Finnerty and Block: Evolution of cytochrome b in the Scombroidei 



83 



hliophorus platyplerus 

 Makaira nigricans 

 Tetrapturus albidus 

 Tetrapturus audax 

 Tetrapturus angustirosrns 

 Tetrapturus pfluegeri 

 Tetrapturus belone 

 Makaira indica 



Xiphias gladius 



Thunnus alalunga 

 Thunnus albacares 

 Thunnus maccoyii 

 Thunnus thynnus 

 Thunnus obesus 

 Katsuwonus pelamis 

 Euthynnus affinis 

 Euthynnus alletleratus 

 Auxis thazard 

 Sarda chiliensis 

 Sarda sarda 

 Scomberomorus cavalla 

 Scomberomorus maculata 

 Acanthocybium solandri 

 Scomber japon icus 



Scomber scombrus 

 Gasterochisma melampus 



Gempylus serpens 

 Ruvettus pretiosus 



Lci'idticxhmm flavohrunneum 



Trichiurus lepturus 



Istiophoridae 



Xiphiidae 



Scombridae 



Gempylidae 

 Tnchiuridae 



Cor\phaena equiselis 

 Mycteroperca interstitialis 

 Morone saxatilis 

 Sphyraena sphyraena 

 Crossostoma lacustre 

 Cyprinus carpio 



Figure 2 



Phytogeny of the Scombroidei based on an unweighted analysis of 248 phylogenetically informa- 

 tive nucleotide sites. The cladogram depicted is a strict consensus of four equally parsimonious 

 trees identified by using a heuristic search procedure on the program PAUP 3.1. (Swofford, 1991): 

 TBR (tree bissection and reconnection) branch swapping was performed on 10 starting trees 

 generated through random stepwise addition of taxa. Crossostoma and Carpio were specified as 

 the outgroup. Length, consistency index, and retention index are the following: L=1595, CI=0.317, 

 RI=0.539. Circled numbers at nodes indicated the percentage of trials in which a given partition 

 between taxa is supported in 1,000 replications of the bootstrap analysis (Felsenstein, 1985). 

 Only nodes supported in >50% of bootstrap replications are indicated. 



sister species. The expected number of each of the six 

 substitution types (S^ -|)was then derived as follows: 



i E[i^j 



-Ifi 



fj)( S 0[total])/3- 



We divide by three because three types of base sub- 

 stitutions are possible for each base, and we are in- 

 terested in obtaining an expectation for one of them. 

 For example, the expected number of A<=>T substitu- 

 tions equals the average frequency of A's (0.23) plus 



