VARIATION IN FEMALE LIFE-HISTORY TRAITS AMONG ALASKAN POPULATIONS OF THE THREESPINE STICKLEBACK, GASTEROSTEUS-ACULEATUS L. (PISCES, GASTEROSTEIDAE)

Life-history characteristics of female threespine stickleback (Gastero steus aculeatus) were examined in 12 populations, 11 freshwater and on e anadromous, within the Cook Inlet region of Alaska. Because this are a has been deglaciated during the last 20 000 years, the freshwater po pulations are recently derived, probably independently, from the local marine or anadromous stickleback. Freshwater threespine stickleback h ave undergone considerable morphological evolution within this region, apparently in response to environmental factors including predatory r egimes and environmental productivity. Our freshwater study population s were selected to sample this range of morphological variation in ord er to determine whether life-history traits and morphologies have foll owed similar evolutionary trajectories. Freshwater populations could b e categorized generally into one of three ecomorphotypes: those inhabi ting relatively productive lakes having one or more piscivorous fishes present, and in which the stickleback exhibit a fully developed pelvi c girdle; those inhabiting low-calcium lakes that lack piscivorous fis hes, and in which the pelvic structures are incomplete; those living i n streams with piscivorous fishes, in which the stickleback have fully developed pelvic girdles. The anadromous population constituted a fou rth ecomorphotype that lives in marine waters, and is robustly armored . The freshwater populations showed considerable variation in all life -history traits assessed, and this variation generally corresponded to our ecomorphological classifications. Nevertheless; within each ecomo rphotype there was sufficient variation to suggest that morphological and life-history traits may not always respond in the same manner in r esponse to the same selective regime. (C) 1997 The Linnean Society of London.