Using plant traits to predict reintroduction success of endangered species

Background/Question/Methods

Reintroduction of endangered species may be necessary to protect them from extinction, provide connectivity between populations, and reach recovery goals under the U.S. Endangered Species Act.  But what factors affect reintroduction success?  Here I propose that there are traits of endangered species that make them more likely to succeed in reintroductions.  Specifically, reintroduction success will be highest for endangered species that share traits with non-rare native species, invasives, and species that excel in restoration projects.  I synthesized the results of six review papers that evaluated traits associated with plant rarity, invasiveness, and successful restoration planting and identified traits common to more than one group to generate a short list of traits that could predict reintroduction success.  To test the usefulness of these traits, I compared reintroduced plant performance (first year survival) of seven plant species from prairies of western Oregon with the number of traits hypothesized to be linked to reintroduction success for each using polynomial regression.

Results/Conclusions

Based on traits in common with rarity, invasiveness, and/or establishment during restoration, I hypothesize that the following plant characteristics may indicate the likelihood of successful reintroduction:  1) long flowering-fruiting period, 2) vegetative growth, 3) competitive ability (including plants that are tall and/or with high leaf area), 4) high seed production and/or intermediate seed size, 5) long distance dispersal mechanism, 6) large geographic range and/or multiple habitats, and 7) generalist pollination and mixed mating system.  Because of its strong association with invasion potential, an additional trait, 8) past history of success, is added to this list.  First year survival of reintroduced plants was positively correlated with the number of these traits in the seven species examined (more than 50% of variability in survival was explained by the number of predictor traits possessed by each species).  These results imply that plant species that are most likely to succeed in reintroduction programs may be predicted from their inherent traits.  Species with few traits linked to reintroduction potential may need additional support to succeed, such as close matching to needed habitat, intensive site preparation, and development of rigorous propagation protocols.