BACKGROUND Nelumbo nucifera Gaertn., a perennial aquatic macrophyte species, has been cultivated in several Asian countries for its economic importance, and medicinal uses. Two distinct ecotypes of the species are recognized based on the geographical location where the genotypes are adapted, i.e., tropical lotus and temperate lotus. The genetic diversity levels and differentiation of the tropical lotus from poorly studied geographic regions still remain unclear. Here, the population genetic diversity and structure of 15 tropical lotus populations sampled from the previous understudied natural distribution ranges, including India, Thailand, and Australia, were assessed using nine polymorphic SSR markers. RESULTS The SSR markers used to genotype the 216 individuals yielded 65 alleles. The highest and lowest genetic diversity estimates were found in Thailand and Indian populations, respectively. STRUCTURE analysis revealed three distinct genetic clusters, with relatively low admixtures, supported by PCoA cluster analysis. Low levels of gene flow (mean N⁠m = 0.346) among the three genetic clusters signified the Mantel test for isolation by distance, revealing the existence of a positive correlation between the genetic and geographic distances (r = 0.448, P = 0.004). Besides, AMOVA analysis revealed a higher variation among populations (59.98%) of the three groups. Overall, the populations used in this study exposed a high level of genetic differentiation (FST = 0.596). CONCLUSIONS The nine polymorphic microsatellite markers used in our study sufficiently differentiated the fifteen tropical N. nucifera populations based on geography. These populations presented different genetic variability, thereby confirming that populations found in each country are unique. The low genetic diversity (HE = 0.245) could be explained by limited gene flow and clonal propagation. Conserving the available diversity using various conservation approaches is essential to enable the continued utilization of this economically important crop species. We, therefore, propose that complementary conservation approaches ought to be introduced to conserve tropical lotus, depending on the genetic variations and threat levels in populations.

中文翻译：

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热带荷花 Nelumbo nucifera Gaertn 的遗传多样性和分化水平。（莲科）来自澳大利亚、印度和泰国。

背景技术 Nelumbo nucifera Gaertn.是一种多年生水生大型植物物种，由于其经济重要性和药用用途，已在多个亚洲国家种植。根据基因型适应的地理位置，识别出该物种的两种不同生态型，即热带荷花和温带荷花。来自研究不足的地理区域的热带莲花的遗传多样性水平和分化仍不清楚。在这里，使用九个多态性 SSR 标记评估了从先前研究的自然分布范围（包括印度、泰国和澳大利亚）取样的 15 个热带莲花种群的种群遗传多样性和结构。结果 用于对 216 名个体进行基因分型的 SSR 标记产生了 65 个等位基因。泰国和印度人群的遗传多样性估计值分别最高和最低。结构分析揭示了三个不同的遗传簇，其混合程度相对较低，并得到 PCoA 簇分析的支持。三个遗传簇之间的低水平基因流（平均 N⁠m = 0.346）表明曼特尔距离隔离检验，揭示了遗传距离和地理距离之间存在正相关性（r = 0.448，P = 0.004）。此外，AMOVA 分析显示三组人群之间的差异较高（59.98%）。总体而言，本研究中使用的群体表现出高水平的遗传分化（FST = 0.596）。结论 我们的研究中使用的九个多态性微卫星标记充分区分了基于地理的 15 个热带 N. nucifera 种群。这些种群呈现出不同的遗传变异性，从而证实每个国家发现的种群都是独一无二的。遗传多样性低（HE = 0.245）可以用有限的基因流和克隆繁殖来解释。使用各种保护方法保护现有多样性对于持续利用这种具有重要经济意义的作物物种至关重要。因此，我们建议根据种群的遗传变异和威胁程度，引入补充性保护方法来保护热带莲花。