Search

African suckermouth catfishes (Mochokidae: Chiloglanis) occur in freshwater throughout tropical Africa. Specimens from all major drainages across Kenya were collected over three field seasons. Here we present a phylogeny inferred from both mitochondrial cytochrome b (cyt b) and introns of the nuclear Growth Hormone gene (GH). The phylogeny inferred from introns is largely congruent with the results from an analysis of cyt b. The length and variability of GH introns make them ideal species level nuclear markers without the problem of introgression commonly encountered with mitochondrial genes. This analysis confirmed the presence of two previously known undescribed Chiloglanis species and also suggests the presence of previously unknown diversity within the Athi River system. The resulting phylogeny also indicates the presence of two separate lineages within C. brevibarbis. The historical biogeography of Chiloglanis within Kenya is discussed. The utility of GH intron for species level phylogenies of Siluriformes is compared to that in other groups., (Copyright © 2014 Elsevier Inc. All rights reserved.)

We have examined phylogenetic relationships of suckers of tribe Moxostomatini (Cypriniformes, Catostomidae) using cytochrome-b and Growth Hormone gene intron sequences. Phylogenies were significantly different from recent estimates of relationships based primarily on morphology (Smith, 1992) and cytochrome-b sequences (Harris et al., 2002). Overall, there was little support for many basal nodes in the phylogeny, however it was clear that Scartomyzon and Moxostoma were not monophyletic, despite morphological evidence provided Robins and Raney (1956, 1957), Jenkins (1970), and Smith (1992). Growth Hormone sequences provided good support for a monophyletic Western Scartomyzon lineage and thus suggested a single ancestral invasion of Scartomyzon-like fishes into drainages of Texas and Mexico. Phylogenetic relationships of Western Scartomyzon are structured geographically and do not conform well to current taxonomy., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Catostomid fishes (suckers) have duplicate copies of the growth hormone gene and other nuclear genes, due to a genome duplication event early in the group's history. Yet, paralogs of GH in suckers are more than 90% conserved in nucleotide (nt) and amino acid (aa) sequence. Within paralogs across species, variation in nt and aa sequence averages 3.33% and 4.46% for GHI, and 3.22% and 2.43% for GHII, respectively. Selection tests suggest that the two GH paralogs are under strong purifying selection. Consensus trees from phylogenetic analysis of GH coding region data for 23 species of suckers, other cypriniform fishes and outgroups resolved cypriniform relationships and relationships among GHI sequences of suckers more or less consistently with analyses based on other molecular data. However, the analysis failed to resolve all sucker GHI and GHII sequences as monophyletic sister groups. This unexpected topology did not differ significantly from topologies constrained to make all GH sequences monophyletic. We attribute this result either to limitations in our GHII data set or convergent adaptive changes in GHII of tribe Catostomini.

The growth hormone (GH) gene has been characterized for a number of fishes and used to establish phylogenetic relationships and population structures. Analysis of tetraploid fishes, such as salmon and some Asian cyprinids, has shown the presence of two GH genes. Fishes in the sucker family (Catostomidae, Cypriniformes) are also tetraploid, and the present study reports the isolation and characterization of two GH cDNAs from a representative species, the smallmouth buffalofish (Ictiobus bubalus). The GH cDNAs of smallmouth buffalofish are 1272 and 1273nt in length, and each codes for a polypeptide of 210 amino acids, predicted to be cleaved to a final product of 188 aa. The GH cDNAs of smallmouth buffalofish are 6% divergent in nt sequence in the coding region, and there are 16 differences in predicted aa sequence. Because the cDNAs have distinct sequences in coding regions and in UTRs, which differed by more than 10%, they were identified as GHI and GHII. The predicted GHI protein contains 4 Cys residues, homologous to other vertebrate GH sequences. On the other hand, GHII has 5 Cys residues, homologous to other ostariophysan sequences. GHI and GHII are most similar to other cypriniform fishes for both nt and protein sequences. Phylogenetically, the sequences of smallmouth buffalofish GH consistently grouped with Asian cyprinids, but not loaches, consistent with morphological evidence suggesting that suckers are most closely related to minnows.