Rapid genetic differentiation between ex situ and their in situ source populations: an example of the endangered Silene otites (Caryophyllaceae)

Abstract

Ex situ cultivation in botanic gardens could be one possibility to preserve plant species diversity and genetic variation. However, old ex situ populations are often sparsely documented. We were able to retrieve three different ex situ populations and their source in situ populations of the endangered plant species Silene otites after 20-36 years of isolation. Furthermore, three additional wild populations were included in the analysis. Population genetic diversity and differentiation were analysed using AFLP markers. Genetic variation in the ex situ populations was lower than the variation found in the in situ populations. Strong differentiation (FST = 0.21-0.36) between corresponding in situ and ex situ populations was observed. Bayesian clustering approach also showed a distinct genetic separation between in situ and ex situ populations. The high genetic differentiation and loss of genetic diversity during spatial and temporal isolation in the ex situ populations can be attributable to small population sizes and unconscious selection during cultivation. Therefore, adequate sampling prior to ex situ cultivation and large effective population sizes are important to preserve genetic diversity. Near-natural cultivation allowing for generation overlap and interspecific competition without artificial selection is recommended as being best for the maintenance of the genetic constitution.

Comparison of the Genetic Structure betweenIn Situ and Ex Situ Populations of DongxiangWild Rice (Oryza rufipogon Griff.)

“…Also, because of the growing and breeding characteristics of DXWR, each plant should be grown in a separate pot to ensure strict reproductive isolation. We also recommend ex situ cultivation in a near-natural environment, allowing for generation overlap, as proposed in previous studies (Volis and Blecher, 2010;Lauterbach et al, 2012). For ex situ conservation, the main goal is to protect populations from extinction and to safeguard representative material for reinforcement programs to establish a remote wild population (Lauterbach et al, 2012).…”

“…important that ex situ collections contain a representative set of the extant in situ diversity, and that their population dynamics are monitored over time to ensure that the original genetic diversity is retained (Lauterbach et al, 2012). After several generations of ex situ cultivation, the population diversity and structure may have changed because multiple samples from different populations have been grown together or due to ecological shifts in mating and reproductive systems; gardener-induced selection may also cause the change (Krauss et al, 2002;Enßlin et al, 2011).…”

“…In situ conservation, which allows species to evolve dynamically with the changing environment, involves the protection of natural populations of endangered species in their original habitat where random mating occurs (Henry et al, 2009). However, when in situ conservation is impractical because of habitat destruction making it too expensive to conserve the original habitat, ex situ conservation can be used to conserve population diversity and genetic variation effectively (Volis and Blecher, 2010;Lauterbach et al, 2012). Ex situ conservation is a resource-limited strategy in which many samples from as many different original habitats as possible are collected and grown together (Namoff et al, 2010).…”

Analysis of genetic structure of Ranunculus baudotii in a Mediterranean wetland. Implications for selection of seeds and seedlings for conservation

“…Ex-situ management inevitably implies selection pressures different from the natural conditions (Lauterbach et al, 2012).…”

“…However, geographical distance is not always the best indicator of a population's genetic similarity (Allendorf and Luikart, 2007). In this context, a genetic molecular approach can provide the opportunity to identify the source of plant material and also to understand the effective level of genetic diversity of seed collections in respect to the natural population (Lauterbach et al, 2012). Furthermore, this approach should be applied at all stages of plant regeneration from seeds, measuring the genetic variation of living collections obtained through different laboratory germination conditions and/or propagation methods, and eventually providing an assessment of the likely success of the whole restoration protocol (Alonso et al, 2014).…”