102 C. J. HUMPHRIES 



distribution of the ancestor of the present Anacyclus species? By way of an answer it is likely that 

 it was a widespread species, perhaps not so widespread as to encompass the present distribution 

 of Anacyclus owing to the very weedy nature of A. radiatus subsp. radiatus, A. x valentinus and 

 A. clavatus, but certainly occurring in the southern Mediterranean region from southern Turkey 

 to the Atlantic coast of Morocco. 



Phylogeny 



As Bremer (1976) and Bremer & Wanntorp (1978, and in press) point out, the theory of phylo- 

 genetic systematics, as described by Hennig (1965, 1966), has had virtually no effect upon the 

 classification of plants. In fact, most publications in botany do not use any cladistics for classifica- 

 tion (Humphries, in press, b) although in my opinion there is a considerable need for them rather 

 than for the methods of the strictly phenetic and the eclectic or evolutionary biology schools. 



Fig. 7 The concept of phylogenetic relationship. Species B and C share a more-recent common 

 ancestor (species X) which is not shared by species A (redrawn from Hennig, 1965). 



Consequently, the construction of 'phylogenetic trees' based on ill-defined principles and the 

 elaboration of nominalistic methods has created considerable disillusionment and disregard of 

 sound phylogenetic discussion. This phenomenon is curious, since a glance at recent volumes of 

 zoological, particularly entomological, literature will reveal that the principles of phylogenetic 

 systematics are considered to be amongst the most erudite of those which advance the under- 

 standing of evolutionary relationships. I think it is necessary to re-emphasize that in the 120 years 

 since the publication of Darwin's Origin of Species (1859) there has never been a serious refutation 

 of the theory of evolution. Thus, since the advent of this theory, one of the tasks of biology has 

 been to investigate the phylogenetic relationships between species (Hennig, 1965). 



The definition of the concept 'phylogenetic relationship' is based on the fact that reproduction 

 is sexual in most organisms, and that it usually takes place within the framework of confined 

 reproductive communities which are isolated from one another. Speciation occurs because parts of 

 existing reproductive communities become externally, or genetically, isolated from one another 

 for extended periods of time. Thus, in divergent evolution, all species which exist at a given time, 

 e.g. the present, have originated by the splitting of older reproductive communities. Thus, the 

 concept of phylogenetic relationship can be demonstrated in a diagram, a cladogram (Fig. 7). 

 Species B is considered to be more closely related to species C than to another species A when B has 

 at least one ancestral species (X) in common with species C which is not ancestral to species A 

 (see Hennig, 1965) (Fig. 7). It becomes the task of systematics, then, to determine monophyletic 

 groups with shared common ancestry. 



It is widely believed in angiosperm systematics that, since so few fossil remains are available, 

 phylogenetic reconstruction of monophyletic groups is not reliable and possesses no method of 

 its own. From this it follows that we can interpret the results of morphological systematics only 



