Is a restricted niche the explanation for species vulnerability? Insights from a large field survey of Astragalus tragacantha L. (Fabaceae)

In this study, we examine the realized niche of A. tragacantha in
Provence. We focus our fieldwork on habitat characteristics, floristic
survey and perform an exhaustive demographic census. We base our analyses
on total density and densities of different size stages of A. tragacantha.
We delineate its realized ecological niche with the Outlying Mean Index
(OMI) multivariate method and estimated the effects of environmental
gradients on A. tragacantha populations with the Generalized Joint
Attribute Modelling method (GJAM). Analyses based on occurrence data did
not support the hypothesis that a too narrow niche by itself explains the
vulnerability of A. tragacantha. However, niche modelling revealed
differences among size stages supporting a restricted regeneration niche
and a wider ecological range in the past. This dataset is accompanying the
manuscript published in Flora "Is a restricted niche the explanation
for species vulnerability? Insights from a large field survey of
Astragalus tragacantha L. (Fabaceae)"