Comparative phylogeography of Zacco platypus and Opsariichthys bidens (Teleostei, Cyprinidae) in China based on cytochrome b sequences

We compared the phylogenetic relationships and the population structure of the sympatric cyprinids Opsariichthys bidens and Zacco platypus across the Yangzte, Pearl and Hai He drainages in Mainland China. We used the mitochondrial cytochrome b gene to evaluate their phylogeographical structure and to discuss further systematic implications. We sequenced 71 new individuals of Z. platypus to add to a previous study and to construct a geographically comparable data set with O. bidens (Mol. Phylogenet. Evol. 31, 2004, 192; Mol. Phylogenet. Evol. 37, 2005, 920). Phylogeographic analysis of Z. platypus identified two additional mtDNA lineages (Zacco E and F) in addition to the previously recovered lineages (Zacco A–D). The geographical range of the Zacco A was extended across the Pearl drainage, broadening considerably the previous distribution that was circumscribed to the Yangtze drainage. Our results show high molecular divergence between all Zacco A–F mtDNA lineages (mean TrN + I + G distance 17.7%, range 4.4–30.8%), and the population analyses showed that most of the genetic variation was found among major river tributaries (90.2%). Values of θ_ST higher than 0.97 corroborated this interruption of gene flow between Zacco A–F mtDNA lineages. Nested clade analysis results were also concordant with the phylogenetic relationships recovered. We found similar phylogeographic patterns in Z. platypus and O. bidens: they exhibited two widespread and common lineages (Zacco A and Opsariichthys 1) ranging across the Yangtze and Pearl drainages, and both taxa had Northern lineages (Zacco F and Opsariichthys 5) clearly differentiated. Similar phylogeographic patterns suggest that common historical factors have shaped current Zacco and Opsariichthys diversity. High genetic distances and θ_ST values suggested that differentiation of Zacco A–F mtDNA lineages and Opsariichthys 1–5 was not recent and was probably favoured by old geological events. However, population parameters and low genetic differentiation inside Zacco A and Opsariichthys 1 suggest a recent gene flow across river drainages. Mitochondrial‐based phylogenies for the combined data sets of Zacco A–F and Opsariichthys 1–5 mtDNA lineages always recovered both taxa as paraphyletic, highlighting the notion that their current systematics need a revision.