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A phylogenetic study of the percoid family Gerreidae at both lower and higher taxonomic levels is presented based on DNA sequence data of four genes: mitochondrial 12S and 16S, and nuclear genes rhodopsin and recombination activating gene 1 (RAG1). The taxonomic sampling includes four genera of Gerreidae from the western Atlantic, 39 additional percomorph representatives and two outgroups. Phylogenetic results confirm the monophyly of the Gerreidae and suggest that the family is divided into two sub-groups (Diapterus auratus plus Eugerres plumieri and Eucinostomus gula plus Gerres cinereus), which correspond to two previously defined taxonomic assemblages characterized by the shape of the preoperculum. Gerreids are placed at an intermediate position in the percomorph tree between two basal clades (L and Q) and a terminal clade N (grouping tetraodontiforms, acanthuroids, lophiiforms, caproids and several percoids). In addition, topology tests indicate that two traditional assemblages, Labroidei (seven representatives sampled) and Percoidei (22 representatives sampled) are not natural groups. Labrids and scarids appear to be more closely related to gerreids and to the members of clade N than to any other basal percomorphs, including their labroid 'allies' sampled in this study, Embiotocidae, Pomacentridae and Cichlidae, which are all nested within clade Q that also includes atherinomorphs, mugiliforms and Chandidae. The percoid taxa included in this study are widely distributed among various percomorph lineages. The percomorph phylogeny obtained is highly congruent with results from recent molecular studies.

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v This paper describes Elops smithi, n. sp., and designates a lectotype for E. saurus. These two species can be separated from the five other species of Elops by a combination of vertebrae and gillraker counts. Morphologically, they can be distinguished from each other only by myomere (larvae) or vertebrae (adults) counts. Elops smithi has 73–80 centra (total number of vertebrae), usually with 75–78 centra; E. saurus has 79–87 centra, usually with 81–85 centra. No other morphological character is known to separate E. smithi and E. saurus, but the sequence divergence in mtDNA cytochrome b (d = 0.023–0.029) between E. smithi and E. saurus is similar to or greater than that measured between recognized species of Elops in different ocean basins. Both species occur in the western Atlantic Ocean, principally allopatrically but with areas of sympatry, probably via larval dispersal of E. smithi by oceanographic currents.

The Amazon sailfin catfish Pterygoplichthys pardalis is native to the Amazon River basin. It has since expanded its range to North America, the Caribbean, and more recently to South Asia, as with some of its congeners. Our paper reviews recent data from Bangladesh, clarifies taxonomic identification, and examines the potential effects of P. pardalis and congeneric species on local aquatic ecosystems and elsewhere in South Asia. Range expansions there probably reflect aquarium releases and escapes from aquaculture farms, as exacerbated by dispersal due to storm flooding and in impacted waters like irrigation canals. Given their potential ecosystem-level effects, we also review potential control mechanisms and human use for these invasive loricariids.

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