Essentialistic Pluralism: The theory of spatio-temporal positioning of species using integrated taxonomy

Maxwell, S. J., Congdon, B. C., & Rymer, T. L. (2020)


The resurrection of essentialist arguments, in the context of the modern evolutionary synthesis, highlights the need for a break from historical definitions of ‘kind’ and ‘essence’ in order to bring a new paradigm in which these terms are used to conceptualise and understand evolutionary processes. The definition of ‘essence’ is herein divided into two distinct parts, namely the structural essence, which is mutable and has an evolutionary context; and the character essence, which is the immutable spatio-temporal expression of the structural essence of an individual. In contrast, the ‘kind’ is herein redefined as a region within a wider phylogenetically constrained organism state that reflects a conflux of character essences that form an immutable semaphoront. This organism state enables the hypothetical delineation of spatio-temporally immutable forms, called species, which are drawn from an evolutionary continuum. These revised definitions and the taxonomic clades derived from them determine the species that are used in the construction of phylogenies that reflect true historical and evolutionary relationships between organisms. The use of integrated taxonomy allows taxonomists to choose the appropriate concept enabling the evolutionary significance of the organism to be explained. This refocuses the argument from the concept back to the criteria, but often at the cost of causal explanation or conceptional explicitness. While integrated taxonomy allows the taxonomist the freedom to delineate species outside of any rigid conceptual framework, we seek to apply to this freedom a limit to the understanding of the evolutionary potential of an organism through the framing of that organism in a fixed spatio-temporal point. We call this confined potential the ‘essence matrix’, and it is these boundaries of this matrix that define the evolutionary potential of past and future forms, as well as define and restrict the field of morphospace upon which convergence and reticulation of taxa can occur. We name this limitation on evolutionary potential, the essentialist arguments used to construct it, and the integrated taxonomic approach to criteria selection, ‘essentialistic pluralism’. Finally, we will examine the complexity of species demarcation, noting the continuing failure for explicitness in conceptual application even if criteria are obvious.