人类的过度开发和不合理的资源利用造成生物多样性的严重丧失,尤其是在物种多样性非常丰富的热带雨林地区。在各地森林遭受强烈破坏和片断化的情况下,许多樟科种类生境恶化、传播和更新受到很大影响,生存受到严重威胁。中科院西双版纳热带植物园李捷研究员带领的植物系统与保护生物学研究组利用三年的时间对樟科濒危植物思茅木姜子开展了保护遗传学方面的研究,并取得了重要进展。
思茅木姜子(Litsea szemaois(Liou)J. Li et H. W. Li),是分布于我国云南西双版纳热带季雨林的高大木本植物,属于狭域分布的濒危物种。过去将其处理为樟科木姜子属(Litsea)越南木姜子的一个变种(Litsea pierrei Lec. var. szemois Liou)。通过对野外调查时所采集众多标本的观察,以及室内对模式标本的对比研究,李捷研究员等提出思茅木姜子和越南木姜子在雌雄蕊与叶形等形态特征及分布范围等方面存在极大差别,应作为独立的一个种,并命名为Litsea szemaois(Liou) J . Li et H.W. Li。该课题组利用AFLP和ISSR两种分子标记对该濒危种进行了遗传多样性和遗传结构的研究,结果显示出较高水平的遗传多样性和一定程度的遗传分化。并据此提出了物种的现状除了与西双版纳地区生境的破碎化有关,还与物种自身的生物学特性相关,如多年生、雌雄异株、木本、虫媒、果实主要靠重力传播等。在研究过程中,采集200多株不同居群的幼苗植入西双版纳植物园苗圃,建立了一个较大的迁地保护居群。
通过此项目研究不仅对濒危的思茅木姜子提出理论上的保护依据,为其迁地保护提出了科学的保护策略和措施,具有重要的现实意义,而且以此研究为基础,深入了解樟科物种(已发现报道一樟科植物新属—孔药楠属Sinopora J. Li,N.H. Xia & H.W. Li),在今后樟科的其它稀有濒危植物的保护生物学研究中发挥重要的指导性作用。该研究的一系列研究论文发表在《植物分类学与进化》(Plant Systematics and Evolution)、“Novon”、《生物多样性》《云南植物研究》等国内外重要期刊。(生物谷Bioon.com)
生物谷推荐原始出处:
Plant Systematics and Evolution,doi:10.1007/s00606-008-0012-4,Xiu-qin Ci,Jie Li
AFLP and ISSR analysis reveals high genetic variation and inter-population differentiation in fragmented populations of the endangered Litsea szemaois (Lauraceae) from Southwest China
Xiu-qin Ci1, 2, Jun-qiu Chen1, 2, Qiao-ming Li1 and Jie Li1, 3
(1) Laboratory of Plant Phylogenetics and Conservation Biology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, 650223 Yunnan, People’s Republic of China
(2) The Graduate School of the Chinese Academy of Sciences, 100039 Beijing, People’s Republic of China
(3) 88 Xuefu Rd., Kunming, 650223 Yunnan, People’s Republic of China
Received: 25 October 2007 Accepted: 23 January 2008 Published online: 27 May 2008
Abstract Litsea szemaois (Lauraceae) is an endemic and endangered species from the tropical rain forests of Xishuangbanna, southern Yunnan, SW China, but habitat fragmentation, especially exacerbated by rubber planting, has caused a decline in population size of the species. AFLP and ISSR were used to investigate the genetic diversity and population structure of eight populations from across its known distribution. Three AFLP and ten ISSR primer combinations produced a total of 203 and 77 unambiguous and repeatable bands respectively, of which 164 (80.8%) and 67 (87.0%) were polymorphic for the two markers. These two markers showed that Litsea szemaois exhibits comparatively high genetic diversity at species level (heterozygosity (hs) = 0.2109) relative to some other Lauraceae. Most of the genetic variation was partitioned within populations, but genetic differentiation between populations was significant and relatively high (Φ st = 0.2420, θB = 0.1986) compared with other tropical plants. The genetic characteristics of L. szemaois may be related to its outbreeding system, insect pollination and fragmented distribution. Because L. szemaois is dioecious and slow to mature, ex situ conservation across its genetic diversity is unlikely to succeed, although seedlings grow well under cultivation. Thus, in situ conservation is very important for this endangered species, especially as only 133 adult individuals are known in the wild. In particular, the Nabanhe and Mandian populations should be given a high conservation priority due to their higher genetic diversity, larger population size and better field condition, but wider sampling is required across all populations to determine additional areas with significant genetic conservation value.