The biological diversity and aquaculture of clariid and pangasiid catfishes in South-East Asia : proceedings of the mid-term workshop of the "Catfish Asia project"

With the aim of detecting phylogenetic relationships among #Pangasiidae$ catfishes, 23 enzyme loci were studied on 18 nominal species of the genera #Pangasius$ and #Helicophagus$ (Roberts and Vidthayanon, 1991). In order to assess the taxonomic position of #Laides$ genus in the #Schilbeidae$ or in the #Pangasiidae$, 2 species belonging to the genus #Laides$ and 1 species of the genus #Pseudeutropius$ (#Siluriformes$, #Schilbeidae$) were added in the study. The results indicate that the species #Laides hexanema$ and #Laides sinensis$ appear to be genetically related with the #Pangasiidae$. The phylogenetic tree obtained shows a clustering of species which validate the genus #Helicophagus$ but indicates that the genus #Pangasius$ is polyphyletic. The genus #Pangasius$ is composed of 3 genetic differentiated groups. Group 1 is composed of 3 species belonging to two different morphological entities validated by Roberts and Vidthayanon (1991) as possible subgenus. #Pangasius hypophthalmus$ and #P. gigas$ which share common genetic characters validate the subenus #Pangasianodon$. The possession of many private alleles by #P. pleurotaenia$ confirms the morphological originality of this species which was therefore considered to belong to the monotypic subgenus #Pteropangasius$. The second groupd consists of #P. micronema$, #P. macronema$, #P. lithostoma$ and #P. polyuranodon$ and the last group represents all the other species of the genus #Pangasius$. By contrast #Neopangasius$ considered as a possible subgenus by Roberts and Bidthayanon (1991) is polyphyletic. Although relative genetic similarities were found between #P. humeralis$ and #P. nieuwenhuisii$ which are located in group 3, the species #P. lithostoma$ appears to be more closely related to species belonging to the group 2... (D'après résumé d'auteur