Can a botanic garden metacollection better conserve wild plant diversity? A case study comparing pooled collections with an ideal sampling model

Premise of research. To safeguard threatened plant species, best-practice guidelines and genetic modeling emphasize that ex situ collections should be composed of high numbers of maternal lines. Threatened species often present challenges to meeting this standard due to biology or logistics. An approach that pools garden collections into a single larger metacollection may be more effective at capturing genetic diversity. This study examines the genetic capture of a metacollection and compares this with an idealized model for ex situ sampling. Methodology. The model species, Pseudophoenix ekmanii (cacheo palm), was chosen for its threat status, presence in collections, and reproductive limitations. In total, 171 in situ plants were compared with 91 ex situ plants via 10 microsatellite markers. Three cohorts representing both legacy (older) collections and a deliberately structured (recent) conservation collection were pooled and compared. Bootstrapped resampling of these ex situ cohorts was compared with resamples of in situ genotypes to evaluate the collection compared with idealized models of allele capture. Pivotal results. Genetic distance analysis and fixation indexes show weak geographic structure of ex situ collections compared with in situ subpopulations and their close identity to the source population. Pooling together ex situ collections increased allele capture and increased efficiency of allele capture. Modeled allele capture from in situ genotypes exceeded allele capture currently found in ex situ collections. Conclusions. These data demonstrate that botanic gardens may better conserve genetic diversity of in situ plants by following three recommendations: (1) pool ex situ resources into metacollections, (2) share data to better inform new collections, and (3) emphasize logistic and biological parameters of the target species over idealized models for ex situ conservation.