Variation in life history traits of organisms is thought to reflect adaptations to environmental forcing occurring from bottom-up and top-down processes. Such variation occurs not only among, but also within species, indicating demographic plasticity in response to environmental conditions. From a broad literature review, we present evidence for ocean basin- and large marine ecosystem-scale variation in intra-specific life history traits, with similar responses occurring among trophic levels from relatively short-lived secondary producers to very long-lived apex predators. Between North Atlantic and North Pacific Ocean basins, for example, species in the Eastern Pacific exhibited either later maturation, lower fecundity, and/or greater annual survival than conspecifics in the Western Atlantic. Parallel variations in life histories among trophic levels also occur in adjacent seas and between eastern vs. western ocean boundaries. We hypothesize that such dichotomies result from frequency and amplitude shifts in resource availability over varying temporal and spatial scales. We propose three primary mechanisms by which environmental forcing affects life history strategies: (1) food-web structure; (2) climate variability affecting the quantity and seasonality of primary productivity; (3) bottom-up vs. top-down forcing. These proposed mechanisms provide a framework for comparisons of ecosystem function among oceanic regions (or regimes) and are essential in modeling ecosystem response to climate change, as well as for creating dynamic ecosystem-based marine conservation strategies .
Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia
Center for Applied Biodiversity Science, Conservation International, Arlington, Virginia
U.S. Geological Survey, Alaska Science Center, Anchorage, Alaska
National Environmental Research Institute, University of Aarhus, Roskilde, Denmark
Centre for Ecology and Hydrology, Edinburgh, UK
Publications and Reports:
Suryan, R.M., V.S. Saba, B.P. Wallace, S.A. Hatch, M. Frederiksen, and S. Wanless. 2009. Environmental forcing on life history strategies: Evidence for multi-trophic level responses at ocean basin scales. Progress in Oceanography, 81:214-222, doi:10.1016/j.pocean.2009.04.012.