Biogeography and Distribution of the Cryptic Species Rosyface Shiner Notropis rubellus and Carmine Shiner Notropis percobromus in Illinois
Conservation and management of cryptic species is particularly challenging since it can be difficult to determine their exact distributions. Knowledge of species distribution is required to recognize management units based on taxonomy and whether there are any pertinent biogeographic patterns that could be relevant to the development of a management plan. Such a situation exists in Illinois with the Rosyface Shiner Notropis rubellus and Carmine Shiner Notropis percobromus. There are no reliable anatomical characters to distinguish between the two species. Instead, they are distinguished by genetic data. Samples were obtained for these two species from across the state from each major watershed in which they are found. Based on cytochrome b sequence variation the two species can be distinguished by 44 species-distinct differences. Notropis percobromus is restricted to the Rock River watershed and nearby Mississippi River tributaries in northwest Illinois. Notropis rubellus is found in the Illinois River basin and Vermilion-Wabash watershed. This is a reflection of historical drainage patterns from the geologic period when eastern Illinois was connected to the Great Lakes, as opposed to today when all the rivers in this study are part of the Mississippi basin. Using a previously published rate of divergence of the cytochrome b gene, we estimated a divergence time for these two species that was consistent with a previous estimate—2.8–2.6 MYA. Statistically, there was no genetic difference among populations within N. rubellus or N. percobromus. Haplotype networks and a phylogenetic analysis do provide some evidence for potential bottlenecks/founder effects and/or haplotype-specific selection within each species.
Distribution map of Notropis rubellus (blue squares) and Notropis percobromus (red circles) haplotypes used to determine the range of the two species in Illinois. Numbers in parentheses indicate how many individuals have the same haplotype at the same location. Rivers shown in dark blue are in the Upper Mississippi watershed, those in light blue are in the Illinois River watershed, and those in purple are in the Wabash River watershed.
Haplotype networks for sequences from this study and all others in GenBank from Illinois, as well as some from Indiana or Michigan (shown as shaded ovals) that were highly similar to sequences in this study (see text for details). The relative size of each oval is roughly proportional to the number of samples represented by the respective haplotypes with the smallest representing single samples. Nodes between ovals represent predicted but unsampled haplotypes. Each haplotype is different from the one above it by one nucleotide. (A) Haplotype network for sequences identified as Notropis rubellus. (B) Haplotype network for sequences identified as Notropis percobromus.
Maximum likelihood phylogenetic tree including all sequences from this study combined with all sequences from a previous phylogenetic analysis conducted by Berendzen et al. (2008). The tree with the highest log likelihood is shown. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. Values shown along branches are bootstrap values. The scale bar represents the number of substitutions per site. Only the portion of the tree that included clades representing N. rubellus and N. percobromus are shown here. The sequences from GenBank from Indiana and Michigan that are shaded in Figure 2 are also shaded in this figure. See text for other details.
Contributor Notes
Associate Editor: M. T. Craig.