Interações planta-polinizador em ecossistemas de veredas: de oferta de recursos florais para a comunidade à rede de interações de palmeiras-chave

Abstract

Pollination is one of the essential ecosystem services for humanity, enabling the vast majority of angiosperms to survive. The distribution of floral resources and the flowering season are essential for maintaining and preserving pollination services in ecosystems. Intraspecific variation in the attributes of individuals and their location in the landscape can influence interactions with their pollinators and the role of each of these individuals in a network of interactions. We identified the pollination syndromes of woody species in a vereda ecosystem and characterized the availability of pollination resources between habitats. In addition, we sought to describe the structure of the network of M. armata individuals and their pollinators, evaluating how variation in attributes and the location of individuals can act in determining their role in the network. For M. flexuosa, we also tried to identify its potential pollinators, taking into account the phenotypic plasticity of the species, which can influence the diversity of pollinators, featuring pollinators that share male and female flowers. To characterize the availability of resources, we carried out phenological monitoring over 24 months and examined the occurrence of flowering using circular statistics. The differences in the occurrence of the pollination syndrome between months and habitats were determined using modularity analysis. With regard to the network of interactions between the key palms, we selected female and male individuals and measured different attributes such as height, circumference at breast height, number of inflorescences, records of nearby species flowering and the group of pollinators. A network of interactions between individuals was set up for M. armata and M. flexuosa and specialization and modularity were calculated for the entire network, using two indices, at the level of individuals for M. armata and M. flexuosa, and species for their pollinators: degree and strength species. We found eight pollination syndromes, with melittophily being the most frequent type of pollination among the woody species in the vereda. Flowering occurs throughout the year in the community and reaches its peak during the transition from the dry to the rainy season. The distribution of syndromes and the availability of resources differed between habitats. Modularity showed complementarity between habitats, with continuous availability of resources throughout the ecosystem. The network of interactions for M. armata showed a specialized and modular structure. The most frequent groups of pollinators were bees, followed by wasps and beetles. There was a difference in the frequency of visits between female and male individuals, suggesting a strategy used by the species. Bees had a higher degree and strength of species, while individuals with a greater number of inflorescences and fewer species flowering in their vicinity had a higher degree and strength of interaction. For the M. flexuosa palm, insects such as bees, wasps, beetles, flies and hemiptera were observed on the inflorescences, with 16 species of pollinators collected from both floral sexes. The network of interactions was not significantly specialized or modular. The inflorescences on male individuals attracted the greatest number of pollinators, with bees having the greatest species strength and bees, beetles and wasps showing the greatest degree in the network. Information on these interactions is necessary to understand the functionality of the vereda ecosystem.