(n) Species Croup of8 2
82
16 2
4 1
41
8 1
4 1
4 3
4
81
81
16 4
4
4(?)
4
2
2Acipenser(n) Species Croup of
Acipenser
8 2
82
16 2
41
4 1
81
4 1
4 3
4
81
8 1
1 6 4
4
4 (?)
4
2
2Figure6. The twoparsimonytrees based on partial sequences(270bp)of the cytochromebgeneregions from 11 species ofAcipenser
(representatives of all groups of species in Table 5),Huso dauricus, Pseudoscaphirhynchus kaufmanni, Scaphirhynchus albus,andPolyo-
don spathula. As in the previous analyses, Amia calva andPolypterus senegaluswere used as outgroups. The ploidy of fishes and the group
number for speciesAcipenserare given to lhe right of species names. The tree statistics is shown in Table 6.
sister-group to A.mikadoi,whereasA.ruthenusis
basaltoall these species. Except for the freshwater
A.ruthenusallother species of theclade are typ-
ically anadromous sturgeons. The difference in the
cytochromebgene sequences between A.mikadoi
andA. mediotrissupports the previous assump-
tion based onDNAploidythatA. mikadoiisasep-
arate species in spite ofthe fact that itismorpholog-
ically indistinguishable fromA. mediostris(Bir-
stein et al. 1993, Birstein 1994b).Unexpectedly, the
ancestral form of this group seems toberelatedto
A.ruthenus
The sccond group is also unexpected. Itconsists
oftwoclades.Thefirst clade includestheEuropean
A.nudiventrisgrouped with theeastern American
A.oxyrinchus(andHusodauricus,see discussion
above). Their sister-group consists ofthe European
A. gueldenstaedtii,SiberianA.baerii,and an east-
ern American species A. brevostrumThese rela-
tionships suggest that: (1) theAtlantic group of spe-
ciesis related to the Ponto-CaspianA.nudiventris;
(2)aPonto-Caspian European A.gueldenstaedtiiis
closely related toaPonto-Caspian Siberian A.bae-
rii; (3) both Ponto-CaspianA.gueldenstaedtiiand
A.baeriiare related totheeasternNorth American