Character Selection During Interactive Taxonomic Identification: “Best Characters”

Software interfaces for interactive multiple-entry taxonomic identification (polyclaves) sometimes provide a “best character” or “separation” coefficient, to guide the user to choose a character that could most effectively reduce the number of identification steps required. The coefficient could be particularly helpful when difficult or expensive tasks are needed for forensic identification, and in very large databases, uses that appear likely to increase in importance. Several current systems also provide tools to develop taxonomies or single-entry identification keys, with a variety of coefficients that are appropriate to that purpose. For the identification task, however, information theory neatly applies, and provides the most appropriate coefficient. To our knowledge, Delta-Intkey is the only currently available system that uses a coefficient related to information theory, and it is currently being reimplemented, which may allow for improvement. We describe two improvements to the algorithm used by Delta-Intkey. The first improves transparency as the number of remaining taxa decreases, by normalizing the range of the coefficient to [0,1]. The second concerns numeric ranges, which require consistent treatment of sub-intervals and their end-points. A stand-alone Bestchar program for categorical data is provided, in the Python and R languages. The source code is freely available and dedicated to the Public Domain

Quantitative traits from leaf morphology in some North American species and hybrids of Populus sections Aigeiros and Tacamahaca, Salicaceae

grantor: University of TorontoThis thesis is a preliminary step towards testing the genetic basis in poplars of quantitative leaf morphology traits that go beyond easily measured traits such as leaf length and width. The emphasis is on elliptic Fourier analysis of entire leaf outlines, and a method is developed for graphical manipulation of distorted leaves that shows promise of reducing the noise factor that is generally troublesome with leaf samples. In the method, digital images of leaf halves are converted to a canonical shape by means of a geometric transformation known as "rubber-sheeting". Some results are included concerning relationships between simple leaf-measurement variables in preformed and neoformed leaves from young poplar trees. These relationships differ between trees in sections Aigeiros and Tacamahaca.M.Sc