Macrostratigraphy and macroevolution in marine environments: testing the common-cause hypothesis

Quantitative patterns in the sedimentary rock record predict many different macroevolutionary patterns in the fossil record, but the reasons for this predictability remain uncertain. There are two competing, but non-mutually exclusive, hypotheses: (1) similarities reflect a sampling bias imposed by variable and incomplete sampling of fossils, and (2) similarities reflect environmental perturbations that influence both the patterns of sedimentation and macroevolution (i.e., commoncause). Macrostratigraphy, which is based on the quantitative analysis of hiatus-bound rock packages, permits variation in the rock record to be expressed in terms of rock quantity and, more importantly, spatiotemporal continuity. In combination with spatially-explicit fossil occurrence data in the Paleobiology Database, it is now possible to more rigorously test alternative hypotheses for similarities in the rock and fossil records and to start distinguishing between geologically-controlled sampling bias and the common-cause hypothesis. Here we summarize results from measuring the intersection of Macrostrat and the Paleobiology Database. Our results suggest that patterns in the fossil record are not dominated by large-scale stratigraphic biases. Instead, they suggest that linkages between multiple Earth systems are driving both spatiotemporal patterns of sedimentation and macroevolution. Darwin (1872, p. 289) famously described the stratigraphic record as ‘a history of the world imperfectly kept.’ This pessimism towards the stratigraphic record of evolution was articulated for the specific purpose of explaining why palaeontologists had failed to sample the innumerable intermediate forms that Darwin expected in his particular formulation of the theory of evolution by natural selection. Although this view of life is demonstrably misguided and macroevolutionary theory, such as punctuated equilibrium (Eldredge & Gould 1972), now accounts for the abundant non-continuous patterns of evolution that are observed in the fossil record, many palaeobiologists remain skeptical about the fidelity of the fossil record. In particular, there is concern that observed patterns of diversity, origination, and extinction in the fossil record are artifacts of the variable quantity and quality of the Phanerozoic sedimentary rock record. This biasoriented perspective is rooted in the pervasive and strong positive correlations that have been documented between many different tabulations of rock quantity and diversity (Gregory 1955; Raup 1976; Smith 2001; Smith et al. 2001; Peters & Foote 2002; Crampton et al. 2003; McGowan & Smith 2008; Wall et al. 2009). Although past diversity can only be sampled from the incomplete rock and fossil records, it may also be the case that variability in the rock record both reflects and controls fundamental changes in Earth systems that in turn directly and/or indirectly influence the macroevolutionary history of life. This alternative interpretation of the observed co-variation between the fossil and rock records is known as the common-cause hypothesis; that is, there is a common set of processes that have similarly shaped both stratigraphic patterns and biological evolution. The common-cause hypothesis has been discussed, if not formalized, by geologists for many decades. Sloss (1963) recognized that the large-scale variability and nature of the preserved stratigraphic record on the craton primarily reflects tectonically-driven cycles in continental flooding, and not the destruction of sedimentary rocks by erosion and metamorphism (see also Melott & Bambach 2011; Meyers & Peters 2011). Similarly, Newell (1952) proposed that mass extinctions, the large die-offs that he first described as such (Bambach 2006), were driven by sea-level fluctuations that resulted in the geographical spread of unconformities (e.g. Simberloff 1974). The common-cause hypothesis has not, however, been tested with quantitative data until very recently. Initial tests of the common-cause hypothesis against the null hypothesis of stratigraphic and preservation-induced sampling bias have been made using an integration of Macrostrat (http:// macrostrat.org) and the Paleobiology Database From: McGowan, A. J. & Smith, A. B. (eds) Comparing the Geological and Fossil Records: Implications for Biodiversity Studies. Geological Society, London, Special Publications, 358, 95–104. DOI: 10.1144/SP358.7 0305-8719/11/$15.00 # The Geological Society of London 2011. (PaleoDB; http://paleodb.org). Macrostrat contains a summarization of the rock record for several different geographical regions, including (as of February 2011) North America, the circumCaribbean, New Zealand, and the deep-sea. Macrostrat is continually growing and improving, but here we use data consisting of 15 773 formation-level lithostratigraphic units from a spatial array of 831 stratigraphic columns in the USA, Canada, Caribbean, eastern Mexico and northern South America (Fig. 1). The PaleoDB is global in scope and contains fossil occurrences that are reported in the primary literature and by individual field investigators. Because both the PaleoDB and Macrostrat contain information on geographical location and basic lithostratigraphic data (Fig. 1a, b), PaleoDB fossil collections located in the study area are matched to specific units in Macrostrat on the basis of time and lithostratigraphy (see Peters & Heim 2010 for full descriptions of the matching procedures). In essence, the fossil record, at least as represented in the PaleoDB, has been returned to its original stratigraphic context, at least as captured by Macrostrat. With this unique integration of large-scale stratigraphic and palaeobiologic data, the common-cause hypothesis can be more rigorously tested against the null hypothesis of stratigraphic bias. Here we explore a few of these tests using the analytical framework of macrostratigraphy.