CONTEXT
Rapidly changing environments combined with increasing global
restoration initiatives require improved seed sourcing strategies for
native revegetation. Sourcing seed from local populations (local
provenancing) has been the long-standing default for native revegetation
for numerous eco-evolutionary reasons including local adaptation and
species co-evolution. However, the evidence-base has shifted, revealing
risks for both non-local and local provenancing in changing
environments. As alternative strategies gain interest, we argue for
effective decision-making that weighs the risks of changing and
not changing seed sourcing strategies in a changing environment that
transcends a default position and the polarising local vs. non-local
debate.
Revegetation aims to restore ecosystems by reintroducing biodiverse
plant communities that support key services and functions that humans
rely upon (e.g., water filtration, carbon sequestration). How to best
source seed to achieve resilient, long-term, self-sustaining plant
populations has received substantial attention (Jones 2013; Proberet al. 2015; Bucharova 2017). Local provenancing targets
adaptations that have evolved to maintain a fitness advantage to the
local environment (Leimu & Fischer 2008; Hereford 2009), enhancing the
establishment and long-term success of the revegetation plantings. Local
provenancing also maintains important co-evolved biotic interactions
such as plant-fungi and plant-pollinator relationships (Grady et
al. 2017; Bucharova et al. 2021) whilst avoiding negative
genetic effects of introducing non-local genotypes, such as outbreeding
depression and swamping of local genotypes (Byrne et al. 2011;
Bucharova et al. 2021). For these reasons, and others, local
provenancing has been the long-standing default strategy for ecosystem
restoration.
However, environmental change and associated impacts on plant fitness
have raised concerns for the long-term viability of the default use of
local provenancing. Changes to local environmental conditions (e.g.,
direct and indirect effects anthropogenic change, such as climate change
and land-use) may decouple adaptation and fitness, resulting in greater
risk of local seed being maladapted (Etterson & Shaw 2001; Anderson
2016). For example, seed sourced from small, fragmented local remnants
can result in genetically depauperate, inbred progeny (Breed et
al. 2015; Aguilar et al. 2019) that are less fit and more
vulnerable to climate change (Nickolas et al. 2019). Thus, the
perception that local provenancing is a ‘safe’ option may be misleading
in a rapidly changing world (Frankham et al. 2011; Ralls et
al. 2018).
Proposed alternative provenancing strategies that mix seed from local
and non-local provenances aim to address these environmental
change-induced issues by increasing genetic diversity or introducing
putatively pre-adapted genotypes that enhance resilience and long-term
adaptability to environmental change. Though there is a shift in
perceptions toward these alternative strategies (e.g Australia, Hancocket al. 2023), concerns remain about the risk of using non-local
provenances, with some sectors continuing to recommend only local
provenancing (Hancock & Encinas-Viso 2021). Such hesitance possibly
reflects a paucity of evidence on outcomes of using non-local
provenances (Twardek et al. 2023). While risks associated with
introducing non-local provenances in a revegetation context are valid,
equally valid are the risks of using local provenances under current and
future conditions.
Here, we argue that the risks of changing and not changing the
local provenancing default in a changing environment needs to be weighed
when determining the most appropriate provenancing strategy. We focus on
the eco-evolutionary risks associated with provenance choice, including
the short- and long-term fitness of plantings and their resilience and
future adaptability, rather than whether provenances are local or
non-local per se . We aim to help move the discussion away from a
polarised local vs. non-local debate, and towards a risk-based,
context-dependent rethinking of how to source seed for revegetation.