von Takach Dukai Brenton, Jack Cameron, Borevitz Justin, Lindenmayer David B, Banks Sam C
Fenner School of Environment and Society The Australian National University Canberra Australian Capital Territory Australia.
ANU Bioinformatics Consultancy, John Curtin School of Medical Research Australian National University Canberra Australian Capital Territory Australia.
Evol Appl. 2019 Feb 12;12(4):845-860. doi: 10.1111/eva.12761. eCollection 2019 Apr.
Conservation management often uses information on genetic population structure to assess the importance of local provenancing for ecological restoration and reintroduction programs. For species that do not exhibit complete reproductive isolation, the estimation of population genetic parameters may be influenced by the extent of admixture. Therefore, to avoid perverse outcomes for conservation, genetically informed management strategies must determine whether hybridization between species is relevant, and the extent to which observed population genetic patterns are shaped by interspecific versus intraspecific gene flow. We used genotyping by sequencing to identify over 2,400 informative single nucleotide polymorphisms across 18 populations of F. Muell., a foundation tree species of montane forests in south-eastern Australia. We used these data to determine the extent of hybridization with another species, L'Hér., and investigate how admixture influences genetic diversity parameters, by estimating metrics of genetic diversity and examining population genetic structure in datasets with and without admixed individuals. We found hybrid individuals at all sites and two highly introgressed populations. Hybrid individuals were not distributed evenly across environmental gradients, with logistic regression identifying hybrids as being associated with temperature. Removal of hybrids resulted in increases in genetic differentiation ( ), expected heterozygosity, observed heterozygosity and the inbreeding coefficient, and different patterns of isolation by distance. After removal of hybrids and introgressed populations, mountain ash showed very little population genetic structure, with a small effect of isolation by distance, and very low global (0.03). Our study shows that, in plants, decisions around provenancing of individuals for restoration depend on knowledge of whether hybridization is influencing population genetic structure. For species in which most genetic variation is held within populations, there may be little benefit in planning conservation strategies around environmental adaptation of seed sources. The possibility for adaptive introgression may also be relevant when species regularly hybridize.
保护管理通常利用遗传种群结构信息来评估本地种源对于生态恢复和重新引入计划的重要性。对于未表现出完全生殖隔离的物种，种群遗传参数的估计可能会受到混合程度的影响。因此，为避免保护工作出现适得其反的结果，基于遗传信息的管理策略必须确定物种间杂交是否相关，以及观察到的种群遗传模式在多大程度上是由种间基因流与种内基因流所塑造的。我们通过测序基因分型，在澳大利亚东南部山地森林的一种基础树种——缪氏桉（Eucalyptus muelleriana）的18个种群中鉴定出了2400多个信息丰富的单核苷酸多态性。我们利用这些数据来确定与另一个物种——直杆桉（Eucalyptus maidenii）的杂交程度，并通过估计遗传多样性指标以及检查有无混合个体的数据集中的种群遗传结构，来研究混合如何影响遗传多样性参数。我们在所有地点以及两个高度渐渗的种群中发现了杂交个体。杂交个体在环境梯度上分布不均，逻辑回归表明杂交个体与温度有关。去除杂交个体后，遗传分化（Fst）、预期杂合度、观察到的杂合度和近亲繁殖系数均增加，并且出现了不同的距离隔离模式。去除杂交个体和渐渗种群后，山灰桉显示出非常少的种群遗传结构，距离隔离效应较小，全局Fst非常低（0.03）。我们的研究表明，在植物中，围绕个体种源进行恢复的决策取决于对杂交是否影响种群遗传结构的了解。对于大多数遗传变异存在于种群内部的物种，围绕种子源环境适应性制定保护策略可能益处不大。当物种经常杂交时，适应性渐渗的可能性也可能具有相关性。
