Distributional and Ecological Notes on the Halfbeaks of Eastern Gulf of Mexico, with a Provisional Key for Their Identification

Several fishes of the halfbeak genus Hyporhamphus occurring in the Mexican Gulf of Mexico and Caribbean Sea have been misidentified or confused in the literature. Most of it has centered around the taxonomic status of H. unifasciatus (including its synonym H. roberti), which is shown to comprise a complex of three species, H. unifasciatus, the recently described H. meeki, from the western Atlantic region, and an undescribed species from the eastern Pacific Ocean. Another eastern Mexico halfbeak is the freshwater form H. mexicanus. Using Banford and Collette (1993), we examined specimens from collections at UANL, UNAM, IPN, and ECOCH and have clarified the Mexican distribution of these species. We here report additional Mexican records of H. meeki, previously known only from United States waters and from the coast of Yucatán, clarify the distribution of H. unifasciatus, and provide the first marine record of the freshwater species H. mexicanus. A distribution map and keys for identification of the eastern Mexican species are provided

Data from: Predation drives morphological convergence in the Gambusia panuco species group among lotic and lentic habitats

Fish morphology is often constrained by a trade-off between optimizing steady vs. unsteady swimming performance due to opposing effects of caudal peduncle size. Lotic environments tend to select for steady swimming performance, leading to smaller caudal peduncles, while predators tend to select for unsteady swimming performance, leading to larger caudal peduncles. However, it is unclear which aspect of performance should be optimized across heterogeneous flow and predation environments and how this heterogeneity may affect parallel phenotypic evolution. We investigated this question among four Gambusia species in northeastern Mexico, specifically the riverine G. panuco, the spring endemics G. alvarezi and G. hurtadoi, and a fourth species, G. marshi, found in a variety of habitats with varying predation pressure in the Cuatro Ciénegas basin and Río Salado de Nadadores. We employed a geometric morphometric analysis to examine how body shapes of both male and female fish differ among species and habitats and with piscivore presence. We found that high-predation and low-predation species diverged morphologically, with G. marshi exhibiting a variable, intermediate body shape. Within G. marshi, body morphology converged in high-predation environments regardless of flow velocity, and fish from high-predation sites had larger relative caudal peduncle areas. However, we found that G. marshi from low-predation environments diverged in morphology between sub-basins of Cuatro Ciénegas, indicating other differences among these basins that merit further study. Our results suggest that a morphological trade-off promotes parallel evolution of body shape in fishes colonizing high-predation environments and that changing predation pressure can strongly impact morphological evolution in these species

An Annotated Distributional Checklist of the Freshwater Fish From Baja California Sur, Mexico

An annotated distributional checklist of thefreshwater fish recorded historically andrecently in Baja California Sur, México, isprovided. Thi