Shiga Takashi, Yokogawa Masashi, Kaneko Shingo, Isagi Yuji
Faculty of Education, Niigata University, Ikarashi-Ninocho, Nishi-ku, Niigata, 950-2181, Japan.
Osaka Museum of Natural History, Nagai Park, Higashisumiyoshi-ku, Osaka, 546-0034, Japan.
J Plant Res. 2017 Jan;130(1):83-93. doi: 10.1007/s10265-016-0869-1. Epub 2016 Nov 22.
Nuphar submersa (Nymphaeaceae) is a critically endangered freshwater macrophyte indigenous to central Japan, with only four small extant populations represented across its entire range. We investigated the genotypic and genetic diversity as well as the genetic structure of all extant individuals of N. submersa based on analysis of 15 microsatellite loci. Among 278 individual ramets, 52 multilocus genotypes were detected: 30 genotypes in Nikko City (NIK), 18 in Nasukarasuyama City (NAS), 3 in Mooka City (MOK), and 1 in Sakura City (SAK). The average number of alleles per locus ranged from 1.20 to 1.93, whereas the observed and expected heterozygosities ranged from 0.11 to 0.33 and from 0.10 to 0.24, respectively. With the exception of SAK, all populations contained multiple clones, but our results indicated low levels of within-population genetic diversity. The populations NIK and NAS comprised few large or middle-sized genets and many small genets. The populations NIK and NAS were suggested to comprise large old, old fragmented, and/or young small genets resulting from seedling establishment. All four populations were differentiated, and gene flow between the populations was restricted (average level of gene flow (Nm) = 0.122, G' = 0.639). Of the total genetic diversity, 67.20 and 9.13% were attributable to inter- and intra-population diversity, respectively. STRUCTURE analysis revealed two or three well-differentiated groups of populations. Cluster I comprised one population (NIK) and cluster II comprised the remaining populations at K = 2. The populations NIK, NAS, and the remaining populations were assigned to clusters I, II, and III, respectively, at K = 3. For conservation practices, we recommend that each cluster be regarded as a different management unit. We further suggest that artificial gene flow among MOK and SAK populations is an appropriate option, whereas NIK should not be reinforced with genotypes from the remaining populations.
沉水萍蓬草（睡莲科）是一种极度濒危的淡水大型植物，原产于日本中部，在其整个分布范围内仅存四个小种群。我们基于对15个微卫星位点的分析，研究了沉水萍蓬草所有现存个体的基因型和遗传多样性以及遗传结构。在278个个体分株中，检测到52个多位点基因型：日光市（NIK）有30个基因型，那须乌山市（NAS）有18个，茂木市（MOK）有3个，樱花市（SAK）有1个。每个位点的平均等位基因数在1.20至1.93之间，而观察到的杂合度和预期杂合度分别在0.11至0.33和0.10至0.24之间。除了SAK，所有种群都包含多个克隆，但我们的结果表明种群内遗传多样性水平较低。NIK和NAS种群由少数大型或中型遗传体和许多小型遗传体组成。NIK和NAS种群被认为包含由幼苗建立产生的大型老龄、老龄破碎化和/或年轻小型遗传体。所有四个种群都有分化，种群之间的基因流受到限制（平均基因流水平（Nm）= 0.122，G' = 0.639）。在总遗传多样性中，分别有67.20%和9.13%归因于种群间和种群内多样性。STRUCTURE分析揭示了两个或三个分化良好的种群组。在K = 2时，聚类I包含一个种群（NIK），聚类II包含其余种群。在K = 3时，NIK、NAS和其余种群分别被分配到聚类I、II和III。对于保护措施，我们建议将每个聚类视为不同的管理单元。我们进一步建议，在MOK和SAK种群之间进行人工基因流是一个合适的选择，而NIK不应与其余种群的基因型进行强化。
