Analyzes on adaptive radiation of semi-desert Asteraceae.

通过两次野外考察，我们收集了澳大利亚菊科和Gnaphalieae科的种群样本550个，并对它们的生境条件进行了调查。测定了菊科9属100种200个居群的染色体数目。在Brachyscome和Calotis属中发现了常见的倍体异常。干旱地区的种类经常表现出一年生习性，果实结构复杂，如翅膀、膨大的海绵状突起和作为种子有效传播的丝质长毛，这些与染色体数较低有关。测定了Gnaphalieae科23属50种的染色体数目。虽然澳大利亚以外的Gnaphalieae的染色体碱基数在x=7上是恒定的，但在Podolepes （n=12-3）、Pogonolepis （n=6-4）、Rhodanthe （n=11-5）和Tricanthodium （n=4-3）中发现了变异的非倍体序列。为了阐明物种间的亲缘关系以及在染色体数目、习性和形态特征等方面的进化趋势，我们比较了不同物种间叶绿体RFLP模式和mat K基因核苷酸序列，构建了短掌藓的分子系统发育树。这两棵树是一致的，支持这一属的单系。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规律，将菖蒲分为4个簇。从n=9开始的异倍体减少，习性从多年生到一年生的变化，以及果实形态从简单到复杂的变化，在几个世系中平行地得到了这些特征，这些特征被认为是适应干旱或季节性干旱条件的。

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.