The α-minimum convex polygon as a relevant tool for isotopic niche statistics

Pauline Fey (1) , Yves Letourneur (1) , Silvere Bonnabel (2, 3)

1 ENTROPIE [Nouvelle-Calédonie] - Ecologie marine tropicale des océans Pacifique et Indien
2 CAOR - Centre de Robotique
3 ISEA - Institut de sciences exactes et appliquées

Ecological (isotopic) niche refers to a surface in a two-dimensional space, where the axes correspond to environmental variables that reflect values of stable isotopes incorporated in an animal's tissues. Carbon and nitrogen stable isotope ratios (δ 13 C-δ 15 N) notably provide precious information about trophic ecology, resource and habitat use, and population dynamics. Various metrics allow for isotopic niche size and overlap assessment. In this paper, we advocate α-minimum convex polygons (MCP)-that have long been used for home range estimationas a relevant tool for isotopic niche size, overlap, and characteristics. The method allows for outlier rejection while being suited to data that are not Gaussian in the bivariate isotopic (δ 13 C-δ 15 N) space. The proposed indicators are compared to other existing approaches and are shown to be complementary. Notably an indicator of divergence within the niche is introduced, and allows for comparisons at low (n > 6) and different sample sizes. The R code is made publicly available and will enable ecologists to perform isotopic niche comparison, contraction and expansion assessment, and overlap, based on various methods.

Domaines: Sciences de l'environnement; Statistiques [stat]

Pauline Fey, Yves Letourneur, Silvere Bonnabel. The α-minimum convex polygon as a relevant tool for isotopic niche statistics. Ecological Indicators, 2021, 130, ⟨10.1016/j.ecolind.2021.108048⟩. ⟨hal-03460350⟩