Junk in the trunk - why the rear range edge matters
Written by Bethany Bradley, edited by Eve Beaury
Summary
Increasing genetic diversity of a species population is thought to increase that population’s resilience to climate change (e.g., Millar et al. 2007). Following invasive species treatments, ‘climate-smart’ restoration projects that include seeds sourced from warmer regions (termed ‘climate-adjusted provenancing’; Prober et al. 2016) could increase the number of individuals adapted to future environmental conditions, and thus support adaptation to climate change. Hampe and Petit (2005) provide another reason for considering sourcing plant material from lower-latitude populations (i.e. ‘southerly’ populations for those of us in the northern hemisphere) in ecological restoration: populations at the rear edge of a species range have higher differentiation and higher regional genetic diversity than populations in other parts of a species range. Rear edge populations are often understudied relative to the core or expanding edge of a species range, but they may contain important genetic diversity that could help ‘northerly’ populations adapt to warmer climate conditions. For Northeast species, rear edge populations (often found in the southeast U.S. and Appalachian mountains) are likely to be the oldest and most genetically diverse because they existed in situ through the last glaciation. With high genetic diversity, a varied, mountainous environment, and plenty of time, these rear edge populations are more likely to have differentiated through natural selection into distinct subpopulations that are each locally adapted to different environmental conditions. Thus, by incorporating seeds from multiple populations at the rear edge, restoration ecologists are likely to introduce both a genetically diverse gene pool as well as individuals adapted to future climate conditions.
Take home points
Populations at the rear edge of a species range are likely to be the most genetically diverse and are more likely to be adapted to varied environmental conditions, which could increase climate resilience.
In the Northeast, many populations are young (they only arrived since the last glaciation) and are likely to have lower genetic diversity and potentially lower resilience to climate change, compared to rear edge populations.
Management implications
Restoration that includes seeds sourced from populations across the rear edge of a species range could enhance resilience and adaptation to climate change.
Related Papers
Keywords: Climate-smart restoration, assisted migration, assisted gene flow, climate adjusted provenancing, forest, managed relocation, plants, restoration