Data from: Evolution and systematics of polyploid Nigritella (Orchidaceae)

Members of the orchid genus Nigritella are widespread in European mountains, but species circumscriptions and evolutionary patterns in the genus are subjects to conflicting opinions. We analyzed a representative material of Nigritella for differentiation at nuclear and plastid marker loci. In agreement with predictions from embryological studies, diploid members of Nigritella are sexual and mostly out-crossing, whereas triploid, tetraploid and pentaploid members are apomicts. The diploid taxa were poorly differentiated in the investigated molecular markers, except for the western N. gabasiana, which was separated in plastid haplotypes. Polyploid Nigritella aggregate into three groups and within each of these groups apomictic polyploids have given rise to new species. Within the N. nigra group, the tetraploid N. nigra ssp. austriaca is somewhat differentiated from the triploid ssp. nigra at nuclear as well as plastid loci. Fusion of an unreduced egg cell from ssp. nigra with a haploid microgamete from Gymnadenia conopsea gave rise to Gymnigritella runei. Within the N. widderi group, N. archiducis-joannis is poorly separated from N. widderi in molecular markers, and the pentaploid N. buschmanniae has evolved by fusion of an unreduced egg cell from N. widderi with a haploid microgamete from a diploid Nigritella. Within the N. miniata group, N. stiriaca is somewhat differentiated from N. miniata at nuclear loci, but no other segregates of N. miniata are supported at species level. Polyploid Nigritella species accumulate genetic diversity by somatic mutations. In the widespread N. nigra ssp. austriaca and N. miniata this diversity is correlated to geography. Although some polyploids may be of recent origins, each polyploid contain genetic markers no longer encountered in diploid members of the genus. According to plastid marker data, Nigritella and Gymnadenia may constitute monophyletic sister genera.

黑兰属（Nigritella）植物广泛分布于欧洲山地，但该属的物种界定与演化模式长期存在学术争议。本研究选取黑兰属的代表性材料，对其核基因与质体标记位点的分化特征展开分析。与胚胎学研究的预测结果一致，黑兰属的二倍体个体以有性繁殖为主，且多为异交；而三倍体、四倍体及五倍体个体则为无融合生殖体。在所检测的分子标记中，二倍体类群的分化程度普遍较低，仅分布于西部的N. gabasiana可通过质体单倍型与其他类群明确区分。多倍体黑兰属植物可聚为三大类群，每一类群内的无融合生殖多倍体均衍生出了多个新物种。在N. nigra类群中，四倍体的N. nigra奥地利亚种（N. nigra ssp. austriaca）与三倍体的N. nigra原亚种（ssp. nigra）在核基因及质体位点上均存在一定分化。由N. nigra原亚种（ssp. nigra）的未减数卵细胞与手掌参（Gymnadenia conopsea）的单倍体雄配子融合，可产生Gymnigritella runei。在N. widderi类群中，N. archiducis-joannis与N. widderi在分子标记中难以明确区分；五倍体的N. buschmanniae则由N. widderi的未减数卵细胞与二倍体黑兰属植物的单倍体雄配子融合演化而来。在N. miniata类群中，N. stiriaca与N. miniata在核基因位点上存在一定分化，但其余N. miniata的分化类群均未达到物种级支持标准。多倍体黑兰属物种通过体细胞突变积累遗传多样性，在分布广泛的N. nigra奥地利亚种（N. nigra ssp. austriaca）与N. miniata中，该遗传多样性与地理分布显著相关。尽管部分多倍体类群可能为近期起源，但所有多倍体均携带了当前二倍体黑兰属植物中已不再存在的遗传标记。基于质体标记数据，黑兰属（Nigritella）与手参属（Gymnadenia）或可构成单系姊妹属。