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Queen of the prairie, Filipendula rubra (Rosaceae), is a clonal plant species inhabiting calcareous fens and wet meadows of the northcentral United States. F. rubra reproduces asexually by underground rhizomes and sexually by seed. While many studies have explored genotype diversity in clonal species with limited sexual reproduction, fewer have been conducted on clonal species with the potential for extensive sexual reproduction. We studied the relationship between the extent of sexual reproduction and genotype diversity. Although genotype diversity in F. rubra was double that reported by others for 27 nearly obligate clonal plant species, it was still quite low. For 25 populations studied, the mean number of genotypes was 5.5 (range = 1–15; SE = 0.964) and the average proportion of distinguishable genotypes was 0.38 (range = 0.03–1.00; SE = 0.07). The production of viable seed was quite variable among populations (mean proportion of viable seeds = 0.242; range = 0.002–0.565; SE = 0.04). Considering that some inflorescences can produce over 5,000 seeds, the potential for recruitment of sexually produced individuals is very large. No correlation was found between seed production and genotype diversity as was expected in a self‐incompatible species in which one‐third of the populations possessed a single genotype. It was hypothesized that the low genotype diversity found in numerous populations may be due to competition limiting recruitment of new seedlings.

Skeletal elements of the gill arches of adult cypriniform fishes vary widely in number, size, and shape and are important characters in morphologically based phylogenetic studies. Understanding the developmental basis for this variation is thus phylogenetically significant but also important in relation to the many developmental genetic and molecularly based studies of the early developing and hence experimentally tractable gill arches in the zebrafish, a cyprinid cypriniform. We describe the sequence of the chondrification and ossification of the pharyngeal arches and associated dermal bones from Catostomus commersonii (Catostomidae, Cypriniformes) and make selected comparisons to other similarly described pharyngeal arches. We noted shared spatial trends in arch development including the formation of ventral cartilages before dorsal and anterior cartilages before posterior. Qualitatively variable gill arch elements in Cypriniformes including pharyngobranchial 1, pharyngobranchial 4, and the sublingual are the last such elements to chondrify in C. commersonii. We show that the sublingual bone in C. commersonii has two cartilaginous precursors that fuse and ossify to form the single bone in adults. This indicates homology of the sublingual in catostomids to the two sublingual bones in the adults of cobitids and balitorids. Intriguing patterns of fusion and segmentation of the cartilages in the pharyngeal arches were discovered. These include the individuation of the basihyal and anterior copula through segmentation of a single cartilage rod, fusion of cartilaginous basibranchials 4 and 5, and fusion of hypobranchial 4 with ceratobranchial 4. Such "fluidity" in cartilage patterning may be widespread in fishes and requires further comparative developmental studies.

The cyprinid fishes Luxilus cornutus and Luxilus chrysocephalus hybridize extensively in a zone extending through the Great Lakes region with extensive introgression of L. cornutus mtDNA occurring in populations of L. chrysocephalus south of the present hybrid zone in Ohio. Western populations of these two species occur adjacent to one another in Missouri but hybridization has never been observed. In order to determine if hybridization has occurred historically in Missouri, allopatric populations of L. chrysocephalus were analysed for mtDNA introgression. Extensive introgression of L. cornutus mtDNA was observed in most populations of L. chrysocephalus in Missouri resulting in the elimination of L. chrysocephalus mtDNA in many populations. Luxilus cornutus mtDNA in L. chrysocephalus is found approximately 300 km south of extant L. cornutus populations in Missouri. Luxilus chrysocephalus mtDNA was replaced by four unique L. cornutus mtDNA haplotypes, with one particular haplotype becoming fixed in several L. chrysocephalus populations. The pattern of introgression suggests that historically L. cornutus occupied a more southern distribution in Missouri bringing it into contact with western populations of L. chrysocephalus and resulting in a hybrid zone.