Individuals that fail in the very basic task of recognizing conspecifics are clearly disadvantaged - thus there is a strong selection pressure for optimal species recognition. Why may this ability be affected by a learning process? After all, the learned features seem categorical and quite straightforward (i.e., conspecific/heterospecific), so why is not this knowledge inherited rather than learned? Although the categories to be distinguished remain distinct, there is considerable variation within the categories. Species-typical properties might change over space and time, as might the environment. Inheriting species recognition is hence potentially disadvantageous, because a change in the gene frequencies of the inherited recognition will be much slower than learning the change in species appearance. A genetically inherited behavior thus gives less flexibility, and inflexible individuals may thus miss out on mating opportunities if they do not recognize a novel conspecific morph. Learning from parents or other tutors may enable the animal to track such changes when they appear, and hence to develop adequate preferences. An advantage of learning mate preferences through imprinting is thus that it offers some flexibility in the face of stochastic events. However, the flexibility offered by learning can also be costly. Ifan animal imprints on the wrong kind ofstimulus object, it might end up courting heterospecifics. Erroneous species recognition may result in futile hybrid mating, or no mating at all. Also, forgetting and relearning of mate recognition in the course of an individual life span may be disadvantageous because repeated stimulus object choice could introduce errors. Imprinting trades off the mixed blessings of flexibility. It limits the error potential of learning by optimizing the timing of the event relative to the presence of adequate stimulus objects. Further, imprinting minimizes the number of learning events and limits learning duration. Note, however, that there seem to be species differences in the degree of sexual imprint-ability, which indicates that the selection pressure favoring a somewhat flexible species recognition is not universal.
Sexual imprinting may also have a function in kin recognition. For instance, quails of both sexes develop a preference for the phenotype of distant relatives of the opposite sex. Kin recognition is advantageous for many reasons, not least optimization ofmate choice with regard to inbreeding and outbreeding.
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