Environmental and geographic data optimize ex situ collections and the preservation of adaptive evolutionary potential

Abstract

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 environmental (isolation-by-environment, IBE) data for ex situ collections where provenance data 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 and environmental factors, and (ii) simulate ex situ collections prioritizing source populations based on pairwise geographic or environmental distances. Specifically, we test the impact prioritizing sampling based on environmental and geographic distances may have on capturing neutral, functional or putatively adaptive genetic diversity and differentiation. We find that collectively IBD and IBE explain a substantial proportion of genetic differences among functional (median 45%) and adaptive (median 71%) loci, but not for neutral loci (median 21.5%). Simulated ex situ collections reveal that inclusion of IBD and 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 geographic distance data can impact genetic variation captured ex situ. This provides value for the vast majority of plant species for which we have no genetic data, informing conservation of genetic variation needed to maintain evolutionary potential within collections.