Data from: The evolution of colour polymorphism in British winter‐active Lepidoptera in response to search image use by avian predators

Phenotypic polymorphism in cryptic species is widespread. This may evolve
in response to search image use by predators exerting negative
frequency‐dependent selection on intraspecific colour morphs, “apostatic
selection”. Evidence exists to indicate search image formation by
predators and apostatic selection operating on wild prey populations,
though not to demonstrate search image use directly resulting in apostatic
selection. The present study attempted to address this deficiency, using
British Lepidoptera active in winter as a model system. It has been
proposed that the typically polymorphic wing colouration of these species
represents an anti‐search image adaptation against birds. To test (a) for
search image driven apostatic selection, dimorphic populations of
artificial moth‐like models were established in woodland at varying
relative morph frequencies and exposed to predation by natural populations
of birds. In addition, to test (b) whether abundance and degree of
polymorphism are correlated across British winter‐active moths, as
predicted where search image use drives apostatic selection, a series of
phylogenetic comparative analyses were conducted. There was a positive
relationship between artificial morph frequency and probability of
predation, consistent with birds utilising search images and exerting
apostatic selection. Abundance and degree of polymorphism were found to be
positively correlated across British Lepidoptera active in winter, though
not across all taxonomic groups analysed. This evidence is consistent with
polymorphism in this group having evolved in response to search image
driven apostatic selection and supports the viability of this mechanism as
a means by which phenotypic and genetic variation may be maintained in
natural populations.