Assisted migration within species range ignores biotic interactions and lacks evidence

Abstract

In the context of climate change, many plant species may have problems adapting or dispersing rapidly enough to keep pace with changing environmental conditions. Given these potential problems, some experts argue against using local plant ecotypes for ecosystem restoration. Instead, they propose to use foreign ecotypes that are adapted to the predicted climate in an approach called assisted migration within species range or predictive provenancing. I argue that such actions may cause a mismatch in biotic interactions and have negative effects on other organisms. As such, assisted migration should only be considered in cases when the local ecotypes would fail to ensure ecosystem services. In fact, there is little experimental evidence on the assisted migration approach so far, and what little there is does not seem to support its use. Even in altered climates, local ecotypes mostly performed equally well or better than foreign ones selected for their adaptations to these climates. The reason is that even if adaptation to climate plays a role, this factor may be overridden by other drivers of local adaptation, such as soil or biotic interactions. Despite assisted migration being a popular concept that is repeatedly commended in scientific literature and propagated among practitioners, it should not be considered a universal tool to improve restoration outcomes during climate change. Given the lack of hard experimental data, I call for large-scale multispecies experimental studies that will provide the necessary evidence to derive general guidelines and recommendations for management of ecosystems during climate change. Implications for Practice• Assisted migration within species range as a tool to help species to adapt to climate change may have unpredictable effects on biotic interactions. • There is little evidence that assisted migration will lead to the desired effect of increased plant performance. However, there is general lack of data. • As long as there is not sufficient evidence, I recommend local or regional provenancing as the default strategy for restoration projects.

Translocations, conservation, and climate change: use of restoration sites as protorefuges and protorefugia

“…Marsico & Hellmann ; Stevens & Emery ), with both these experiments finding that species distribution was dispersal limited. Finally, with respect to this, we would concur with Bucharova () that we do indeed need to experimentally test species we are aiming to conserve in their potential new locations, ideally using large‐scale field trials where possible.…”

Integrating climate change and habitat fragmentation to identify candidate seed sources for ecological restoration

“…Decisions about where and how much to sample will need to consider the ecological and genetic implications of moving genotypes around the landscape (Bucharova ). These can include (1) the potential for inter‐ and intra‐specific hybridization through pollen dispersal which could lead to heterosis (superiority of hybrid over pure stock) (Costa e Silva et al ), outbreeding depression caused by disruption of locally adapted gene combinations (Costa e Silva et al ), or off‐site genetic contamination (Potts et al ); and (2) the spread of wildings, weeds, diseases, or pathogens (Ricciardi & Simberloff ).…”

Assisted gene flow in the context of large‐scale forest management in California,USA

“…Despite the large body of literature on common garden and provenance tests, only a few empirical studies to date have directly evaluated the outcome of assisted gene flow-that is, specifically moving genotypes into sites where the environment has changed to more closely match the relocated genotype's historical source environment (or at least some component of it) (Bucharova 2017). One study tested assisted gene flow in a tree species (Populus tremuloides Michx.)…”