Chromosomal and molecular evolution in the genus Brachyscome (Asteraceae)

对29个种或种复合体的145个居群的S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。剩余的计数支持先前报道的测定，并增加了对染色体数量分布的了解。核型分析。Sade在30个亚种上，在亚硝化中期，25个紫杉在中生期。根据单倍体染色体组的总大小来区分两组。在Aboye两组杂交组合的三个杂交组合中，来自两个亲本来源的染色体的凝集方式存在显着差异或不同步。然而，无论它们是不是单系的，都是仍然存在的。上述两组单倍体染色体的总大小与染色体数无关，在n=9~2之间基本不变。短体类在进化过程中没有出现核型不对称的总体趋势。总DNA提取…从19个分类群中分离出12个内切酶。DNA片段在1.0%琼脂糖凝胶上分离，变性后转移到尼龙膜上。在杂交中，我使用了烟草中的cpDNA。突变被用一套密切相关的外群--紫荆属--极化。共检测到17个突触位点突变。19个分类群的系统发育重建使用Wagner persis和计算机程序PAUP程序包来寻找最短的系统发育树。系统发育树表明，该属的染色体数目从n=4增加到5、6和9，而不是减少，只有从n=4增加到3。这些数据表明：1)染色体数目从n=9急剧减少到4，染色体数目居中的物种灭绝。2)在n=4水平上发生了爆炸性的次生物种形成。3)现存的n=5、6、7、8和9种(部分)是染色体数目从n=4增加的衍生种。较少

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