Bee-Plant Interaction Networks in a Seasonal Dry Tropical Forest of the Colombian Caribbean.

Mutualistic interactions between bees and flowering plants have been widely recognized as one of the most important for the maintenance of these communities throughout ecosystems. Consequently, understanding how these interactions occur is highly important, especially in seasonal dry tropical forest (SDTF), one of the most endangered ecosystems in northern South America. In this study, we analyzed the changes between interaction networks across two well-defined seasons, dry and wet, in a SDTF of the Colombian Caribbean in Taganga, Magdalena. We also determined changes in species composition and their role in interaction networks. To study this system, we compared two approaches: (1) networks constructed with data from direct collections in flowering plants, and (2) networks constructed with pollen data obtained from bees' bodies. A total of 44 species were collected in 18 species of flowering plants; also, we registered 16 additional plants presented in the records only as pollen types. We found that network metrics, connectance, nestedness, specialization (H2'), and interaction strength asymmetry remain stable through seasons. However, when the two types of approximations were compared, there were significant differences. Networks constructed with pollen data are more connected, less specialized, and with lower values of interaction strength asymmetry. The major difference between seasons relied on the interacting species composition, due to a high species turnover. Bee community was more diverse in dry season. Apidae family, mainly eusocial species, persisted in the community, being more abundant and relevant in wet season. For dry season, Megachile and other solitary species from Apidae and Halictidae families were better represented and relevant for the community. We found that Fabaceae is an important resource for bees in both seasons. In addition, herbaceous species from Asteraceae and Convolvulaceae were preferred in wet season, while shrub and tree species from Fabaceae and Polygonaceae were the main resource in dry season.