Nistelberger H, Gibson N, Macdonald B, Tapper S-L, Byrne M
Science and Conservation Division, Department of Parks and Wildlife, Bentley , Western Australia, Australia.
Heredity (Edinb). 2014 Nov;113(5):454-63. doi: 10.1038/hdy.2014.46. Epub 2014 Jul 2.
Phylogeographic studies of flora in species-rich south-western Australia point to complex evolutionary histories, reflecting patterns of persistence and resilience to climatic changes during the Pleistocene. We asked whether coastal areas of the mid-west and south, as well as granite outcrops and inland ranges, have acted as major refugia within this region during Pleistocene climatic fluctuations by analysing phylogeographic patterns in the shrub Calothamnus quadrifidus R.Br. (Myrtaceae). We determined variation in chloroplast DNA data for 41 populations across the geographic range. Relationships and major clades were resolved using parsimony and Bayesian analyses. We tested for demographic and spatial expansion of the major clades and estimated clade divergence dates using an uncorrelated, lognormal relaxed clock based on two conservative chloroplast mutation rates. Two distinct phylogeographic clades were identified showing divergence during the Pleistocene, consistent with other phylogeographic studies of south-west Australian flora, emphasising the impact of climatic oscillations in driving divergence in this landscape. The southern clade was more diverse, having higher haplotype diversity and greater genetic structure, while the northern clade showed evidence of fluctuation in population size. Regions of high haplotype diversity with adjacent areas of low diversity observed in each clade indicated the locations of two coastal refugia: one on the south coast and another along the mid-west coast. This is the first evidence for major Pleistocene refugia using chloroplast genetic data in a common, widespread species from this region.
对物种丰富的澳大利亚西南部植物群的系统地理学研究表明，其进化历史复杂，反映了更新世期间对气候变化的持续存在和恢复模式。我们通过分析灌木四裂串钱柳（Calothamnus quadrifidus R.Br.，桃金娘科）的系统地理模式，来探究中西部和南部的沿海地区以及花岗岩露头和内陆山脉在更新世气候波动期间是否曾作为该地区的主要避难所。我们确定了该物种地理分布范围内41个种群的叶绿体DNA数据变异情况。使用简约法和贝叶斯分析法解析了各关系和主要分支。我们对主要分支进行了种群统计学和空间扩张测试，并基于两个保守的叶绿体突变率，使用不相关的对数正态松弛时钟估计了分支分化日期。识别出两个不同的系统地理分支，显示出在更新世期间的分化，这与澳大利亚西南部植物群的其他系统地理学研究一致，强调了气候振荡对该地区分化的推动作用。南部分支更为多样，单倍型多样性更高，遗传结构更复杂，而北部分支则显示出种群大小波动的证据。在每个分支中观察到的高单倍型多样性区域与相邻的低多样性区域，表明了两个沿海避难所的位置：一个在南海岸，另一个在中西部海岸。这是利用叶绿体遗传数据，在该地区一种常见且分布广泛的物种中首次证明存在主要的更新世避难所。
