Koehler Samantha, Cabral Juliano S, Whitten W Mark, Williams Norris H, Singer Rodrigo B, Neubig Kurt M, Guerra Marcelo, Souza Anete P, Amaral Maria do Carmo E
Department of Botany, Biology Institute, P.O. Box 6109, University of Campinas, UNICAMP, 13083-970, Brazil.
Ann Bot. 2008 Oct;102(4):491-507. doi: 10.1093/aob/mcn128. Epub 2008 Aug 7.
Species' boundaries applied within Christensonella have varied due to the continuous pattern of variation and mosaic distribution of diagnostic characters. The main goals of this study were to revise the species' delimitation and propose a more stable classification for this genus. In order to achieve these aims phylogenetic relationships were inferred using DNA sequence data and cytological diversity within Christensonella was examined based on chromosome counts and heterochromatin patterns. The results presented describe sets of diagnostic morphological characters that can be used for species' identification.
Phylogenetic studies were based on sequence data of nuclear and plastid regions, analysed using maximum parsimony and maximum likelihood criteria. Cytogenetic observations of mitotic cells were conducted using CMA and DAPI fluorochromes.
Six of 21 currently accepted species were recovered. The results also support recognition of the 'C. pumila' clade as a single species. Molecular phylogenetic relationships within the 'C. acicularis-C. madida' and 'C. ferdinandiana-C. neowiedii' species' complexes were not resolved and require further study. Deeper relationships were incongruent between plastid and nuclear trees, but with no strong bootstrap support for either, except for the position of C. vernicosa. Cytogenetic data indicated chromosome numbers of 2n = 36, 38 and 76, and with substantial variation in the presence and location of CMA/DAPI heterochromatin bands.
The recognition of ten species of Christensonella is proposed according to the molecular and cytogenetic patterns observed. In addition, diagnostic morphological characters are presented for each recognized species. Banding patterns and chromosome counts suggest the occurrence of centric fusion/fission events, especially for C. ferdinandiana. The results suggest that 2n = 36 karyotypes evolved from 2n = 38 through descendent dysploidy. Patterns of heterochromatin distribution and other karyotypic data proved to be a valuable source of information to understand evolutionary patterns within Maxillariinae orchids.
由于诊断特征的连续变异模式和镶嵌分布，克里斯滕森兰属内的物种界限有所不同。本研究的主要目标是修订物种界定，并为该属提出更稳定的分类。为实现这些目标，利用DNA序列数据推断系统发育关系，并基于染色体计数和异染色质模式研究了克里斯滕森兰属内的细胞学多样性。所呈现的结果描述了可用于物种鉴定的诊断形态特征集。
系统发育研究基于核区和质体区的序列数据，采用最大简约法和最大似然法进行分析。使用CMA和DAPI荧光染料对有丝分裂细胞进行细胞遗传学观察。
目前公认的21个物种中有6个被重新确定。结果还支持将“矮小克里斯滕森兰”分支识别为一个单一物种。“针状克里斯滕森兰 -
疯狂克里斯滕森兰”和“费迪南德克里斯滕森兰 - 新维迪克里斯滕森兰”物种复合体内部的分子系统发育关系尚未解决，需要进一步研究。质体树和核树之间的深层关系不一致，但除了翠绿克里斯滕森兰的位置外，两者均无强有力的自展支持。细胞遗传学数据表明染色体数为2n = 36、38和76，并且CMA / DAPI异染色质带的存在和位置存在大量变异。
根据观察到的分子和细胞遗传学模式，提出认可克里斯滕森兰属的10个物种。此外，还为每个认可的物种呈现了诊断形态特征。带型模式和染色体计数表明发生了着丝粒融合/裂变事件，特别是对于费迪南德克里斯滕森兰。结果表明2n = 36核型是通过后代非整倍体从2n = 38进化而来的。异染色质分布模式和其他核型数据被证明是理解颚唇兰亚科兰花进化模式的宝贵信息来源。
