Collevatti Rosane Garcia, Rabelo Suelen Gonçalves, Vieira Roberto F
Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, SGAN 916, Mod. B, 70790-160, Brasília, DF, Brasil.
Ann Bot. 2009 Sep;104(4):655-64. doi: 10.1093/aob/mcp157. Epub 2009 Aug 5.
Lychnophora ericoides (Asteraceae) presents disjunct geographical distribution in cerrado rupestre in the south-east and central Brazil. The phylogeography of the species was investigated to understand the origin of the disjunct geographical distribution.
Populations in the south and centre of Serra do Espinhaço, south-east Brazil and on ten other localities in Federal District and Goiás in central Brazil were sampled. Analyses were based on the polymorphisms at chloroplast (trnL intron and psbA-trnH intergenic spacer) and nuclear (ITS nrDNA) genomes. From 12 populations, 192 individuals were sequenced. Network analysis, AMOVA and the Mantel test were performed to understand the relationships among haplotypes and population genetic structure. To understand better the origin of disjunct distribution, demographic parameters and time to most recent common ancestor (T(MRCA)) were estimated using coalescent analyses.
A remarkable differentiation between populations from the south-east and central Brazil was found and no haplotype was shared between these two regions. No significant effect of isolation by distance was detected. Coalescent analyses showed that some populations are shrinking and others are expanding and that gene flow between populations from the south-east and central Brazil was probably negligible.
The results strongly support that the disjunct distribution of L. ericoides may represent a climatic relict and that long-distance gene flow is unlikely. With an estimated time to most recent common ancestor (T(MRCA)) dated from approx. 790,655 +/- 36,551 years bp (chloroplast) and approx. 623,555 +/- 55,769 years bp (ITS), it was hypothesized that the disjunct distribution may be a consequence of an expansion of the geographical distribution favoured by the drier and colder conditions that prevailed in much of Brazil during the Kansan glaciation, followed by the retraction of the distribution due to the extinction of populations in some areas as climate became warmer and moister.
刺苞菜（菊科）在巴西东南部和中部的塞拉多岩地呈现间断的地理分布。对该物种的系统地理学进行了研究，以了解这种间断地理分布的起源。
对巴西东南部埃斯皮尼亚苏山脉南部和中部以及巴西中部联邦区和戈亚斯州其他十个地点的种群进行了采样。分析基于叶绿体（trnL内含子和psbA-trnH基因间隔区）和核（ITS nrDNA）基因组的多态性。对12个种群的192个个体进行了测序。进行了网络分析、AMOVA和Mantel检验，以了解单倍型之间的关系和种群遗传结构。为了更好地理解间断分布的起源，使用溯祖分析估计了种群统计参数和最近共同祖先的时间（T(MRCA)）。
发现巴西东南部和中部的种群之间存在显著差异，这两个区域之间没有共享单倍型。未检测到距离隔离的显著影响。溯祖分析表明，一些种群在缩小，而另一些种群在扩大，并且巴西东南部和中部种群之间的基因流动可能可以忽略不计。
结果有力地支持了刺苞菜的间断分布可能代表一种气候遗迹，并且远距离基因流动不太可能。估计最近共同祖先时间（T(MRCA)）约为790,655 +/- 36,551年前（叶绿体）和约为约623,555 +/- 55,769年前（ITS），据此推测，间断分布可能是由于堪萨冰川期巴西大部分地区普遍存在的干燥和寒冷条件有利于地理分布的扩张，随后随着气候变暖变湿，一些地区的种群灭绝导致分布范围收缩的结果。
