Phylogeny, Systematics and Evolution of Cactaceae, Subfamilies Opuntioideae and Cactoideae

小行星9527884 仙人掌科，仙人掌科，包括大约1500种在北美和南美（与一个引进西非），并包括形态多样的生活形式，从柱状，树状桶到乙烯和附生。在适应干旱和沙漠条件下，这些“茎肉质植物”可能平行地聚集在类似的营养形状和形式上，这使得旨在区分家族内谱系的进化分析变得困难和混乱。为了获得分类学和系统发育分析的可靠和独立的比较数据，爱荷华州州立大学的罗伯特·华莱士博士正在研究来自仙人掌亚科和仙人掌亚科两大亚科的仙人掌样本中叶绿体和细胞核基因的DNA变异。 正在从几个基因中收集DNA核苷酸序列，并将这些序列进行比对，以比较和评估物种之间的突变差异。然后基于这些突变差异的测量构建系统发育树。以植物谱系（或分类单元谱系）作为属和种之间谱系关系的指南，人们可以研究整个美洲沙漠栖息地的适应性辐射模式，以及伴随或使进化成为不同地区和栖息地的形态变化。系统发育分析也将提供一个更稳定的分类仙人掌，并指导选择的关键字符的物种鉴定的目的。

9527884 Wallace The cactus family, Cactaceae, comprises some 1500 species in North and South America (with one introduction to West Africa) and includes morphologically diverse life forms ranging from columnar, tree-like to barrel to viny and epiphytic. In adapting to dry and often desert conditions, these "stem succulents" have likely in parallel converged on similar vegetative shapes and forms, which renders evolutionary analysis designed to distinguish the lineages within the family difficult and confusing. In order to obtain robust and independent comparative data for taxonomic and phylogenetic analyses, Dr. Robert Wallace of Iowa State University is studying DNA variation in genes of the chloroplast and nucleus, from samples of cacti from the two large subfamilies Opuntioideae and Cactoideae. DNA nucleotide sequences are being gathered from several genes, and these will be aligned for comparison and assessed for mutational differences between species. Phylogenetic trees are then constructed based upon these measures of mutation difference. With the phylogenies (or taxon genealogies) as guide to lineage relationships among genera and species, one can study the pattern of adaptive radiation into desert habitats throughout the Americas, and the morphological changes that accompany or enable evolution into various regions and habitats. The phylogenetic analysis also will inform a more stable classification of cacti, and direct the choice of key characters for purposes of species identification.