Meta‐analysis of genetic representativeness of plant populations under ex situ conservation in contrast to wild source populations

Abstract

Ex situ conservation is widely used to protect wild plant species from extinction. However, it remains unclear how genetic variation of ex situ plant collections reflects diversity of wild source populations. We conducted a global meta‐analysis of the genetic representativeness of ex situ populations by comparing genetic diversity (i.e., AR, allelic richness; He, expected heterozygosity; PPB, percent polymorphic bands; and SWI, Shannon–Winner index), inbreeding coefficient (FIS), and genetic differentiation between ex situ plant collections and their wild source populations. Genetic diversity (i.e., He, PPB, and SWI) was significantly lower in ex situ populations than their wild source populations, whereas genetic differentiation between ex situ and wild populations (ex‐situ‐wild FST), but not that among ex situ populations, was significantly higher than among wild populations. Outcrossing species, but not those with mixed mating system, had significantly lower genetic diversity in ex situ populations and significantly higher ex‐situ‐wild FST. When the collection size for ex situ conservation was ≥30 or 50, PPB, He, and ex‐situ‐wild FST were not significantly different between ex situ and wild populations, indicating a relatively high genetic representativeness. Collecting from the entire natural distribution range and mixing collections from different sources could significantly increase the genetic representativeness of ex situ populations. Type of ex situ conservation (i.e., planting or seed bank) had no effect on genetic representativeness. The effect size of He decreased and the effect size of ex‐situ‐wild FST increased as the duration of ex situ conservation increased. Our results suggest that current ex situ plant collections do not effectively capture the genetic variation of wild populations. Low genetic representativeness of ex situ populations was caused by both initial incomplete sampling from wild populations and genetic erosion during ex situ conservation. We emphasize that it is necessary to employ more thorough sampling strategies in future collecting efforts and to add new individuals where needed.

Global Commitments to Conserving and Monitoring Genetic Diversity Are Now Necessary and Feasible

“…Genetic data can provide crucial knowledge on how landscape structure impedes or supports gene flow and genetic diversity and informs large landscape planning. Finally, for many species, ex situ collections in seed banks, zoos, and botanic gardens help forestall the loss of genetic diversity and sometimes conserve genetic variation no longer extant in the wild, although most are currently not sufficiently large, representative, or replicated (Khoury et al 2019 , Hoban et al 2020b, Wei and Jiang 2021 ). Genetic data collected before and after any of these actions can determine whether they have succeeded (also see the “Looking ahead: Challenges” section below).…”

The effect of recent habitat change on genetic diversity at putatively adaptive and neutral loci in Primula veris in semi-natural grasslands

“…Besides, in the overall SNP set (Figure S 7), there was no significant effect of habitat type on genetic diversity, which indicates that genetic diversity of an overall SNP set represents rather neutral genetic patterns (Dauphin et al, 2020). In conservation genetics and restoration, most assessments have been based on overall or neutral genetic diversity so far (González et al, 2019; Wei & Jiang, 2020), even though it is most likely the putatively adaptive regions of a genome that are important for the fate of a population in a changed environment.…”

“…The only existing studies that explicitly account for a difference in neutral and adaptive loci in plants concentrated on climatic factors (Dauphin et al, 2020; Sun et al, 2020). Moreover, in conservation genetics, most studies focussed on overall or genetic diversity at neutral loci so far, often using a set of neutral microsatellite markers, while ignoring adaptive regions of the genome (González et al, 2019; Wei & Jiang, 2020). However, it is exactly the adaptive regions that are important for the fate of a population.…”

New developments in the field of genomic technologies and their relevance to conservation management

“…Genomic techniques allow us to detect DNA sequence variation at single nucleotides (i.e. single-nucleotide polymorphism: SNP, see glossary) that can be used to evaluate the effects of historic founder selection (Gomes Viana et al 2018;Frandsen et al 2020;Ogden et al 2020;Wei and Jiang 2021) and set guidance on how to increase levels of genetic diversity and minimise genetic similarity (Bragg et al 2020) via selective addition of unrepresented lines (Wildt et al 2019;Galla et al 2020;Miller et al 2010). The efficiency of ex situ management partly relies on the profound knowledge of a species' taxonomic status and recent demographic history.…”