T. cristaus and T. marmoratus (marbled newts) overlap in some areas in France where their habitat preferences overlap; this allows them to hybridize. T. cristaus has been known to occupy increasingly larger areas due to climate change fragmenting the habitat of the marbled newt. Despite the loss of habitat, the marbled newt has experienced more reproductive success.
In certain areas of France, the habitats of T. cristaus and T. marmoratus (marbled newts) overlap, allowing them to interbreed. Despite climate change leading to habitat fragmentation for the marbled newt, it has still experienced increased reproductive success.