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1. The temporal dynamics of plant phenology and pollinator abundance across seasons should influence the structure of plant-pollinator interaction networks.Nevertheless, such dynamics are seldom considered, especially for diverse tropical networks.2. Here, we evaluated the temporal variation of four plant-pollinator networks in two seasonal ecosystems in Central Brazil (Cerrado and Pantanal). Data were gathered on a monthly basis over 1 year for each network. We characterized seasonal and temporal shifts in plant-pollinator interactions, using temporally discrete networks. We predicted that the greater floral availability in the rainy season would allow for finer partitioning of the floral niche by the pollinators, i.e. higher specialization patterns as previously described across large spatial gradients.Finally, we also evaluated how sampling restricted to peak flowering period may affect the characterization of the networks.3. Contrary to our expectations, we found that dry season networks, although characterized by lower floral resource richness and abundance, showed higher levels of network-wide interaction partitioning (complementary specialization and modularity). For nestedness, though, this between-seasons difference was not consistent. Reduced resource availability in the dry season may promote higher interspecific competition among pollinators leading to reduced niche overlap, thus explaining the increase in specialization. There were no consistent differences between seasons in species-level indices,indicating that higher network level specialization is an emergent property only seen when considering the entire network. However, bees presented higher values of specialization and species strength in relation to other groups such as flies and wasps, suggesting that some plant species frequently associated with bees are used only by this group.5. Our study also indicates that targeted data collection during peak flowering generates higher estimates of network specialization, possibly because species activity spans longer periods than the targeted time frame. Hence, depending on the period of data collection, different structural values for the networks of interactions may be found.6. Synthesis. Plant-pollinator networks from tropical environments have structural properties that vary according to seasons, which should be taken into account in the description of the complex systems of interactions between plants and their pollinators in these areas. K E Y W O R D SCerrado, functional diversity, modularity, nestedness, network sampling, Pantanal, resource availability, seasonality | 2411Journal of Ecology SOUZA et Al.

We present the floristic composition and reproductive phenological data for a remnant of Arborized Stepic Savanna, vegetation type of humid Chaco, Porto Murtinho, Mato Grosso do Sul State, Brazil. We recorded 87 species of 31 families; Leguminosae presented the highest richness (14 species), followed by Malvaceae (9), Cactaceae (7) and Asteraceae (7). The herbaceous layer is relevant in the seasonal studied community (53.5% of the species) and there is predominance of non-perennial species (hemicryptophytes and therophytes), which demonstrate the importance of underground structures or seed banks in the vegetation. The community has continual flowering and fruiting with highest intensity in the rainy season, the most favorable period for plant growth and reproduction. The predominance of autochoric species in relation to anemochoric and zoochoric ones suggests partial independence of seed/fruit dispersal agents. Zoochorous species predominated in the rainy season, whereas anemochorous and autochorous species were more representative in the dry season.

Summary When describing plant–animal interaction networks, sampling can be performed using plant‐ or animal‐centred approaches. Despite known effects of sampling on network structure, how samplings affect the estimates of interaction β‐diversity across networks is still unresolved. We investigated how the sampling method affects the assessment of β‐diversity of interactions, turnover and rewiring. We contrasted plant‐ and animal‐centred sampling methods applied to pollination networks across habitats in a heterogeneous tropical landscape, the Pantanal Wetlands. We also asked whether plant traits influence the difference in interaction specialization according to sampling. Plant‐centred networks resulted in higher β‐diversity of interactions in space than animal‐centred networks. Turnover explained most of the β‐diversity in both methods, but rewiring was proportionately more important when using the animal‐centred method. While the plant‐centred method indicated lower network modularity and specialization, floral traits modulated the effects of the sampling method on species‐level network metrics. Combining animal‐ and plant‐centred approaches returned intermediate values for β‐diversity of interactions and network metrics. Distinct methods may also be better suited for answering questions at different scales. Our results point out that the method choice, or combination of methods, should always reflect the appropriate scale of the factors determining the interactions being investigated.

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Life on Earth is supported by an infinite number of interactions among organisms. Species interactions in these networks are influenced by latitude, evolutionary history and species traits. We performed a global‐scale literature analysis to build up a database of interactions between anuran communities and their preys, from a wide range of geographical areas, using a network approach. For this purpose, we compiled a total of 55 weighted anuran–prey interaction networks, 39 located in the tropics and 16 in temperate areas. We tested the influence of latitude, as well as anuran taxonomic, functional and phylogenetic richness on network metrics. We found that anuran–prey networks are not nested, exhibit low complementary specialization and modularity and high connectance when compared to other types of networks. The main effects on network metrics were related to latitude, followed by anuran taxonomic, functional and phylogenetic richness, a pattern similar to the emerging in mutualistic networks. Our study is the first integrated analysis of the structural patterns in anuran–prey antagonistic interaction networks in different parts of the world. We suggest that different processes, mediated mainly by latitude, are modeling the architecture of anuran–prey networks across the globe.

Phenology is the basis for understanding the life cycle of plants or animals throughout the year. Thus, we surveyed diurnal anthophilous fauna on plant species in the Brazilian Chaco to determine (1) groups of floral visitors and occurrence; (2) richness and abundance of fauna in relation to flowering flora and meteorological variables; (3) groups of visitors that pollinate or thieving flora; (4) distribution of herbaceous and woody strata throughout the year of flowering; (5) variation in flowering as a whole community, in the context of abiotic factors; and (6) the predominant plant families and species. We sampled eight groups of floral visitors, totalling 105 sampled species and 644 specimens. The flies and bees were the richest groups, with bees forming the most abundant group. The phenology of the fauna and flora was not clustered and exhibited a continuous and bimodal flowering. The abundance and richness of floral visitors were positively related to the quantity of plant species and flowering, as well as rainfall. Herbaceous and woody strata are important for the maintenance of anthophilous fauna throughout the year. Plant species with the highest abundance and the longest flowering period presented the highest richness and/or abundance of floral visitors. The percentage of pollination was higher than that of resource theft. Bees and flies were the main groups of pollinators, whereas flies were the main thieves. The present survey is only a starting point for future studies on the networks of interactions between plants and their floral visitors in the Brazilian Chaco.

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