39 



OVERALL PARSIMONY ANALYSIS 



The main goal of this section is to present, and preliminarily discuss the robustness of, 

 the solution to an overall parsimony analysis of the data matrix found in Appendix C. The 

 following two sections will then build on this theme by using a number of techniques to 

 more fully examine the support for this cladistic hypothesis. The morphological description 

 of each character is deferred until the Character Analysis section, where it can be 

 combined with a description of their evolutionary pathway (i.e., character reconstruction) 

 as inferred from the phylogeny presented and subsequently analyzed in this and the 

 following two sections. 



Incidence of polymorphism (Appendix C) 



The characters examined in this study, which are primarily osteological and largely relating 

 to the head skeleton, are characterized by a high degree of intraspecific polymorphism, 

 especially among the phocids. Fully 150 of the 196 characters (76.5%) reveal at least one 

 polymorphic taxon. Of these characters, the vast majority demonstrate taxa that maximally 

 possess a two-state polymorphism (124 or 63.6% of all characters), but three- (24 or 

 12.2%) and four-state (2 or 1.0%) polymorphisms are also present. These ratios are 

 virtually identical in the 168 characters that were retained for analysis - altogether, 129 

 displayed polymorphic taxa (76.8%), with the taxa in 106 being maximally two-state 

 polymorphic (63.1%), three-state in 21 (12.5%), and four-state in two (1.2%) - indicating 

 that polymorphic characters do not appear to be inferior to monomorphic ones, and that 

 polymorphism appears to be intrinsic to the morphology of these taxa [as intimated for 

 the pinnipeds at least by Mivart (1885), Doutt (1942), Davies (1958b), and Ray (1976b)]. 

 The average number of polymorphic characters for the 27 taxa examined here was 20.8, 

 or roughly 12.4% of the 168 included characters. The range extended from a low of four 

 characters (=2.4%) for Cards, to a high of 32 (=19.0%) for both Leptonychotes and 

 Ommatophoca. 



Overall solution (Fig.5) 



A parsimony analysis of the 19 extant phocid species (including Monachus tropicalis), 

 with eight outgroup taxa, and employing inverse character weighting yielded two equally 

 most parsimonious solutions, each of 69,834 steps (Fig.5A). The differences between these 

 solutions are limited to a subset of the phocines, and arise from the variable placement 

 of Phoca vitulina relative to Erignathus, Histriophoca, Pagophilus (which consistently 

 form a monophyletic clade), and Pusa spp. One solution holds for Phoca vitulina being 

 the sister group of all these taxa (with Pusa being monophyletic), while the other has 

 Phoca vitulina disrupting Pusa, rendering it paraphyletic. However, Pusa hispida and Pusa 

 sibirica remain as sister taxa in both solutions. 



Both the strict and majority rule consensus trees for these equally most parsimonious 

 solutions converge on the same cladogram (Fig.5B) with the conflict between the above 

 taxa being visualized as a polytomy within the phocines. The slightly higher length (70,084 

 steps) of the consensus tree reflects PAUP's use of hard polytomies (which must satisfy 



