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Breaking down the lithification bias: the effect of preferential sampling of larger specimens on the estimate of species richness, evenness, and average specimen size

  • Andrew D. Hawkins (a1), Michał Kowalewski (a2) and Shuhai Xiao (a1)

Lithification, the transition of unconsolidated sediments to fully indurated rocks, can potentially bias estimates of species richness, evenness, and body size distribution derived from fossil assemblages. Fossil collections made from well-indurated rocks consistently exhibit lower species richness, lower evenness, and larger average specimen size relative to collections made from unconsolidated sediments, even when collections are drawn from the same assemblage. This phenomenon is known as “lithification bias.” While the bias itself has been demonstrated empirically, much less attention has been paid to its causes. Proposed causes include taphonomic processes (e.g., destruction of small specimens during early diagenesis) and methodological differences (e.g., sieving vs. counting specimens on outcrops, bedding surfaces, or mechanically split surfaces). Here we investigate the potential effects of preferential intersection that could also result in a methodologically related bias: the preferential sampling of larger specimens relative to smaller ones when fossils are counted on rock surfaces. We used an analogue model to simulate preferential intersection (fossil collection via splitting fossiliferous rocks) and compare the results with a random-draw model that approximates the effects of sieving. The model was parameterized using nine different combinations of species abundance and species size distributions. The results show that, with rare exceptions, species richness is 5–23% lower, evenness 5–25% lower, and average specimen size 24–150% larger in preferential-intersection than in random-draw simulations. We conclude that preferential intersection can impose a significant bias independent of other mechanisms (e.g., preferential destruction of smaller specimens during diagenetic or sampling processes), that the magnitude of this bias is partially dependent on the species abundance and size distributions, and that this bias alone does not fully account for empirically observed lithification bias on species richness (i.e., other sources of bias are also at work).

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Alroy, J., Aberhan, M., Bottjer, D. J., Foote, M., Fürsich, F. T., Harries, P. J., Hendy, A. J., Holland, S. M., Ivany, L. C., and Kiessling, W.. 2008. Phanerozoic trends in the global diversity of marine invertebrates. Science 321:97100.
Bulmer, M. 1974. On fitting the Poisson lognormal distribution to species-abundance data. Biometrics 39:101110.
Bush, A. M., and Bambach, R. K.. 2015. Sustained Mesozoic–Cenozoic diversification of marine Metazoa: a consistent signal from the fossil record. Geology 43:979982.
Cherns, L., and Wright, V. P.. 2000. Missing molluscs as evidence of large-scale, early skeletal aragonite dissolution in a Silurian sea. Geology 28:791794.
Cherns, L., and Wright, V. P.. 2009. Quantifying the impacts of early diagenetic aragonite dissolution on the fossil record. Palaios 24:756771.
Daley, G. M., and Bush, A. M.. 2012. How and why does lithification bias biodiversity? A test based on experimental lithification of unconsolidated sediments. Geological Society of America Abstracts with Programs 44:33.
Daley, G. M., and Bush, A. M.. 2014. Lithification does not neccessarily bias diversity: experimental evidence from synthetic rocks. Geological Society of America Abstracts with Programs 46:329.
Fisher, R. A., Corbet, A. S., and Williams, C. B.. 1943. The relation between the number of species and the number of individuals in a random sample of an animal population. Journal of Animal Ecology 12:4258.
Foote, M., Crampton, J. S., Beu, A. G., and Nelson, C. S.. 2015. Aragonite bias, and lack of bias, in the fossil record: lithological, environmental, and ecological controls. Paleobiology 41:245265.
Garvie, C. L. 1996. The Molluscan Macrofauna of the Reklaw Formation, Marquez Member (Eocene, Lower Claibornian), in Texas. Bulletin of American Paleontology 111:1177.
Hendy, A. J. 2009. The influence of lithification on Cenozoic marine biodiversity trends. Paleobiology 35:5162.
Hendy, A. J. 2011. Taphonomic overprints on Phanerozoic trends in biodiversity: lithification and other secular megabiases. Pp. 1977 in P. A. Allison, and D. J. Bottjer, eds. Taphonomy. Springer, New York.
Kidwell, S. M. 2005. Shell composition has no net impact on large-scale evolutionary patterns in mollusks. Science 307:914917.
Kidwell, S. M., and Brenchley, P. J.. 1994. Patterns in bioclastic accumulation through the Phanerozoic: changes in input or in destruction? Geology 22:11391143.
Kowalewski, M., and Hoffmeister, A. P.. 2003. Sieves and fossils: effects of mesh size on paleontological patterns. Palaios 18:460469.
Kowalewski, M., Carroll, M., Casazza, L., Gupta, N. S., Hannisdal, B., Hendy, A., Richard, A. Jr, LaBarbera, M., Lazo, D. G., and Messina, C.. 2003. Quantitative fidelity of brachiopod-mollusk assemblages from modern subtidal environments of San Juan Islands, USA. Journal of Taphonomy 1:4365.
Kowalewski, M., Wood, S. L. B., Kiessling, W., Aberhan, M., Fürsich, F. T., Scarponi, D., and Hoffmeister, A. P.. 2006. Ecological, taxonomic, and taphonomic components of the post-Paleozoic increase in sample-level species diversity of marine benthos. Paleobiology 32:533561.
Li, X., and Droser, M. L.. 1999. Lower and Middle Ordovician shell beds from the Basin and Range province of the western United States (California, Nevada, and Utah). Palaios 14:215233.
McKinney, M. L. 1986. Estimating volumetric fossil abundance from cross-sections: a stereological approach. Palaios 1:7984.
Nawrot, R. 2012. Decomposing lithification bias: preservation of local diversity structure in recently cemented storm-beach carbonate sands, San Salvador Island, Bahamas. Palaios 27:190205.
Peterson, T. D. 1996. A refined technique for measuring crystal size distributions in thin section. Contributions to Mineralogy and Petrology 124:395405.
Pielou, E. C. 1966. The measurement of diversity in different types of biological collections. Journal of Theoretical Biology 13:131144.
Powell, M. G., and Kowalewski, M.. 2002. Increase in evenness and sampled alpha diversity through the Phanerozoic: comparison of early Paleozoic and Cenozoic marine fossil assemblages. Geology 30:331334.
Raup, D. M. 1966. Geometric analysis of shell coiling: general problems. Journal of Paleontology 40:11781190.
Roy, K., Jablonski, D., and Martien, K. K.. 2000. Invariant size–frequency distributions along a latitudinal gradient in marine bivalves. Proceedings of the National Academy of Sciences USA 97:1315013155.
Sanders, M. T., Merle, D., and Villier, L.. 2015. The molluscs of the “Falunière” of Grignon (Middle Lutetian, Yvelines, France): quantification of lithification bias and its impact on the biodiversity assessment of the Middle Eocene of Western Europe. Geodiversitas 37:345365.
Sessa, J. A. 2009. The diversity, ecology, climate, and preservation of marine communities in the twenty million years following the end cretaceous mass extinction. Ph.D. dissertation, Pennsylvania State University, University Park, Penn.
Sessa, J. A., Patzkowsky, M. E., and Bralower, T. J.. 2009. The impact of lithification on the diversity, size distribution, and recovery dynamics of marine invertebrate assemblages. Geology 37:115118.
Wagner, P. J., Kosnik, M. A., and Lidgard, S.. 2006. Abundance distributions imply elevated complexity of post-Paleozoic marine ecosystems. Science 314:12891292.
Warwick, R., and Clarke, K.. 1996. Relationships between body-size, species abundance and diversity in marine benthic assemblages: facts or artefacts? Journal of Experimental Marine Biology and Ecology 202:6371.
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