Complementarity-based algorithms for selecting sites to preserve grassland plant species

Complementarity-based algorithms, that delimit sets of sites maximizing the representation of biodiversity, may be useful for targeting management resources to a group of prioritised grassland sites. A heuristic algorithm MSET was applied to select complementarity sets of semi-natural grassland sites in southern Finland. Site selection was carried out for three different data sets (grassland, indicator and rare species) of vascular plant species occurrences, and three target levels of species occurrences (1, 5 or 10 times). The overlap of the derived sets of sites varied between 46% and 88%, suggesting that algorithms can be sensitive to the delimitation of target species set. The results of algorithms based on species-occurrence data only should be critically evaluated with regard to the habitat quality and other species persistence issues. When applied with caution, complementarity-based methods, therefore offer a promising approach in prioritising grasslands.