Life-history strategies of calanoid congeners under two different climate regimes: a comparison

To evaluate the relationship between different environmental temperature regimes and life-history traits of key planktonic taxa, the life cycles of congener pairs of Temora and Centropages species at two sites, a cold-temperate shelf sea (Helgoland Island, North Sea) and a warm-temperate oceanic site (Bay of Villefranche, Mediterranean) were compared in a multi-annual time-series. In an attempt to assemble a variety of parameters - some detailed, others sporadically measured - a synthesis of the life cycle is presented for each population. Although closely related, congeners showed distinct temperature preferences and specific adaptations of their life cycles to temperature regime. On the other hand, co-existing species such as T longicornis and C. hamatus in the North Sea showed some analogous life-history traits. C. typicus occupied an intermediate position and was able to tolerate both temperature regimes by shifting its reproductive period between seasons. We point out interannual and inter-site variability in the populations investigated and identify the unsolved questions in regard to the seasonal dynamics of these species that require verification, (C) 2004 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.