Restricted gene flow in a moving hybrid zone of the newts Triturus cristatus and T. marmoratus in western France

Abstract

The factors that govern the distribution of cristatus vs. marmoratus in Mayenne, W France are forestation and relief. The parapatric hybrid zone running through Mayenne is narrow but widens to c20 km in an area with mixed habitat, where most breeding sites are shared and F1 hybrids form c4% of the total population. The cristatus-marmoratus hybrid zone bears characteristics of both the clinal (parapatric) hybrid zone model and the mosaic hybrid zone model. Such a mixed model (reticulate hybrid zone) can be appreciated only if studied over a two-dimensional geographic area and also through time. -from Authors