PARENT SESSION
Symposium 5: Marine macroecology
Organized by: JD Witman and K Roy
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 517 B, Level 5, Palais des congrès de Montréal

Historical underpinnings of marine macroecological relationships.

Roy, Kaustuv^*,1, Valentine, James², Hunt, Gene¹, ¹ University of California, San Diego, La Jolla, CA, USA² University of California, Berkeley, Berkeley, CA, USA

ABSTRACT- It is generally acknowledged that historical processes such as past extinctions, originations and shifts in geographic distributions of taxa are important determinants of macroecological relationships observed in modern ecosystems. However, the exact roles of historical processes in generating specific macroecological relationships remain poorly explored. Data from the marine fossil record, in conjunction with phylogenetic analyses, provide an excellent means to explore the roles historical processes have played in generating various macroecological relationships, ranging from shapes of size frequency distributions to relationships between species richness and environmental variables. For example, among the macroecological hypotheses proposed to explain global variation in species richness, the species-energy hypothesis has emerged as a leading contender, and the relationships between present day environmental variables (e.g. temperature and primary productivity) and species richness have been investigated for a number of organisms, ranging from trees to coral reefs. However, whether such correlations are sufficient to demonstrate that current environmental factors are the main determinants of species richness of a region remains a subject of considerable debate. The alternative is that historical processes such as speciation, extinction or other past events unique to each area are the main determinants of present day species richness and the correlation with present climate may not necessarily imply causation. Testing between these alternatives remains a difficult problem but here we show that data from the Quaternary fossil record, which represent natural experiments involving changes in climate across glacial-interglacial cycles, are particularly useful for separating the historical versus ecological explanations of species-energy relationships. Similarly, competing hypotheses about the evolution of species body size distributions can be tested using data from the Cenozoic fossil record, analyzed in a phylogenetic context.

Key words: macroecology, marine, species richness, body size