Phylogenetic relationships of the North American cyprinid subgenus Hydrophlox.

Notropis is one of the largest genera of North American fishes and is composed of a number of morphologically diagnosed subgroups; however, the validity of many has not been tested in a phylogenetic framework. One such subgroup is the subgenus Hydrophlox, which is composed of brilliantly colored species that engage in the symbiotic reproductive behavior of nest association. Although they have long been recognized as a cohesive group due to their nuptial coloration and fin tuberculation, very little is known about the relationships of species within Hydrophlox. We tested the monophyly of Hydrophlox using a mitochondrial marker (ND2) and two nuclear markers (ITS1 and RH), with Maximum Parsimony and Bayesian inference approaches. A well supported clade of "core"Hydrophlox was recovered and is composed of five taxa: Notropis chiliticus, Notropis rubricroceus, Notropis lutipinnis, Notropis chlorocephalus, and Notropis chrosomus. Hydrophlox s.l. is paraphyletic with respect to three taxa: Notropis baileyi, Notropis leuciodus and Notropis nubilus. While there was some discordance among the individual marker topologies, a combined evidence analysis recovered a topology that incorporated elements from all single-gene trees. Our analyses suggest that Hydrophlox is composed of five nominal species and additional undescribed diversity exists within this clade.

Small fish, large river: Surprisingly minimal genetic structure in a dispersal-limited, habitat specialist fish.

Genetic connectivity is expected to be lower in species with limited dispersal ability and a high degree of habitat specialization (intrinsic factors). Also, gene flow is predicted to be limited by habitat conditions such as physical barriers and geographic distance (extrinsic factors). We investigated the effects of distance, intervening pools, and rapids on gene flow in a species, the Tuxedo Darter (Etheostoma lemniscatum), a habitat specialist that is presumed to be dispersal-limited. We predicted that the interplay between these intrinsic and extrinsic factors would limit dispersal and lead to genetic structure even at the small spatial scale of the species range (a 38.6 km river reach). The simple linear distribution of E. lemniscatum allowed for an ideal test of how these factors acted on gene flow and allowed us to test expectations (e.g., isolation-by-distance) of linearly distributed species. Using 20 microsatellites from 163 individuals collected from 18 habitat patches, we observed low levels of genetic structure that were related to geographic distance and rapids, though these factors were not barriers to gene flow. Pools separating habitat patches did not contribute to any observed genetic structure. Overall, E. lemniscatum maintains gene flow across its range and is comprised of a single population. Due to the linear distribution of the species, a stepping-stone model of dispersal best explains the maintenance of gene flow across its small range. In general, our observation of higher-than-expected connectivity likely stems from an adaptation to disperse due to temporally unstable and patchy habitat.

Population genetics of seaside Sparrow (Ammodramus maritimus) subspecies along the gulf of Mexico.

Seaside Sparrows (Ammodramus maritimus) along the Gulf of Mexico are currently recognized as four subspecies, including taxa in Florida (A. m. juncicola and A. m. peninsulae) and southern Texas (Ammodramus m. sennetti), plus a widespread taxon between them (A. m. fisheri). We examined population genetic structure of this "Gulf Coast" clade using microsatellite and mtDNA data. Results of Bayesian analyses (Structure, GeneLand) of microsatellite data from nine locations do not entirely align with current subspecific taxonomy. Ammodramus m. sennetti from southern Texas is significantly differentiated from all other populations, but we found evidence of an admixture zone with A. m. fisheri near Corpus Christi. The two subspecies along the northern Gulf Coast of Florida are significantly differentiated from both A. m. sennetti and A. m. fisheri, but are not distinct from each other. We found a weak signal of isolation by distance within A. m. fisheri, indicating this population is not entirely panmictic throughout its range. Although continued conservation concern is warranted for all populations along the Gulf Coast, A. m. fisheri appears to be more secure than the far smaller populations in south Texas and the northern Florida Gulf Coast. In particular, the most genetically distinct populations, those in Texas south of Corpus Christi, occupy unique habitats within a very small geographic range.