An extension of presence/absence coefficients to abundance data: a new look at absence

Authors

  • Júlia Tamás,

    1. Department of Plant Taxonomy and Ecology, L. Eötvös University, Ludovika tér 2, H-1083 Budapest, Hungary
    2. Research Institute for Botany and Ecology, Hungarian Academy of Sciences, H-2163 Vácrátót, Hungary
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  • János Podani,

    Corresponding author
    1. Department of Plant Taxonomy and Ecology, L. Eötvös University, Ludovika tér 2, H-1083 Budapest, Hungary
      Corresponding author; Fax +361 3338764; E-mail podani@ludens.elte.hu
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  • Péter Csontos

    1. Ecological Modelling Research Group, Hungarian Academy of Sciences, Ludovika tér 2, H-1083 Budapest, Hungary
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Corresponding author; Fax +361 3338764; E-mail podani@ludens.elte.hu

Abstract

Abstract. Alternative community analyses, based on quantitative and presence/absence data, are comparable logically if the data type is the only factor responsible for differences among results. For presence/absence indices that consider mutual absences, no quantitative alternatives are known. To facilitate such comparisons, a new family of similarity coefficients is proposed for abundance data. Formally, this extension is achieved by generalizing the four cells of the usual 2 × 2 contingency table to the quantitative case. This implies an expanded meaning of absence: for a given species at a given site it is understood as the difference between the actual value and the maximum detected in the entire study. The correspondence between 10 presence/absence coefficients and their quantitative counterparts is evaluated by graphical comparisons based on artificial data. The behaviour of the new functions is also examined using field data representing post-fire regeneration processes in grasslands and a chronosequence pertaining to forest regeneration after clear-cut. The examples suggest that the new coefficients are most informative for data sets with low beta-diversity and temporal background changes.

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