IS IT WHAT’S ON THE INSIDE THAT COUNTS? LITHIFICATION BIAS AND COMMUNITY PALEOECOLOGY IN CARBONATE SETTINGS

To examine the effects of lithification bias on our interpretation of fossil community functional ecology, I sampled three classes of storm-beach deposits in different stages of lithification. Samples were taken from an outcrop along Sand Dollar Beach on San Salvador Island, the Bahamas, consisting of samples from deposits of unlithified storm-beach sand, poorly lithified limestone, and heavily lithified calcarenite. Rapid lithification in the region is evident from radiocarbon dates which indicate the rocks of this sequence date to 80 years B.P. for the oldest rocks (the lithified calcarenite), effectively controlling for the influence of possible confounding variables such as climate fluctuations or local extinctions. Taxa present in the three stages were counted and identified to the highest possible taxonomic level, and then quantified using a 12-dimensional quantitative ecospace framework. I assessed the possibility that high functional redundancy (the presence of more than one species in a given ecospace) increases paleoecological signal fidelity through lithification (by increasing the chance that at least one representative of a given ecospace will be preserved). Ecospace models for each lithification class were compared visually using non-metric multidimensional scaling, and quantitatively using Jaccard-Chao dissimilarity. Results suggest that despite loss of diversity and abundance data through lithification, the presence of ecological redundancy results in a similar estimate of total ecospace disparity across all classes. This fidelity is even higher in the poorly lithified rock, which showed effectively identical ecospace estimates, and similar taxonomic composition and abundances as the unlithified sand, supporting previous findings that community-level studies should focus on poorly lithified rock where possible.