Moving towards a comprehensive view of the spatial processes in seed dispersal networks: Embracing metacommunities.

The current biodiversity crisis requires efficient approaches to address the ongoing impoverishment of natural communities and the depletion of ecosystem services and functions. In this sense, identifying key species that promote the functioning of ecological processes can be strategic to guide actions aiming at the conservation and restoration of biodiversity. Node-level metrics in interaction networks can be helpful to identify those key species, as they measure the role each species plays in organizing the interactions. Moreover, ecological correlates of species structural roles may vary between local and global networks of interactions, reflecting distinct mechanisms acting at different spatial scales. By studying local seed dispersal networks and one global meta-network combining those local networks, Moulatlet et al. identified the most important traits explaining bird species centrality at varying spatial scales. They found that body mass was the main trait explaining centrality at the local scale, whereas range size was the main predictor of species centrality at the global scale. In this contribution, besides assessing local interaction networks, Moulatlet et al. adopt a biogeographical perspective to seed dispersal systems, extending our knowledge about the possible mechanisms that underlie the organization of interacting assemblages when changing the spatial scale of observation. Future efforts on this field could include an intermediate scale, comprising the level of metacommunities, shedding light on the interplay between local and spatial processes, both embedded in biogeographical realms, when determining the organization of interactions and the ecological correlates of species roles.

A atual crise da biodiversidade requer abordagens eficientes para lidar com o empobrecimento contínuo das comunidades naturais e com o esgotamento das funções e dos serviços ecossistêmicos. Neste sentido, identificar espécies-chave que promovam o funcionamento dos processos ecológicos pode ser estratégico para guiar ações que visam a conservação e a restauração da biodiversidade. Métricas em nível dos nós em redes de interação podem ser úteis para identificar tais espécies-chave, já que quantificam o papel que cada espécie desempenha em organizar as interações. Além disso, os correlatos ecológicos dos papéis estruturais das espécies podem variar entre redes de interações locais e globais, refletindo os distintos mecanismos que atuam em diferentes escalas espaciais. Ao estudar redes de dispersão de sementes locais e uma meta-rede global que combina essas redes locais, Moulatlet et al. identificaram as características mais importantes para explicar a centralidade das espécies de aves em diferentes escalas espaciais. Eles encontraram a massa corporal como principal característica que explicava a centralidade na escala local, enquanto o tamanho da distribuição foi o principal preditor da centralidade das espécies na escala global. Nesta contribuição, além de avaliar redes de interação locais, Moulatlet et al. adotaram uma perspectiva biogeográfica ao tratar os sistemas de dispersão de sementes, ampliando nosso conhecimento sobre os possíveis mecanismos subjacentes à organização das interações quando mudamos a escala espacial de observação. Esforços futuros neste campo poderiam incluir uma escala intermediária, compreendendo o nível de metacomunidades, buscando esclarecer as relações entre processos locais e processos espaciais, ambos inseridos em domínios biogeográficos, ao determinar a organização das interações e os correlatos ecológicos dos papéis estruturais das espécies.

The robustness of plant-pollinator assemblages: linking plant interaction patterns and sensitivity to pollinator loss.

Most flowering plants depend on pollinators to reproduce. Thus, evaluating the robustness of plant-pollinator assemblages to species loss is a major concern. How species interaction patterns are related to species sensitivity to partner loss may influence the robustness of plant-pollinator assemblages. In plants, both reproductive dependence on pollinators (breeding system) and dispersal ability may modulate plant sensitivity to pollinator loss. For instance, species with strong dependence (e.g. dioecious species) and low dispersal (e.g. seeds dispersed by gravity) may be the most sensitive to pollinator loss. We compared the interaction patterns of plants differing in dependence on pollinators and dispersal ability in a meta-dataset comprising 192 plant species from 13 plant-pollinator networks. In addition, network robustness was compared under different scenarios representing sequences of plant extinctions associated with plant sensitivity to pollinator loss. Species with different dependence on pollinators and dispersal ability showed similar levels of generalization. Although plants with low dispersal ability interacted with more generalized pollinators, low-dispersal plants with strong dependence on pollinators (i.e. the most sensitive to pollinator loss) interacted with more particular sets of pollinators (i.e. shared a low proportion of pollinators with other plants). Only two assemblages showed lower robustness under the scenario considering plant generalization, dependence on pollinators and dispersal ability than under the scenario where extinction sequences only depended on plant generalization (i.e. where higher generalization level was associated with lower probability of extinction). Overall, our results support the idea that species generalization and network topology may be good predictors of assemblage robustness to species loss, independently of plant dispersal ability and breeding system. In contrast, since ecological specialization among partners may increase the probability of disruption of interactions, the fact that the plants most sensitive to pollinator loss interacted with more particular pollinator assemblages suggest that the persistence of these plants and their pollinators might be highly compromised.