Molecular systematics of western North American cyprinids (Cypriniformes: Cyprinidae)

Abstract

The phylogenetic or evolutionary relationships of species of Cypriniformes, as well as their classification, is in a era of flux. For the first time ever, the Order, and constituent Families are being examined for relationships within a phylogenetic context. Relevant findings as to sister-group relationships are largely being inferred from analyses of both mitochondrial and nuclear DNA sequences. Like the vast majority of Cypriniformes, due to an overall lack of any phylogenetic investigation of these fishes since Hennig's transformation of the discipline, changes in hypotheses of relationships and a natural classification of the species should not be of surprise to anyone. Basically, for most taxa no properly supported phylogenetic hypothesis has ever been done; and this includes relationships with reasonable taxon and character sampling of even families and subfamilies. As such, like others, many western North American cyprinid genera have had a controversial taxonomic and systematic history.Our effort to better understand the evolutionary history of this artificial geographic grouping of species (Western) surveyed taxa and characters broadly. We analyzed 127 taxa (71 species) from 36 genera, including representative taxa from all 22 western genera hypothesized to form the Western Clade sensu Coburn and Cavender (1992). Our evaluation also included additional sampling from a heterogeneous array of species from the western genera Algansea, Gila, Lepidomeda, Ptychocheilus and Siphateles. Resulting phylogenetic inferences, based on one mitochondrial and three nuclear genes (mtDNA: cytb; nDNA: Rag1, Rhod, S7), consistently resolved a well-supported Western Clade, but one inclusive of Chrosomus erythrogaster. This taxon, always formed the sister group to the extant species of Gila plus 10 other western genera. Our Western Clade is qualitatively different from that of prior studies and does not include the genera Agosia, Algansea, Iotichthys, Lepidomeda, Meda, Mylocheilus, Plagopterus, Pogonichthys, Rhinichthys, Tiaroga or Yuriria. All of these taxa were, however, included in Coburn and Cavender´s (1992) Western Clade. Our broader-scale survey and increased character sampling were always resolved these latter taxa within one of two different major clades: the OPM Clade (sensu Mayden 1989) and the Creek Chub-Plagopterin Clade (sensu Simons et al. 2003). Our hypothesized Western Clade places Orthodon sister to a Western Chub-Pikeminnow Clade also inclusive of Acrocheilus, Eremichthys, Gila, Hesperoleucus, Lavinia, Moapa, Mylopharodon, Ptychocheilus, Relictus and Siphateles. The latter taxa have traditionally been recognized at the generic level, simply on the basis of their morphological distinctiveness and not on the basis of a phylogenetic evaluation of relationships. Composition of our Western Chub-Pikeminnow Clade also reveals genetic divergences between species of some genera (Gila, Ptychocheilus, Siphateles) comparable to genetic divergences documented between genera within the Western Clade. Relationships for th...

Biogeography and divergent patterns of body size disparification in North American minnows

“…Our phylogenetic hypothesis is largely congruent with other recent but less well-sampled phylogenies (Schönhuth et al, 2012(Schönhuth et al, , 2014Hollingsworth et al, 2013). We recovered a strongly supported sister relationship between the Western and CC-P clades, a result which Schönhuth et al (2012) found only with mitochondrial data; this may be due to the strong mitochondrial signal in our dataset or the relatively large amount of missing nuclear data. We also recovered numerous non-monophyletic genera, most of which have been noted by previous authors; the Western clade is particularly in need of revision (e.g.…”

“…We also recovered numerous non-monophyletic genera, most of which have been noted by previous authors; the Western clade is particularly in need of revision (e.g. Schönhuth et al, 2012Schönhuth et al, , 2014, while the OPM genus Notropis has long been used as a bin for species of questionable affinity. Most notably, our phylogeny did not recover the distinctive pikeminnows (genus Ptychocheilus) as monophyletic, in agreement with other studies (Simons et al, 2003;Mayden, 2010a, 2010b;Houston et al, 2010;Schönhuth et al, 2012Schönhuth et al, , 2014.…”

“…Most of the potentially useful representatives from the Oligocene, Miocene, and Pliocene of western North America (e.g. Smith, 1981;Cavender, 1991) are in need of reinterpretation in light of recent taxonomic revisions, especially in the Western clade (Schönhuth et al, 2012(Schönhuth et al, , 2014 which has presumably undergone extensive morphological evolution, including several instances of apparent convergence (e.g. pikeminnows, genus Ptychocheilus).…”

“…Schönhuth et al, 2012Schönhuth et al, , 2014, while the OPM genus Notropis has long been used as a bin for species of questionable affinity. Most notably, our phylogeny did not recover the distinctive pikeminnows (genus Ptychocheilus) as monophyletic, in agreement with other studies (Simons et al, 2003;Mayden, 2010a, 2010b;Houston et al, 2010;Schönhuth et al, 2012Schönhuth et al, , 2014. Relationships within the hyperdiverse OPM clade were unsurprisingly less stable among runs (including many preliminary phylogenetic analyses) and among our sample of trees, and its backbone received lower support values.…”

“…Excluding Notemigonus crysoleucas, which is thought to be a member of the EU leuciscin clade (Saitoh et al, 2011), most authors have recognized three primary clades of North American minnows: the Open Posterior Myodome (OPM), Creek ChubPlagopterin (CC-P), and Western clades (Coburn and Cavender, 1992), although the precise compositions of these clades have been more variable (Mayden, 1989;Simons and Mayden, 1997Simons et al, 2003;Schönhuth et al, 2008;Schönhuth and Mayden, 2010;Mayden, 2010a, 2010b). Only recently have systematists begun to incorporate multiple genetic markers with broader taxon sampling of North American cyprinids (Western clade: Schönhuth et al, 2012Schönhuth et al, , 2014OPM clade: Hollingsworth et al, 2013), but we still lack a comprehensive phylogenetic hypothesis for the clade as a whole.…”