Examining Previously Neglected Aspects of Ex Situ Gene Conservation in Two IUCN Threatened Plant Species: Rare Alleles, Redundancy, Ecogeographic Representativeness, and Relatedness

During the present biodiversity crisis, rare and endangered plants can be conserved ex situ in botanic gardens or seed banks. Ex situ collections distributed among multiple locations-"metacollections"-can safeguard against extinction but must represent adequate genetic diversity to be resilient to changing environments. Previous analyses have revealed strategies to create genetically diverse metacollections of plants with diverse life histories. However, past work has neglected important aspects of metacollection conservation: rare alleles, redundancy (duplication of alleles to be resilient to loss), geographic coverage, and relatedness. Therefore, we assessed two existing large metacollections (>250 individuals) of two International Union for Conservation of Nature (IUCN) Red List threatened plant species-Quercus acerifolia, a wind-pollinated oak, and Zamia integrifolia, an insect-pollinated cycad-for these previously neglected aspects of metacollection genetic conservation. We found that large metacollections of both species conserved genetic diversity well: over 80% of all alleles were conserved in at least one copy, and similar to 70% of alleles were represented in five to 10 copies. Metacollections, however, could still be improved. The rare genetic diversity of Z. integrifolia was less well conserved than that of Q. acerifolia, and several wild populations of both species are precariously undersampled. Ex situ collections also contained high relatedness, which may hamper restoration efforts. Although large metacollections are commendable for their size and breadth, examining metacollections for these facets allowed a more holistic evaluation of genetic diversity conservation.