The mission of the Desert Fishes Council is to preserve the biological integrity of North America's desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

The mission of the Desert Fishes Council is to preserve the biological integrity of North America's desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

Convergence has long been of interest to evolutionary biologists. Cave organisms appear to be ideal candidates for studying convergence in morphological, physiological, and developmental traits. Here we report apparent convergence in two cave-catfishes that were described on morphological grounds as congeners: Prietella phreatophila and Prietella lundbergi. We collected mitochondrial DNA sequence data from 10 species of catfishes, representing five of the seven genera in Ictaluridae, as well as seven species from a broad range of siluriform outgroups. Analysis of the sequence data under parsimony supports a monophyletic Prietella. However, both maximum-likelihood and Bayesian analyses support polyphyly of the genus, with P. lundbergi sister to Ictalurus and P. phreatophila sister to Ameiurus. The topological difference between parsimony and the other methods appears to result from long-branch attraction between the Prietella species. Similarly, the sequence data do not support several other relationships within Ictaluridae supported by morphology. We develop a new Bayesian method for examining variation in molecular rates of evolution across a phylogeny.

The Mexican Neovolcanic Plateau sharply divides the vertebrate fauna of Mesoamerica where the climate of both the neotropics 12 and temperate North America gradually blend. Only a few vertebrate groups such as the Heroine cichlids, distributed from South 13 America to the Rio Grande in North America, are found both north and south of the Neovolcanic Plateau. To better understand the 14 geography and temporal diversification of cichlids at this geologic boundary, we used mitochondrial DNA sequences of the cy- 15 tochrome b (cyt b) gene to reconstruct the relationships of 52 of the approximately 80 species of Heroine cichlids in Mesoamerica. 16 Our analysis suggests several cichlids in South America should be considered as part of the Mesoamerican Heroine clade because 17 they and the cichlids north of the Isthmus of Panama are clearly supported as monophyletic with respect to all other Neotropical 18 cichlids. We also recovered a group containing species in Paratheraps + Paraneetroplus+ Vieja as the sister clade to Herichthys. 19 Herichthys is the only cichlid clade north of the Mexican Plateau and it is monophyletic. Non-parametric rate smoothing of cichlid 20 cyt b sequence resulted in an estimated divergence time of approximately 6 million years for Herichthys. This temporal diversifi- 21 cation is concordant with divergence times estimated for anurans in the genus Bufo, a group that exhibits a similar geographic 22 distribution. Our results indicate the 5-million-year-old extension of the Mexican Neovolcanic Plateau to the Gulf Coast of Mexico 23 has strongly influenced the current transition between the vertebrate faunas of the Neotropics and Nearctic

Nymphophilus minckleyi is a hydrobiid snail endemic to the freshwater spring ecosystem of Cuatro Ciénegas, Mexico. We used seven allozyme loci to examine the genetic substructure of N. minckleyi from 14 sites (subpopulations) in the basin and to test the hypothesis that spring pools in Cuatro Ciénegas are separated into seven hydrologically distinct drainages. Hierarchical F-statistics suggest significant population structure exists among the fourteen populations but not among the seven proposed drainages. Cluster analysis of Nei's genetic distance did not show populations grouping according to drainages, although it did reveal alternative clusters. We found two distinct morphotypes that were supported as genetically distinct groups by the allozyme data. Genetic studies of vagile species in desert spring ecosystems can be used to reveal hydrologic connections and identify genetically unique sub-populations.