Abrupt changes in defence and trophic morphology of the giant threespine stickleback (Gasterosteussp.) following colonization of a vacant habitat

Abstract

(8%: 0.5%), lateral plate 2 frequency (46%: 17%), lateral plate 3 height (17%: 18%), pelvic spine length (12%: 6%), dorsal spine length (21%: 16%), gill raker number (5%: 1%), and gill raker length (37%: 43%), and an increase in gill raker spacing (+5%: 0%), jaw length (+5%: +4%), and eye diameter (+8%: +7%). These changes within eight generations represent one-third of the morphological differences observed between naturally established large lake and pond populations in these archipelago and are all in the direction predicted from the change in habitat. Field samples indicate strong selection in the colonists although lab-reared individuals implicate an additional role of plasticity for dorsal spine and gill raker lengths, which may contribute to the rapid adaptation into novel and highly divergent selective landscapes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 494‐509. ADDITIONAL KEYWORDS: benthic adaptation ‐ freshwater colonization ‐ Gasterosteidae ‐ gigantism ‐ Haida Gwaii ‐ Haldanes ‐ macroinvertebrate ‐ plasticity ‐ rapid evolution ‐ selective landscape.