Classification of species in the genus Trapa by morphometric fruiting features

Botanical Garden-Institute FEB RAS, Vladivostok, Russia

The paper discusses new approaches for solving the taxonomic problem of Trapa species, that occur in the territory of Primorsky krai (Russian Far East). At the present time, the problem of classification of Trapa species is still open, mostly, because of high variability of its morphological features. Therefore, deriving significant methods of discriminating between a specific set of objects is very difficult. It is generally accepted that Trapa fruit morphological features are used for Trapa species discrimination. In this work, attempts for improving existing classification schemes of Trapa species are based on two positions. First of these: to classify properly, one has to use most informative morphometric features of fruits, controlling feature extraction process by some cross-validation technique. The second is to follow treatments that are statistically valid. As a result of our research, we built a classification system of Trapa species. The system uses up to 27 morphmetric features of Trapa fruits belonging to 8 species growing at the territory of Primorsky krai. Computations are based on classical and modern pattern recognition techniques (linear classification, knn-classification, consensus clustering, analysis of variance) and implemented in Python. It is shown, that Trapa species could be determined by its common morphometric features with high accuracy. For instance, misclassification errors for linear classification algorithm computed by leave-one-out cross-validation method are the following: T. incisa – 1.3 %, T. nedoluzhkoi – 0 %, T. maximowiczii – 2.5 %. The server of the classification system is built over the Django Web Framework and includes additional Python modules contributed by authors of the work. As generalization of features extraction procedure, a hierarchical classification tree was formed. It is presented as ensemble of nested dichotomies leading to specific Trapa species.

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