Wuhan Botanical Garden/Wuhan Institute of Botany, Chinese Academy of Sciences, Wuhan 430074, Hubei, China.
Conserv Biol. 2010 Feb;24(1):246-55. doi: 10.1111/j.1523-1739.2009.01357.x. Epub 2009 Nov 10.
For endangered plants interspecific hybridization occurring in ex situ collections may lead to failure of reintroduction actions. We used Sinojackia xylocarpa, a well documented Chinese endemic species that is extinct in the wild, as a model case to address this concern. We used paternity analyses to assess the spontaneous hybridization and patterns of pollen flow between S. xylocarpa and its congener species, S. rehderiana, in conserved populations in Wuhan Botanic Garden. Interspecific hybridization events were detected in seven out of eight maternal trees of S. xylocarpa, and an average of 32.7% seeds collected from maternal trees of S. xylocarpa were hybrids. The paternity of 93 out of 249 seedlings from S. xylocarpa assigned to S. rehderiana provided convincing evidence that spontaneous interspecific hybridization occurred extensively in the living garden collection we studied. Different patterns of pollen dispersal (predominantly short-distance vs. long-distance pollination) were observed between intra- and interspecific hybridization events in the garden. Pollen dispersal within the ex situ populations was not restricted by distance, as evidenced by a lack of significant correlations between the average effective pollen dispersal distance (delta) and the geographic distances (d1 and d2) between maternal and paternal trees. The interspecific pollen-dispersal distance ranged from 10 to 620.1 m (mean 294.4 m). Such extensive hybridization in ex situ collections could jeopardize the genetic integrity of endangered species and irrevocably contaminate the gene pool if such hybrids are used for reintroduction and restoration. We recommend strongly that measures be taken to minimize the genetic risks of this kind of hybridization, including establishing buffer zones in ex situ collections, manipulating flowering phenology, testing seed lots before use in reintroduction programs, and controlling pollination for seed purity.
对于处于原地保护下的濒危植物，种间杂交可能导致重新引入行动的失败。我们以中国特有的受威胁物种中华蚊母（Sinjackia xylocarpa）为模型案例来处理这一问题，该物种野外灭绝，其在原地保护下的种群已得到很好的记录。我们使用亲子鉴定分析来评估中华蚊母及其近缘种鄂西红豆（S. rehderiana）在武汉植物园保护种群中的自然杂交和花粉流模式。在 8 株中华蚊母母树中，有 7 株检测到了种间杂交事件，从中华蚊母母树采集的种子中有平均 32.7%为杂交种子。来自中华蚊母的 249 株幼苗中的 93 株被鉴定为鄂西红豆，这为我们研究的活体园林收集物中广泛发生的自然种间杂交提供了确凿的证据。在园林中，种内和种间杂交事件的花粉传播模式不同（主要是短距离和长距离授粉）。花粉在原地种群中的传播不受距离限制，因为母树和父树之间的平均有效花粉扩散距离（δ）与地理距离（d1 和 d2）之间没有显著相关性。种间花粉扩散距离范围为 10 至 620.1 米（平均值 294.4 米）。如果这些杂种用于重新引入和恢复，那么原地收集物中如此广泛的杂交可能会危及濒危物种的遗传完整性，并不可逆转地污染基因库。我们强烈建议采取措施来最小化这种杂交的遗传风险，包括在原地收集物中建立缓冲区，操纵开花物候，在重新引入计划中使用种子前进行测试，以及控制授粉以保证种子纯度。
