Comparing genetic diversity in three threatened oaks

Genetic diversity is a critical resource for species’ survival during times of environmental change. Conserving and sustainably managing genetic diversity requires understanding the distribution and amount of genetic diversity (in situ and ex situ) across multiple species. This paper focuses on three emblematic and IUCN Red List threatened oaks (Quercus, Fagaceae), a highly speciose tree genus that contains numerous rare species and poses challenges for ex situ conservation. We compare the genetic diversity of three rare oak species-Quercus georgiana, Q. oglethorpensis, and Q. boyntonii-to common oaks; investigate the correlation of range size, population size, and the abiotic environment with genetic diversity within and among populations in situ; and test how well genetic diversity preserved in botanic gardens correlates with geographic range size. Our main findings are: (1) these three rare species generally have lower genetic diversity than more abundant oaks; (2) in some cases, small population size and geographic range correlate with genetic diversity and differentiation; and (3) genetic diversity currently protected in botanic gardens is inadequately predicted by geographic range size and number of samples preserved, suggesting non-random sampling of populations for conservation collections. Our results highlight that most populations of these three rare oaks have managed to avoid severe genetic erosion, but their small size will likely necessitate genetic management going forward

Ex situ conservation of oak (Quercus l.) in botanic gardens : a North American perspective

Lyons, Robert E.Oaks have significant ecological, economic and aesthetic importance, but are threatened by habitat loss, invasive species, shifting climates, and pests and pathogens like sudden oak death. Recalcitrant acorns lose viability when dried, rendering long-term seed bank storage futile. Conservation through living collections is currently the only ex situ conservation option. This research investigated the representation of North American threatened oaks in living collections. Using BGCI’s PlantSearch database a survey of ex situ living collections of North American native oak taxa was conducted to determine their prevalence in botanic gardens. A detailed survey of four oak taxa, Quercus acerifolia (E. J. Palmer) Stoynoff & W. J. Hess, Q. arkansana Sarg., Q. boyntonii Beadle and Q. georgiana M.A. Curtis, was conducted to gain insight into the ex situ conservation of wild-collected plants of known provenance in living collections. Botanic gardens growing the four taxa were contacted individually to gain information about the number of accessions, number of individuals and provenance. Among the 97 North American oak taxa presently recognized by the Flora of North America (north of Mexico), six were not represented in botanic gardens and only 2% of records represent the most threatened taxa. However, the four oaks studied here were relatively well represented in collections, and the most threatened oaks (Q. acerifolia and Q. boyntonii) had a higher percent representation of wild collections than less threatened oaks (Q. arkansana and Q. georgiana). Q. georgiana is highlighted as a case study by asking whether oak genetic diversity in living collections represents genetic diversity in the wild through use of DNA fingerprinting techniques. Twenty-four individuals from living collections were compared to 224 individuals from nine populations across the range of the species using microsatellite markers developed for Q. rubra. Genetic diversity was high in wild populations, while less than 63% the genetic variation identified in wild populations was present in known ex situ collections. Results from this study can be used to assist in making management decisions about ex situ conservation of oaks such that genetic diversity within species is maximized in living collections, which has long-term implications for restoration and reintroduction efforts.University of Delaware, Department of Agriculture and Natural ResourcesM.S.University of Delaware, Program in Public Horticultur

Comparing Genetic Diversity in Three Threatened Oaks

Genetic diversity is a critical resource for species’ survival during times of environmental change. Conserving and sustainably managing genetic diversity requires understanding the distribution and amount of genetic diversity (in situ and ex situ) across multiple species. This paper focuses on three emblematic and IUCN Red List threatened oaks (Quercus, Fagaceae), a highly speciose tree genus that contains numerous rare species and poses challenges for ex situ conservation. We compare the genetic diversity of three rare oak species—Quercus georgiana, Q. oglethorpensis, and Q. boyntonii—to common oaks; investigate the correlation of range size, population size, and the abiotic environment with genetic diversity within and among populations in situ; and test how well genetic diversity preserved in botanic gardens correlates with geographic range size. Our main findings are: (1) these three rare species generally have lower genetic diversity than more abundant oaks; (2) in some cases, small population size and geographic range correlate with genetic diversity and differentiation; and (3) genetic diversity currently protected in botanic gardens is inadequately predicted by geographic range size and number of samples preserved, suggesting non-random sampling of populations for conservation collections. Our results highlight that most populations of these three rare oaks have managed to avoid severe genetic erosion, but their small size will likely necessitate genetic management going forward