Figure 1.
The potential effect of asymmetric mtDNA introgression on estimating the niche divergence of species.
Schematic with two species shown in blue and in red, mtDNA shown by hard colors inside symbols, nuDNA shown by soft colors in the background, and range sections shown as I, II and III. In (a) the two species possess their own mtDNA in range sections I and III whereas in range section II the blue species possesses mtDNA of the red species. Treating mtDNA as species diagnostic overestimates the range of the red species. The other two panels illustrate environmental conditions under which species niche divergences are flawed by following the mtDNA guidance. Note the difference in occupied niche space in range section II that under scenario (b) results in an underestimate of the true species niche divergence and yields an overestimate in scenario (c).
Figure 2.
Map showing ranges and localities of three Triturus species in SE Europe and adjacent Asia.
The ranges shown by light shading reflect nuDNA composition, whereas the localities shown by dots reflect the observed mtDNA type. In part of their ranges both T. macedonicus and the candidate species possess mtDNA derived from T. ivanbureschi [22], [36]. Five range sections are recognized: range section A where T. macedonicus possesses species-specific mtDNA, range section B where T. macedonicus possesses introgressed mtDNA, range section C where T. ivanbureschi possesses species-specific mtDNA, range section D where the candidate species possesses introgressed mtDNA, and range section E where the candidate species possesses species-specific mtDNA.
Figure 3.
Scatterplot for the first and second axis in a principal component analysis of bioclimatic values.
Filled circles represent species with species-specific mtDNA with T. macedonicus in green, T. ivanbureschi in red and the candidate species in blue. The grey x and+represent T. macedonicus and the candidate species with introgressed mtDNA. In (a) the T. macedonicus case and in (b) the candidate species case is presented. Ellipses represent mean values plus and minus one standard deviation.
Table 1.
Differences in environmental space as defined from principal component analysis.
Figure 4.
Species distribution models for the three Triturus species.
Species distribution models as delineated based on nuDNA (left) or mtDNA (right). Species’ ranges are outlined in white lines (cf. Fig. 2).
Table 2.
Differences in the geographical overlap of species distribution models.