Identifying Preferential Associates to Initiate Restoration Plantings

Ecological restoration typically aims to re-establish dominant plant species and their native associates, despite the lack of guidance on which associates to introduce initially. Analysis of naturally occurring plant communities can provide criteria to shorten the list of species that are associated with dominants, in order to focus revegetation efforts on species likely to establish. Using the example of sedge meadows, we evaluated wetland vegetation data from Laurentian Great Lakes wetlands to identify “preferential associates,” that is, species that co-occur more frequently than expected based on their overall abundance. A total of 176 taxa occurred within the two hundred and thirty-nine 1 × 1 m² plots in 48 wetlands that contained Carex stricta, a widespread tussock-forming sedge. Of 58 species that co-occurred with C. stricta where it was dominant (≥50% plot cover), we identified 26 associates using Bray–Curtis similarities and we determined that 12 of the 26 were preferential using an electivity index. The electivity index identified preferential associates even when they occurred infrequently or had low mean cover per plot. We provide guidance on how to initiate restoration with preferential associates.