PHYLOGENETIC ANALYSIS OF THE SUBCLASS PTERIOMORPHIA (BIVAVIA) BASED ON PARTIAL 28S rRNA SEQUENCE
基于28S rRNA基因片段的翼形亚纲(Bivalvia:Pteriomorphia)系统发育的初步研究

The phylogenetic relationships among 11 superfamilies of the subclass Pteriomorphia(Bivavia) were reconstructed based on partial sequences of the nuclear 28S ribosomal DNA retrieved from GenBank.Unambiguously aligned sequences(1252bp) of 80 species were subjected to partitioned maximum likelihood and Bayesian analyses.Sequence analysis showed that there were 359 variable sites,occupying 28.67% of all sites,and 300 parsimony informative sites,occupying 23.96% of all sites.The average content of A+T was 41.6%,obviously lower than G+C,showing that the base compositions were biased in favor of G+C.The genetic distances among species within superfamilies ranged from 0.01 to 0.14,which were obviously smaller than those among superfamilies.The resultant molecular phylogeny was compared with previously published phylogenetic hypotheses inferred from morphological characteristics and other molecular analyses.The molecular phylogenetic analyses strongly supported the monophyly of Pteriomorphia,which were congruent with previous results of based on morphological characters.The resulting trees clearly indicated that the 11 superfamilies were divided into three clades:cladeⅠincluded Pterioidea,Ostreoidea,and Pinnoidea;cladeⅡincluded Arcoidea,Limopsoidea,and Mytiloidea;and cladeⅢincluded Pectinoidea,Anomioidea,Dimyoidea,Plicatuloidea,and Limoidea.Based on the results of the present study and information compiled from other’s classification system,a revised classification of the extant superfamilies of Pteriomorphia is presented.