the relative influence of functional traits and phylogenetic relationships on the plant–seed disperser interactions on an island and a mainland site. The island site allowed us to investigate the organization of the plant–seed disperser community in the natural absence of key frugivore groups (bulbuls and barbets) of Asian tropics. The endemic Narcondam Hornbill was the most abundant frugivore on the island and played a central role in the community. Species strength of frugivores (a measure of relevance of frugivores for plants) was positively associated with their abundance. Among plants, figs had the highest species strength and played a central role in the community. Island‐mainland comparison revealed that the island plant–seed disperser community was more asymmetric, connected, and nested as compared to the mainland community. Neither phylogenetic relationships nor functional traits (after controlling for phylogenetic relationships) were able to explain the patterns of interactions between plants and frugivores on the island or the mainland pointing toward the diffused nature of plant–frugivore interactions. The diffused nature is a likely consequence of plasticity in foraging behavior and trait convergence that contribute to governing the interactions between plants and frugivores. This is one of the few studies to compare the plant–seed disperser communities between a tropical island and mainland and demonstrates key role played by a point‐endemic frugivore in seed dispersal on island.

FENOLOGIA REPRODUTIVA DE RUBIACEAE JUSS. NA MATA ATLÂNTICA PARAIBANA

Phenological studies help determine the reproductive and vegetative patterns of plants, contributing to knowledge about dynamics in an environment. We studied the reproductive phenological patterns of five Rubiaceae species in an Atlantic Forest area, evaluating their seed dispersal syndromes and the effects of climatic variables on flowering and fruiting phenology. We monitored reproductive individuals of five species biweekly from February 2015 to February 2016 (one-year period). For each reproductive phenophase, we evaluated the Fournier index and intrapopulational synchronicity. Spearman’s rank correlation was used to determine possible correlations between phenological phenophases and rainfall, temperature and photoperiod. Seed dispersal syndromes were based on morphological analysis and Van der Pijl classification. The Rubiaceae community showed a continuous pattern of flowering and fruiting. However, when analysing phenological patterns by species, there was a higher concentration of phenophases and synchronicity of populations in the rainy season. Flowering and fruiting were positively correlated with temperature and historical average rainfall. Zoochory was the predominant seed dispersal syndrome, indicating the importance of the Rubiaceae family as a year-round resource for frugivorous communities. Temperature and rainfall regulate the reproductive phenophases similarly, resulting in a high level of synchrony between them.

Plant origin and fruit traits shape fruit removal patterns by native birds in invaded plant communities

Biotic interactions and mutualisms in particular have an important role in ecosystem structure and functioning as well as in the maintenance of biodiversity. Understanding how communities respond to the introduction of non-native species and what determines the establishment of novel interactions between native and introduced species will help in determining the potential impacts of biological invasions. The aims of this work were to assess patterns of frugivory and fruit removal in environments with invasion of non-native fleshy-fruited plants and to evaluate whether novel associations between native frugivores and non-native plants are determined by fruit traits. For this we selected eight study sites in areas with different degrees of invasion of non-native fleshy-fruited plants. In each site, we measured fruit availability and fruit traits of native and non-native plants. In addition, we conducted direct frugivory observations. We found that native and non-native fruits differed based on morphological trait variables, such as fruit weight and dimensions. Only two birds, Elaenia albiceps (smaller and migrant) and Turdus falcklandii (bigger and resident), are the main frugivorous present in the area. At the scale of the community of frugivores, neither visit nor fruit removal rates differ between natives and non-natives. However, at the species scale, while E. albiceps preferentially foraged on native plants, T. falcklandii preferred non-natives. Thus, some generalist frugivorous species like T. falcklandii can play a key role in promoting the invasion of non-native plants.

The community structure of bird assemblages on urban strangler figs

AbstractFigs have been regarded as keystone plant resources that support diverse tropical vertebrate frugivore communities. Planting or conserving large fig trees, such as stranglers, have therefore been proposed for enhancing urban biodiversity. We compared the diversity and community structure of bird assemblages on strangler figs with non‐fig urban trees as well as between the fruiting and non‐fruiting fig trees in an urban setting in Singapore. The total bird abundance across all the fig trees when in fruit was 4.5‐fold higher than on non‐fig trees and 3.5‐fold higher than when the same fig trees were not fruiting, but only attracted two more species. On individual trees, after accounting for the presence of mistletoes, tree height, the area covered by buildings, road lane density, and the distance to natural vegetation, mean diversity was not different between non‐fig trees and fig trees when they were not in fruit. On the other hand, when fruiting, each fig tree on average had 1.4 more species, 3 more counts of non‐native birds, and 1.6 more counts of insectivorous birds than when not fruiting. There was significant compositional turnover between non‐fig trees and non‐fruiting fig trees, while community dispersion was significantly lower among fig trees in fruit. Our results demonstrate that fig trees provide fruit and non‐fruit resources for birds in an urban landscape but do not necessarily support more diverse total bird assemblages than non‐fig trees. Instead, bird communities on fruiting urban figs would be highly homogeneous and dominated by a few species.Abstract in Malay is available with online material.

Functional traits of avian frugivores have shifted following species extinction and introduction in the Hawaiian Islands

Abstract The extinction and introduction of species can alter ecological processes owing to the loss or gain of species roles. In vertebrate‐dependent seed dispersal, mutualisms between frugivores and fruiting plants depend, in part, on matching of functional traits. High species turnover of frugivores has occurred on the Hawaiian Islands, owing to both the loss of native frugivores and the introduction of a new suite of frugivores. How this turnover has altered the functional traits of frugivores and the potential impacts on seed dispersal remain unclear. We investigated how avian frugivore traits differed between historic and modern assemblages of the Hawaiian Islands. We also tested how traits shifted within foraging guilds (ground vs. arboreal) to distinguish potential impacts on plants within low versus high forest strata. Compared to historic frugivores, the modern assemblage is smaller in gape width and body mass in both ground and arboreal guilds. Wing shape did not significantly change between assemblages. From the results, we postulate that changes in the frugivore community have likely altered seed dispersal processes by reducing (a) the size of seeds consumed, (b) frugivory rates per animal and (c) seed dispersal distances. Owing to seed size placing strong constraints on consumption, we reviewed recent studies on frugivory by modern birds in the Hawaiian Islands and compared the size of seeds consumed versus seeds available. We found that larger‐seeded plants (>8.1 mm seed width) were not consumed by modern birds and were more likely to be of conservation risk compared to smaller‐seeded plants. Consequently, dispersal limitation may threaten Hawaiian plant communities, with larger‐seeded plants at greatest risk of extinction. Broadly, we show that extensive turnover within assemblages may lead to significant changes in functional traits, with potential knock‐on effects for mutualistic interactions and communities. A free Plain Language Summary can be found within the Supporting Information of this article.