Chromosomal and molecular evolution in the genus Brachyscome (Asteraceae)

本文对短尾藻属29个种或种复合体的145个居群进行了染色体数目测定。其中6种为首次报道，2种为新报道。剩余计数支持先前报告的测定，并增加了染色体数目分布的知识。核型分析。其中30个在硝酸盐中期，25个在分裂前中期。两个群体的区别是总大小的单倍体染色体组。在两个群体间三个杂交组合的杂种中，两个亲本来源的染色体的凝聚型有显著差异或相似。然而，它们是否是单系的问题仍然存在。在上述两个群体中，单倍体染色体组的总大小与染色体数目无关，在n=9 ~ 2范围内是恒定的。在短尾藻的进化过程中，染色体组型的不对称性并没有普遍的趋势。总DNA提取物 ...更多信息 用12种内切酶对19个分类群的艾德进行酶切。在1.0%琼脂糖凝胶上分离DNA片段，变性并转移到尼龙膜上。为了进行杂交，我使用了烟草中的cpDNA。突变极化使用一套密切相关的外群，属紫菀。共检测到17个突触位点突变。利用瓦格纳的系统发育分析法和计算机程序PAUP软件包对19个类群进行系统发育重建，得到最短的系统发育树。系统发育树表明，除n =4 ~ 3外，从n=4 ~ 5、6和9，染色体数目都在增加而不是减少。这些数据表明该属的染色体进化如下：1）染色体数目从n=9急剧减少到4，然后具有中间染色体数目的物种已经灭绝。2)次生物种形成在n=4水平上呈爆发性发生。3)现存的n=5、6、7、8和9（部分）的种是染色体数目从n=4开始增加的衍生物。少

Chromosome number determination s form 145 populations attributed to 29 species or species complexes of Brachyscome are made. First reports for 6 species and new reports for two species are presented. Remaining counts support previously reported determinations and add to knowledge of chromoso me number distribution. Karyotype analyses. are sade on 30 iaxa at Nitoticmetaphase and 25 taxs at mltotic prometaphase. Two groups are distinguished by the total size of haploid chromosome set. In the hybrids from three cross combinations between aboye two groups there are marked differences or asynchrony in the condensation patterns of the chromosomes from the two Parental sources. lt is, however, remained whether they are monophyletic or not, respectlyely. In above two groups the total size of haplold chromosome set are not correlated with chromosome number, rather constant from n=9 to 2. There is no general trend toward asymmetry of karyotype during evolution in Brachyscome. Total DNAs extract … More ed from 19 taxa were digeited with 12 endonucleases. DNA fragments were separated on 1.0% agarose gels, denatured and transferred to a nylon membrane. For hybridizations I used cpDNA from tobacco. Mutations were polarized using a suite of closely related outgroup, the genus Aster. Seventeen synapomorphic site mutations were detected. Phylogenetic reconstruction of 19 taxa used Wagner persisony and the computer Program PAUP package to find the shortest phylogenetic tree. This phylogenetic tree indicats the increase in chromosome number from n=4 to 5, 6 and 9 rather than the decrease, except from n=4 to 3. These data suggest the following chromosomal evolution in this genus ; 1)the reduction in chromosome number from n=9 to 4 has occurred drastically and then the species with the intermediate chromosome numbers have been extinct. 2)the secondary speciation has been occurred explosively at the n=4 level. 3)the extant species with n=5, 6, 7, 8 and 9(in part)are the derivatives with the increase in chromosome number from n=4. Less