Shipwrecked on the Rock, or Not Quite: Gypsophytes and Edaphic Islands

Species-area relationships (SAR) constitute a key aspect of ecological theory and are integral to other scientific disciplines, such as biogeography, which have played a crucial role in advancing biology. The theory of insular biogeography provides a clear example. This theory initially expanded from true islands to other types of systems characterized by their insularity. One such approach was linked to geoedaphic islands, as seen in gypsum outcrops. While these continental areas have been considered insular systems, only limited and mostly indirect evidence thereof has been provided. This study utilized SAR to advance the understanding of gypsum outcrops as insular continental territories. It is hereby hypothesized that gypsum outcrops are edaphic islands, although their insular nature depends on the different functional or ecological plant types, and this nature will be reflected in the potential Arrhenius model z values. The results obtained support both hypotheses and provide insight into the ecological factors that help interpret the insularity of these areas. This interpretation goes beyond their mere extent and the distance among outcrops, emphasizing the importance of environmental filters. Said filters vary in permeability depending on the degree of gypsophily, or preference for gypsum, exhibited by different species.