Myxomatous mitral valve disease in Miniature Schnauzers and Yorkshire Terriers: 134 cases (2007-2016).

Objective: To characterize features of myxomatous mitral valve disease (MMVD) in Miniature Schnauzers and Yorkshire Terriers.

Animals: 69 Miniature Schnauzers and 65 Yorkshire Terriers, each with MMVD.

Procedures: Medical record data for each dog were collected; the study period was January 2007 through December 2016.

Intraspecific adaptive radiation: Competition, ecological opportunity, and phenotypic diversification within species.

Intraspecific variation in resource-use traits can have profound ecological and evolutionary implications. Among the most striking examples are resource polymorphisms, where alternative morphs that utilize different resources evolve within a population. An underappreciated aspect of their evolution is that the same conditions that favor resource polymorphism-competition and ecological opportunity-might foster additional rounds of diversification within already existing morphs.