Evol Ecol Res 5: 759-779 (2003)     Full PDF if your library subscribes.

Of rats and Maoris: a novel method for the analysis of patterns of extinction in the New Zealand avifauna before European contact

Derek A. Roff* and Robin J. Roff

Department of Biology, University of California, Riverside, CA 92521, USA

Author to whom all correspondence should be addressed.
e-mail: derek.roff@ucr.edu


The avifauna of New Zealand underwent a large-scale extinction event before its discovery by Europeans. This extinction coincides with the colonization of New Zealand by the Maoris and it is currently thought that the decimation of the avifauna was a direct and indirect effect of this colonization. Some species were eliminated through direct hunting, while others probably fell prey to the pacific rat, Rattus exulans, which was introduced by the Maoris. The destruction of habitat by both the Maoris and the pacific rat may have also played a role. To date, there has been no systematic statistical analysis of the factors that characterize the species that went extinct and those that persisted. In this paper, we introduce a novel statistical approach, the regression tree, for the analysis of such data. The purpose of the analysis is to generate a hierarchical predictive tree. The method establishes predictive characteristics from which causal mechansims can be hypothesized. Using regression tree analysis, we identify four main patterns in the avifaunal extinctions: (1) very large (> 3.75 kg) bird species all went extinct (whether volant or flightless); (2) the probability of flightless species less than 3.75 kg going extinct decreased with body size; (3) volant species nesting in cavities in the ground (petrels) showed a qualitatively similar pattern (i.e. probability of extinction decreased with body size); (4) in contrast, the probability of volant species nesting in other sites going extinct increased with body size. We discuss possible mechanisms that could generate these patterns.

Keywords: extinction, logistic regression, Maoris, pacific rat, regression trees.

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