Extensive selfing in an endangered population of Pinus parviflora var. parviflora (Pinaceae) in the Boso Hills, Japan
Extensive selfing in an endangered population of Pinus parviflora var. parviflora (Pinaceae) in the Boso Hills, Japan
复制标题
濒临灭绝的小花松种群中的广泛自交。
DOI：
10.1007/s11295-012-0585-5
复制
发表时间：
2013
影响因子：
2.4
通讯作者：
Takaya
中科院分区：
文献类型：
--
作者：
Iwasaki;Takaya
风媒传粉的树木，如针叶树，由于其大量的空气传播花粉，被认为相对抵抗破碎和低密度的有害影响。然而，一些研究表明，即使在风媒传粉的树木中，种群密度也会影响交配系统。本研究对一个濒危种群（Boso）的交配系统和遗传结构进行了研究。在过去的四分之一世纪里，它的大小减少了80%。利用4个核微卫星标记进行的遗传分析表明，该群体处于Hardy-Weinberg平衡状态，具有与较大群体相当的高水平遗传变异。此外，在局部斑块中仅检测到弱遗传结构。另一方面，Boso群体的种子异交率（MLTR为0.277，父系分析为0.297）明显低于该物种更大群体的异交率（MLTR为0.778）。在波索种群中，每棵母树的异交率与树周围的局部密度呈正相关。这表明，广泛的自交可能是种群密度极低导致的花粉限制的直接结果：局部斑块平均每公顷0.201棵树。由于成年种群处于HWE状态，目前产生的自交种子很可能无法促进种群更新。目前的研究表明，低种群密度甚至会增加风媒传粉针叶树种群的灭绝风险。
Wind-pollinated trees such as conifers have been considered relatively resistant to the deleterious effects of fragmentation and low density by virtue of their abundant production of airborne pollen. However, some studies indicated that population density affects the mating system even in wind-pollinated trees. In the present study, we examined the mating system and genetic structure of an endangered population (Boso) ofPinus parvifloravar.parviflora, whose size has fallen by 80 % in only the last quarter century. Genetic analyses using four nuclear microsatellite markers showed that the population was in Hardy–Weinberg equilibrium and harbored a high level of genetic variation comparable to that of a larger population. Additionally, only weak genetic structure was detected among local patches. On the other hand, the outcrossing rate of seeds in the Boso population was much lower (0.277 from MLTR and 0.297 from paternity analysis) than that found in a larger population of the species (0.778 from MLTR). The outcrossing rate for each mother tree was found to correlate positively with local density around the tree in the Boso population. This suggests that the extensive selfing would be a direct result of pollen limitation caused by the extremely low density of the population: an average of 0.201 trees per hectare for local patches. Because the adult population was in HWE, it is likely that the selfed seeds produced at present cannot contribute to population regeneration. The present study suggests that low population density would increase extinction risk even for wind-pollinated conifer populations.