Influence of ecological characteristics and phylogeny on native plant species' commercial availability.

Plant vendors generate a commercial species pool, the subset of species in a regional flora that is purchasable. The availability of plant species from commercial vendors can influence the composition and outcomes of conservation, landscaping, and restoration plantings. Although previous research suggests that most plant species are unavailable, there is little information that identifies the plant characteristics associated with commercial availability. We studied the composition of the commercial species pool by examining the ecology, phylogeny, and phenology of a regional flora in the Midwestern United States. We used a database of native plant species sold by 557 vendors throughout the Midwest (USA) to characterize species' availability. We compiled ecological characteristics of all plant species, including range size, growth form, moisture requirements, and conservatism-meaning fidelity to high-quality natural areas. We characterized phenological (bloom time) data for a subset of the regional flora. Finally, we constructed a regional phylogeny to assess the phylogenetic signal of plant availability. We expected that commercially unavailable species would be niche specialists or short-lived (often nonconservative "weedy") species, and that they would bloom earlier in the season and for a shorter time. We found that commercially available species were more long-lived, had larger range sizes, had intermediate fidelities to wetlands and high-quality or disturbed natural areas, and were associated with certain plant types, especially shrubs and trees. In contrast, ferns and graminoids were underrepresented in the commercial trade. There was a strong phylogenetic signal associated with commercial availability; some plant families had nearly all or none of their species commercially available. Example families with low representation included Orchidaceae, Potamogetonaceae, Cyperaceae, and fern families. Longer bloomed species were more commercially available, but we did not find differences in availability between early- and late-blooming species. Despite the diversity of the commercial pool in the Midwest, it is an unrepresentative, nonrandom subset of the regional species pool. This finding may promote the mismatch in species diversity and composition between remnant natural habitats and restorations because many specialized species are commercially unavailable to conservation and restoration practitioners. We encourage strategies to promote the availability of underrepresented plant diversity in the commercial species pool.