Generalist Frugivores Research Articles

Loss of endangered frugivores from seed dispersal networks generates severe mutualism disruption.

Many tropical seed-dispersing frugivores are facing extinction, but the consequences of the loss of endangered frugivores for seed dispersal is not well understood. We investigated the role of frugivore endangerment status via robustness-to-coextinction simulations (in this context, more accurately described as robustness-to-partner-loss simulations) using data from the Brazilian Atlantic Forest biodiversity hotspot. By simulating the extinction of endangered frugivores, we found a rapid and disproportionate loss of tree species with dispersal partners in the network, and this surprisingly surpassed any other frugivore extinction scenario, including the loss of the most generalist frugivores first. A key driver of this pattern is that many specialist plants rely on at-risk frugivores as seed-dispersal partners. Moreover, interaction compensation in the absence of endangered frugivores may be unlikely because frugivores with growing populations forage on fewer plant species than frugivores with declining populations. Therefore, protecting endangered frugivores could be critical for maintaining tropical forest seed dispersal, and their loss may have higher-than-expected functional consequences for tropical forests, their regeneration processes, and the maintenance of tropical plant diversity.

Individual‐based networks reveal the highly skewed interactions of a frugivore mutualist with individual plants in a diverse community

While plant–animal interactions occur fundamentally at the individual level, the bulk of research examining the mechanisms that drive interaction patterns has focused on species or population levels. In seed‐dispersal mutualisms between frugivores and plants, little is known about the role of space and individual‐level variation among plants in structuring patterns of frugivory and seed dispersal in a plant community. Here we use a zoocentric approach to examine how space and variation between individual plants affect movement and visitation by frugivores foraging on individual fruiting plants. To do this, we used a spatially explicit network approach informed by observations of the movement and foraging of a frugivorous lemur species Eulemur rubriventer among individual plants in a diverse plant community in Madagascar. The resulting hierarchical networks show a few individual plants receiving the bulk of the interactions, demonstrating that a generalist frugivore species could act as an individual‐plant specialist within a plant community. The few individual plants that dominated interactions with lemurs shaped the modular spatial structure of frugivory interactions in the community and facilitated visitation to near neighbors. This interaction structure was primarily driven by extrinsic factors, as lemur movements among plants were significantly influenced by the individual plant's spatial position and the fruiting plant richness in its immediate neighborhood. Individual plants in central spatial locations with large fruit crops received the most visits. The observed inequality in the interactions of a generalist frugivore within a highly diverse plant community highlights the importance of considering individual‐level variation for essential ecosystem processes such as seed dispersal.

Sowing forests: a synthesis of seed dispersal and predation by agoutis and their influence on plant communities.

Granivorous rodents have been traditionally regarded as antagonistic seed predators. Agoutis (Dasyprocta spp.), however, have also been recognized as mutualistic dispersers of plants because of their role as scatter-hoarders of seeds, especially for large-seeded species. A closer look shows that such definitions are too simplistic for these Neotropical animals because agoutis can influence plant communities not only through seed dispersal of large seeds but also through predation of small seeds and seedlings, evidencing their dual role. Herein, we summarize the literature on plant-agouti interactions, decompose agouti seed dispersal into its quantitative and qualitative components, and discuss how environmental factors and plant traits determine whether these interactions result in mutualisms or antagonisms. We also look at the role of agoutis in a community context, assessing their effectiveness as substitutes for extinct megafaunal frugivores and comparing their ecological functions to those of other extant dispersers of large seeds. We also discuss how our conclusions can be extended to the single other genus in the Dasyproctidae family (Myoprocta). Finally, we examine agoutis' contribution to carbon stocks and summarize current conservation threats and efforts. We recorded 164 interactions between agoutis and plants, which were widespread across the plant phylogeny, confirming that agoutis are generalist frugivores. Seed mass was a main factor determining seed hoarding probability of plant species and agoutis were found to disperse larger seeds than other large-bodied frugivores. Agoutis positively contributed to carbon storage by preying upon seeds of plants with lower carbon biomass and by dispersing species with higher biomass. This synthesis of plant-agouti interactions shows that ecological services provided by agoutis to plant populations and communities go beyond seed dispersal and predation, and we identify still unanswered questions. We hope to emphasise the importance of agoutis in Neotropical forests.

Inducing seed dispersal by generalist frugivores: A new technique to overcome dispersal limitation in restoration

Abstract Dispersal limitation severely impairs the trajectory of restoration, mainly due to the lack of seed vectors bringing seeds from nearby habitats; a role played by many frugivorous vertebrates that can be absent or reduced in restored or degraded sites. Here we propose a new technique named Induced Seed Dispersal, that amplifies the role that many generalist frugivores have in seed dispersal. It consists in the offering of seeds embedded in the pulp of commercial fruits or whole native fleshy fruits in feeders to generalist frugivores, which ingest the seeds and defecate them elsewhere. We set feeders in a restored site and monitored the visiting pattern of these frugivores with cameras‐traps. We also set seed traps to retrieve seeds dispersed by frugivores and offered around 1,500 seeds of Cecropia hololeuca (Urticaceae) per week for 1 year. We recorded at least 24 generalist frugivore species of terrestrial mammals, bats and birds, which ingested/removed the seeds/fruits from the feeders. Seeds of C. hololeuca dispersed by marmosets were retrieved in the seed traps and germinated. We estimated a potential seed rain of more than 600 C. hololeuca seeds ha−1 mo−1. Synthesis and applications. Our study demonstrates that this new technique can make use of generalist frugivores to assist restoration or regeneration into sites where seed dispersal is compromised by the lack of dispersers or limited seed arrival. Inducing seed dispersal by generalist frugivores is a low‐cost and easy‐managed technique that can be applied year‐round in restoration and forest enrichments at all scales.

Wild Bornean orangutan (Pongo pygmaeus wurmbii) feeding rates and the Marginal Value Theorem.

The Marginal Value Theorem (MVT) is an integral supplement to Optimal Foraging Theory (OFT) as it seeks to explain an animal's decision of when to leave a patch when food is still available. MVT predicts that a forager capable of depleting a patch, in a habitat where food is patchily distributed, will leave the patch when the intake rate within it decreases to the average intake rate for the habitat. MVT relies on the critical assumption that the feeding rate in the patch will decrease over time. We tested this assumption using feeding data from a population of wild Bornean orangutans (Pongo pygmaeus wurmbii) from Gunung Palung National Park. We hypothesized that the feeding rate within orangutan food patches would decrease over time. Data included feeding bouts from continuous focal follows between 2014 and 2016. We recorded the average feeding rate over each tertile of the bout, as well as the first, midpoint, and last feeding rates collected. We did not find evidence of a decrease between first and last feeding rates (Linear Mixed Effects Model, n = 63), between a mid-point and last rate (Linear Mixed Effects Model, n = 63), between the tertiles (Linear Mixed Effects Model, n = 63), nor a decrease in feeding rate overall (Linear Mixed Effects Model, n = 146). These findings, thus, do not support the MVT assumption of decreased patch feeding rates over time in this large generalist frugivore.

The spatial complexity of seed movement: Animal‐generated seed dispersal patterns in fragmented landscapes revealed by animal movement models

AbstractLarge animals provide crucial seed dispersal services, yet face continued threats and are susceptible to changes in landscape composition and configuration. Thus, there is a growing imperative to improve understanding of animal‐generated seed dispersal using models that incorporate spatial complexity in a realistic, yet tractable, way.We developed a spatially explicit agent‐based seed dispersal model, with disperser movements informed by biotelemetry data, to evaluate how landscape composition and configuration affect seed dispersal patterns. We illustrated this approach for the world's second largest ratite, the emu (Dromaius novaehollandiae), a highly mobile generalist frugivore considered an important long‐distance disperser for many plant species across Australia.When animal movement is unrestricted, model parameters related to seed gut passage largely determine seed dispersal kernels. However, as habitat loss and fragmentation increase, the extent of long‐distance dispersal events is reduced and seed shadows became progressively more aggregated. This effect is due to the emu not being able to move between disconnected parts of the landscape, with small changes in habitat structure causing decreased long‐distance dispersal.We simulated seed dispersal patterns generated by three commonly used generic models of animal movement – unbiased and biased correlated random walks and Lévy walks – to evaluate how different representations of movement affect estimations of animal movements and emergent seed dispersal patterns. Simulated movements informed by the emu biotelemetry data resulted in longer median seed dispersal distances than do the three generic models.Synthesis.Changes in landscape composition and configuration can dramatically alter patterns of zoochorous seed dispersal as they influence animal movement. However, when models are used to simulate the patterns of seed dispersal, decisions about how animal movement is represented also affect estimates of seed dispersal.

Reward regulation in plant\u2013frugivore networks requires only weak cues

Theory assumes that fair trade among mutualists requires highly reliable communication. In plant–animal mutualisms the reliability of cues that indicate reward quality is often low. Therefore, it is controversial whether communication allows animal mutualists to regulate their reward intake. Here we show that even loose relationships between fruit brightness and nutritional rewards (r2 = 0.11–0.35) allow birds to regulate their nutrient intake across distinct European plant–frugivore networks. Resident, over-wintering generalist frugivores that interact with diverse plant species select bright, lipid-rich fruits, whereas migratory birds select dark, sugar- and antioxidant-rich fruits. Both nutritional strategies are consistent with previous physiological experiments suggesting that over-wintering generalists aim to maximize their energy intake, whereas migrants aim to enhance the build-up of body fat, their immune response and oxidative status during migration. Our results suggest that animal mutualists require only weak cues to regulate their reward intake according to specific nutritional strategies.

Plant-disperser mutualisms in a semi-arid habitat invaded by Lantana camara L.

Dispersal is an important ecological process that affects plant population structure and community composition. Invasive plants with fleshy fruits rapidly form associations with native and invasive dispersers, and may affect existing native plant-disperser associations. We asked whether frugivore visitation rate and fruit removal was associated with plant characteristics in a community of fleshy-fruited plants and whether an invasive plant receives more visitation and greater fruit removal than native plants in a semi-arid habitat of Andhra Pradesh, India. Tree-watches were undertaken at individuals of nine native and one invasive shrub species to assess the identity, number and fruit removal by avian frugivores. Network analyses and generalised linear mixed-effects models were used to understand species and community-level patterns. All plants received most number of visits from abundant, generalist avian frugivores. Number of frugivore visits and time spent by frugivores at individual plants was positively associated with fruit crop size, while fruit removal was positively associated with number of frugivore visits and their mean foraging time at individual plants. The invasive shrub, Lantana camara L. (Lantana), had lower average frugivore visit rate than the community of fleshy-fruited plants and received similar average frugivore visits but greater average per-hour fruit removal than two other concurrently fruiting native species. Based on the results of our study, we infer that there is little evidence of competition between native plants and Lantana for the dispersal services of native frugivores and that more data are required to assess the nature of these interactions over the long term. We speculate that plant associations with generalist frugivores may increase the functional redundancy of this frugivory network, buffering it against loss of participating species.

Retracted: Co‐fruiting plant species share similar fruit and seed traits while phylogenetic patterns vary through time

Summary Co‐fruiting plant species are subject to a variety of biotic and abiotic processes that may influence patterns of fruiting phenology and the functional and phylogenetic diversity of co‐fruiting taxa in a community. Understanding the seasonal patterns of functional and phylogenetic diversity of fruiting in a community will shed new light on potential mechanisms structuring plant communities. Using rain forest trees in south‐eastern Madagascar as our system, we predicted there would be clustering of fruit and seed traits and phylogenetic relationships among co‐fruiting species because plants are vying for seed‐dispersal services from a limited set of generalist frugivore taxa. We also predicted that seasonal variations in rainfall would mediate fluctuations in functional trait and phylogenetic diversity of co‐fruiting assemblages. Despite fluctuating patterns in their functional trait diversity over time, co‐fruiting assemblages displayed consistent clustering of fruit/seed traits across time. Phylogenetic diversity was not clustered overall, but fluctuated non‐randomly in time, between clustered and overdispersed, such that strong shifts in rainfall were associated with the co‐fruiting of more closely related species. Synthesis. We suggest that it may be more beneficial for co‐fruiting plant species to share similar fruit and seed traits than to diversify traits, when they rely on a comparatively small set of generalist frugivorous taxa for seed dispersal. Results also demonstrate that rainfall‐driven environmental filtering may cause seasonal fluctuations in the phylogenetic patterns of phenology in a community. Results highlight the importance of a temporal context in examining structural patterns of communities.

Dispersal by generalist frugivores affects management of an invasive plant

AbstractIn the past century, our understanding of the processes driving plant invasion and its consequences for natural and anthropogenic systems has increased considerably. However, the management of invasive plants remains a challenge despite ever more resources being allocated to their removal. Often invasive plants targeted for ‘eradication’ are well‐established, have multiple modes of reproduction, long‐term seed banks, and strong associations with native and non‐native mutualists that ensure dispersal and facilitate spread. The pantropical weed, Lantana camara (Lantana), is one of the most invasive woody plants globally. We illustrate that, for Lantana, eradication is an unrealistic management goal given the short‐term removal approaches, irrespective of the effectiveness of removal methods. We assessed the role of dispersal by avian frugivores in the recolonization of managed areas by Lantana in the seasonally dry, tropical forests of northern and southern India. We estimated the distribution of Lantana, its dispersal potential and the proximity between managed areas and source populations. We found that Lantana was dispersed by many generalist frugivorous birds and that most managed areas were well within the median dispersal distance from source plants facilitating rapid recolonization of managed areas. We conclude that given the difficulty of eradicating long‐established invasive plants, management practices should entail long‐term monitoring and control in priority areas for as long as Lantana occurs in the landscape.

Population dynamics of an invasive tree, Sorbus aucuparia, in the understory of a Patagonian forest

Exotic fleshy fruited plants are often dispersed by generalist frugivores into undisturbed or weakly disturbed forests. The establishment and spread of these plants in the understory may pass unnoticed until their abundance and size turns them a nuisance. Sorbus aucuparia is a fleshy fruited tree recently established in temperate forests of northwestern Patagonia. Our aim was to determine the invasion dynamics of S. aucuparia in a Nothofagus pumilio forest. We analyzed age structure, minimum age of reproduction, the time from colonization to effective recruitment (lag time), and demographic parameters to pinpoint critical stages for management. Currently, the population of S. aucuparia is increasing. Large numbers of suppressed, potentially reproductive individuals were found. Lag time was relatively short (25 years) in comparison to other invasive woody plants. The minimum reproductive age was 10 years, and all reproductive individuals were located in high light conditions. The number of trees at the reproductive stage made the most significant contribution to population growth; a 5 % reduction in this number would be enough for the population growth rate to be negatively affected. Thus, the reproductive stage is key to the control of S. aucuparia. Forest disturbance leading to increase light availability may result in higher rates of growth and reproduction among currently suppressed individuals, triggering further expansion events and increasing the number of invasion foci. Management strategies for tree species which present an inconspicuous bank of individuals in the understory, like S. aucuparia, should focus on early detection and eradication of reproductive individuals while avoiding the increase in light availability in the affected environment.

Chaco Chachalaca (Ortalis canicollis, Wagler, 1830) feeding ecology in a gallery forest in the South Pantanal (Brazil).

Cracids are generalist frugivores, which often exploit plant food resources such as flowers and leaves, mainly when fruit production declines. The Chaco chachalaca (Ortalis canicollis) is the most abundant cracid in the Pantanal (Brazil), and particularly common in the gallery forests. However, the factors related to their occurrence in this habitat type are unclear. In this study I describe the feeding habits and feeding niche breadth fluctuations of the Chaco chachalaca in relation to food resources abundance and diversity at the Miranda river gallery forest (Southern Pantanal). I also analyzed the relationships between Chaco chachalacas feeding activity and food resources abundance. This parameter (flowers and fruits) exhibited significant seasonal differences of abundance in which flowers were plentiful at the end of the dry, while fruits were abundant during the early wet season. However, food resources diversity to Chaco chachalacas exhibited no seasonal difference. Their feeding activity paralleled the availability of food resources, so that when some items were massively available an enhanced number of Chaco chachalacas foraged in the gallery forest, particularly during the prolonged dry season when they extensively used flowers and Genipa americana fruits. In fact, the Chaco chachalaca feeding niche breadth value presented low values in this period, while high values were common in the rest of the year. The flexible diet of this cracid, potentially favors their year round presence in the gallery forest, mainly during the prolonged dry season when the propensity for famine might be high. Since the Chaco chachalaca is among the largest and most abundant canopy frugivores in the gallery forest, it may contribute to forest regeneration, an underscored role due to the impact of annual floods and meandering dynamics on tree loss.

Diverse guilds provide complementary dispersal services in a woodland expansion process after land abandonment

Summary Land abandonment due to increasing depopulation of rural areas is an ongoing trend in developed countries worldwide. Abandoned lands represent an opportunity for ecosystem recovery, an urgent need for biodiversity conservation. Seed dispersal services provided by animals are a key feature for this process. Different dispersers may differentially contribute to plant recruitment under different ecological conditions, leading to complementary dispersal services. We studied the dispersal services, quantified as the contribution to plant recruitment, provided by the main dispersal guilds of Spanish juniper Juniperus thurifera L.: small‐to‐medium‐sized strongly frugivorous birds (thrushes) and medium‐to‐large‐sized carnivorous mammals (red fox and stone marten). To do this, we studied seed fate from seed dispersal to seedling survival during 2 years and estimated seed dispersal effectiveness (seedlings recruited per m2) in two ecological contexts derived from ecosystem recovery after a historical period of degradation: remnant woodlands and old fields. Results showed a clear shift in the contribution to plant recruitment between these guilds, resulting in complementary and non‐redundant dispersal services. Thrushes were the main contributors to plant recruitment in woodlands (73%), leading to population growth but with a reduced impact on the colonization of old fields where carnivores contributed to 80% of recruitment (42% red fox, 38% stone marten). The dispersal complementarity observed for thrushes and carnivores is a consequence of their functional diversity, mainly driven by their differences in feeding and movement behaviour. Synthesis and applications. The combination of short‐distance, strongly frugivorous dispersers (e.g. passerine birds) together with big generalist frugivores with long‐distance movements (e.g. carnivorous mammals) maintained (i) effective seed dispersal services in remnant woodlands and (ii) the connectivity between patches promoting old fields colonization and woodland expansion. Thus, it is in heterogeneous landscape mosaics ecosystems (e.g. agro‐environments) where functionally diverse disperser communities play a key role in ecosystem recovery. By performing effective dispersal services across an array of habitat types, functionally diverse disperser communities assist natural restoration of human‐impacted ecosystems all over the world. Thus, dispersal communities provide an important ecosystem service that may replace costly human‐mediated restoration projects.

Seasonal patterns in community composition of bats in forest fragments of the Alto Rio Paraná, southern Brazil

We studied seasonal patterns in richness and abundance in bat communities in Atlantic Forest fragments along the Paraná River in Brazil. There were differences in species composition among fragments but these appear more related to habitat quality than to fragment size. All fragments had high rates of captures of generalist frugivores and a scarcity of species known to be susceptible to disturbance. Richness and abundance were slightly lower during the dry season, but differences were significant only in the most degraded fragment.

Wild cherries invading natural grasslands: unraveling colonization history from population structure and spatial patterns

Invasive success of many fleshy-fruited plants has been linked to opportunistic interactions with generalist frugivores. Prunus mahaleb is a small tree, producing large quantities of little, bright black, sugary drupes that are consumed by vertebrates. It is native to the Mediterranean region but has become invasive in several countries. This study was carried out at a nature reserve including remnant mountain grasslands of high conservation value in the southern Argentine Pampas. Our aim is to reconstruct the colonization history of invading populations proposing a generalized model to describe the invasion process: colonization events result in the establishment of a founder tree followed by a lag phase until it reaches massive seed production and enables an increase in local recruitment and plant density. To test this hypothesis, we analyzed population age structures and contrasted them with those predicted using a Leslie matrix growth model. We found that matrix model predictions fit well to actual age structures. Our results reveal the existence of an 8–18-year lag period between the establishment of the founder tree and local effective recruitment. The end of this lag coincides with an abrupt increase in individual fruit production that may have a strong effect on bird attraction and successful seed dispersal. This lag phase represents an opportunity for preventing further spread of P. mahaleb. Early detection and rapid eradication of new invasion focuses should be targeted as a principal aim of an effective control strategy.

The Relative Contribution of Specialists and Generalists to Mistletoe Dispersal: Insights from a Neotropical Rain Forest

AbstractMistletoes rely on birds for seed dispersal, but the presumed importance of mistletoe‐specialist frugivores has not been critically examined nor compared with generalist frugivores and opportunistic foragers. The contribution of these three groups was compared directly by quantifying bird visitation to fruiting mistletoe plants ( Oryctanthus occidentalis: Loranthaceae) at Barro Colorado Island, Panama, and by comparing these results with proportions calculated from other empirical studies of mistletoe visitation conducted elsewhere. After more than 100 h of timed watches, 23 bird species were recorded visiting eight heavily infected host trees ( Luehea seemannii: Tiliaceae). Eight of these species visited mistletoe, of which five (all tyrannids) consumed mistletoe fruit. Although two mistletoe specialist frugivores ( Tyrannulus elatus and Zimmerius vilissimus) removed most fruit (73%), more than a quarter was consumed by one generalist frugivore ( Mionectes oleagineus) and two opportunists ( Myiozetetes cayanensis and Myiozetetes similis). Post consumption behaviour varied: the specialists flew from mistletoe to mistletoe, the generalist rested in the subcanopy and understory, and the opportunists spent most time hawking insects and resting high in the canopy. Integrating these data with previous work, the dietary specialization, short gut passage rate and strict habitat preferences of mistletoe specialists suggests that their services relate primarily to intensification and contagious dispersal, while species with broader diets are more likely to visit uninfected trees and establish new infections. The presumed importance of mistletoe‐specialist frugivores was not supported and mistletoes are considered to be comparable to many other bird‐dispersed plants, relying on both specialist and generalist frugivores, while opportunists may be disproportionately important in long‐distance dispersal.

Advantages of granivory in seasonal environments: feeding ecology of an arboreal seed predator in Amazonian forests

Specialized seed predators are uncommon in arboreal vertebrate assemblages, and the hypothesis that consuming seeds of immature fruits – which may be available for relatively long periods compared to mature fruit – could reduce seasonal food scarcity experienced by generalist frugivores remains largely untested. To test this hypothesis, we examined the diet and feeding ecology of bald‐faced saki monkeys Pithecia irrorata in a largely intact forest mosaic of southeastern Peru based on systematic monitoring of five habituated groups over a three‐year period and compared the relative availability of ripe and unripe fruits in their diet. Plant phenology data from individual tree crowns showed that, compared to ripe fruits, immature fruits were available in more tree species, in greater quantities, and for longer periods. Despite pronounced community‐wide seasonal changes in fruit production at our study area, feeding patterns of bald‐faced saki remained largely invariant: fruits comprised approximately 95% of the species’ monthly diet, with seeds alone accounting for 75%, with no major monthly dietary shifts. The flexible exploitation by this species of a consistently available food supply for which it faces little competition likely reduces foraging effort and consumption of less desirable foods, even during prolonged periods of overall fruit scarcity. The relative rarity of immature fruit specialists in tropical forests may reflect the fact that processing the hard pericarps and neutralizing the toxicities of immature seeds present substantial evolutionary hurdles that few arboreal vertebrate species have overcome.

Maintenance of bird functional diversity in a traditional agroecosystem of Madagascar

In Madagascar, despite acute land use pressure on forests coupled with unprecedented loss of endemic species and natural habitats, data on species distributions outside natural habitats are strikingly scarce. In this study, this gap is addressed by measuring bird diversity both within a protected forest corridor, and in the agricultural mosaic surrounding it. Results show that the diversity of all birds, and also of several functional guilds was higher in the mosaic than in the corridor. Moreover, 69% of all species found in the forest (61% of those classified as forest species) also occupied the agricultural mosaic. The diversity of frugivores, canopy insectivores and forest species in the mosaic was highly dependent upon the variety of scattered trees, small forest patches, plantations and secondary habitats distributed throughout the landscape. Generalist frugivores were particularly abundant in the mosaic, implying high potential for the maintenance of seed dispersal and fallow regeneration ecosystem services. Forest species in the mosaic were more generalist and less abundant, however, than those in the forest, suggesting the presence of both source–sink dynamics and potential biotic homogenization of the community in this landscape. Although under current conditions of heterogeneity and composition, the agricultural mosaic harbors a significant proportion of the endemic bird community, this study confirms the need for both sustained protection of large forest areas, and for adequate management of the agricultural landscape, particularly through the maintenance and enhancement of old-growth and isolated tree structures and fragments.

The restricted seed rain of a mistletoe specialist

Specialist frugivores are the dominant consumers of mistletoe fruit in many regions and have been shown to intensify infections of host plants as a result of their rapid gut passage rates and dependence on existing infections. The role of specialist frugivores in long distance dispersal of mistletoe and establishment of new infections is unclear, and has not been explicitly evaluated previously. Here we critically examine the premise that specialists are the dominant dispersers by examining the role of an Australian mistletoe specialist (mistletoebird Dicaeum hirundinaceum Dicaeidae) in dispersing mistletoe (Amyema preissii Santalales: Loranthaceae) seeds beyond infected host stands. We use two primary lines of evidence – presence of birds using remote call recorders, and presence of dispersed seeds via surveys for defecated seeds on host branches. The observed and inferred movements of the mistletoebird were wholly restricted to habitat patches containing mistletoe, and this bird was not observed to transport seeds to nearby uninfected host stands within the study system. While mistletoe specialists may provide much of the within‐stand dispersal service for mistletoes, this serves only to aggregate and intensify existing infections. We suggest that long distance dispersal of mistletoe seeds beyond existing hosts and infection centres is not performed by these dietary specialists, these services more likely to be provided by generalist frugivores and other occasional mistletoe fruit consumers.

Network models of frugivory and seed dispersal: Challenges and opportunities

Network analyses have emerged as a new tool to study frugivory and seed dispersal (FSD) mutualisms because networks can model and simplify the complexity of multiple community-wide species interactions. Moreover, network theory suggests that structural properties, such as the presence of highly generalist species, are linked to the stability of mutualistic communities. However, we still lack empirical validation of network model predictions. Here we outline new research avenues to connect network models to FSD processes, and illustrate the challenges and opportunities of this tool with a field study. We hypothesized that generalist frugivores would be important for forest stability by dispersing seeds into deforested areas and initiating reforestation. We then constructed a network of plant–frugivore interactions using published data and identified the most generalist frugivores. To test the importance of generalists we measured: 1) the frequency with which frugivores moved between pasture and forest, 2) the bird-generated seed rain under perches in the pasture, and 3) the perching frequency of birds above seed traps. The generalist frugivores in the forest network were not important for seed dispersal into pastures, and thus for forest recovery, because the forest network excluded habitat heterogeneities, frugivore behavior, and movements. More research is needed to develop ways to incorporate relevant FSD processes into network models in order for these models to be more useful to community ecology and conservation. The network framework can serve to spark and renew interest in FSD and further our understanding of plant–animal communities.