Are local plants the best for ecosystem restoration? It depends on how you analyze the data

Abstract

One of the key questions in ecosystem restoration is the choice of the seed material for restoring plant communities. The most common strategy is to use local seed sources, based on the argument that many plants are locally adapted and thus local seed sources should provide the best restoration success. However, the evidence for local adaptation is inconsistent, and some of these inconsistencies may be due to different experimental approaches that have been used to test for local adaptation. We illustrate how conclusions about local adaptation depend on the experimental design and in particular on the method of data analysis. We used data from a multispecies reciprocal transplant experiment and analyzed them in three different ways: (1) comparing local vs. foreign plants within species and sites, corresponding to tests of the “local is best” paradigm in ecological restoration, (2) comparing sympatric vs. allopatric populations across sites but within species, and (3) comparing sympatric and allopatric populations across multiple species. These approaches reflect different experimental designs: While a local vs. foreign comparison can be done even in small experiments with a single species and site, the other two approaches require a reciprocal transplant experiment with one or multiple species, respectively. The three different analyses led to contrasting results. While the local/foreign approach indicated lack of local adaptation or even maladaptation, the more general sympatric/allopatric approach rather suggested local adaptation, and the most general cross‐species sympatric/allopatric test provided significant evidence for local adaptation. The analyses demonstrate how the design of experiments and methods of data analysis impact conclusions on the presence or absence of local adaptation. While small‐scale, single‐species experiments may be useful for identifying the appropriate seed material for a specific restoration project, general patterns can only be detected in reciprocal transplant experiments with multiple species and sites.

Stability of species and provenance performance when translocated into different community assemblages

“…However, we found no evidence that the local provenances of either species were maladapted despite the growing period tested being consistently warmer than average (MAT was 0.43°C and MAP was 9.7 mm above the contemporary [1976–2005] average; unpublished data). This is consistent with the local‐is‐best scenario (Bucharova et al ), although this is not the case in a nearby study site involving an endemic eucalypt species E. gunnii where translocated lower‐altitude provenance performed better than the local (Prober et al ). If translocations for future climates (e.g.…”

“…The accelerating pace of global climate change requires greater consideration of the planting material used in restoration (Breed et al ). The last decade has seen active debate on the paradigm shift from a traditional “local‐is‐best” scenario (Mortlock ; Bucharova et al ) to strategies that enrich plantings with seed from provenances growing in environments matching predicted future climates (i.e., climate‐adjusted provenancing—Prober et al ). There is little experimental evidence for such translocation strategies (Whittet et al ; Bucharova ; Montwé et al ), which in the present case would be consistent with upslope translocations of drier, lower altitude provenances.…”

Parallel genetic adaptation across environments differing in mode of growth or resource availability

“…; Bucharova et al. ). However, our work shows that environments that appear to be similar may in fact select for dissimilar sets of adaptive mutations.…”

Rapid evolution in native plants cultivated for ecological restoration: not a general pattern

“…To obtain more general results and develop more comprehensive management guidelines, we need to test many more species (Bucharova et al . ), compare cultivated generations with wild‐collected seed, and relate possible negative effects to species traits and cultivation methods. For the time being, we suggest that seed production for restoration should be accompanied by a rigorous genetic and phenotypic assessment that includes source populations and the different generations of seed production in order to assure high performance and adaptive potential of the restored populations.…”