Speciation and taxonomy of the endemic family Aucubaceae in Sino-Japanese floristic region

桃科唯一的桃属，是中日植物区系的特有种，在中国西南地区分布广泛。在该属中发现了10 ~ 20种雌雄异株的常绿灌木或乔木，但由于其性状变化较大，在分类上存在混淆。在染色体数目方面，认为粳稻是该属中唯一的多倍体复合体。我们先前基于叶绿体系统发育的研究表明，四倍体化在粳稻中至少独立发生了三次。中国的其他物种可能包括多倍体。本研究(1)为了评价粳稻的染色体进化，(2)为了了解粳稻的物种形成过程，(3)为了修正粳稻属的分类，我们对来自中国及邻近地区的几种粳稻进行了基于叶绿体DNA非编码区和核DNA （ITS区和GapC基因外显子）附加序列的系统发育分析和流式细胞术分析。结果表明：(1)该属被划分为花深紫色的灌木和花淡黄色的高大种两个谱系；(2)传统的认识被误解了；(3)一些种是多倍体，其中大部分是异源多倍体，包括粳稻

Aucuba, the only genus in the family Aucubaceae, is endemic to the Sino-Japanese floristic region, and is diversified around southwestern China. In the genus 10 to 20 dioecious evergreen shrub or tree species were recognized, but there are taxonomic confusions because of quite variable characters. For the chromosome numbers, it is thought that A. japonica was the only polyploid complex in the genus. Our previous study based on chloroplast phylogeny indicated that tetraploidization occurred independently at least three times within A. japonica. It is possible that other species in China might include polyploids. In the present study, (1) to evaluate the chromosomal evolution, (2) to understand the speciation process of A. japonica, (3) to revise the classification of the genus , we conducted the phylogenetic analysis based on additional sequences of chloroplast DNA noncoding regions and nuclear DNA (ITS region and exon of GapC gene) and the flow cytometric analysis for several species obtained from China and its neighboring regions. Our results indicate that 1) the genus is divided into two lineages of shrub having dark purple flowers and tall-species having pale yellow flowers, 2) the traditional recognition of A. chinensis has been misinterpreted, and 3) several species were polyploids and most of them, including A. japonica, were originated by allopolyploidizatios