Mutualistic interaction network structure between bird and plant species in a semi-arid Neotropical environment

Mutualistic interactions between animals and plants are essential for ecosystem functioning, providing ecosystem services such as pollination and seed dispersal. The temporal dynamics of plant phenology and animal abundance, induced by seasonal variation in precipitation and resource availability, may influence the structure of animal-plant interaction network. In this paper, we analyzed the mutualistic network structure between birds and plants in a seasonally tropical dry forest in Brazil during the dry and rainy seasons. We recorded 160 interactions between 21 bird species and 11 plant species. In general, networks had low connectance (C = 26%), nestedness (wNODF = 27.54), and modular pattern (Qw = 0.33). Despite the number of interactions being higher in the rainy season, network parameters were consistent across the seasons and presented no explicit differences. However, the network connectance was slightly higher in the rainy season than in the dry season, while the specialization index was higher in the dry season than in the rainy season. Elaenia sp., Mimus saturninus, and Cyanocorax cyanopogon were the bird species that presented the highest number of links. On the other hand, Xiquexique gounellei, Cereus jamacaru, and Pilosocereus pachycladus were the most consumed plant species. The generalized pattern observed suggests that bird-plant interaction in Caatinga may be appropriate to the variable and irregular patterns found in dry forests. Our data reinforce the role of species of the Cactaceae family in maintaining bird communities in semiarid environments. Therefore, due to the high functional importance of those cacti species in influencing both the network stability and the species maintenance in the community, priority attention should be given to them in conservation programs.