[Taxacom] Molecular evidence (in 2017) supports my 2014 theory about rafting killifish

Kenneth Kinman kinman at hotmail.com
Mon Dec 21 14:40:21 CST 2020

Hi All,
      Rivulidae (a.k.a. Cynolebiini) are New World killifish once thought to have arisen in the Cretaceous before South America fully separated from Africa.  However, molecular evidence in 2017 indicates they arose in the Eocene.   They say: "Our estimates indicate that divergence between the clades comprising New World and Old World aplocheiloids occurred during the Eocene, about 50 Mya, much more recent than the Gondwanan fragmentation scenario assumed in previous studies. This estimation is nearly synchronous to estimated splits involving other South American and African vertebrate clades, which have been explained by transoceanic dispersal through an ancient Atlantic island chain during the Palaeogene."
      This makes me quite happy since I brought up this possibility back in 2014, in a post here on Taxacom entitled: transoceanic "rafting" fish (great candidate).
      The early branching genus Kryptolebias just happens to be a great candidate for a fish that could disperse on a raft of vegetation from Africa to South America:   (1) It's not only very tolerant of salt water, but also and more importantly (2) it can survive out of water for weeks at a time (66 days in one case).  (3) And guess where Kryptolebias marmoratus spends much of its time while out of the water----in logs and cavities of trees (which would be the main structural components of a large transoceanic raft).
         Those are the three things I thought of offhand which pointed to possible trans-Atlantic dispersal.  But then I began wondering about yet another strange thing about Kryptolebias fish.  They often exhibit various types of hermaphroditism, and even its most extreme form (self-fertilization, which is apparently absent in vertebrates except for Kryptolebias).  So just a few of these fish (or even a single individual) could have established a population on another continent.   The molecular evidence in 2017 supports my theory.    https://www.sciencedirect.com/science/article/abs/pii/S1055790317300386?casa_token=ONKSbcnOLNEAAAAA:roWXxXgD1F0NqnWh9fozphZ4BbyAngOtCQwxXkyr552h7rNz1M366R2yniah-HK5hDFbRaaV



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