TAXONOMIC IDENTIFICATION AND TYPE I AND II ERROR IN THE BIOLOGICAL RESPONSE TO CLIMATE CHANGE: EXAMPLES FROM FOSSIL BIRDS

As studies of the response of biota to past climate change become more important as proxies for near future responses, scientists must strive to examine and compare biotic data in a consistent manner. Examination of the evolutionary and geographic changes among taxa coincident with climatic change must proceed within an explicit phylogenetic framework. Individuals (fossils, living, or museum specimens) should be placed into identifiable monophyletic units in order to study the potential responses by those organisms through past climate shifts. That approach is necessary because the responses (evolution, extinction, and geographic range changes) are exhibited by groups (with ancestor-descendant relationships) and not by individuals. The application of overall similarity or a phenetic approach for allocating individuals to species level taxa can result in type I and type II error among the hypothesized organismal responses to climate change. Species concepts vary in their application, and it is only the use of an apomorphy based identification system that can reduce those types of error by placing individuals into diagnosable clades. Birds exhibit significant phenological, evolutionary, and geographic responses to climate change of the recent past, and they should have responded in much the same way in the deep past. The extinct Conkling Roadrunner is known from the Pleistocene of Southwestern North America. Previous workers have hypothesized that the Conkling Roadrunner became extinct during the Holocene. Additionally, those workers have suggested that the Conkling Roadrunner and the extant Greater Roadrunner coexisted sympatrically during part of the Holocene. Application of an apormorphy-based identification approach to the Holocene fossils indicates a much different pattern with an earlier extinction followed by much greater change in geographic range. Another exemplar of the need for phylogenetic placement of specimens is the presence of Pleistocene fossils in Texas allocated to the Black-Billed Magpie far outside of its extant geographic range. Depending on the phylogenetic placement of the Texas fossils (at present not known to have species level apomorphies), geographic range change, extinction, or speciation might be supported as the potential response to climate change.