Stronger phylogenetic effects on birds than on plants, and on seed dispersal than on pollination mutualistic networks, in a subtropical evergreen broadleaf forest

Uncovering the underlying mechanisms that contribute to the structure of ecological networks is crucial and presents a significant challenge. It has been reported that phylogenetically related species tend to have similar characteristics within ecological networks, with the strength of the phylogenetic signal varying among interacting groups. However, the patterns of phylogenetic signal in different interacting groups (e.g. plants and birds) across various network types (e.g. seed dispersal and pollination) has yet to be thoroughly investigated. Furthermore, the question of whether phylogenetic specialists also exhibit high degree of interaction specialization in partner selection remains unresolved. We investigated the phylogenetic effect on the structure of annual and monthly plant-bird seed dispersal and pollination networks within a subtropical evergreen broadleaf forest in Ailao Mountains, southwest China. Our study focused on examining phylogenetic signals in species degree, as well as in taxonomic and phylogenetic composition of interacting partners for both birds and plants of these two types of mutualistic networks. Additionally, we explored the relationship between phylogenetic specialization and interaction specialization of each plant/bird species within networks. We found weak phylogenetic signal in species degree for both plants and birds in any of the networks. However, we found variations in the strength of phylogenetic signals that are associated with taxonomic and phylogenetic composition among different interacting groups. Closely related bird species exhibited a tendency to interact with partners that had similar taxonomic and phylogenetic composition, particularly for frugivorous birds. This pattern was not observed in either fruiting or flowering plants. In addition, phylogenetically specialized frugivorous bird species tend to also be interaction specialists. However, no such association was observed among birds within pollination networks or among plants in either type of networks. The phylogenetic effects of birds are stronger than those of plants in plant-bird mutualistic networks. This trend is particularly pronounced in the context of seed dispersal networks, as compared to those involving pollination. Our findings highlight the evolutionary fingerprint on the structure of plant-bird mutualistic networks, revealing varying phylogenetic effects across different interaction groups and network types within a subtropical evergreen broadleaf forest.