Using environmental and geographic data to optimize ex situ collections and preserve evolutionary potential.

Maintenance of biodiversity through seed banks and botanical gardens, where the wealth of species' genetic variation may be preserved ex situ, is a major goal of conservation. However, challenges can persist in optimizing ex situ collections where trade-offs exist between expense, effort, and conserving species evolutionary potential, particularly when genetic data is not available. Within this context, we evaluate the genetic consequences of guiding population preservation using geographic (isolation-by-distance, IBD) and/or environmental (isolation-by-environment, IBE) distance for ex situ collections where population provenance is available. We use 19 genetic and genomic datasets from 15 plant species to (i) assess the proportion of population genetic differentiation explained by geographic, environmental or both factors, and (ii) simulate ex situ collections prioritizing source populations using pairwise geographic distance, environmental distance or both. Specifically, we test the impact prioritizing sampling based on these distances may have on capturing neutral, functional or putatively adaptive genetic diversity and differentiation. Individually, IBD and IBE alone explain limited population genetic differences across all three genetic marker classes (IBD: 10%-16%, IBE: 1%-5.5%). However, together, they explain a substantial proportion of population genetic differences for functional (45%) and adaptive (71%) variation. Consistent with these results, simulated ex situ collections reveal that inclusion of IBD and/or IBE increases both allelic diversity and genetic differentiation captured among populations, particularly for loci that may be important for adaptation. Thus, prioritizing population collections using environmental and/or geographic distance data can optimize genetic variation captured ex situ. For the vast majority of plant species for which we have no genetic information, these data are invaluable to conservation, guiding preservation of genetic variation needed to maintain evolutionary potential within collections. Article impact statement: Sampling using environmental and geographic information increases potential adaptive and functional genetic variation conserved in collections. This article is protected by copyright. All rights reserved.