Dear Marmam readers, We are pleased to announce the publication of the following article in Marine and Freshwater Research. For a pdf copy please send requests to: aramaral@fc.ul.pt Amaral AR, Sequeira M, Coelho MM (2007) A first approach to the usefulness of cytochrome c oxidase I barcodes in the identification of closely related delphinid cetacean species. Marine and Freshwater Research 58: 505-510. http://www.publish.csiro.au/nid/126/paper/MF07050.htm The DNA barcode initiative has gained particular popularity as a promising tool to assist in species identification by using a single mitochondrial gene, cytochrome c oxidase I (COI). In some animal groups, COI barcodes have proved efficient in separating closely related taxa. However, several issues remain for discussion, namely how efficient this tool will be in animal groups with an unresolved taxonomy. Here, we examined COI sequences in delphinid cetaceans, a group where taxonomic uncertainty still exists. We analysed species belonging to the genera Stenella, Tursiops and Delphinus in the North-east Atlantic using cytochrome b gene sequences for comparison. We obtained values of COI interspecific genetic divergence ranging from 1.47% to 2.45%, which suggests a recent separation of the analysed taxa. S. coeruleoalba and D. delphis were the most similar species, with COI phylogenetic trees failing to separate them. On the other hand, the phylogenetic tree obtained with cytochrome b sequences correctly clustered species with high bootstrap support values. We thus consider that the application of COI barcodes in delphinid cetaceans should be done with caution; not only has the cytochrome b gene shown to be phylogenetically more informative, but relying only on mitochondrial DNA genes alone may be problematic. Best wishes, Ana Rita Amaral Departamento de Biologia Animal Faculdade de Ciências Universidade de Lisboa Edifício C2, 3ºpiso Lab.2.3.12/2.3.25 Campo Grande 1749-016 Lisboa Portugal Tel:(+351)21 750 00 00 Ext. 22312 E-mail: aramaral@fc.ul.pt ..¸<º))))><`·.¸¸.·´¯`·.¸.<º))))><.¸. , . .·´¯`·..