More loach splitting on the way?

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Scientists have produced an evolutionary family tree for the Botia loach family which sheds new light on how the fishes are related.

The study of the Botiidae family shows that two species, Yashuhikotakia sidthimunki and Y. nigrolineata, form a monophyletic lineage with the Sinibotia genus, which suggests that the fishes may be moved into this genus at a later date if further analyses support the findings.

The work, which was undertaken by Jorg Freyhof of Leibniz Institute of Freshwater Ecology and Inland Fisheries and Vendula Slechtova, Petr Rab and Jorg Bohlen of the Institute of Animal Physiology and Genetics of the Academy of Sciences of the Czech Republic, has recently been published in the journal Molecular Phylogenetics and Evolution.

The scientists produced an evolutionary history for the Botiidae loaches by sequencing the mitochondrial cytochrome b and 12s ribosomal RNA genes and analysing the results with some sophisticted phylogenetics software.

The resulting phylogeny shows a major split in the Botiidae family, with the Leptobotiinae subfamily on one side and the Botiinae subfamily on the other. The Leptobotiinae includes Parabotia and Leptobotia, while the Botiinae includes the fish previously known as Botia, which following Kottelat's revision, consists of seven genera called Botia, Chromobotia, Syncrossus, Yasuhikotakia and Sinibotia.

Previous studies by Kottelat and Nalbant have both placed the Sinibotia genus along with Parabotia and Leptobotia, but the genetic evidence here suggests that the genus is actually more closely related to the botiine genera.

The Yasuhikotakia genus, which was erected by Maurice Kottelat in his 2004 revision of the botiine loaches, was found to be non-monophyletic in this study. Two of these, sidthimunki and nigrolineata, do not appear to be closely related to other members of the Yasuhikotakia genus, and there's 96-100% probability that they're actually members of the genus Sinibotia.

Botiidae?
For a long time, the group of loaches that includes the Botia has been termed the Botiinae subfamily and was placed within the Cobitidae family. However, in July 2005, Tang, Xiong, Yang and Liu of the Chinese Academy of Science and Huazhong Agricultural University produced an evolutionary family tree (phylogeny) for the botiine loaches using their mitochondrial ctyochrome b gene sequences.

They found the group so distinct from other loaches, that they suggested placing the fish in a new family - the Botiidae. Those changes seem to have been fully accepted by the scientific community now, who are placing the loaches in the Botiidae family, and splitting them further into the Leptobotiinae and Botiinae subfamilies.

Colour morphs
Among the fish examined were a number of different populations of single species, such as Yasuhikotakia modesta, which can vary slightly in colouration. Interestingly, in the case of modesta, specimens with yellow fins appeared to differ genetically from those with red fins.

Similarly, Yasuhikotakia eos with transparent fins were genetically different to the forms with red fins. Syncrossus berdmorei had particularly high levels of genetic variation, suggesting that further taxonomic work on these three might lead to some new species being described.

For more details see the paper: Slechtova V, Bohlen J, Freyhof J and P Rab (2006) - Molecular phylogeny of the Southeast Asian freshwater fish family Botiidae (Teleostei: Cobitoidea) and the origin of polyploidy in their evolution. Molecular Phylogenetics and Evolution 39(2006) 529-541.