Analyzes on adaptive radiation of semi-desert Asteraceae.

通过两次野外调查，收集了550个居群的紫菀属和鼠曲草族植物，对紫菀属9属100种200个居群的染色体数目进行了测定。异倍体现象在短序菊属和海芋属中较为常见。干旱地区的植物多为一年生植物，具有果实的复杂结构，如翅、膨大的海绵状突起和丝状长毛等，是种子传播的有效媒介，这些都与染色体数目较低有关。对鼠曲草族23属50种植物的染色体数目进行了测定。虽然澳大利亚以外鼠曲草族的染色体基数在x=7时是恒定的，但在Podolepes（n=12-3），Pogonolepis（n=6-4），Rhodanthes（n=11-5）和Tricanthropium（n=4-3）中发现了可变的异倍体系列。比较了不同种间叶绿体matK基因的RFLP图谱和核苷酸序列，构建了短孢囊菌的分子系统发育树。这两个树是一致的，并支持该属的单系。根据花药附属物和花柱的形态、地理分布和染色体数目的变异模式，将Brahcyscome分为4个类群。异倍体从n=9的减少，从多年生到一年生的习性变化和果实形态从简单到复杂的变化已经平行的几个谱系，这些衍生的字符被认为是适应干旱或季节性干旱条件下。

We have collected 550 population samples of Australian Astereae and Gnaphalieae and investigated their habitat conditions by two field expeditions.Chromosome numbers from 200 populations attributed 100 species of nine genera of Astereae were determined. The frequent dysploidy has been found in the genera of Brachyscome and Calotis. Species of arid regions frequenthy display an annual habit and have the complex structures of fruit, such as wings, inflated spongy projections and silky long hairs served as the effective seed dispersal, and these are correlated with lower chromosome numbers. Chromosome numbers from 50 species of 23 genera of Gnaphalieae were determined. Although the chromosome base number of Gnaphalieae outside of Australia is constant on x=7, the variable dysploidy series in Podolepes (n=12-3), Pogonolepis (n=6-4), Rhodanthe (n=11-5) and Tricanthodium (n=4-3) were found. To clarify the species relationship and the evlolutionary trends in chromosome number, habit and morphological characters, we have compared the pattern of RFLP and the nucleotide sequence of mat K gene of chlorplast between species and constructed the molecular phylogenetic trees of Brachyscome. Both trees are consistent and support the monophyly of this genus. They also inditate that Brahcyscome is divided into 4 clusters corresponding to the morphology of anther appendage and style, geographical distribution and the variation pattern of chromosome number. The dysploid reductions from n=9, the change of habit from perennial to annual and the change of fruit morphology from simple to complex have been derived in parallel of several lineages and these derived characters are regarded to be adaptive under the arid or seasonally dry conditions.