DIFFERENTIAL NICHE DYNAMICS AMONG MAJOR MARINE INVERTEBRATE CLADES

Niche conservatism, or the tendency for a taxon’s niche to remain stable over time, has the potential to influence numerous aspects of ecology and evolution. In addition, the degree to which organisms retain their environmental preferences is of utmost importance in predicting their fate in a world of rapid climate change. Nonetheless, only a few studies have looked at niche conservatism in marine systems, even though they face similar environmental challenges from global climate change, habitat fragmentation, and invasive species, as terrestrial systems. Here we present the first global analysis of niche conservatism in marine invertebrate taxa. We estimated habitat affinities of marine invertebrate genera and using occurrence data from the Paleobiology Database and Bayesian inference. We found that niche conservatism is prevalent in the oceans, and largely determined by the strength of initial environmental preference. There is also substantial variation in niche conservatism among major clades, with corals and sponges at the most conservative end of the spectrum. Correlation with geological proxy data suggest that niche conservatism is linked to nutrient flux and is enhanced during times of elevated nutrient flux, whereas niche shifts tend to occur after mass extinctions or during periods of widespread change in relative habitat availability. Although there is a significant correlation between species turnover and niche shifts over time, most shifts seem to be governed by adaptation within species.