Introduction to Comparisons among Taxa at the Level of Species, Genus and Family

Abstract

The power of landmark-based morphometries lies in their potential for comparative description. Description has been the cornerstone of comparative biology for the past 200 years, so it might seem at least superficially, that the new landmark-based methods don't provide biologists with anything they didn't have already. Ironically, nothing could be further from the truth. Geometric morphometries allow us to recognize features of organisms that we may previously not have noticed by providing analytical and graphical means to decompose variation into components that reflect differences at different spatial scales. At one end of the scale, these components reflect shape differences that are restricted to highly localized subregions, at the other, they reflect differences that are globally and diffusely spread over the entire form. In essence the new methods provide a set of filters that can be used, individually or in combination, to sequester particular aspects of the ensemble morphological variation so as to leave a clearer, less confounded view of the aspects that remain.