Scoles et al.: Globa! phylogeography of Scomber 
835 
S. australasicus (11,12) 
"Ubiquitous Lineage" 
S. australasicus (10) 
"Unique Lineage" 
S. japonicus (7) 
California 
S. japonicus (6) 
California 
S. australasicus (8, 9) 
Red Sea 
S. japonicus (5) 
Italy 
S. scombrus (4) 
S. scombrus (3) 
R. kanagurta (2) 
R. kanagurta (1) 
Figure 5 
Majority rule consensus of two equally parsimonious trees drawn by using cytochrome b se- 
quences of selected individuals of the major lineages chosen on the basis of results of parsi- 
mony and cluster analyses of restriction site data. The sequence numbers in parentheses 
correspond to the numbered sequences in Table 5. The tree is rooted to Rastrelliger kanagurta 
(sequence no. 2). Numbers at nodes indicate the percentage of times the node was supported 
in 1000 bootstrap replications with a heuristic search. There were 86 informative characters 
used to draw the tree which is 113 steps in length. The consistency index is 0.89. 
australasicus. Parsimony analysis of cytochrome b 
sequences also revealed paraphyly in both S. japon- 
icus and S. australasicus. 
Discussion 
Relationships at the generic level 
Early studies of Scomber demonstrated considerable 
morphological divergence between species. Charac- 
terized by the presence of a swimbladder, S. japonicus 
and S. australasicus were once placed in the genus 
Pneumatophorus, leaving only S. scombrus in the 
genus Scomber (Starks, 1921). The two genera were 
subsequently united because many other morphologi- 
cal characters were shared among the three species 
(Fraser-Brunner, 1950; Matsui, 1967) and because the 
presence of a swimbladder can vary intraspeeifically 
in the Scombridae (Collette and Gibbs, 1963). 
Concordant with morphological dissimilarities be- 
tween these two groups, the level of genetic diver- 
gence between S. scombrus and the S. australasicus- 
S. japonicus group estimated from mtDNA restric- 
tion fragment data was high (5=11.2%). The diver- 
gence of these groups estimated from direct sequence 
analysis of the cytochrome b gene was also high 
(5=16.7%). For comparison, we calculated divergences 
among 29 scombroid species and drew a phenetic tree 
(UPGMA), using the 600-bp cytochrome b sequences 
reported by Block et al. (1993). 2 The lowest interge- 
neric divergence in the tree was 5=3.0% between 
Makaira and Istiophorus, whereas the greatest was 
5=31% between Trichiurus and Gempylus. The great- 
est divergence between species within a single ge- 
nus was 5=14.6% between Scomber japonicus and S. 
scombrus, slightly lower than our estimate. Other 
interspecific divergences were 5=13.5% between 
Scomberomorus cavalla and Scomberomorus macu- 
latus, 3.9% between Sarda chiliensis and Sarda 
sarda, 1.2-5% among five species of Thunnus, and 
0.3-5. 2% among five species of Tetrapturus. Although 
the clonal inheritance of mtDNA can result in high 
levels of divergence compared with estimates deter- 
mined from nuclear DNA markers, the high values 
seen in Scomber suggest that a re-evaluation of ge- 
neric taxonomy in Scomber may be in order. 
Relationships at the species level 
The current taxonomy of Scomber is based on mul- 
tiple morphological characters, including the num- 
ber of interneural bones under the first dorsal fin, 
length of the space between the dorsal fins in rela- 
2 GenBank accession nos. L11532-L11562. 
