MOVING AWAY FROM A DEFAULT
Reframing provenancing strategies on eco-evolutionary risks highlights
that all strategies come with risks, even local provenancing. We
recommend moving the discussion beyond the local vs. non-local debate
and towards context-dependant choices that enhance resilience and future
adaptability. Growing evidence suggests that no single strategy will be
appropriate for all contexts. Rather, the most appropriate strategy in
any situation will be influenced by a range of context-dependant
factors.
To create resilient plantings, provenancing must consider the dynamic
conditions imposed by environmental change (Aitken & Bemmels 2016).
Genetic variation is a key factor in long-term evolutionary resilience
and adaptability (Sgrò et al. 2011; Kardos et al. 2021).
Provenancing strategies that mix local and non-local provenances aim to
boost resilience by increasing genetic diversity, including adaptive
variation. Considering eco-evolutionary genetics can therefore help
guide whether local, non-local or a combination of both may be most
appropriate to enhance genetic variation and thus adaptability in any
given situation (Hoffmann et al. 2020). While we focussed on the
eco-evolutionary risks associated with provenance choice, other factors
may influence provenance choice, including ecological (e.g., biotic
interactions; (Bucharova et al. 2021), logistical (e.g.,
availability of seed; (Broadhurst et al. 2016) and socio-cultural
(e.g., significance of local genetic identity of plants; Mauriceet al. 2013). However, these factors need to be weighed against
the eco-evolutionary risks associated with not changing provenancing
strategy, especially in changing environments.
Moving forward, it will be important to address barriers and knowledge
gaps that currently inhibit context-dependant provenancing decisions.
These include better understanding of the long-term performance, and
risks associated with, both local and non-local provenances for
different species in different restoration contexts and deriving
practical guidance on provenancing choice (Breed et al. 2018).
Greater direct evidence on the long-term performance of not only
different provenances (e.g., local and non-local provenances) but also
different provenancing strategies will also assist decision-making
(Bailey et al. 2021). Determining whether generalized
recommendations can be derived based on plant life history, functional
traits and/or genomic information across species will also help guide
recommendations for species without empirical data.
Several initiatives are working to address these knowledge gaps. For
example, there are already several practitioner guides that incorporate
climate uncertainty, evolutionary genetics, and landscape fragmentation
into seed sourcing decisions with the aim of increasing genetic
diversity and adaptability (Harrison et al. 2017; Rossettoet al. 2019). Establishing long-term provenance trials (as per
example 1 above), especially those that are embedded within mixed
species revegetation plantings (e.g. Bailey et al. 2021), will
help generate long-term fitness data on provenances in a relevant
revegetation context and thus help enable adaptive seed sourcing
decisions into the future.
CONCLUDING
REMARKS
With a focus on eco-evolutionary factors, our viewpoint is that no
provenancing strategy is risk free. The risk of changing from the
default local provenancing strategy needs to be weighed against the risk
of not changing. We do not suggest local provenancing is no longer
appropriate, nor that provenancing strategies must change from local.
There are clear situations where local will be most appropriate and
where factors not discussed in depth here (e.g., logistics and cultural)
may influence provenance choice more than eco-evolutionary factors.
Rather, the choice of provenancing strategy should consider all risks
when determining the most appropriate provenancing strategy for a given
species and context. As such, the intention of our paper is to move the
discussion of provenancing away from a default strategy and whether
local provenances are more-or-less appropriate than non-local
provenances, and towards conscious and context-dependent provenancing
decisions.