Contemporary evolution of armour and body size in a recently introduced population of threespine stickleback Gasterosteus aculeatus (In English)
Steven M. VAMOSI
D e p a r t m e n t o f B i o l o g i c a l S c i e n c e s , U n i v e r s i t y o f C a l g a r y , C a n a d a
Contemporary introductions of populations into novel environments offer researchers rare opportunities to make inferences about past microevolutionary changes that led to adaptation in populations that historically colonized new habitats. A population of threespine stickleback (Gasterosteus aculeatus L.) has been examined multiple times since its deliberate introduction to Heisholt Lake, British Columbia in 1967 to determine the effects of isolation in freshwater on the relative fitness of the completely plated (CP) morph. Individuals of the CP morph were common in earlier samples (20.3% – 31.7%), and rare in contemporary samples (0% – 5.0%). Latter samples were dominated by the low-plated morph, which is the typical condition in most freshwater populations. I estimated that the rate of evolution of lateral plate number in one of the basins of Heisholt Lake between the period of 1974 and 1997 was –0.029 haldanes, which is lower than most estimates of contemporary evolution in recently introduced or isolated populations of threespine stickleback. Finally, CP individuals from Heisholt Lake were significantly smaller than those in the stream that served as the source for the introduction. Overall, I observed changes in body size and lateral plate number in the introduced population that parallel changes documented in established natural freshwater populations of threespine stickleback, implying that adaptation to the multiple challenges associated with life in freshwater environments may occur rapidly[Acta Zoologica Sinica 52(3): 483–490, 2006].
Body size, Contemporary evolution, Lateral plates, Threespine stickleback, Gasterosteus aculeatus