野牡丹属两个海南特有种与同属广布种自然杂交的分子证据

doi:10.17520/biods.2017060

摘要/Abstract

摘要：

自然杂交既可以在物种形成、遗传交换和适应性进化方面发挥重要作用, 也可以造成稀有种的下降甚至灭绝以及超级入侵种的产生。涉及到稀有种的自然杂交研究可以为稀有种的保护提供重要的信息。紫毛野牡丹(Melastoma penicillatum)和枝毛野牡丹(M. dendrisetosum)是野牡丹属的两个海南特有种, 其中枝毛野牡丹已处于濒危状态。我们的野外调查和形态观察发现, 海南吊罗山存在紫毛野牡丹和野牡丹(M. candidum)以及枝毛野牡丹和毛菍(M. sanguineum)的嫌疑杂种个体。本研究测定并分析了这些嫌疑杂种及其嫌疑亲本的4个核基因和5个叶绿体基因间隔区序列, 发现嫌疑杂种个体在嫌疑亲本物种的固定替换位点上均为嫌疑亲本物种碱基的杂合状态, 单倍型网络分析表明所有嫌疑杂种个体在每个核基因上均具有来自两个嫌疑亲本的等位基因, 证实了紫毛野牡丹和野牡丹, 以及枝毛野牡丹和毛菍之间确实存在自然杂交。另外, 相对于其他野牡丹属物种, 枝毛野牡丹具有极低的遗传多样性。因为紫毛野牡丹和野牡丹、枝毛野牡丹和毛菍之间均存在很强的生态隔离, 所以因公路修建而造成的生境干扰可能造成了这两个杂交事件的发生。因此避免生境干扰是保护这两个海南特有种最关键的手段。除此之外, 在实验室条件下进行种子萌发或枝条扦插繁殖, 然后将幼苗种植到合适生境中是扩大种群的另一个可行方法。

关键词: 野牡丹属, 自然杂交, 濒危物种, 核基因, 叶绿体基因间隔区, 保护

Abstract

Natural hybridization plays an important role in speciation, genetic exchange, and adaptive evolution. However, it can also lead to the extinction of rare species or can generate super invasive species. Studies of natural hybridization involving rare species can therefore provide valuable information for species protection. In Melastoma, M. penicillatum and M. dendrisetosum are endemic to Hainan, China. M. dendrisetosum is at the edge of extinction, with a wild population of less than 300 individuals. Based on morphological observations during our field survey, we found that there are putative hybrids formed between the two endemic species and their widespread congeners, i.e. M. candidum × M. penicillatum and M. sanguineum × M. dendrisetosum. In this study, we sequenced four low-copy nuclear genes and five chloroplast DNA intergenic spacers of the putative hybrids and their putative parents. We found that these putative hybrids showed chromatogram signal additivity between putative parental species on differentially fixed sites at these nuclear genes. Haplotype networks also showed that at all four nuclear loci analyzed, alleles of the putative hybrids were shared with those of their putative parental species. The results above confirmed that hybridization occurred between M. candidum and M. penicillatum, and between M. sanguineum and M. dendrisetosum. Also, we found an extremely low level of genetic diversity in M. dendrisetosum relative to the three other species of Melastoma. It appears that there are strong ecological isolation between M. candidum and M. penicillatum as well as between M. sanguineum and M. dendrisetosum, and habitat disturbance caused by highway construction may have promoted hybridization between these species. Therefore, the key to protecting these two species endemic to Hainan is to reduce habitat disturbance. Artificial propagation of the species is another possible way to expand their population sizes.

Key words: Melastoma, natural hybridization, endangered species, nuclear genes, chloroplast intergenic spacer, conservation

周秋杰, 蔡亚城, 黄伟伦, 吴伟, 代色平, 王峰, 周仁超 (2017) 野牡丹属两个海南特有种与同属广布种自然杂交的分子证据. 生物多样性, 25, 638-646. DOI: 10.17520/biods.2017060.

Qiujie Zhou, Yacheng Cai, Wei Lun Ng, Wei Wu, Seping Dai, Feng Wang, Renchao Zhou (2017) Molecular evidence for natural hybridization between two Melastoma species endemic to Hainan and their widespread congeners. Biodiversity Science, 25, 638-646. DOI: 10.17520/biods.2017060.

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链接本文: https://www.biodiversity-science.net/CN/10.17520/biods.2017060

https://www.biodiversity-science.net/CN/Y2017/V25/I6/638

图/表 7

图1 紫毛野牡丹、野牡丹及其嫌疑杂种的部分形态学特征。A: 紫毛野牡丹; B: 紫毛野牡丹和野牡丹的嫌疑杂种; C: 野牡丹; D、E、F分别为紫毛野牡丹、嫌疑杂种和野牡丹的果。

Fig. 1 Morphological comparison between Melastoma penicillatum, M. candidum and their putative hybrid. (A) M. penicillatum, (B) putative hybrid, (C) M. candidum. Fruits of M. penicillatum (D), putative hybrid (E) and M. candidum (F).

图2 枝毛野牡丹、毛菍及其嫌疑杂种的部分形态学特征。A、B、C分别为枝毛野牡丹、嫌疑杂种和毛菍的果。D、E从左到右分别为枝毛野牡丹(左)、嫌疑杂种(中)和毛菍(右)的叶和幼枝。

Fig. 2 Morphological comparison between Melastoma dendrisetosum, M. sanguineum and their putative hybrid. Fruits of M. dendrisetosum (A), putative hybrid (B) and M. sanguineum (C). D, Leaves of M. dendrisetosum (left), putative hybrid (middle) and M. sanguineum (right). E, Young twigs of M. dendrisetosum (left), putative hybrid (middle) and M. sanguineum (right).

表1 4个野牡丹属物种和2个嫌疑杂种的采样信息

Table 1 Sampling details of four species of Melastoma and two putative hybrids used in this study

类群 Taxon	采样地点 Location	个体数量 Sample size
野牡丹 M. candidum (Cf)	福建龙海 Longhai, Fujian	19
野牡丹 M. candidum (Ch)	海南吊罗山 Diaoluoshan, Hainan	20
毛菍 M. sanguineum (S)	海南吊罗山 Diaoluoshan, Hainan	20
紫毛野牡丹 M. penicillatum (P)	海南吊罗山 Diaoluoshan, Hainan	20
枝毛野牡丹 M. dendrisetosum (D)	海南吊罗山 Diaoluoshan, Hainan	20
紫毛野牡丹与野牡丹的嫌疑杂种 Putative hybrid between P and C	海南吊罗山 Diaoluoshan, Hainan	1
枝毛野牡丹与毛菍的嫌疑杂种 Putative hybrid between D and S	海南吊罗山 Diaoluoshan, Hainan	4

表2 紫毛野牡丹和野牡丹在cam和tpi基因上的固定变异位点及其嫌疑杂种在这些位点上的碱基组成(R = A + G; Y = C + T; W = T + A)

Table 2 The base composition of the differentially fixed sites at the cam and tpi genes between Melastoma penicillatum and M. candidum in their putative hybrid (R = A + G; Y = C + T; W = T + A)

类群 Taxon	cam		tpi
类群 Taxon	292	244	204	225	258	272	315	340	568
野牡丹 Melastoma candidum (C)	A	G	T	T	T	G	A	T	C
紫毛野牡丹 M. penicillatum (P)	G	A	A	C	C	A	G	C	T
紫毛野牡丹和野牡丹的嫌疑杂种 Putative hybrid between P and C	R	R	W	Y	Y	R	R	Y	Y

表3 枝毛野牡丹和毛菍在4个基因上的固定变异位点及其嫌疑杂种在这些位点上的碱基组成(R = A + G; Y = C + T; W = T + A; M = A + C; S = C + G)

Table 3 The base composition of the differentially fixed sites at the four nuclear genes between Melastoma dendrisetosum and M. sanguineum in their putative hybrid (R = A + G; Y = C + T; W = T + A; M = A + C; S = C + G)

类群 Taxon	cam			chi		gbss		tpi
类群 Taxon	190	329	661	79	258	315	414	80	240	286
毛菍 M. sanguineum (S)	T	C	G	C	A	G	G	G	T	A
枝毛野牡丹 M. dendrisetosum (D)	C	T	A	T	C	A	C	A	C	T
枝毛野牡丹和毛菍的嫌疑杂种 Putative hybrid between D and S	Y	Y	R	Y	M	R	S	R	Y	W

图3 4个野牡丹属物种及2个嫌疑杂种在4个核基因上的单倍型网络图。A、B、C、D分别为tpi、gbss、chi和cam基因的单倍型网络图。两个单倍型之间的连线上的数字代表突变步骤, 未标出数字的均表示一个突变步骤。黑色小圆圈代表未取样到的单倍型或假设的单倍型。

Fig. 3 Median-joining networks of tpi (A), gbss (B), chi (C) and cam (D) genes of the four Melastoma species and the two putative hybrids. The numbers around the connecting lines between haplotypes represent the number of mutational steps between them, while those without numbers represent only one mutational step. Small black circles represent hypothetical or unsampled haplotypes.

表4 野牡丹属2个嫌疑杂种个体在4个核基因上的基因型。PC为紫毛野牡丹和野牡丹的嫌疑杂种个体; DS_1-DS_4为枝毛野牡丹和毛菍的4个嫌疑杂种个体。单下划线、双下划线、波浪线和虚线分别代表与野牡丹、紫毛野牡丹、毛菍和枝毛野牡丹共享该单倍型。单倍型命名同图3。

Table 4 Genotypes of two putative hybrids of Melastoma at four nuclear genes (tpi, cam, chi and gbss). Haplotypes with single, double, wavy, or dotted underlines have identical sequences with those of M. candidum, M. penicillatum, M. sanguineum, and M. dendrisetosum, respectively. Haplotypes without underline are unique to the putative hybrids.

类群 Taxon	个体编号 Sample ID	tpi	cam	chi	gbss
紫毛野牡丹和野牡丹的嫌疑杂种 Putative hybrid (PC)	PC	PC1PC2	PC1PC2	PC1PC2	PC1 PC2
枝毛野牡丹和毛菍的嫌疑杂种 Putative hybrid (DS)	DS_1	DS1DS2	DS1DS4	DS1 DS2	DS1DS2
	DS_2	DS1DS3	DS2DS4	DS1DS3	DS3DS4
	DS_3	DS1DS4	DS3DS5	DS3DS4	DS1DS2
	DS_4	DS1DS5	DS2DS4	DS1DS3	DS1DS5

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