The different crested newt species typically have very distinct mitochondrial DNA. However, as these guys hybridize like rabbits, often the mitochondrial DNA of one species has locally been transferred (introgressed) into the wrong species. ‘Locally’ can refer to quite an extensive range actually. Species distribution modelling of distinct geographical populations, only recognizable based on DNA divergence, is a good way to test whether they represent cryptic species – multiple species erroneously classified as a single one because no one previously realized they were distinct. However, if you would use mitochondrial DNA to identify the putative species, introgression would cause misidentifications and could lead to under- or overestimation of the ecological niche of the putative species. We explore this problem in a paper just out in PLoS ONE.

This figure shows the setting in which we test the effect of introgressed mitochondrial DNA on niche estimation. The two areas with red dot on the wrongly colored background are causing trouble. If using mitochondrial DNA as a guidance, you would interpret these localities as beloning to the red species, while excluding them from the green or blue species.

Reference: Wielstra, B., Arntzen, J.W. (2014). Exploring the effect of asymmetric mitochondrial DNA introgression on estimating niche divergence in morphologically cryptic species. PLoS ONE 9(4): e95504.

I conducted this work as a Newton International Fellow.