Genome size and species co-occurrence
Biotic interactions among plant species in the community that share a common set of environmental tolerances, in whole or in part, can also be an important driver of variation in species composition (Cornell & Lawton 1992; Tilman 1994; Stephens et al. 2020). We evaluated the direction and magnitude of these species’ interactions via the residual species-to-species association matrices derived from the HMSC analysis (Fig. S6). We found that the frequencies of both positive and negative interactions (90% posterior probability) were greater when both members of the interacting pair had large genomes, compared with when one or both members possessed a small genome. Such difference became larger as the threshold used to differentiate large and small genome size increased (Fig. S6). In other words, both facilitation and competition were more likely to occur among the large-GS plants than with the small-GS plants. An outcome of these interactions could be that facilitation among the large-GS plants could lead to communities dominated by those species in resource-rich environments, while competition among those species under resource-limiting conditions may be responsible for the loss of the large-GS plants. Regardless, our results indicate that the importance of biotic filtering in structuring β-diversity was higher for the large-GS species.