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Understanding the mechanisms that shape the architecture, diversity, and adaptations of genomes and their ecological and genetic interfaces is of utmost importance to understand biological evolution. Transposable elements (TEs) play an important role in genome evolution, due to their ability to transpose within and between genomes, providing sites of nonallelic recombination. Here we investigate patterns and processes of TE-driven genome evolution associated with niche diversification. Specifically, we compared TE content, TE landscapes, and frequency of horizontal transposon transfers (HTTs) across genomes of flower-breeding Drosophila (FBD) with different levels of specialization on flowers. Further, we investigated whether niche breadth and ecological and geographical overlaps are associated with a potential for HTT rates. Landscape analysis evidenced a general phylogenetic pattern, in which species of the D. bromeliae group presented L-shaped curves, indicating recent transposition bursts, whereas D. lutzii showed a bimodal pattern. The great frequency of highly similar sequences recovered for all FBD suggests that these species probably experienced similar ecological pressures and evolutionary histories that contributed to the diversification of their mobilomes. Likewise, the richness of TEs superfamilies also appears to be associated with ecological traits. Furthermore, the two more widespread species, the specialist D. incompta and the generalist D. lutzii, presented the highest frequency of HTT events. Our analyses also revealed that HTT opportunities are positively influenced by abiotic niche overlap but are not associated with phylogenetic relationships or niche breadth. This suggests the existence of intermediate vectors promoting HTTs between species that do not necessarily present overlapping biotic niches.

The diversity of fruits and frugivorous species is especially high in tropical regions where frugivory and seed dispersal interactions are particularly critical for the structure and functioning of terrestrial communities. However, the increasing urbanization in tropical areas has caused profound landscape changes, affecting species interactions and associated ecosystems functions. Here, we present an overview of the studies on frugivory and seed dispersal in tropical urban areas, discussing emergent patterns and processes underlying plant-frugivore interactions as well as major research gaps. Our review highlights an uneven geographical distribution of studies, which are more frequent in the Neotropics in comparison to Indomalayan and Afrotropical regions. We found that in tropical urban areas: (i) the most frequently studied group are flying frugivores (birds and bats), (ii) fruits of Myrtaceae, Moraceae, and Arecaceae are most frequently reported as consumed by frugivores, (iii) introduced plants are often present in frugivores’ diets, and become more common with urbanization, (iv) frugivores niche breadths vary with seasonality in fruit availability, (v) a higher diversity of fruits are consumed by frugivores in (or near) habitats that preserve more natural characteristics, such as higher proportion of green areas. Since suitable habitats within cities are highly variable in size, shape, connectivity, patterns of human activity, vegetation management and socioeconomic contexts, we recommend future studies to sample gradients in such variables. Furthermore, as new urban areas are often planned in advance, ‘before-after impact’ studies may be particularly insightful to understand how frugivores respond to urbanization and how to create frugivore-friendly areas without promoting undesirable (invasive) plants. Although the scarcity of studies and their geographical bias limit generalizations across distinct tropical regions, based on our review we provide a preliminary list of broad recommendations of management practices towards creating biodiversity-friendly urban areas.

While network analyses have stimulated a renewed interest in understanding patterns and drivers of specialization within communities, few studies have explored specialization within populations. Thus, in plant populations, causes and consequences of individual variation in their interactions with mutualistic animals remain poorly understood. Studying a Brazilian pepper (Schinus terebinthifolia) population, we measured the extent of individual variation in interactions with seed dispersers and tested whether connectivity (number of seed dispersers) and specialization (exclusiveness of partners) are associated with phenotypic and phenological traits of individuals and their spatial context. We found that: (i) individuals varied broadly in their connectivity and specialization on seed dispersers; (ii) phenotypic traits and spatial context matter more than fruiting duration in determining how many and how exclusive are seed dispersers of an individual; (iii) the individual-based network was nested and indicated that the less connected individuals were shorter, occurred in neighborhoods with fewer fruits, and tended to interact with a subset of the partners of more generalist individuals which, in turn, were taller and inserted in higher fruit density neighborhoods; (iv) modularity indicated the existence of subsets of individuals that interacted disproportionately with distinct groups of partners, which may occur due to differences in bird habitat use across the landscape. Our study underlines a remarkable interindividual variation that is overlooked when interactions are compiled to describe species-level interactions. Traits and spatial contexts that define variation among individuals may have important implications not only for fitness but also for sampling and description of interactions at species level.

Invasive species are one of the most important threats to ecosystems. While invasive plants can interact directly with native pollinators, wind-pollinated grasses can also indirectly affect plant-pollinator networks by changing plant and animal community composition and, ultimately, decreasing ecosystem functioning. Here, we investigated the effect of invasive grass on pollinator richness, visitation number, and the structure of plant-pollinator networks. Further, we tested the impact of the non-native honeybee on pollinator richness, visitation number, and network structure in the Caatinga. Invasive grass negatively affected native pollinators and reduced visitation number on native plants. The dominance of the invasive grass increase plant competition, which led to an increased of niche overlap among native pollinators but did not affect the number of visits by non-native honeybees. However, increase in visitation number by honeybees reduced native pollinator richness by 60%. Our findings suggest a negative potentialized effect of invasive grass and non-native honeybee on the native plant-pollinator dynamics. The invasive grasses reduce the number of pollinators visits indirectly through changes in plant community composition that may reduce the attractiveness of patches dominated by invasive grasses. Honeybees were not affected by the invasive grass but reduced the richness of native pollinator species and the number of visits they perform, suggesting an important effect of biological invasion on ecosystem resilience. Our research helps to understand how invasive species, directly and indirectly, impact the plant-pollinator interactions and his influence on ecosystem functioning in abandoned lands in dry semiarid ecosystems.

As human-caused extinctions and invasions accumulate across the planet, understanding the processes governing ecological functions mediated by species interactions, and anticipating the effect of species loss on such functions become increasingly urgent. In seed dispersal networks, the mechanisms that influence interaction frequencies may also influence the capacity of a species to switch to alternative partners (rewiring), influencing network robustness. Studying seed dispersal interactions in novel ecosystems on O‘ahu island, Hawai‘i, we test whether the same mechanisms defining interaction frequencies can regulate rewiring and increase network robustness to simulated species extinctions. We found that spatial and temporal overlaps were the primary mechanisms underlying interaction frequencies, and the loss of the more connected species affected networks to a greater extent. Further, rewiring increased network robustness, and morphological matching and spatial and temporal overlaps between partners were more influential on network robustness than species abundances. We argue that to achieve self-sustaining ecosystems, restoration initiatives can consider optimal morphological matching and spatial and temporal overlaps between consumers and resources to maximize chances of native plant dispersal. Specifically, restoration initiatives may benefit from replacing invasive species with native species possessing characteristics that promote frequent interactions and increase the probability of rewiring (such as long fruiting periods, small seeds and broad distributions).

Functional traits can determine pairwise species interactions, such as those between plants and pollinators. However, the effects of biogeography and evolutionary history on trait-matching and trait-mediated resource specialization remain poorly understood.We compiled a database of 93 mutualistic hummingbird-plant networks (including 181 hummingbird and 1,256 plant species), complemented by morphological measures of hummingbird bill and floral corolla length. We divided the hummingbirds into their principal clades and used knowledge on hummingbird biogeography to divide the networks into four biogeographical regions: Lowland South America, Andes, North & Central America, and the Caribbean islands. We then tested: (a) whether hummingbird clades and biogeographical regions differ in hummingbird bill length, corolla length of visited flowers and resource specialization, and (b) whether hummingbirds' bill length correlates with the corolla length of their food plants and with their level of resource specialization.Hummingbird clades dominated by long-billed species generally visited longer flowers and were the most exclusive in their resource use. Bill and corolla length and the degree of resource specialization were similar across mainland regions, but the Caribbean islands had shorter flowers and hummingbirds with more generalized interaction niches. Bill and corolla length correlated in all regions and most clades, that is, trait-matching was a recurrent phenomenon in hummingbird-plant associations. In contrast, bill length did not generally mediate resource specialization, as bill length was only weakly correlated with resource specialization within one hummingbird clade (Brilliants) and in the regions of Lowland South America and the Andes in which plants and hummingbirds have a long co-evolutionary history. Supplementary analyses including bill curvature confirmed that bill morphology (length and curvature) does not in general predict resource specialization.These results demonstrate how biogeographical and evolutionary histories can modulate the effects of functional traits on species interactions, and that traits better predict functional groups of interaction partners (i.e. trait-matching) than resource specialization. These findings reveal that functional traits have great potential, but also key limitations, as a tool for developing more mechanistic approaches in community ecology.A free Plain Language Summary can be found within the Supporting Information of this article.

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.

Indirect interactions are central to ecological and evolutionary dynamics in pollination communities, yet we have little understanding about the processes determining patterns of indirect interactions, such as those between pollinators through shared flowering plants. Instead, research has concentrated on the processes responsible for direct interactions and whole-network structures. This is partly due to a lack of appropriate tools for characterising indirect interaction structures, because traditional network metrics discard much of this information. The recent development of tools for counting motifs (subnetworks depicting interactions between a small number of species) in bipartite networks enables detailed analysis of indirect interaction patterns. Here we generate plant–hummingbird pollination networks based on three major assembly processes—neutral effects (species interacting in proportion to abundance), morphological matching and phenological overlap—and evaluate the motifs associated with each one. We find that different processes produce networks with significantly different patterns of indirect interactions. Neutral effects tend to produce densely connected motifs, with short indirect interaction chains, and motifs where many specialists interact indirectly through a single generalist. Conversely, niche-based processes (morphology and phenology) produced motifs with a core of interacting generalists, supported by peripheral specialists. These results have important implications for understanding the processes determining indirect interaction structures. A free Plain Language Summary can be found within the Supporting Information of this article.

Patterns of specialization and the structure of interactions between bats and ectoparasitic flies have been studied mostly on non-urban environments and at local scales. Thus, how anthropogenic disturbances influence species interactions and network structure in this system remain poorly understood. Here, we investigated patterns of interaction between Phyllostomidae bats and ectoparasitic Streblidae flies, and variations in network specialization and structure across Cerrado patches within urbanized landscapes in Brazil and between local and regional scales. We found high similarity in the richness and composition of bat and fly species across communities, associated with low turnover of interactions between networks. The high specialization of bat–streblid interactions resulted in little connected and modular networks, with the emergence of modules containing subsets of species that interact exclusively or primarily with each other. Such similarities in species and interaction composition and network structure across communities and scales suggest that bat–fly interactions within Cerrado patches are little affected by the degree of human modification in the surrounding matrix. This remarkable consistency is likely promoted by specific behaviors, the tolerance of Phyllostomidae bats to surrounding urbanized landscapes as well as by the specificity of the streblid–bat interactions shaped over evolutionary time.

In altered communities, novel species’ interactions may critically impact ecosystem functioning. One key ecosystem process, seed dispersal, often requires mutualistic interactions between frugivores and fruiting plants, and functional traits, such as seed width, may affect interaction outcomes. Forests of the Hawaiian Islands have experienced high species turnover, and introduced galliforms, the largest of the extant avian frugivores, consume fruit from both native and non-native plants. We investigated the impact of two galliform species on seed dispersal processes in Hawaiian forests. Using captive Kalij Pheasants (Lophura leucomelanos) and Erckel’s Francolins (Pternistis erckelii), we measured the probability of seed survival during gut passage and seed germination following gut passage. We also examined which seeds are being dispersed in forests on the islands of O‘ahu and Hawai‘i. We found that galliforms are major seed predators for both native and non-native plants, with less than 5% of seeds surviving gut passage for all plants tested and in both bird species. Gut passage by Kalij Pheasants significantly reduced the probability of seeds germinating, especially for the native plants. Further, larger-seeded plants were both less likely to survive gut passage and to germinate. In the wild, galliforms dispersed native and non-native seeds at similar rates. Overall, our results suggest the introduced galliforms are a double-edged sword in conservation efforts; they may help reduce the spread of non-native plants, but they also reduce seed dispersal of native plants. Broadly, we show mutualism breakdown may occur following high species turnover, and that functional traits can be useful for predicting outcomes from novel species’ interactions.

1. Species interact with one another in communities forming complex interaction networks which are shaped by multiple non‐exclusive processes. Although plant–hawkmoth interactions have been studied for over a century, how processes underlying species' specialisation influence community‐level patterns of niche partitioning and contribute to the emergence of network structures remains poorly investigated. 2. This study described a mutualistic plant–hawkmoth network sampled for 18 consecutive months in Southern Brazil and tested (i) whether it presents modular and/or nested structures and (ii) what drivers (morphologies, phenologies, or abundances) are more important in defining interaction intensities. 3. Network structure was modular, presenting three distinct modules, and had a nestedness value lower than null model expectations. Interaction frequencies were primarily defined by morphological matching and phenological overlap but were not importantly influenced by species' relative abundances. Module composition reinforced the importance of morphological matching, as well as barriers imposed by morphology, and also suggested that modularity may be a consequence of other factors, such as timing between hawkmoth flight period and plants' anthesis. 4. This study's data contribute to filling the shortage of plant‐centred interaction networks involving hawkmoths and plants and reveal that modularity emerges likely as a consequence of processes thought to shape niche partitioning in this system, as well as in other pollination networks. The findings of this study are in agreement with the neutral‐niche continuum model, which predicts that, in systems with high trait functional variation (morphologies and phenologies in this case), niche‐based processes such as trait matching must be relatively more important than abundances as drivers of interspecific interactions.

While functional traits can facilitate or constrain interactions between pair of species in ecological communities, relative abundances regulate the probabilities of encounter among individuals. However, the relative importance of traits and relative abundances for the role species play in seed dispersion networks remains poorly explored. Here, we analyzed 20 Neotropical seed dispersal networks distributed from Mexico to southeastern Brazil to evaluate how relative abundance and functional traits influence bat species' roles in seed dispersal networks. We tested how bat relative abundance and traits relate to species contribution to between-module (c metric) and within-module connectivity (z metric) and their position and potential to mediate indirect effects between species (betweenness centrality). Our results indicate that relative abundance is the main determinant of the role bats play in the networks, while traits such as aspect ratio show modest yet statistically significant importance in predicting specific roles. Moreover, all seed dispersal networks presented two or three superabundant obligatory frugivore species that interacted with a high number of plants. The modest influence of the functional traits on species' roles is likely related to the low variation of morphological traits related to foraging ecology, which reduces the chances of morphological mismatching between consumers and resources in the system. In this scenario, abundant bats have higher chances of encountering resources and being capable of consuming them which leads such species to play critical roles in the community by acting as module hubs and network connectors.

The great fruit-eating bat (Artibeus lituratus) is a large-sized species that forages primarily on fruits. This species is widespread throughout the Neotropics, where it is common in natural areas and also occupies forest patches and cities. In this study, we review the composition of Artibeus lituratus diet in Brazil as well as the size of fruits and seeds, plant geographic origin, and sampling methods used in natural versus urban habitats. We show that Artibeus lituratus is able to consume a higher proportion of exotic fruits with large seeds in urban environments than in natural areas. Fruit diameter was not statistically different between environments, but both fruit and seed diameters are smaller when detected by fecal sampling than by other methods. This difference is likely due to the fact that in natural habitats studies are predominantly based on fecal samples, which hinders the detection of large unswallowed seeds. Consequently, we recommend the use of complementary sampling methods (not only the widely used technique of fecal sorting) in order to produce more accurate descriptions of frugivorous bats’ diets. We suggest that the ability to exploit fruits of exotic plant species including the ones with large seeds may be a key trait for the persistence of A. lituratus in urban habitats.

Understanding patterns of ecological specialization, the processes underlying niche partitioning and how they translate into the structure of interaction networks is a persistent challenge in ecology. Advances on this regard are limited by the prevalent focus on single spatial scales, lack of tests of the mechanisms underlying specialization, and scarce investigation of some types of interactions. Here we investigated the patterns of interaction between plants and florivores (flower‐breeding drosophilids, FBD) at species‐ and community‐level and at local and regional scales, and tested the relative importance of multiple potential drivers of frequencies of interactions in a local network. First, based on a year‐round collection of 42 322 flowers belonging to 82 plant species, we investigated species specialization and network structure and tested whether frequencies of interactions were related to plant–consumer temporal overlap and resource availability. Second, we built a regional florivore–plant meta‐network for the Neotropical region and tested its structure for nestedness, modularity and overall specialization. Our findings revealed that although FBD species span a broad range of degrees of specialization, most species were highly specialized. At both local and regional scales, network structure was highly modular and non‐nested, presenting high complementary specialization. Moreover, phenological overlap between FBD and their hosts was the most influential driver of frequency of interactions, in comparison to abundance and traits. By describing the structure of FBD–plant networks, our results illustrate how a highly diverse and specialized system retains interaction patterns found in other types of interaction networks which are often driven by different processes. Furthermore, despite undersampling of interactions in the meta‐network caused by the lack of studies on this system and the high diversity of Neotropical FBD's, the high modularity and consistency of some clade–clade modules across spatial scales suggests the importance of evolutionary history and physiological constraints in shaping interactions in this system.

Flowering plant species and their nectar-feeding vertebrates exemplify some of the most remarkable biotic interactions in the Neotropics. In the Brazilian Atlantic Forest, several species of birds (especially hummingbirds), bats, and non-flying mammals, as well as one lizard feed on nectar, often act as pollinators and contribute to seed output of flowering plants. We present a dataset containing information on flowering plants visited by nectar-feeding vertebrates and sampled at 166 localities in the Brazilian Atlantic Forest. This dataset provides information on 1902 unique interactions among 515 species of flowering plants and 129 species of potential vertebrate pollinators and the patterns of species diversity across latitudes. All plant-vertebrate interactions compiled were recorded through direct observations of visits, and no inferences of pollinators based on floral syndromes were included. We also provide information on the most common plant traits used to understand the interactions between flowers and nectar-feeding vertebrates: plant growth form, corolla length, rate of nectar production per hour in bagged flowers, nectar concentration, flower color and shape, time of anthesis, presence or absence of perceptible fragrance by human, and flowering phenology as well as the plant's threat status by International Union for Conservation of Nature (IUCN) classification. For the vertebrates, status of threat by IUCN classification, body mass, bill or rostrum size are provided. Information on the frequency of visits and pollen deposition on the vertebrate's body is provided from the original source when available. The highest number of unique interactions is recorded for birds (1771) followed by bats (110). For plants, Bromeliaceae contains the highest number of unique interactions (606), followed by Fabaceae (242) and Gesneriaceae (104). It is evident that there was geographical bias of the studies throughout the southeast of the Brazilian Atlantic Forest and that most effort was directed to flower-hummingbird interactions. However, it reflects a worldwide tendency of more plants interacting with birds compared with other vertebrate species. The lack of similar protocols among studies to collect basic data limits the comparisons among areas and generalizations. Nevertheless, this dataset represents a notable effort to organize and highlight the importance of vertebrate pollinators in this hotspot of biodiversity on Earth and represents the data currently available. No copyright or proprietary restrictions are associated with the use of this data set. Please cite this data paper when the data are used in publications or scientific events.

Understanding how disturbances influence interaction networks is a central but still poorly explored issue in ecology and management. The goal of this study was to test how the structure of plant–pollinator networks and the structuring processes are influenced by grazing in a subtropical grassland community on the southern hemisphere. Twelve sampling plots were allocated in order to cover a grazing gradient ranging from overgrazed to ungrazed sites. For each plot, we created a quantitative matrix containing all observed pairwise insect–plant interactions and described morphology, phenology and abundances of each species. We fitted a series of models to test the influence of grazing intensity on metrics describing networks structure. We finally used probabilistic matrices, maximum likelihood and model selection to investigate the processes influencing frequencies of interactions across the gradient of disturbance. Grazing intensity influenced connectance, specialization and interaction evenness, while the number of species and links, nestedness and modularity were less variable. Species abundance was the most important determinant of interaction frequencies regardless of grazing intensity. In contrast to northern hemisphere pollination networks studied so far, these subtropical plant–pollinator networks and their structuring processes were remarkably consistent along the grazing gradient. We argue that this results from the dominance of generalist Asteraceae species, which are selectively avoided by cattle and play a core role in attracting a wide range of pollinators and thereby structuring plant–pollinator interactions, providing therefore stability.

Birds, like most animals, are expected to adjust their foraging activity in response to biotic and abiotic variations to optimize energy intake and reduce costs associated with finding and ingesting food. This may lead to temporal variation in the exploitation of food resources, which has been investigated for birds of different feeding guilds but remains poorly understood for frugivorous species. Here, we tested whether the frugivory activity of birds on Schinus terebinthifolia trees varies throughout the day during the austral autumn and winter and whether variation is related to weather conditions. For two consecutive years, we quantified frugivory events for 304 h in 19 individuals of S. terebinthifolia observed across four time periods throughout the day. We found that the number of frugivory events was similar irrespective of the time period, both for the entire assemblage (all species pooled together) and for the most common species analyzed individually. We additionally found that frugivory activity was slightly influenced by temperature and wind. The lack of any effect of daytime period on fruit consumption may relate to the high and prolonged levels of fruit availability in S. terebinthifolia and the short photoperiod of the autumn–winter, which favors frequent feeding throughout the day. Such constant removal of fruits by a diverse assemblage of generalist fruit consumers probably enhances seed dispersal and may have important implications for the population dynamics of this abundant plant. Our results also demonstrate that data on avian frugivory in temperate, open-vegetation environments can be quantified throughout the entire daytime during the cold season without temporal bias, which has important methodological implications for studies on bird–plant interactions.

Cities harbour considerable biodiversity and there has been an increased concern about the conservation of pollinators in urban environments. Here, we evaluated how urbanization affects plant-hummingbird interactions at two spatial scales. First, in a medium-sized city from southeastern Brazil (>600,000 inhabitants), we contrasted interaction networks from urban and natural areas, and used artificial nectar feeder stations to evaluate changes in the composition of hummingbird assemblages across an urbanization gradient. Second, we compiled data on six urban plant-hummingbird interaction networks from south and southeastern Brazil to identify the characteristics associated with the most important plants. Locally, urbanization affected hummingbird communities by promoting higher generalization and dominance by more aggressive hummingbirds. Notably, specialized long-billed hermits were absent both in the urban interaction network and at feeder stations from more urbanized areas. Across networks, trees were more important for hummingbirds than shrubs/herbs as were specialized ornithophilous flowers in relation to non-ornithophilous flowers. Plant origin (native or exotic) did not matter. Our results indicate that urban plant-hummingbird communities are organized differently than their counterparts from natural areas, which usually feature key hermits and few trees. Since hermits provide important pollination services, especially for specialized ornithophilous plants, initiatives such as green corridors and preference for native plants with specialized hummingbird-pollinated flowers in urban landscaping may contribute to community restoration and ecosystem functioning.

Habitat loss and fragmentation typically lead to species loss and, consequently, changes in the structure and stability of interaction networks. These changes may lead to important limitation of crucial ecosystems services such as seed dispersal. Here, we compared the spatial structure and species composition of bat-fruit interaction networks in continuous and fragmented forests based on the compilation of 14 datasets from the highly diverse and threatened Atlantic Forest sites in Brazil. As predicted, the number of bat-dispersed species was reduced in fragmented forests. Surprisingly, in both continuous and fragmented forests, bat-fruit networks were nested and modular and presented high complementary specialization. Bat species from genera Artibeus, Carollia, and Sturnira, as well as five plant genera (Cecropia, Ficus, Piper, Solanum, and Vismia) played a central role in both continuous and fragmented forests, revealing small effects of habitat loss on the phylogenetic identity of core species. These bats are considerably tolerant to habitat loss and may support seed dispersal of they preferred plants also in fragmented forests, which explains the similarities of the networks between continuous and fragmented forests. In addition, these key plants provide food resources continuously throughout the year, which facilitates the persistence of seed disperser bats year-round in the community. Although our results indicate that habitat loss had little influence on the structure of the bat-fruit interactions, we evidenced that fragmentation reduces the number of resources consumed and dispersed by bats, which may have negative impacts on forest dynamics and ecosystem functioning.

Fire is a frequent disturbance in most grasslands around the world, being key for the structure and dynamics of the biodiversity in such ecosystems. While grassland species may be resilient, little is known on how plant–pollinator networks reassemble after fire. Here, we investigate the structure and dynamics of plant–pollinator networks and the variation in species roles over a 2-year post-fire chronosequence on grassland communities in Southern Brazil. We found that both network specialization and modularity were similar over the chronosequence of time-since-fire, but in freshly burnt areas, there were more species acting as network hubs. Species roles exhibited high variation, with plant and pollinator species shifting roles along the post-disturbance chronosequence. Interaction dissimilarity was remarkably high in networks irrespective of times-since-fire. Interaction dissimilarity was associated more with rewiring than with species turnover, indicating that grassland plant and pollinator species are highly capable of switching partners. Time-since-fire had little influence on network structure but influenced the identity and diversity of pollinators playing key roles in the networks. These findings suggest that pollination networks in naturally fire-prone ecosystems are highly dynamic and resilient to fire with both plants and pollinators being highly capable of adjusting their interactions and network structure after disturbance.

Ecosystems with a mix of native and introduced species are increasing globally as extinction and introduction rates rise, resulting in novel species interactions. While species interactions are highly vulnerable to disturbance, little is known about the roles that introduced species play in novel interaction networks and what processes underlie such roles. Studying one of the most extreme cases of human-modified ecosystems, the island of O'ahu, Hawaii, we show that introduced species there shape the structure of seed dispersal networks to a greater extent than native species. Although both neutral and niche-based processes influenced network structure, niche-based processes played a larger role, despite theory predicting neutral processes to be predominantly important for islands. In fact, ecological correlates of species' roles (morphology, behavior, abundance) were largely similar to those in native-dominated networks. However, the most important ecological correlates varied with spatial scale and trophic level, highlighting the importance of examining these factors separately to unravel processes determining species contributions to network structure. Although introduced species integrate into interaction networks more deeply than previously thought, by examining the mechanistic basis of species' roles we can use traits to identify species that can be removed from (or added to) a system to improve crucial ecosystem functions, such as seed dispersal.

Interactions between species are influenced by different ecological mechanisms, such as morphological matching, phenological overlap and species abundances. How these mechanisms explain interaction frequencies across environmental gradients remains poorly understood. Consequently, we also know little about the mechanisms that drive the geographical patterns in network structure, such as complementary specialization and modularity. Here, we use data on morphologies, phenologies and abundances to explain interaction frequencies between hummingbirds and plants at a large geographical scale. For 24 quantitative networks sampled throughout the Americas, we found that the tendency of species to interact with morphologically matching partners contributed to specialized and modular network structures. Morphological matching best explained interaction frequencies in networks found closer to the equator and in areas with low-temperature seasonality. When comparing the three ecological mechanisms within networks, we found that both morphological matching and phenological overlap generally outperformed abundances in the explanation of interaction frequencies. Together, these findings provide insights into the ecological mechanisms that underlie geographical patterns in resource specialization. Notably, our results highlight morphological constraints on interactions as a potential explanation for increasing resource specialization towards lower latitudes.

In semi-arid environments, the marked contrast in temperature and precipitation over the year strongly shapes ecological communities. The composition of species and their ecological interactions within a community may vary greatly over time. Although intra-annual variations are often studied, empirical information on how plant–bird relationships are structured within and among years, and how their drivers may change over time are still limited. In this study, we analyzed the temporal dynamics of the structure of plant–hummingbird interaction networks by evaluating changes in species richness, diversity of interactions, modularity, network specialization, nestedness, and β-diversity of interactions throughout four years in a Mexican xeric shrubland landscape. We also evaluated if the relative importance of abundance, phenology, morphology, and nectar sugar content consistently explains the frequency of pairwise interactions between plants and hummingbirds across different years. We found that species richness, diversity of interactions, nestedness, and network specialization did vary within and among years. We also observed that the β-diversity of interactions was high among years and was mostly associated with species turnover (i.e., changes in species composition), with a minor contribution of interaction rewiring (i.e., shifting partner species at different times). Finally, the temporal co-occurrence of hummingbird and plant species among months was the best predictor of the frequency of pairwise interactions, and this pattern was consistent within and among years. Our study underscores the importance of considering the temporal scale to understand how changes in species phenologies, and the resulting temporal co-occurrences influence the structure of interaction networks.

Made available in DSpace on 2018-11-26T17:55:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-01. Added 1 bitstream(s) on 2019-10-09T18:27:51Z : No. of bitstreams: 1 S0102-33062018000300386.pdf: 1047685 bytes, checksum: 57b1bc1e74dcec638d108f4a395975d7 (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Most angiosperms rely on animals for pollination, and insects, especially bees, are the most frequent pollinators. Many native Neotropical plants are frequently visited by the invasive honeybee (Apis mellifera), but its role in the pollination of these plants has been little investigated. We assessed the contribution of various floral visitors, including native bees and the honeybee, on the pollination of a generalist rupestrian grassland daisy, Aspilia jolyana (Asteraceae), in Serra do Cipo, Espinhaco Mountain Range, Brazil. We recorded floral visitors and measured the seed set resulting from one single visitation. We observed a total of 442 visits, mostly by bees, with Bombus pauloensis and Apis mellifera being the most common floral visitors. Other visitors included many other species of bees, flies, hummingbirds, wasps and butterflies. Pollinators significantly increased seed set in comparison to non-visited (bagged) capitula. Moreover, there was no difference among bee species/groups in their contribution to seed set. Thus, A. jolyana benefits from its generalized pollination strategy, and frequent bee visitors, including several native species and the invasive honeybee, are equally effective pollinators for this generalist daisy of rupestrian grasslands. Univ Estadual Campinas, Inst Biol, Dept Biol Vegetal, BR-13083970 Campinas, SP, Brazil Univ Fed Uberlandia, Inst Biol, BR-38405302 Uberlandia, MG, Brazil Univ Illinois Champaign Urbana, Nat Resources & Environm Sci Dept, Urbana, IL 61820 USA Univ Copenhagen, Ctr Macroecol Evolut & Climate, Nat Hist Museum Denmark, DK-2100 Copenhagen, Denmark Univ Estadual Paulista, Inst Biociencias, Dept Bot, Lab Fenol, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Bot, Lab Fenol, BR-13506900 Rio Claro, SP, Brazil CNPq: 400717/2013-1 FAPESP: 2013/50155-0 FAPESP: 2015/21457-4

Multiple factors drive species interactions in ecological networks, such as morphological barriers, spatio–temporal distribution, abundances and evolutionary histories of species. Novel methods are making it possible to evaluate the relative importance of each of these drivers. However, the lack of appropriate methods has prevented evaluating the extent to which interaction networks are shaped by species’ evolutionary histories. This study includes the evolutionary histories of species among the potential drivers of interactions, allowing the comparative analysis of its importance in structuring ecological networks. We hypothesized different possible phylogenetic scenarios to predict frequencies of interactions between species by combining concepts from the fields of ecological networks and ecophylogenetics. The usage of these scenarios is illustrated in a plant–hummingbird interaction network database from the Atlantic Forest, southeastern Brazil. We first evaluated which phylogenetic hypotheses better predict the observed network; subsequently, we evaluated the relative importance of species evolutionary histories, abundances, and matching on species morphologies and phenologies as drivers of their frequencies of interactions. The results suggest that the evolutionary histories of hummingbirds are more important than the species abundances in structuring the studied plant–hummingbird network but less important than the morphological and phenological matching among species. The approach developed here offers the potential to advance our understanding of the multiple factors structuring ecological networks.

Plant species within communities may overlap in pollinators' use and influence visitation patterns of shared pollinators, potentially engaging in indirect interactions (e.g., facilitation or competition). While several studies have explored the mechanisms regulating insect-pollination networks, there is a lack of studies on bird-pollination systems, particularly in species-rich tropical areas. Here, we evaluated if phenotypic similarity, resource availability (floral abundance), evolutionary relatedness and flowering phenology affect the potential for indirect effects via shared pollinators in hummingbird-pollinated plant species within four communities in the Brazilian Atlantic forest. Among the evaluated factors, phenotypic similarity (corolla length and anther height) was the most important variable, while resource availability (floral abundance) had a secondary importance. On the other hand, evolutionary relatedness and flowering phenology were less important, which altogether highlights the relevance of convergent evolution and that the contribution of a plant to the diet of the pollinators of another plant is independent of the level of temporal overlap in flowering in this tropical system. Interestingly, our findings contrast with results from multiple insect-pollinated plant communities, mostly from temperate regions, in which floral abundance was the most important driver, followed by evolutionary relatedness and phenotypic similarity. We propose that these contrasting results are due to high level of specialization inherent to tropical hummingbird-pollination systems. Moreover, our results demonstrated that factors defining linkage rules of plant-hummingbird networks also determinate plant-plant potential indirect effects. Future studies are needed to test if these findings can be generalized to other highly specialized systems. Overall, our results have important implications for the understanding of ecological processes due resource sharing in mutualistic systems.

Managing ecological disturbances at different spatial scales is paramount for maintaining or restoring faunal diversity in grasslands. Whereas some studies have reported varying net effects of livestock disturbance intensity upon species richness in grasslands, most analysis reveal strong effects on beta-diversity. However, beta-diversity can be further partitioned into a nestedness and turnover components, which allows complementary insights on the effects of disturbance on biodiversity across spatial scales. Here we tested for differences in avian species richness and beta-diversity across three intensity levels of livestock disturbance in southern Brazilian grasslands under commercial livestock production. We also tested how disturbance influences the nestedness and turnover components of beta-diversity separately. We found no difference in rarified-extrapolated species richness between disturbance levels. In contrast, we found a significant difference in species composition between disturbance levels, which was attributable to the turnover, but not to the nestedness component. Specifically, livestock disturbance had a predictable effect upon beta-diversity, with turnover of species composition occurring along the gradient of vegetation height in pastures. Our study illustrates the importance of differentiating the turnover and nestedness components of beta-diversity to detect effects of disturbance gradients on biodiversity patterns. We argue that conservation strategies should focus on preserving the mosaic of short- and tall-grass physiognomies associated with the disturbance gradient imposed by livestock production.

Competitive pressure from invasive species tends to have a particularly strong impact on remote islands, and knowledge of such phenomena can be crucial to the conservation of endemic biodiversity. Of the two hummingbird species inhabiting Robinson Crusoe Island, Juan Fernandez Archipelago, Chile, one (Green-backed Firecrown, Sephanoides sephaniodes) has a wide mainland distribution while the other (Juan Fernandez Firecrown, Sephanoides fernandensis) is endemic and critically endangered. Even though habitat degradation and predation by exotic mammal species are known to pose major threats, little attention has been given to the influence of interspecific competition for floral nectar resources. In this study, we investigated the existence of interspecific competition by testing for spatial segregation of the two species using point counts dispersed within their suitable habitats. We additionally considered the influence of habitat type and flower abundance, which could also cause spatial segregation between the species. We found a negative association between the point count abundance of the two hummingbirds species, which remained consistent when accounting for the role of habitat type and flower abundance. Together, this could be an indication of interspecific competition in which individuals of S. fernandensis may benefit from aggregation by sharing the individual costs of chasing the vastly more abundant S. sephaniodes.

International audience; Species are entangled within communities by their interactions in such a manner that their local extinction may unchain coextinction cascades and impact community dynamics and stability. Despite increasing attention, simulation models to estimate the robustness of interaction networks largely neglect the important role of interaction rewiring, that is, the ability of species to switch partners. Here we propose a new method to incorporate the potential of species to replace lost partners into a widely used coextinction model to estimate network robustness. In this model, species are allowed to rewire their interactions after initial loss of partners according to probabilities derived from well‐known mechanisms that determine mutualistic interactions, for example, trait matching, phenological overlap and abundances. To illustrate the use of this method, we analyzed a well‐sampled dataset of mutualistic plant–hummingbird interactions. We found that (a) in general, rewiring increases the estimated robustness, (b) networks are similarly robust to the loss of pollinators or plants, (c) morphological matching and phenological overlap leads to higher robustness, (d) when multiple rewiring mechanisms are combined, however, robustness increases little, and (e) rewiring tends to increase robustness more in scenarios when the loss of generalist species occurs first. Our results suggest that the same mechanisms known to drive plant–hummingbird network structure are relevant in buffering the effects of species loss via rewiring. The method proposed here can be applied to a wide range of interaction networks and is flexible to the inclusion of other variables important in determining interactions for specific systems. It also allows changes on the assumptions regarding the importance of distinct mechanisms, for instance including a hierarchical relationship, which facilitates insights into the relative importance of multiple variables influencing network disassembling. The analytical framework we offer here represents a step towards a more realistic estimation on how species loss may affect the integrity of interaction networks.

Abundant pollinators are often more generalised than rare pollinators. This could be because abundance drives generalisation: neutral effects suggest that more abundant species will be more generalised simply because they have more chance encounters with potential interaction partners. On the other hand, generalisation could drive abundance, as generalised species could have a competitive advantage over specialists, being able to exploit a wider range of resources and gain a more balanced nutrient intake. Determining the direction of the abundance-generalisation relationship is therefore a ‘chicken-and-egg’ dilemma. Here we determine the direction of the relationship between abundance and generalisation in plant-hummingbird pollination networks sampled from a variety of locations across the Americas. For the first time we resolve the direction of the abundance-generalisation relationship using independent data on animal abundance. We find evidence that hummingbird pollinators are generalised because they are abundant, and little evidence that hummingbirds are abundant because they are generalised. Additionally, a null model analysis suggests this pattern is due to neutral processes: most patterns of species-level abundance and generalisation were well explained by a null model that assumed interaction neutrality. These results suggest that neutral processes play a key role in driving broad patterns of generalisation in animal pollinators across large spatial scales.DeclarationsFunding – BIS is supported by the Natural Environment Research Council as part of the Cambridge Earth System Science NERC DTP [NE/L002507/1]. JVB was funded by CERL - Engineer Research and Development Center. PKM was funded by the São Paulo Research Foundation (FAPESP grant #2015/21457-4). PAC was funded by the David Lack studentship from the British Ornithologists’ Union and Wolfson College, University of Oxford. CL was funded by the ESDEPED-UAT grant. MAM acknowledges the Consejo Nacional para Investigaciones Científicas y Tecnológicas (Costa Rica), German Academic Exchange Service and the research funding program ‘LOEWE-Landes-Offensive zur Entwicklung Wissenschaftlichö konomischer Exzellenz’ of Hesse’s Ministry of Higher Education, Research, and the Arts (Germany). ROP was funded by CONACyT (project 258364). MAR was supported by the State of São Paulo Research Foundation (FAPESP) within the BIOTA/FAPESP, The Biodiversity Institute Program (www.biota.org.br) and the ‘Parcelas Permanentes’ project, as well as by Coordenação de Pessoal de Nível Superior (CAPES), Fundo de Apoio ao Ensino e à Pesquisa (FAEP)/Funcamp/Unicamp and The Nature Conservancy (TNC) of Brazil. LCR was supported by CNPq and Capes. MS was funded by CNPq (grant #302781/2016-1). AMMG is supported through a Marie Skłodowska-Curie Individual Fellowship (H2020-MSCA-IF-2016-704409). LVD was supported by the Natural Environment Research Council (grants NE/K015419/1 and NE/N014472/1). AMMG, JS, CR and BD thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate (grant no. DNRF96). WJS is funded by Arcadia.

PLANT-POLLINATOR INTERACTIONS IN HIGHLAND VEGETATION IN THE ATLANTIC FOREST Tropical high-altitude vegetation is unique due to susceptibility to severe weather conditions in relation to lower for­mations, and by the peculiarity of its flora with many relictual components. Studies on plant-pollinator interactions in high-altitude rocky outcrops and forests of the Atlantic Forest are scarce, but compilation of information allows us to identify some patterns: low frequency of visits, high floral longevity and generalized pollination system. In tropical mountain ecosystems, the degree of generalization of pollination systems in functional (pollinator groups) and ecological (number of species) terms tends to be high, mainly due to the over-representation of certain plant taxa ( e.g . , Asteraceae in rocky outcrops and Fabaceae, Myrtaceae, Rubiaceae and Sapindaceae in montane forests). Generalized pollination systems and autogamy may be advantageous for tropical high-altitude plants due to the more severe weather conditions ( e.g. , low temperature), which decrease abundance and limit the activity of pollinators, resulting in lower visitation frequency. Nevertheless, some well represented groups in forests, such as orchids and plants pollinated by hummingbirds and bats, exemplify cases of higher functional specialization, as well as plants with poricidal anthers pollinated by bees in the high-altitude grasslands. However, in rocky outcrops, for some functional groups of pollinators ( e.g ., hummingbirds, bats, beetles and hawkmoths), the availability of resources does not allow the maintenance of all species throughout the year, favoring possible local or altitudinal migrations. Thus, rocky outcrops and high-altitude forests constitute a unit in the sense of sustaining the pollinator community. Indeed ro­cky outcrops and high-altitude forests share an evolutionary history at the regional scale since they passed through similar events of expansion and retraction in response to climate changes in the Quaternary. This could explain the complementarity between the two types of vegetation in the use of floral resources by pollinators. Besides the associations identified here, the ecology and evolution of plant-pollinator interactions in high-altitude vegetation of the Atlantic Forest remain poorly understood, making urgent the development of an integrative research program, as well as projects on issues related to climate change and biodiversity conservation.

Despite great interest in metrics to quantify the structure of ecological networks, the effects of sampling and scale remain poorly understood. In fact, one of the most challenging issues in ecology is how to define suitable scales (i.e., temporal or spatial) to accurately describe and understand ecological systems. Here, we sampled a series of ant-plant interaction networks in the southern Brazilian Amazon rainforest in order to determine whether the spatial sampling scale, from local to regional, affects our understanding of the structure of these networks. To this end, we recorded ant-plant interactions in adjacent 25 × 30 m subplots (local sampling scale) nested within twelve 250 × 30 m plots (regional sampling scale). Moreover, we combined adjacent or random subplots and plots in order to increase the spatial sampling scales at the local and regional levels. We then calculated commonly used binary and quantitative network-level metrics for both sampling scales (i.e., number of species and interactions, nestedness, specialization and modularity), all of which encompass a wide array of structural patterns in interaction networks. We observed increasing species and interactions across sampling scales, and while most network descriptors remained relatively constant at the local level, there was more variation at the regional scale. Among all metrics, specialization was most constant across different spatial sampling scales. Furthermore, we observed that adjacent assembly did not generate more variation in network descriptor values compared to random assembly. This finding indicates that the spatially aggregated distribution of species/individuals and abiotic conditions does not affect the organization of these interacting assemblages. Our results have a direct impact on our empirical and theoretical understanding of the ecological dynamics of species interactions by demonstrating that small spatial sampling scales should suffice to record some patterns commonly found in ant-plant interaction networks in a highly diverse tropical rainforest.