5、1 Cladistics ⚫ 支序分类学的原理和基本方法
5、1 Cladistics ⚫ 支序分类学的原理和基本方法
1、Introduction to cladistic concepts ▪ Claclistics is a method of classification ▪ Cladistics can be used to organize any comparative data （e．g． linguistics） ▪ but its greatest application has been in the field of biological systematics
1、Introduction to cladistic concepts ▪ Claclistics is a method of classification ▪ Cladistics can be used to organize any comparative data （e．g． linguistics） ▪ but its greatest application has been in the field of biological systematics
▪ Cladistic methods were made explicit hy the German entomologist， Wilii Hennig （1950）， ▪ But became widely known to English speakers in 1965 and 1966 under the name "phylogenetic systematics
▪ Cladistic methods were made explicit hy the German entomologist， Wilii Hennig （1950）， ▪ But became widely known to English speakers in 1965 and 1966 under the name "phylogenetic systematics
2、Definition of relationship ▪ Hennig`s most important contributions were to offer a precise definition of biological relationship ▪ Formerly， the meaning of biological relationship was defined only vaguely． ▪ These definitions of relationship were absolute （X is related to y ） ▪ not shared with the shark or any other taxon．
2、Definition of relationship ▪ Hennig`s most important contributions were to offer a precise definition of biological relationship ▪ Formerly， the meaning of biological relationship was defined only vaguely． ▪ These definitions of relationship were absolute （X is related to y ） ▪ not shared with the shark or any other taxon．
▪ the lizard and the salmon are considered to be more closely related to each other than either is to the shark because they share a common ancestor， 'x' （which lived at time t2）， that is
▪ the lizard and the salmon are considered to be more closely related to each other than either is to the shark because they share a common ancestor， 'x' （which lived at time t2）， that is