Institute of Botany, Academy of Sciences of the Czech Republic, CZ-252 43 Průhonice, Czech Republic.
Ann Bot. 2011 Jan;107(1):77-87. doi: 10.1093/aob/mcq217. Epub 2010 Nov 7.
One of the prerequisites for polyploid research in natural systems is knowledge of the geographical distribution of cytotypes. Here inter- and intrapopulational ploidy diversity was examined in the Gymnadenia conopsea aggregate in central Europe and potential explanations and evolutionary consequences of the observed spatial patterns investigated.
DAPI flow cytometry supplemented by confirmatory chromosome counts was used to determine ploidy in 3581 samples of the G. conopsea aggregate from 43 populations. The fine-scale spatial pattern of cytotype distribution (intra- and interploidy associations) was analysed with univariate and bivariate K-functions.
Gymnadenia tissues undergo a progressively partial endoreplication, which accounts for about 60 % and 75 % of the total genome in G. conopsea and G. densiflora, respectively. Flow cytometric profiles are therefore species-specific and can be used as a marker for rapid and reliable species recognition. Two majority (4x, 8x) and three minority (6x, 10x, 12x) cytotypes were found, often in mixed-ploidy populations (harbouring up to all five different ploidy levels). The scarcity of the minority cytotypes (about 2·7 %) suggests the existence of strong pre- or postzygotic mating barriers. Spatial structure was observed in plots of populations with the highest cytotype variation, including clumping of individuals of the same ploidy and negative association between tetra- and octoploids.
The remarkable ploidy coexistence in the G. conopsea aggregate has reshaped our perception of intrapopulational ploidy diversity under natural conditions. This system offers unique opportunities for studying processes governing the formation and establishment of polyploids and assessing the evolutionary significance of the various pre- and postzygotic mating barriers that maintain this ploidy mixture.
自然系统中多倍体研究的前提之一是了解细胞型的地理分布。本研究调查了中欧地区 Gymnadenia conopsea 聚集体的种内和种间多倍体多样性，并探讨了观察到的空间模式的潜在解释和进化后果。
使用 DAPI 流式细胞术（辅以确认性染色体计数）来确定来自 43 个种群的 3581 个 Gymnadenia conopsea 聚集体样本的倍性。使用单变量和双变量 K 函数分析细胞型分布的细尺度空间模式（种内和种间多倍体关联）。
Gymnadenia 组织经历逐渐的部分内复制，分别占 Gymnadenia conopsea 和 Gymnadenia densiflora 总基因组的约 60%和 75%。因此，流式细胞术图谱是种特异性的，可以用作快速可靠的物种识别标记。发现了两种主要（4x、8x）和三种次要（6x、10x、12x）细胞型，通常存在于混合倍性种群中（拥有所有五种不同的倍性水平）。少数细胞型（约 2.7%）的稀缺性表明存在强烈的合子前或合子后交配障碍。在具有最高细胞型变异的种群的图中观察到空间结构，包括同种倍性个体的聚集和四倍体和八倍体之间的负关联。
在 Gymnadenia conopsea 聚集体中显著的倍性共存改变了我们对自然条件下种内倍性多样性的认识。该系统为研究控制多倍体形成和建立的过程以及评估维持这种倍性混合的各种合子前和合子后交配障碍的进化意义提供了独特的机会。
