LIVE COLOR PATTERNS DIAGNOSE SPECIES: A TALE OF TWO HERICHTHYS

Abstract

The Rio Grande Cichlid, Herichthys cyanoguttatus, is native to the drainages of the Gulf Coast of northern Mexico and southern Texas and has been introduced at several sites in the US. Previous observations have suggested that non-native populations in Louisiana that are currently recognized as H. cyanoguttatus resemble another species, the Lowland Cichlid, H. carpintis. Traditional morphological and genetic techniques have been insufficient to differentiate these species, but H. carpintis has been reported to differ from H. cyanoguttatus in color pattern, so we turned to novel electronic photo archives to determine the identity of the species introduced in Louisiana. First, we used the public databases Nonindigenous Aquatic Species Database and Fishes of Texas to infer the historical distributions of these species in the US. We then used museum specimens, live specimens, and two additional databases, The Cichlid Room Companion and iNaturalist, to compare morphology and color patterns among individuals obtained from their native and introduced ranges in Mexico, Texas, and Louisiana. Our general observations found that H. cf. cyanoguttatus from Louisiana tended to have an obliquely oriented mouth and a more rounded ventral profile than H. cyanoguttatus from Texas, consistent with previous descriptions of H. carpintis, but our morphological analyses were unable to identify any significant differences among populations. Our analyses of color patterns found that H. cf. cyanoguttatus from Louisiana had larger iridescent spots than H. cyanoguttatus from Texas as well as black breeding coloration that extended anteriorly to the tip of the mouth, characters consistent with H. carpintis. Our observations indicate that at least some of the cichlids introduced in Louisiana are not H. cyanoguttatus but are instead H. carpintis, and that their presence there is likely due to release by humans. This is the first record of H. carpintis establishing a population in the US. Understanding the biology of not one, but two, species of Herichthys will be necessary to predict and mitigate their continued colonization of new environments in the US.