文獻來源: Inoue, J. G., Kumazawa, Y., Miya, M., Nishida, M. 2009. The historical biogeography of the freshwater knifefishes using mitogenomic approaches: A Mesozoic origin of the Asian notopterids (Actinopterygii: Osteoglossomorpha). Molecular Phylogenetics and Evolution, in press. [doi:10.1016/j.ympev.2009.01.020]這是由目前任職於倫敦大學學院楊子恆教授研究群的井上潤博士後研究員以及東京大學海洋科學研究所西田睦研究室所共同完成的研究. 俗稱飛刀的駝背魚科(Notopteridae)被認為是骨舌魚超目中較晚近分化出來的類群. 對於牠們在東南亞, 印度次大陸以及非洲大陸的分布格局, 長期以來至少有兩個互斥的假說嘗試解釋這種格局的演化起源. 這篇文章使用了mtDNA genome的分析證實了亞洲的駝背魚(皇冠飛刀, 七星飛刀等)起源自非洲大陸, 而牠們與產於非洲的類群, 如鑽石飛刀, 的分化年代則可能在白堊紀的早期. 而那個年代則是馬達加斯加+印度次大陸與非洲分離, 印度次大陸漸漸漂向歐亞大陸的時刻. 然而由於馬達加斯加缺乏駝背魚科的化石記錄, 以及各種分子定年模式所獲結果的差異, 非洲與亞洲馱背魚科生物皆起源於盤古大陸, 而在勞拉西亞大陸與岡瓦納大陸分離後才分道揚鑣的可能性亦不能排除.
Abstract. The continental distributions of freshwater fishes in the family Notopteridae (Osteoglossomorpha) across Africa, India, and Southeast Asia constitute a long standing and enigmatic problem of freshwater biogeography. The migrational pathway of the Asian notopterids has been discussed in light of two competing schemes: the first posits recent transcontinental dispersal while the second relies on distributions being shaped by ancient vicariance associated with plate-tectonic events. In this study, we determined complete mitochondrial DNA sequences from 10 osteoglossomorph fishes to estimate phylogenetic relationships using partitioned Bayesian and maximum likelihood methods and divergence dates of the family Notopteridae with a partitioned Bayesian approach. We used six species representing the major lineages of the Notopteridae and seven species from the remaining osteoglossomorph families. Fourteen morederived teleosts, nine basal actinopterygians, two coelacanths, and one shark were used as outgroups.
Phylogenetic analyses indicated that the African and Asian notopterids formed a sister group to each other and that these notopterids were a sister to a clade comprising two African families (Mormyridae and Gymnarchidae). Estimated divergence time between the African and Asian notopterids dated back to the early Cretaceous when India–Madagascar separated from the African part of Gondwanaland. Thus, stimated time of divergence based on the molecular evidence is at odds with the recent dispersal model. It can be reconciled with the geological and paleontological evidence to support the vicariance model in which the Asian notopterids diverged from the African notopterids in Gondwanaland and migrated into Eurasia on the Indian subcontinent from the Cretaceous to the Tertiary. However, we could not exclude an alternative explanation that the African and Asian notopterids diverged in Pangea before its complete separation into Laurasia and Gondwanaland, to which these two lineages were later confined, respectively.
