The roles of mass extinction and biotic interaction in large-scale replacements: a reexamination using the fossil record of stromboidean gastropods

-The macroevolutionary processes underlying large-scale biotic replacements are still poorly understood. Opinion remains divided regarding the roles of mass extinction, biotic interaction, and environmental perturbations in these replacement events. Previous attempts to test replacement hypotheses have largely focused on taxonomic diversity patterns. Taxonomic data alone, however, provide little insight about ecological interactions and hence other approaches are needed to understand mechanics of biotic replacements. Here I propose a conceptual model of replacement based on predation-mediated biotic interactions, and attempt a test using analysis of the Cenozoic replacement of the gastropod family Aporrhaidae by a closely related group, the Strombidae. Taxonomic, morphologic, and geographic data analyzed in this study all suggest a replacement of aporrhaids by strombids following the end-Cretaceous mass extinction. While most of the taxonomic replacement was associated with a mass extinction, some replacement also occurred during background times and was mediated by higher origination rates in strombids rather than by higher extinction rates in aporrhaids. Morphologically, the replacement was largely confined to the portion of the morphospace unaffected by the end-Cretaceous extinction. At a global scale, the geographic overlap between the two groups declined through the Cenozoic, reflecting increasing restriction of aporrhaids to colder, temperate waters while strombids flourished in the tropics. However, at a finer geographic scale a more mosaic pattern of replacement is evident and coincides with Eocene and Oligocene climatic fluctuations. The results of this study suggest that mass extinction, long-term biotic interaction, and environmental change can all play significant roles in biotic replacements. Since the relative importance of each factor would vary from one event to another, an understanding of the general nature of large-scale biotic replacements requires a knowledge of the relative intensities of each of these processes. Kaustuv Roy. Department of Biology, 0116, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-01 16 Accepted: February 20, 1996 Introduction discussion in Allmon 1994). A similar debate The replacement of one major group of oralso exists regarding the role of mass extincganisms by another has been a recurrent feations in biotic replacements. The common poture in the history of life. While a number of sition in this regard has been that mass exsuch replacements have been documented, littinctions are important in mediating replacetie is known about the underlying evolutionments as reduce the estabary mechanisms. In particular, the role of bilished groups and hence provide taxa a otic interactions in replacements is still debatchance to radiate (e.g., Benton 1987, 1991; Jaed (see Benton 1987, 1991 for review). While blonski 1989; Hallam 1990; Rosenzweig and some workers have argued that ecological McCord 1991). Some workers, however, recompetition plays a negligible role in largemain skeptical, and such a role for extinction scale replacements (e.g., Raup et al. 1973; has recently been challenged from a concepGould and Calloway 1980; Benton 1987,1991; tual perspective (Masters and Rayner 1993). Masters and Rayner 1993), others have posA significant obstacle to resolving this detulated a more central role for biotic interacbate is methodological. Most of the debate on tion (Stanley and Newman 1980; Krause 1986; large-scale replacements is based either on Jackson 1988; Maas et al. 1988; Miller and Sepconceptual arguments or on taxonomic diverkoski 1988; Rosenzweig and McCord 1991; sity patterns (e.g., Gould and Calloway 1980; Lidgard et al. 1993; Van Valen 1994; also see Benton 1987,1991; Masters and Rayner 1993).