Dispersal plays a key role in determining the assembly of ecological communities. This is particularly important for plant communities, as individuals require particular conditions to establish, grow, and reproduce, and don’t move post-germination. Dispersal to appropriate niche-space can be facilitated via associations with animals, which have been shown to disproportionately deposit propagules in particular microsites in many plant species.
Despite the influence of animal behavior on plant dispersal outcomes, little is known about this relationship between animals and bryophytes. Our recent work has demonstrated that a variety of birds harbor spores topically, and that spore load differs by avian behavior and individual size. Furthermore, we found these spores to be viable, providing strong evidence for a dispersal relationship between birds and bryophytes. In order to better understand this phenomenon, we sought to determine whether species-specific patterns exist in a bryophyte-bird dispersal network.
We determined the identity of 162 individual bryophytes found on birds by comparing amplified chloroplast trnF-L sequences with both published sequences and an in-house library consisting of known species from the study site. Relationships were evaluated to assess whether specific associations varied by species and behavioral group of birds, as well as growth habits of bryophytes.
Results/Conclusions
We found that bryophyte spores carried by birds displayed species-specific patterns of association. In particular, ground foraging birds were more associated with ground dwelling mosses with upright growth forms. Epiphytic mosses were more likely to be associated with tree-foraging avian species, likely reflecting their use of particular niche-space. Swainson’s Thrushes were found to associate with a wide array of mosses, suggesting that their particular behavioral suite is well suited to transporting propagules from a variety of microsites. Co-occurance of some moss species on bird surfaces was found to be greater than would be expected due to random assortment, indicating that co-dispersal of particular species assemblages may occur frequently. Some species were negatively associated, likely reflecting discerning avian use of available microsites within habitat patches.
We provide the first evidence that avian behavior may differentially influence the dispersal of bryophyte propagules. Given the role that birds play in facilitating directed dispersal to appropriate microsites within the tracheophytes, we expect that the species-specific associations we observed may enhance arrival of bryophyte propagules to particular locales within the greater overall habitat. This may be of importance in areas that are experiencing reforestation, or when aerial dispersal across dominant wind patterns may be limited.