Covariation in shape and foraging behaviour in lateral plate morphs in the three-spined stickleback

In three-spined stickleback (Gasterosteus aculeatus) colonisation of freshwater has led to rapid evolution in various morphological and behavioural traits. Examples are reduction in lateral plate number and increased benthic foraging. These changes are believed to result from natural selection, but the evolutionary mechanisms driving behavioural changes and how such changes are associated with phenotypes, are poorly understood. Here, we study three different lateral plate morphs from a brackish water lake and one morph from a river upstream. We investigate if the lateral plate morphs differ in overall body shape and then experimentally test how foraging behaviour differ among morphs and with body shape. Foraging behaviour is measured as the consumption efficiency of benthic and pelagic prey types. The results show that lateral plate morphs differ in overall body shape and that body shape significantly co-varies with foraging behaviour.