Relaxed predation selection on rare morphs of Ensatina salamanders (Caudata: Plethodontidae) promotes a polymorphic population in a novel dune sand habitat

The Ensatina ring species represents a classic example of locally adapted lineages. The Monterey Ensatina (Ensatina eschscholtzii eschscholtzii) is a cryptic subspecies with brown coloration, however, a recently discovered polymorphic population within a wind-blown sand region also contains leucistic (pink) and xanthistic (orange) morphs. Leucism/xanthism frequency was mapped across the subspecies’ range revealing that these morphs are generally rare or absent except within regions containing light-colored substrate. Attack rates were estimated using clay models of the three morphs, deployed only at the crepuscular period and during the night, on both light and dark substrates at a site within the dune sand region. Model selection found that the interaction between morph and substrate color best predicted attack rates. Typical morphs had equal attack rates on both substrates while xanthistic and leucistic morphs incurred significantly fewer attacks on light versus dark substrate, and th...