PARENT SESSION
Symposium #29: Scaling the implications of organismal size across evolutionary time and ecological space: A synthesis of recent advances and insights..
Organized by: BJ Enquist, F Smith, and PA Marquet
Thursday, August 8. 1:00 PM to 3:45 PM. Crystal Ballroom, TCC.
Macroecology of body size: a marine perspective.
Roy, Kaustuv*,1, Jablonski, David2, 1 Section of Ecology, Behavior & Evolution, La Jolla, CA 92037-01162 Department of Geophysical Sciences, Chicago, IL 60637
ABSTRACT- Size-frequency distributions (SFDs) of species within assemblages or clades represent macroecological and macroevolutionary expression of the forces operating on body sizes over large temporal and spatial scales, and several models have attempted to explain the shapes of these distributions. However, most of these insights are based on data from terrestrial vertebrates and their applicability to aquatic invertebrates remains uncertain. We analyzed living and fossil marine invertebrates to show that: (i) for marine bivalves and echinoderms interspecific size frequency distributions are either left-skewed or log normal, in contrast to the right-skewed distributions characteristic of vertebrates. This difference is consistent with the predictions of an energetic model of body size evolution and could reflect differences in life history scaling. Furthermore data from the fossil record show that modal size as well as the range of bivalve SFD has been stable since the Miocene. (ii) The SFDs of northeastern Pacific bivalves at the provincial level are surprisingly invariant despite a four-fold change in species richness from the tropics to the Arctic. (iii) Despite the constancy of the modal size in time and space, molluscan lineages do not preferentially evolve toward that size category. (iv) However, body size plays an important role in mediating the responses of marine bivalves to climate change. A comparison of Pleistocene and Recent distributional patterns along the NE Pacific coast reveals that large-bodied bivalves preferentially shifted their range limits in response to glacial-interglacial climatic changes. In addition, successful invasive species of bivalves in present-day marine habitats also tend to be large-bodied, as do invaders following the end-Cretaceous mass extinction, further indicating that body size and its correlates need to be considered when attempting to predict the responses of marine communities to climate change, biotic interchanges, and human-mediated invasions.
KEY WORDS: Body size, marine invertebrates, climate change