Extension of the gambin model to multimodal species abundance distributions

Thomas Matthews, Michael K. Borregaard, Colin S. Gillespie, François Rigal, Karl I. Ugland, Rodrigo Ferreira Krüger, Roberta Marques, Jonathan Sadler, Paulo A. V. Borges, Yasuhiro Kubota, Robert J. Whittaker

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3 Citations (Scopus)
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1. Species abundance distributions (SADs) are one of the most widely used tools in macroecology, and it has become increasingly apparent that many empirical SADs can best be described as multimodal. However, only a few SAD models have been extended to incorporate multiple modes and no software packages are available to fit multimodal SAD models. In this study, we present an extension of the gambin SAD model to multimodal SADs.

2. We derive the maximum likelihood equations for fitting the bimodal gambin distribution and generalise this approach to fit gambin models with any number of modes. We present these new functions, along with additional functions to aid in the analysis of multimodal SADs, within an updated R package (‘gambin’; version 2.4.0) that enables the fitting, plotting and evaluating of gambin models with any number of modes.

3. We use a mixture of simulations and empirical datasets to test our new models, including tests of the sensitivity of the model parameters to the number of individuals and the number of species in a sample. We show that the new multimodal gambin models perform well under a variety of circumstances, and that the application of these new models to empirical SAD and other macroecological (e.g. species range size distributions) datasets can provide interesting insights. The updated software package is simple to use and provides straightforward yet flexible statistical analyses of multimodality in SAD-type datasets.
Original languageEnglish
Pages (from-to)432-437
Number of pages6
JournalMethods in Ecology and Evolution
Issue number3
Early online date13 Nov 2018
Publication statusPublished - Mar 2019

Bibliographical note

Matthews TJ, Borregaard MK, Gillespie CS, et al. Extension of the gambin model to multimodal species abundance distributions. Methods Ecol Evol. 2018;00:1–6. https://doi.org/10.1111/2041-210X.13122


  • compound distributions
  • gambin
  • horse flies
  • multimodal species abundance distributions


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