Low beta diversity of Maastrichtian dinosaurs of North America - PubMed (original) (raw)

Low beta diversity of Maastrichtian dinosaurs of North America

Matthew J Vavrek et al. Proc Natl Acad Sci U S A. 2010.

Abstract

Beta diversity is an important component of large-scale patterns of biodiversity, but its explicit examination is more difficult than that of alpha diversity. Only recently have data sets large enough been presented to begin assessing global patterns of species turnover, especially in the fossil record. We present here an analysis of beta diversity of a Maastrichtian (71-65 million years old) assemblage of dinosaurs from the Western Interior of North America, a region that covers approximately 1.5 x 10(6) km(2), borders an epicontinental sea, and spans approximately 20 degrees of latitude. Previous qualitative analyses have suggested regional groupings of these dinosaurs and generally concluded that there were multiple distinct faunal regions. However, these studies did not directly account for sampling bias, which may artificially decrease similarity and increase turnover between regions. Our analysis used abundance-based data to account for sampling intensity and was unable to support any hypothesis of multiple distinct faunas; earlier hypothesized faunal delineations were likely a sampling artifact. Our results indicate a low beta diversity and support a single dinosaur community within the entire Western Interior region of latest Cretaceous North America. Homogeneous environments are a known driver of low modern beta diversities, and the warm equable climate of the late Cretaceous modulated by the epicontenental seaway is inferred to be an underlying influence on the low beta diversity of this ancient ecosystem.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Fig. 1.

Approximate locations of Maastrichtian-aged dinosaur-bearing formations from the Western Interior of North America used in this analysis. (A) Abbreviations of formation names are as follows: A, Aguja; D, Denver; Fe, Ferris; Fr, Frenchman; HM, Hell Creek Montana; HN, Hell Creek North Dakota; HS, Hell Creek South Dakota; HC, Horsehshoe Canyon; J, Javelina; Kp, Kaiparowits; Kd, Kirtland; LM, Lance Montana; LS, Lance South Dakota; LU, Lance Utah; LW, Lance Wyoming; LaC, Laramie Colorado; Law, Laramie Wyoming; M, McRae; N, North Horn; P, Pinyon Conglomerate; Sc, Scollard; SA, St. Mary's River Alberta; SM, St. Mary's River Montana; T, Tornillo Texas. (B) Locations of occurrences of the three indicator taxa, Alamosaurus (A), Leptoceratops (L), and Triceratops (T). Greyed area to the east is the approximate location of the inland seaway.

Fig. 2.

Fig. 2.

Comparison of methods of sample size correction. (A) Smoothed curves for rarefaction using Coleman's random placement method, up to n = 100. (B) Smoothed curves for Chao 1 values up to n = 100. (C) ACE values. (D) Jacknife 1 values.

Fig. 3.

Fig. 3.

Relative pairwise similarities between localities. (A) Map of the localities used in the analysis with an MST added to indicate the relative similarities between localities. The more similar two localities are to one another on the basis of the species present, the darker the line connecting them will be. Note that no clusters are formed, and many localities are more similar to far-ranging ones than neighboring localities. (B) Plot of the relative positions of an NMDS of the localities, showing no apparent clusters. (C) Pairwise dissimilarity of sites in comparison with their geographic distance from one another. As dissimilarity increases, the sites are interpreted to be less similar to one another. The line represents a locally weighted sum of squares function. The sites show a slight decay over distance, although a linear regression is not significantly different from 0. These graphs indicate low beta diversities for this assemblage. Abbreviations as defined in Fig. 1.

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