Data in support of: Species-specific interactions in an avian-bryophyte dispersal network

Animal dispersal of plant propagules fundamentally alters the success of dispersal events, and thus shapes plant community composition through time. While this is well-documented in seed plants, spore-bearing plants have received little attention with regard to this phenomenon. Birds are particularly attractive as a potential bryophyte dispersal vector given their highly motile nature as well as their association with bryophytes when foraging and building nests. Despite this, species-specific dispersal relationships between birds and bryophytes have never been examined. We captured birds in Gifford Pinchot National Forest in the Pacific Northwest of the United States to sample their legs and tails for bryophyte spores. We found 24 bryophyte species across 34 species of bird. We examined the level of specialization 1) within the overall interaction network to assess community-level patterns and 2) at the plant species level to determine the effect of bird behavioral type on the plant-animal interaction. Our results suggest that associations within the network are more constrained (specialized) than expected by chance. Additionally, we found that avian foraging guild impacted the variety of bryophytes found on an individual bird. Foliage gleaners and ground foragers had particularly specialized associations within the overall disperser-bryophyte network. Our findings suggest that diffuse bird-bryophyte dispersal networks are likely to be common in habitats where birds readily encounter bryophytes and that further work aimed at understanding individual bird-bryophyte species relationships may prove valuable in determining nuance within this newly described dispersal mechanism.