Cryptic Species and Their Evolutionary Significance

Abstract Cryptic species are detected at an ever‐increasing rate, mainly due to the application of molecular data. While the impact of this hidden diversity on macro‐ecology and conversation biology is widely recognized, its evolutionary significance is rarely. In recent years, it became apparent that definitions of cryptic species are too ambiguous to allow the differentiation between natural phenomena from human‐made artefacts. Hence, recently, a unifying conceptual framework has been proposed highlighting the necessity to test the degree of reduced phenotypic disparity in cryptic species. Within this reduced disparity also lies the evolutionary significance, as cryptic species can be regarded as the opposite of adaptive radiations. Specifically, studies on evolutionary stasis can substantially benefit from including these by addressing both patterns of reduced disparity and processes resulting in the lack of phenotypic evolution. In addition, this will allow connecting macro‐evolutionary and paleontological studies with micro‐evolutionary investigations of genotype‐phenotype linkage. Key Concepts Cryptic species are phenotypically highly similar species. Species complexes resulting from taxonomic artefacts should not be considered as cryptic species. To identify cryptic species, first one should establish species boundaries and only then study processes resulting in phenotypic similarity. Cryptic species could result from recent speciation, parallelism, convergence or stasis. Evolution of cryptic species through stasis holds the potential to enlighten us about deceleration of phenotypic evolution. Cryptic species (shallow morphological differences, pronounced genetic divergence) could be considered as the opposite of adaptive radiation (pronounced morphological differences, shallow genetic divergence).