Dispersal syndromes are more influenced by habitat quality then habitat patchiness in serpentine communities

Background/Question/Methods

Dispersal plays an important role in structuring communities yet there are still gaps in the understanding of how different factors influence the distribution of dispersal syndromes among communities. Habitat patchiness may select for more directed vertebrate dispersal syndromes which facilitate dispersal to other patches of suitable habitat. However, low habitat quality may constrain the availability and efficiency of dispersal syndromes within a community. Our objective was to assess how dispersal syndromes differ between serpentine and non-serpentine communities and if these differences can indicate the importance of habitat quality or habitat patchiness in determining the composition of dispersal syndromes within a community. We hypothesized that if habitat patchiness is more important, vertebrate dispersal syndromes should be more prevalent in serpentine habitats due to its island-like patchy distribution. Alternatively, if habitat quality is more important, less expensive wind dispersal syndromes should more prevalent in serpentine habitats due to lower resource availability. Using three published data sets consisting of 511 species in grassland, chaparral and forest vegetation types, we analyzed differences in 5 dispersal syndromes (passive, wind, water, vertebrate, and ant) between communities on serpentine and non-serpentine soils while accounting correlated functional traits, vegetation type, phylogenetic relatedness, and habitat patchiness.

Results/Conclusions

Communities on serpentine and non-serpentine significantly differed in dispersal syndrome composition. Serpentine communities contained a significantly greater proportion of wind dispersal syndromes and a significantly smaller proportion of vertebrate dispersal syndromes. There was no difference in the proportion of species with passive, water, or ant dispersal syndromes between soil types. The greater proportion of less expensive wind dispersal syndromes and the lower proportion of more directed vertebrate dispersal syndromes support the role of habitat quality constraining the availability of dispersal syndromes in serpentine communities. Additionally, these patterns were not related to correlated functional traits, phylogenetic relatedness, or habitat patchiness. While vegetation types significantly differed in overall dispersal syndrome composition, within each vegetation type we found the same pattern of serpentine communities containing a significantly greater proportion of wind dispersal and a significantly smaller proportion of animal dispersal. Our results suggest that habitat quality may limit the dispersal syndromes within communities regardless of vegetation type or other co-varying factors. Thus, habitat quality may constrain the dispersal potential of a community making communities in low quality habitats more vulnerable to stochastic extinctions and global change.