半蒴苣苔复合群的多样性、地理分布和物种界限

Diversity,geographical distribution and species boundary of the Hemiboea subcapitata complex

半蒴苣苔(Hemiboea subcapitata),为苦苣苔科半蒴苣苔属多年生草本植物。该种形态变异幅度大,曾包括多个变种;分布范围广,在多种类型的生境基质上皆有分布。该研究的材料包括典型半蒴苣苔和与之近缘且曾被归为其变种的翅茎半蒴苣苔(H. pterocaulis),以及新发现的与两者形态上分别最相近的另两种变异类型,对其关键形态、微形态的多样性进行了描述和比较;结合查阅标本、文献资料以及长期的野外追踪调查,统计分析了半蒴苣苔不同类型间的地理和生境分布;通过DNA证据,初步重建各物种及变异类型间的系统发育和单倍型进化关系。结果表明:(1)通过茎、叶、花和开花物候等多性状组合能够区分半蒴苣苔复合群各类型。(2)半蒴苣苔复合群四类型间在叶表皮细胞形状和气孔分布等方面无区别,而在表皮毛的有无、复表皮层数、维管束数量和排布存上存在差别,或有助于分类。(3)典型半蒴苣苔广泛分布于我国中部至南部,向南延伸至越南北部,在石灰岩、丹霞等生境基质上皆有分布;翅茎半蒴苣苔仅分布于广西桂林市小部分区域的喀斯特山石灰岩基质上;另两种变异类型分布更为狭域,仅分布于桂林市永福县一个或相邻的数个喀斯特山石灰岩基质上。(4) DNA单倍型网络图分析表明,半蒴苣苔复合群四类型各自独享单倍型;重建的分子系统发育关系表明,金钟山居群与翅茎半蒴苣苔聚为一支,两者亲缘关系最近但相互之间不成单系,金钟山居群是否为独立物种还需更多证据加以检验;半蒴苣苔与永福半蒴苣苔两者间互为单系,支持两者为独立物种。

Hemiboea subcapitata is a group of perennial herbs in Gesneriaceae,which has great morphological variations and large distributional range,growing on various edaphic substrates in different habitats. In this study,focusing on Hemiboea subcapitata,H. pterocaulis,and two other related variations,we investigate and describe the diversities of the morphology and micromorphology;outlined the geographic distributions and habitats by consulting specimens and literature,and long-term field surveys;in addition,the phylogenetic relationship and haplotype network among all types are inferred based on DNA data of the nuclear ITS sequences. The results were as follows:( 1) Different variations of the Hemiboea subcapitata complex are able to be distinguished through the combination of multiple traits from stems,leaves,flowers and phenology.( 2) The leaf cross-section anatomical micromorphologies are highly similar in terms of basic tissue compositions,epidermal cell shape and stomatal distribution,while there are differences in presence versus absence of the epidermal hair,number of the vascular bundles and arrangement,which are seemingly helpful for the classification.( 3) Typical H. subcapitata is widely distributed in central and South China and extends to North Vietnam,growing on different types of rocks,e.g. limestone and sandstone in the limestone region and/or Danxia landform etc.,and H. pterocaulis possesses a narrow range in Guilin,Guangxi and is endemic to limestone,while other two types are only distributed in one or a few adjacent limestone hills in Yongfu County,Guilin and restricted to limestone substrates as well.( 4) The haplotype network show that each type of H. subcapitata complex has its own unique and unshared haplotypes;the molecular phylogenetic relationships indicate that Hemiboea sp. and H. pterocaulis group together,but the monophyletic lineage consisting of all indivuduals of the former type( i.e. Hemiboea sp. from Jinzhongshan) is nested within the latter;H. subcapitata and H. yongfuensis are reciprocally monophyletic,supporting both of them as independent species. In conclusion,at least three indenpendent species are able to be indentified as the H. subcapitata complex. The sympatric distribution of all the four variations in South China,and even the coexistence of the three of them at the same sites in the same limestone hills do not necessarily mean sympatric speciation,though they likely diverged sympatrically via key trait change( s) such as phenological transition of different flowering times that can have resulted in reproductive isolation.