Incongruent gene trees, complex evolutionary processes, and the phylogeny of a group of North American minnows (Hybognathus Agassiz 1855).

Hybognathus is a putatively monophyletic group of North American minnows containing seven extant species. Although much is known about the taxonomy, biology, and life history of Hybognathus species, their phylogenetic relations with each other remain unclear. We address this problem with partial sequences of mitochondrial cytochrome-b, 16S rRNA, and ND4 mtDNA genes and nuclear growth hormone (GH) and S7 introns from representatives of all Hybognathus species and four outgroup taxa. Phylogenetic analyses of these data corroborated previous studies on the monophyly of seven recognized species of Hybognathus, and indicated weak support for monophyly of the genus. Topological tests, however, revealed significant (all P<0.001) conflict among molecular data sets. Ad hoc removal of taxa from topologies and subsequent testing indicated that incongruence was localized to two specific ingroup taxa (H. hayi and H. regius) and suggested that the conflict is a function of underlying processes that have generated the observed phylogenetic patterns. Hybridization (ancestral), which is commonplace in cyprinids, may best explain topological disagreements among datasets; however, retention of ancestral polymorphism and natural selection remain as alternative hypotheses. Our results highlight methodological and topological problems associated with estimating interspecific phylogenies from multiple genes.

Permanent genetic resources added to Molecular Ecology Resources Database 1 August 2010-30 September 2010.

This article documents the addition of 229 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Acacia auriculiformis × Acacia mangium hybrid, Alabama argillacea, Anoplopoma fimbria, Aplochiton zebra, Brevicoryne brassicae, Bruguiera gymnorhiza, Bucorvus leadbeateri, Delphacodes detecta, Tumidagena minuta, Dictyostelium giganteum, Echinogammarus berilloni, Epimedium sagittatum, Fraxinus excelsior, Labeo chrysophekadion, Oncorhynchus clarki lewisi, Paratrechina longicornis, Phaeocystis antarctica, Pinus roxburghii and Potamilus capax. These loci were cross-tested on the following species: Acacia peregrinalis, Acacia crassicarpa, Bruguiera cylindrica, Delphacodes detecta, Tumidagena minuta, Dictyostelium macrocephalum, Dictyostelium discoideum, Dictyostelium purpureum, Dictyostelium mucoroides, Dictyostelium rosarium, Polysphondylium pallidum, Epimedium brevicornum, Epimedium koreanum, Epimedium pubescens, Epimedium wushanese and Fraxinus angustifolia.

Genetic and ecological dynamics of species replacement in an arid-land river system.

Museum records indicate that Hybognathus placitus was introduced into the Pecos River, New Mexico during the early 1960s. Approximately 10 years later, a congener, Hybognathus amarus, was extirpated from the system. We used microsatellite and mtDNA data, ecological data and modelling, and a computer simulation approach to reconstruct the history of invasion and species replacement. To identify the potential role of hybridization and introgression, we genetically screened H. amarus (n = 389) from the Rio Grande, New Mexico, and H. placitus (n = 424) from the Pecos River, New Mexico using four nuclear microsatellites and a partial fragment of the mtDNA ND4 gene. Assignment tests excluded hybridization as a primary factor in species replacement and suggested a role for interspecific competition. Genetic analyses showed that H. placitus were introduced into the Pecos River from at least two genetically distinct source populations in the Canadian and Red rivers, Oklahoma. Lotka-Volterra models of interspecific competition indicated that the number of founding individuals could have been as few as 20 for H. placitus to have competitively displaced H. amarus in the Pecos River in 10 to 15 generations. Observed differences of allele frequencies between source and founder populations indicated that between 32 and 115 H. placitus individuals founded the Pecos River. Genetic and ecological data suggest that interspecific competition could have led to species replacement in this arid-land river system.