A mathematical comparison of classification structures: The case of the USDA Soil Taxonomy

Biologists have not paid much attention to the mathematical structures of biological classifications and their interpretations. A few have made such an analysis mainly using statistical distribution models. Comparisons with nonbiological classifications are needed to know if such structures are the result of biological evolution or of taxonomic practices, utilitarian bias, and/or subconscious cognitive rules. We compare the biological classification of a target group of soil borne plant parasitic nematodes (the Tylenchina suborder) with a non-biological one (the USDA 8th edition of the Keys to Soil Taxonomy). The authors made use of the same tools used in previous papers by biologists introducing other classifications. The results show that both taxonomies are information systems that try to optimize the information flow and fit well to the same distribution models. The analysis does not show any idiosyncrasies of biological classifications with respect to pedological ones, thus, supporting the idea that these products are the result of subconscious cognitive rules used by humankind to classify the world.