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Incumbency, diversity, and latitudinal gradients

¹ James W. Valentine. Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, California 95720. jwvsossi@socrates.berkeley.edu
² David Jablonski and Andrew Z. Krug. Department of Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637. djablons@uchicago.edu, akrug@uchicago.edu
³ Kaustuv Roy. Section of Ecology, Behavior and Evolution, Division of Biological Sciences, University of California, San Diego, 9500 Gillman Drive, La Jolla, California 92093. kroy@biomail.ucsd.edu

Accepted 5 November 2007

The first 20% of the full text of this article appears below.

Physical environmental factors have been seen as paramount in determining many large-scale biodistributional patterns in time and space. Although this is probably correct for many situations, this view has become so pervasive that it has led to the neglect of the role of biotic interactions in setting large-scale diversity patterns. (In this paper diversity denotes taxonomic richness.) New approaches to this perennial debate on the roles of physical and biotic forces in paleoecology and macroevolution are needed, and here we explore an argument for the role of incumbency or priority effects in the dynamics behind the most dramatic spatial pattern in biodiversity, the latitudinal diversity gradient.

A global analysis of the fossil record of living marine bivalve genera and subgenera (hereafter simply genera) of the continental shelves provides perhaps the strongest evidence for the Out of the Tropics (OTT) dynamic associated with the formation of the present marine latitudinal diversity gradient (LDG) (Jablonski et al. 2006). The marine LDG appears to be driven primarily by the origin of novel lineages in the Tropics, some of which then expand their ranges into higher, extratropical latitudes (see Jablonski 1993, 2005; Clark and Crame 2003; Goldberg et al. 2005; Jablonski et al. 2006; Martin et al. 2007). Support for this pattern comes from the overwhelmingly tropical first fossil occurrences of living bivalve genera and their subsequent appearances in higher latitudes. Some genera are first found in the extratropical fossil record, but these never match, at any latitude, the number or proportion of genera that have expanded from the Tropics (the ratio is generally 3:1), and even this smaller number is probably an overestimate, because the extratropical post-Paleozoic fossil record is so much better sampled than that of the Tropics (Allison and Briggs 1993; . . . [Full Text of this Article]

This article has been cited by other articles:

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