Statistical Measures of Fidelity Applied to Diagnostic Species in Plant Sociology

Manuel Peinado,Francisco Manuel Ocaña-Peinado,Gustavo Díaz,Alejandro Aparicio,Juan Luis Aguirre,José Delgadillo,Miguel Ángel Macías

doi:10.5539/mas.v7n6p106

Abstract

The idea of a diagnostic species is an important concept in plant sociology. However, since over a century ago, when the term “association” was introduced, the identification of diagnostic species has been among the most controversial topics in phytosociological practice. With the aim of promoting methodological standardization in plant sociology, this paper addresses: 1) the need to distinguish between the concepts and methods involved in the definition of syntaxa (analysing releves, characterization, diagnosis, naming and typification), and 2) the need to support and improve existing syntaxonomical classification schemes using statistical measures of fidelity to identify diagnostic species. The phytosociological literature describes numerous different approaches to the designation of diagnostic species. Here, we examine two such approaches to determine diagnostic species using as an example the class Atriplici julaceae-Frankenietea palmeri within the context of a data set of 5092 releves taken of coastal plant communities distributed along the Pacific rim of North America. Diagnostic species were determined using both the phi-coefficient of association to detect differential species and the Ochiai index to designate character species. Our findings support the results obtained by combining classic phytosociological methods (expert knowledge, rearrangement of releve tables, presence tables, etc.) with clustering methods.

Highlights

Over one hundred years have passed since the Third International Botanical Congress held in Brussels in 1910 coined the first formal definition of the plant association, which marked the birth of plant sociology (Blasi, Biondi, & Izco, 2011)
The aim of the present study was to promote methodological standardization in syntaxonomy by stressing two main points: the need to explicitly distinguish between the procedures involved in the definition of syntaxa, and the need to support and improve the syntaxa defined using statistical measures of fidelity, a process included within the broad concept of “consistency in assignment” (De Cáceres & Wiser, 2011)
If we use as reference groups data sets with many relevés, both these contexts will be expanded with the consequence of the increased diagnostic and bioindicator value of a given species

Summary

Introduction

Over one hundred years have passed since the Third International Botanical Congress held in Brussels in 1910 coined the first formal definition of the plant association, which marked the birth of plant sociology (Blasi, Biondi, & Izco, 2011). In his revision of the phytosociological association concept, Willner (2006) suggested going back to Flahaut and Schröter’s definition, and a similar definition of association was provided by the US National Vegetation Classification (Jennings, Faber-Langendoen, Loucks, Peet, & Roberts, 2009). Despite being such a comprehensive definition, there is still no consensus as to the practical application of the concept (Willner, 2006; Biondi, 2011). This is in large measure because the original concept required at least one clarification: What exactly is a “definite floristic composition”?

Objectives

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Discussion

Conclusion