The relative importance of specialization and generalization has prompted a lively debate in studies of plant-pollinator associations and pollination syndromes. However, most work focuses on floral and pollinator morphology as determinants of interactions, with less consideration of how pollinator competition may determine interactions with plants. We propose that pollinator competition also plays a role in explaining patterns of plant-pollinator specialization, generalization, and pollination syndromes, especially when explanations based solely on floral and plant morphology fail to predict plant-pollinator interactions. We begin with a brief discussion of theoretical works on pollinator competition, focusing on competitive asymmetries in foraging efficiency between pollinators and how such asymmetries can lead to resource partitioning (specialization), reproductive isolation, and floral divergence in plants (including pollination syndromes). We then review works on how pollinator foraging costs relate to morphology of flowers and pollinators and provide examples on how expectations based on morphologically determined foraging costs differ from how bumble bee, hummingbird, and bat pollinators forage when under competition in the field. Next, we illustrate how pollinator competition influences plant reproductive isolation in a specialized plant-hummingbird association when plant traits fail to do so. We conclude with examples of how pollinator competition can be evaluated in field studies, from experimental manipulations of plants and pollinators to “before and after” studies on the effects of natural disturbance events on plant-pollinator associations. Studies taking pollinator competition into account may provide novel insights to plant-pollinator associations, especially when morphology fails to predict interactions.

Anthropogenic activities severely impair biodiversity and ecosystem functionality. A prime example is the loss of frugivores and their corresponding seed dispersal services due to defaunation (the decline of animal populations), ultimately affecting the continued persistence of plant species that lack their ecological partners. Loss of frugivores and their biotic interactions can be particularly severe on islands due to their isolation and relatively small area, which is often associated with low functional redundancy. From field observations on the Caribbean Virgin Islands, we found that only 1% of documented seed dispersal events occurred in large-fruited plants, with dispersal probability closely tied to overlap between fruit width and gape size of the largest nonthreatened frugivore. Using fruit-frugivore trait matching to extrapolate this pattern to the rest of the Caribbean, we found that large-fruited plant species are effectively "orphaned" due to the absence of animal dispersers, resulting in elevated rates of endangerment across islands. Threat status of plant species was better explained by trait matching than other pressures such as human use, suggesting that extinction or reduced abundance of large-bodied frugivores is compromising their plant mutualists' ability to persist. These results argue strongly for the need to restore populations of large-bodied frugivores across the Caribbean, either through population enhancement of currently endangered species or rewilding with close relatives of extinct species.

Habitat loss and fragmentation threaten biodiversity by reducing species richness and disrupting ecological interactions. But it is poorly understood how reduced habitat area and increased isolation impact community persistence, as measured by its capacity to maintain multispecies coexistence. We draw on an intensive, multi-year field study of mutualistic interactions in plant-frugivore and plant-pollinator networks across 41 islands in an insular fragmented landscape formed by dam construction in 1959. We show that the loss of island area after inundation is the primary driver that reduces the persistence of mutualistic assemblages, beyond merely reducing species richness. We further identify structural mechanisms of persistence: on larger islands, decreasing network modularity enhances persistence in both plant-frugivore and plant-pollinator communities, whereas increasing nestedness contributes to persistence only in plant-pollinator communities. These findings represent a conceptual advance in understanding the impact of habitat loss on biodiversity by showing that species loss in small habitat fragments may result from the reduced capacity of their mutualistic communities to support species coexistence, mediated by changes in network structure. We urge to include evaluations of community persistence into the design of conservation and habitat restoration strategies to more effectively mitigate the long-term impacts of habitat loss and fragmentation on biodiversity. Habitat loss can disrupt mutualistic interactions that sustain biodiversity. This study shows that larger habitat islands support more persistent plant-frugivore and plant-pollinator assemblages, linked to network modularity and nestedness.

There is a global concern about the decline of wild pollinators and the ecosystem services they provide. Although land-use change is a major threat to biodiversity, it is still poorly understood how land-use heterogeneity (or land-use structure) impacts pollinator communities and entomophilous crop production. Based on a literature review, we performed a meta-analysis to (1) assess how landscape structure, both composition and configuration, affects pollinator species richness and abundance, and (2) examine the impact of landscape structure on the production of key entomophilous crops. We extracted information on pollinator communities and crop production from 101 studies with a total of 920 site replicates distributed widely across the globe. To obtain landscape structure (total area of all crops, crop diversity, and landscape Shannon's Diversity Index) information, we sourced data from the database Map-SPAM as well as satellite images. We found that pollinator species richness increased with the number of crop species in the surrounding area. Pollinator abundance increased with the number of different crops but decreased with increasing agricultural area in the surrounding landscape. Crop production of several crops was associated with landscape heterogeneity. Notably, fruit set increased with an increasing number of crop species in neighbouring fields and decreased with increasing agricultural area, that is, when nature is substituted with agriculture in the surrounding landscape. We also found positive correlations between edge density of an area and pollinator species richness and entomophilous crop production suggesting that edge density can be used as a landscape structure indicator to assess pollinator diversity. The effects of landscape structure were more pronounced in crops with high pollinator dependence, showing stronger relationships with both pollinator diversity and crop production. These findings highlight the importance of maintaining landscape heterogeneity through crop diversity and natural habitats to support pollinators and their services, though unmeasured factors such as intensification or local management may also play a role.

Islands have long been foundational to the development of ecological and evolutionary theory, serving as model systems for studying patterns of biodiversity. However, pervasive anthropogenic impacts-particularly species extinctions and introductions-have substantially altered island ecosystems, complicating inferences drawn from contemporary data. Here, we review how these human-driven changes have reshaped key biodiversity patterns on islands, including patterns of species richness, community composition, evolution, and species interactions. We show that many current ecological and evolutionary patterns observed on islands reflect not just natural processes but also a legacy of human-induced change spanning millennia. Approaches that better incorporate paleoecological evidence, along with improved island biodiversity databases and modeling techniques, can help better reconstruct prehuman biodiversity baselines on islands.

ABSTRACT Biotic invasions represent one of the leading environmental threats, with non‐native mammals being particularly damaging to native biodiversity on oceanic islands. One way that such damages may occur is through the disruption of frugivory, a fundamental process for plant reproduction and healthy ecosystem function. To investigate such disruptions, we explored (1) the magnitude of non‐native mammalian frugivore activity, (2) whether it affects native frugivory interaction rates, and (3) which local, biotic, biogeographic, and socio‐economic factors best predict non‐native mammal frugivory levels. We used artificial fruits and camera traps to measure native and non‐native frugivory interactions on 13 islands in the eastern Caribbean, an important biological hotspot. Overall, we found that non‐native Rattus sp. were responsible for nearly 80% of all frugivorous activity detected by camera traps and that increased non‐native mammalian frugivore activity was associated with significant declines in avian frugivory rates. Non‐native mammalian frugivore activity, in turn, was positively associated with road proximity and neighboring island proximity, illustrating the potential for both human activity and island geography to influence non‐native mammal frugivory interactions. These results suggest that non‐native mammals are dominating frugivory dynamics in understory vegetation in the eastern Caribbean, with consequences for native frugivory interactions. Given the generally seed predatory behavior of Rattus sp., we argue that plant dispersal could be negatively affected on islands with abundant non‐native mammal populations. Thus, we emphasize the need for controlling non‐native mammal populations and highlight the diverse inter‐trophic effects that non‐native mammals can have on insular tropical ecosystems.

As climate change increases the frequency and severity of extreme events, targeted and proactive conservation measures must be implemented to protect endemic tropical island species from the extinction risk posed by cyclones.

Pollination is a key ecological process sustaining biodiversity and food security, yet global patterns of plant–pollinator specialisation have remained unresolved. Using the largest global dataset of quantitative networks (>3,400 networks, >110,000 interactions), we show that the latitudinal specialisation gradient (LSG) exists, but it is non-linear, hemispherically asymmetric, and strongly taxon-dependent. Network-level and pollinator specialisation were lowest in the tropics and peaked at northern mid-latitudes, whereas plants tended to become more specialised toward higher latitudes. Climate consistently outperformed latitude, species richness, and environmental productivity as a predictor of these patterns. Specialisation declined with increasing temperature, rose with moderate rainfall before declining at the wettest sites, and increased with temperature seasonality, but plants and pollinators responded differently to these drivers. Functional groups diverged strongly: ectothermic insects were most specialised in cooler, seasonal climates, while birds showed weaker links to latitude but reduced specialisation in wetter regions. These findings demonstrate that climate, rather than latitude or species richness, structures global variation in specialisation. Because warmer and less seasonal climates promote generalisation, climate change is likely to disrupt the most specialised pollination systems, unevenly across taxa and regions, with important consequences for biodiversity and ecosystem stability. ### Competing Interest Statement The authors have declared no competing interest. Czech Science Foundation, https://ror.org/01pv73b02, 21-24186M, 19-14620S Alexander von Humboldt Foundation, https://ror.org/012kf4317, 1134644 São Paulo Research Foundation, 2023/03083-6, 2023/02881-6, 2023/17728-9 Consulate General of France in São Paulo Bavarian State Ministry of Science and Art Biotechnology and Biological Sciences Research Council Center for Research on Biodiversity Dynamics and Climate Change CEPID-FAPESP, 2021/10639-5 National Council for Scientific and Technological Development, CNPq, 308559/2022-3, 141736/2020-8, 311665/2022-5, 400904/2019-5, 423939/2021-1, 310508/2019-3, 309893/2023-2, 177005/2024-6, 305204/2024-6 CAPES, Finance Code 001; COOPBRASS: 88887.947041/2024-00, 177005/2024-6, PROEX 88882.347259/2019-01 Brazilian Biodiversity Fund, FunBio, 004/2021, 029/2022 Rufford Foundation, https://ror.org/02bxrrf91, 377031, 28478-1 German Research Foundation DFG, 152112243 Dirección General de Investigación, Universidad de San Carlos de Guatemala, 4.8.63.2.27-2012, 4.8.63.8.60-2018, 4.8.63.4.41-2020 FAPEMIG, RED-00039-23 INCT Pollination (CNPq/CAPES/FAPERJ Call 58/2022) Faculty for Future, Schlumberger Foundation the Human Frontier Science Program, RGP023/2023 European Research Council ERC, 101054177, 819374 Knut and Alice Wallenberg Foundation, KAW 2019.0202 LIFE project Olivares Vivos+, LIFE20 NAT/ES/001487 Missouri Department of Conservation, K02442-PI0242-022 National Science Foundation, DGE-2244337 OAPN, 014/2009 CONAHCYT, CBF2023-2024-216 Spanish Ministry of Science, Innovation and Universities, PID2021-127900NB-I00, PGC2018-098498-A-100, RYC2021-032351-I Israel Ministry of Environmental Protection, 121-5-13 German Research Foundation DFG, FZT 118, 202548816

Human-induced habitat loss and isolation have severe impacts on biodiversity, with indirect effects on plantanimal interactions. We investigate how forest loss and isolation (distance) from a large continuous forest affect mutualistic plant-bat interaction networks based on a seven-years survey across 20 sites surrounding the Serra da Bodoquena National Park, Brazil. Our results showed that landscapes with 30-70 % forest cover at 1 kmradius buffer had more species (9 bat species: r2 = 0.50, p = 0.01; 24 plant species: r2 = 0.54, p = 0.001) and interactions than those at the extremes, either heavily deforested or fully forested landscapes. Plant-bat networks were also larger and more modular (0.60), with lower connectivity (0.18), in landscapes with intermediate than in extremes forest cover values (r2 = 0.51, p = 0.03; r2 = 0.73, p = 0.002; respectively). Richness of interacting bats (9 species) and network modularity (0.60) were higher at 10 km from the park's continuous forest than in sites closer or further away (r2 = 0.39, p = 0.05; r2 = 0.54, p = 0.002; respectively). Overall results indicate that forest loss and isolation from the park nonlinearly affect the size and structure of plant-bat networks, with intermediate levels of forest cover and isolation supporting larger and more modular networks. These outcomes highlight the importance of keeping a considerable area of forest remnants in human-modified landscapes, and the crucial role of large protected forests to maintain pollination and seed-dispersal plant-bat interactions.

Functional traits determine interactions between plants and pollinators, and to increase pollination efficiency, many plants have evolved traits to attract specific pollinator groups. However, biogeographical setting may influence trait evolution and biotic interactions. For instance, plants pollinated by hummingbirds often have ornithophilous traits, that is, flowers with elongated corollas, dilute nectar and red colours, but—due to colonization history, depauperate biotas and unstable environmental conditions—it might be disadvantageous for species to rely on mutualistic partners with specific functional traits on oceanic islands. Hummingbird‐visited plants on islands are thus expected to have fewer ornithophilous traits and be functionally less diverse in their interactions with hummingbirds. We compiled an extensive dataset of plant—hummingbird interactions (1030 plant and 181 hummingbird species) and associated functional traits. We divided the data into four biogeographical regions across the American mainland and the Caribbean islands and then tested whether biogeographical regions differed in the proportion of ornithophilous floral traits and functional diversity of plant—hummingbird interactions. We found that hummingbird‐visited plant communities of the Caribbean islands displayed the lowest proportion of traits typically associated with a functional adaptation towards bird‐mediated pollination, with on average the shortest corollas, the highest nectar concentrations and the largest proportion of non‐ornithophilous colours. Contrary to our expectations, plants in the Caribbean interacted with hummingbirds that were morphologically more distinct than the plants of mainland regions. Overall, we document a strong imprint of insularity on floral traits and interactions with hummingbirds. While hummingbird‐visited plants in the Caribbean displayed floral traits that support island theory, predicting less specific pollination systems on oceanic islands, the functional diversity of plant–hummingbird interactions in the Caribbean communities was higher than on the mainland, possibly driven by competition over resources. These results highlight the influence of insularity on functional traits and plant–pollinator interactions. Read the free Plain Language Summary for this article on the Journal blog.

Habitat fragmentation is causing the collapse of seed dispersal interactions and ecosystem functioning. When management and conservation strategies aim to sustain ecosystem functioning of fragmented forests, species' traits and functional performance are critical in guiding decisions. However, to date, we lack a quantitative understanding of the role of frugivores' body size and dispersal ability in ecosystem sustainability among fragmented forests. Focusing on avian frugivory and seed dispersal in a multi- island setting, we address the data gap by recording more than 20,000 frugivory events in an artificial insular fragmented landscape constructed in 1959 and nearby unfragmented forests on the mainland. We show that large- bodied and dispersal- limited frugivorous birds are largely confined to large islands and the unfragmented mainland, whereas on small islands, small- bodied and highly mobile birds predominantly engage in frugivory interactions. The plant-frugivore meta- network exhibits a distinct compartmentalization, driven by island area and bird mobility. Birds with smaller size and greater mobility have higher topological importance, and the presence of small- bodied birds significantly enhances meta- network robustness. These results suggest that among insular fragmented forests where frugivory interactions are degraded, small- bodied and highly mobile birds disproportionately contribute to meta- community cohesion and ecosystem functioning because of the lack of large- bodied and dispersal- limited birds. We thus advocate for the restoration of landscapes to facilitate seed dispersal and functional connectivity, ensuring the presence of large patches along with small patches as stepping- stones. Meanwhile, we recommend prioritizing conservation on small- bodied and highly mobile birds in fragmented landscapes, a subset of underappreciated species that yet play crucial roles in ecosystem functioning.

Global change will create new species interactions and alter or eliminate existing ones, a process known as interaction rewiring. This rewiring can significantly affect how ecosystems function. To better predict the future structure of ecological networks, assessing their ability to adapt to changes is crucial. Here, we introduce two concepts: 'rewiring capacity' of a single species (the multidimensional trait space of all its potential interaction partners within a region) and 'rewiring potential' of a local community (the total trait space covered by interaction partners of the species at the target trophic level locally). To quantify the rewiring capacity and potential, we apply existing methods for determining species' functional interaction niches in a novel way to assess species' and communities' ability to form new interactions and the functional resilience of interaction networks to global change. To illustrate the applicability of these concepts, we quantified the rewiring capacity and potential of interactions between 1002 flowering plant species and 318 hummingbird species across the Americas. The rewiring capacity and potential metrics offer a new way to understand and quantify network resilience, allowing us to map how ecological networks respond to global change.

Proximity to natural habitat is known to enhance pollination services in large-scale agriculture, but it remains unclear whether this holds in tropical smallholder farms. These systems are embedded in ecologically complex landscapes, central to global food security, and depend heavily on biodiversity-derived ecosystem services. We conducted a systematic review and meta-analysis of 35 studies assessing the relationship between distance to natural habitat and pollinator abundance, species richness, and crop fruit set in tropical smallholder farms. We found no consistent patterns in pollinator abundance and crop fruit set with increasing distance, with relationships highly variable across studies. Similarly variable, yet slightly negative, was the relationship between distance and pollinator species richness. Our findings suggest limited support for the 'proximity to natural habitat' hypothesis in tropical smallholder farms, indicating that the inherent complexity of these landscapes may buffer negative effects of distance on pollination. This underscores the importance of maintaining and restoring landscape complexity to sustain biodiversity and ecosystem services such as crop pollination. We also highlight the need for greater methodological consistency and publicly available raw data in future studies to strengthen the evidence base and support management strategies for safeguarding pollination services in tropical smallholder farms.

Urbanization has reshaped the distribution of biodiversity on Earth, but we are only beginning to understand its effects on ecological communities. While urbanization may have homogenization effects strong enough to blur the large- scale patterns in interaction networks, urban community patterns may still be associated with climate gradients reflecting large- scale biogeographical processes. Using 103 hummingbird-plant mutualistic networks across continental Americas, including 176 hummingbird and 1,180 plant species, we asked how urbanization affects species interactions over large climate gradients. Urban networks were more generalized, exhibiting greater interaction overlap. Higher generalization was also associated with lower precipitation in both urban and natural areas, indicating that climate affects networks irrespective of habitat type. Urban habitats also showed lower hummingbird functional trait diversity and over/ underrepresentation of specific clades. From the plant side, urban communities had a higher prevalence of nonnative nectar plants, which were more frequently visited by the hummingbird species occurring in both urban and natural areas. Therefore, urbanization affected hummingbird-plant interactions through both the composition of species and traits, as well as floral resource availability. Taken together, we show that urbanization consistently modifies ecological communities and their interactions, but climate still plays a role in affecting the structure of these novel communities over the scale of continents.

An often-overlooked question of the biodiversity crisis is how natural hazards contribute to species extinction risk. To address this issue, we explored how four natural hazards, earthquakes, hurricanes, tsunamis, and volcanoes, overlapped with the distribution ranges of amphibians, birds, mammals, and reptiles that have either narrow distributions or populations with few mature individuals. To assess which species are at risk from these natural hazards, we combined the frequency and magnitude of each natural hazard to estimate their impact. We considered species at risk if they overlapped with regions where any of the four natural hazards historically occurred (n = 3,722). Those species with at least a quarter of their range subjected to a high relative impact were considered at high risk (n = 2,001) of extinction due to natural hazards. In total, 834 reptiles, 617 amphibians, 302 birds, and 248 mammals were at high risk and they were mainly distributed on islands and in the tropics. Hurricanes (n = 983) and earthquakes (n = 868) affected most species, while tsunamis (n = 272), and volcanoes (n = 171) affected considerably fewer. The region with the highest number of species at high risk was the Pacific Ring of Fire, especially due to volcanoes, earthquakes, and tsunamis, while hurricane-related high-risk species were concentrated in the Caribbean Sea, Gulf of Mexico, and northwestern Pacific Ocean. Our study provides important information regarding the species at risk due to natural hazards and can help guide conservation attention and efforts to safeguard their survival.

Generalism in resource use is commonly considered a critical driver of population success, species distribution and extinction risk. This idea can be questioned as generalism may be a result rather than the cause of species abundance and range size. We tested these contrasting causal hypotheses focusing on host use in three databases encompassing approximately 44,000 mutualistic (hummingbird-plant), commensalistic (lichen-plant) and parasitic (flea-mammal) interactions in 617 ecological communities across the Americas and Eurasia. Across all interaction types, our analyses indicated that range size and abundance influence the probability of encountering hosts and set the arena for species to express generalism potentials or adapt to new hosts. Hence, our findings support the hypothesis that generalism is a consequence of species ecological success. This highlights the importance of ecological opportunity in driving species characteristics considered key for their survival and conservation. Generalism is often assumed to be a cause of species success. This analysis of mutualistic, commensalistic and parasitic interactions supports the alternative causal hypothesis that generalism is the consequence of ecological success.

Hurricanes are natural phenomena, but anthropogenic climate change will cause hurricanes to be stronger and more frequent in the future. It has long been known that hurricanes impact plants and animals, but only recently has the impact on biodiversity been mapped globally, showing that species at risk of extinction due to hurricanes are largely restricted to tropical islands. Tropical islands harbor many plants and animals found nowhere else, many of which are currently threatened, and tropical islands have already suffered a disproportionate number of species extinctions due to human activity and introductions of non-native species. The big question is whether species on tropical islands are adapted to hurricane disturbance and will be able to cope with stronger and more frequent storms, or whether tropical islands will see a wave of hurricane-induced extinctions in the future. Here, we discuss this question and how hurricanes will reshuffle interactions between species — such as those between nectarivorous birds and their flowers — and will alter evolutionary trajectories for coadapted species. Moreover, we discuss the role of life history and other taxa-specific traits, such as diet preferences and dispersal ability, both to survive the direct and indirect impact of hurricanes and to recolonize islands when local populations have been eliminated. We also highlight how topographic complexity and island area may buffer against hurricanes; thus, biodiversity on small and low-lying islands should be more impacted than biodiversity on large and mountainous islands. We end by discussing conservation efforts to diminish the detrimental ecological and evolutionary effects of stronger and more frequent hurricanes on tropical islands.