One consequence of animal movement and dispersal is gene flow between populations. Gene flow is generally thought to limit local adaptation and population divergence, since local selection is opposed by the homogeneising effects of gene flow. In spite of this, we often find that populations differ in morphological, physiological and behavioural traits, and one way why such population divergence can be achieved is through adaptive phenotypic plasticity. In terms of behavioural traits, it is increasingly being recognized that learning can be important, particularly when it comes to population divergence of mate preferences.
We have studied the effects of learning on the development of female mate preferences in a charismatic insect species: the banded demoiselle (Calopteryx splendens). Males of different species in these calopotergid damselflies are well-known for their enigmatic melanized wing patches, which serve multiple ecological functions, including mate recognition and species recognition for females.
Recently, we have showed that female mate preferences are not entirely genetic, but are partly learned, and develops in females as a result of physical pre-mating interactions and/or during mating with males. The result of this learning is that populations that are even close to each other and hence experience a lot of gene flow in between them, can diverge substantially in mate preferences, due to such learning. It is interesting that even these small insects have such advanced cognitive ability so that they can actually learn whom to mate with, and who is the wrong mate! Our paper has recently been published in the journal Evolution, where we also contributed with the cover photo of a male banded demoiselle aggressively defending his valuable territory (a water lilly). Our article was also covered by the popular science site and media outlet Science Daily.
Below is the link to the article and the abstract:
A ROLE FOR LEARNING IN POPULATION DIVERGENCE OF MATE PREFERENCES
Erik I. Svensson, Fabrice Eroukhmanoff, Kristina Karlsson, Anna Runemark & Anders Brodin
Learning and other forms of phenotypic plasticity have been suggested to enhance population divergence. Mate preferences can develop by learning, and species recognition might not be entirely genetic. We present data on female mate preferences of the banded demoiselle (Calopteryx splendens) that suggest a role for learning in population divergence and species recognition. Populations of this species are either allopatric or sympatric with a phenotypically similar congener (C. virgo). These two species differ mainly in the amount of wing melanization in males, and wing patches thus mediate sexual isolation. In sympatry, sexually experienced females discriminate against large melanin wing patches in heterospecific males. In contrast, in allopatric populations within the same geographic region, females show positive (“open-ended”) preferences for such large wing patches. Virgin C. splendens females do not discriminate against heterospecific males. Moreover, physical exposure experiments of such virgin females to con- or hetero-specific males significantly influences their subsequent mate preferences. Species recognition is thus not entirely genetic and it is partly influenced by interactions with mates. Learning causes pronounced population divergence in mate preferences between these weakly genetically differentiated populations, and results in a highly divergent pattern of species recognition at a small geographic scale.
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