FISHERY BULLETIN: VOL. 81, NO. 2 



U ciliatus 



U- collaterahs 



U. anonymous j 



U mycterobius 



U. reductus 



[1] [2] [2] [5] [2,4] [2.4] [2.3,4] 



FIGURE 23. — Occurrence of species of Unicolax on scombrids in the 

 tribes Scomberomorini, Sardini, and Thunnini. Copepods are rank- 

 ed from most plesiomorphic (top) to most apomorphic (bottom). 

 Scombrids are arranged to depict hypothesized phylogenetic re- 

 lationships. 



parasite by host tree whereas U. collateralis occupies 

 this position on the parasite phylogeny. This dis- 

 crepancy occurs because parasites U. anonymous, U. 

 collateralis, and U. mycterobius are all found on the 

 host Euthynnus (9), at node (2) on the parasite by 

 host tree (Fig. 25). Unicolax collateralis and U. myc- 

 terobius are then grouped because they co-occur on 

 host taxa 5 (Sarda) and 8 (Auxis) as well as nodes 



(16) and (18) of the host phylogeny (Fig. 21). Hypo- 

 thesized hosts, which are not shared (autapomorph- 

 ies), include Scomberomorus and host node (20) for 

 U. ciliatus, Katsuwonus and host node (12) for U. 

 reductus, and Orcynopsis, Cybiosarda, and host node 



(17) for U. collateralis. The parasite by host tree (Fig. 

 25) presents no homoplasy. 



If we make the assumption that the host and para- 

 site phylogenies, which are based on morphological 

 data, are both true, how do we explain the current dis- 

 tribution of parasites on hosts? This question is anal- 

 ogous to questions of biogeography. We know by 

 generating a host tree from parasitic phylogenetic in- 

 formation and by generating a parasite tree from host 

 phylogenetic information that the two data sets are 



s 



2 



CO 

 3 



co 



3 

 C 



c 



CO 



3 

 C 

 O 



3 

 W 



TO 



-5 



co 



CO 

 CO 



X 



3 



co 



3 

 C 

 C 



3 



UU 



 4 



*-o 



-6 



• 7 



4> 



FIGURE 24. — Host tree based on parasitic phylogenetic information. 

 Numbers in brackets at top of figure represent infestation by 1) 

 Unicolax ciliatus, 2) U. collateralis, 3) U. anonymous, 4) U. 

 mycterobius, and 5) U. reductus. Numbers crossing branches on tree 

 represent acquisitions of parasites or parasite ancestors, except for 

 number 2 leading to Katsuwonus which indicates a loss. 



CO 



3 



I 



1 19 



I A 1 



FIGURE 25. — Parasite tree of Unicolax species based on host 

 phylogenetic information. Numbers crossing branches on tree re- 

 present historic infestations of hosts or host ancestors by parasites 

 or parasite ancestors. 



258 



