Why do traditional dispersion indices used for analysis of spatial distribution of plants tend to become obsolete?

• Published in: Population ecology Vol. 64; no. 2; pp. 80 - 92
• Main Authors: Freitas Alves, Gabriella, Santana, Denise Garcia
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.04.2022; Blackwell Publishing Ltd
• Subjects: Agglomeration; aggregate distribution; Aggregates; Aggregation; Dimensions; Dispersion; Distribution; Geographical distribution; Identification methods; Lexian Dispersion Theory; Morisita index; Paepalanthus; Paepalanthus chiquitensis; population ecology; researchers; Spatial analysis; Spatial data; spatial dependence; Spatial distribution; Variance
• ISSN: 1438-3896; 1438-390X
• DOI: 10.1002/1438-390X.12105

It is common to characterize the spatial distribution of plant patterns as random, aggregate, or uniform. In this context, a major challenge for the researcher is the choice of the method to identify the spatial pattern correctly as well as the factors related to it. The vast literature on the subject is not recent, especially regarding the dispersion indices. The aim of this review was to conduct a critical and temporal analysis of these dispersion indices and test their effectiveness in determining the spatial distribution of Paepalanthus chiquitensis Herzog (Eriocaulaceae). This species is a meaningful model due to its occurrence in specific sites. The Lexis, Charlier, dispersion, relative variance, aggregation, Green, inverse of k of the negative binomial, Morisita, and standardized Morisita indices were limited to indicating that the individuals of the species are aggregate and did not provide information on neither spatial dimension (scale) where the aggregation occurs, nor the factors related to this aggregation. Although they have distinct magnitudes, the algebraic expressions of dispersion, relative variance, aggregation, Green, inverse of k, Morisita, and standardized Morisita indices exhibited a close relationship with each other and little progress from their precursors Lexis and Charlier. By disregarding the possibility of spatial dependence, these indices make it impossible to generate important hypotheses for the investigation of factors related to spatial structure. Therefore, they became obsolete and are falling into disuse. It should be noted that these measurements accomplished their role and contributed to science in times of limited technologies for spatial data. This review analyzed the main dispersion indices and coefficients published between 1915 and 1975 and applied to the analysis of the spatial distribution of plant species. Despite a long history in ecological studies, these measurements do not meet the growing interest of ecologists in identifying factors related to distribution patterns. By disregarding the possibility of spatial dependence and did not providing information on the spatial dimension (scale) where the patterns occur, these indices make it impossible to generate important hypotheses for the investigation of these factors and, therefore became obsolete.