van Welzen Peter C, Strijk Joeri S, van Konijnenburg-van Cittert Johanna H A, Nucete Monica, Merckx Vincent S F T
Naturalis Biodiversity Center, sector Herbarium, Leiden, The Netherlands ; Institute Biology Leiden, Leiden University, Leiden, The Netherlands.
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan Province, P.R. China.
PLoS One. 2014 Jan 17;9(1):e85713. doi: 10.1371/journal.pone.0085713. eCollection 2014.
Molecular phylogenies and estimates of divergence times within the sister genera Macaranga and Mallotus were estimated using Bayesian relaxed clock analyses of two generic data sets, one per genus. Both data sets were based on different molecular markers and largely different samples. Per genus three calibration points were utilised. The basal calibration point (crown node of all taxa used) was taken from literature and used for both taxa. The other three calibrations were based on fossils of which two were used per genus. We compared patterns of dispersal and diversification in Macaranga and Mallotus using ancestral area reconstruction in RASP (S-DIVA option) and contrasted our results with biogeographical and geological records to assess accuracy of inferred age estimates. A check of the fossil calibration point showed that the Japanese fossil, used for dating the divergence of Mallotus, probably had to be attached to a lower node, the stem node of all pioneer species, but even then the divergence time was still younger than the estimated age of the fossil. The African (only used in the Macaranga data set) and New Zealand fossils (used for both genera) seemed reliably placed. Our results are in line with existing geological data and the presence of stepping stones that provided dispersal pathways from Borneo to New Guinea-Australia, from Borneo to mainland Asia and additionally at least once to Africa and Madagascar via land and back to India via Indian Ocean island chains. The two genera show congruence in dispersal patterns, which corroborate divergence time estimates, although the overall mode and tempo of dispersal and diversification differ significantly as shown by distribution patterns of extant species.
利用两个属数据集（每个属一个）的贝叶斯松弛时钟分析，估计了姊妹属血桐属（Macaranga）和野桐属（Mallotus）内的分子系统发育和分歧时间估计值。两个数据集都基于不同的分子标记和大体不同的样本。每个属使用了三个校准点。基部校准点（所用所有分类群的冠节点）取自文献并用于两个分类群。其他三个校准基于化石，每个属使用其中两个化石。我们使用RASP中的祖先区域重建（S-DIVA选项）比较了血桐属和野桐属的扩散和多样化模式，并将我们的结果与生物地理和地质记录进行对比，以评估推断年龄估计的准确性。对化石校准点的检查表明，用于确定野桐属分歧时间的日本化石可能必须附着到一个较低的节点，即所有先锋物种的茎节点，但即便如此，分歧时间仍比化石的估计年龄年轻。非洲的化石（仅用于血桐属数据集）和新西兰的化石（用于两个属）似乎放置可靠。我们的结果与现有地质数据以及存在踏脚石的情况一致，这些踏脚石提供了从婆罗洲到新几内亚-澳大利亚、从婆罗洲到亚洲大陆的扩散途径，此外至少有一次通过陆地扩散到非洲和马达加斯加，并通过印度洋岛屿链回到印度。这两个属在扩散模式上表现出一致性，这证实了分歧时间估计，尽管现存物种的分布模式表明，扩散和多样化的总体模式和速度存在显著差异。
