GENETIC DIVERSITY ASSESSMENT OF EX SITU COLLECTIONS OF ENDANGERED QUERCUS HINCKLEYI

Premise of research. Conservation of imperiled plant species can benefit from ex situ collections, including the living collections of botanic gardens and arboreta. Such living collections should strive to capture and maintain the genetic diversity found in the remaining wild populations. Ex situ collections may also harbor genetic variability that has been lost from wild populations. Quercus hinckleyi is an extremely rare (International Union for Conservation of Nature and Natural Resources [IUCN] Critically Endangered) oak known from a few sites in Presidio County, Texas. It is the only native US oak protected under the Endangered Species Act. Here we evaluate the genetic variation of the Q. hinckleyi ex situ metacollection relative to that of the remnant in situ population. Methodology. We apply microsatellite genotyping to Q. hinckleyi sampled from plants growing in ex situ collections (N=22, from nine gardens) and compare the results with genetic studies of the in situ population. We compare allelic diversity, genotypic diversity, and population structure. Pivotal results. The ex situ metacollection is small but has high allelic diversity and captures about 57% of the allelic diversity of the wild population. Ex situ plants contain 22 new alleles that contribute 13% of the species' total allelic diversity. All ex situ individuals have unique genotypes, none of which were found in situ, and thus they comprise 15% of the species' genotypic variation. The ex situ plants align with only one of three genetic clusters identified in situ, demonstrating an important gap in the ex situ metacollection. Conclusions. The ex situ collection of Q. hinckleyi, while small, is genetically diverse and provides additional allelic and genotypic diversity not currently existing in situ. However, a significant portion of genetic diversity is lacking from ex situ plants, with the metacollection likely derived from only one of the in situ clusters. Collecting seed from the other clusters is a high priority.