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Depending on their specificity to gypsum, plants can be classified as gypsophiles (gypsum exclusive) and gypsovags (non-exclusive). The former may further be segregated into wide and narrow gypsophiles, depending on the breadth of their distribution area. Narrow gypsum endemics have a putative similar chemical composition to plants non-exclusive to gypsum (i.e. gypsovags), which may indicate their similar ecological strategy as stress-tolerant plant refugees on gypsum. However, this hypothesis awaits testing in different regions of the world. We compared the chemical composition of four narrow gypsum endemics, one widely distributed gypsophile and six gypsovags from Turkey. Further, we explored the plasticity in chemical composition of Turkish gypsovags growing on high- and low-gypsum content soils. Differences were explored with multivariate analyses (RDA) and mixed models (REML). Narrow gypsum endemics segregated from gypsovags in their chemical composition according to RDAs (mainly due to higher K and ash content in the former). Nevertheless, differences were small and disappeared when different nutrients were analysed individually. All the gypsovags studied accumulated more S and ash when growing on high-gypsum than on low-gypsum soils. Similar to narrow gypsum endemics from other regions of the world, most local gypsum endemics from Turkey show a similar chemical composition to gypsovags. This may indicate a shared ecological strategy as stress-tolerant plants not specifically adapted to gypsum. Nevertheless, the narrow gypsum endemic Gypsophila parva showed a chemical composition typical of gypsum specialists, indicating that various strategies are feasible within narrowly distributed gypsophiles.

Abstract. Gypseous substrates are well-recognised as supporting distinctive and unique flora assemblages, including numerous gypsum endemic (gypsophile) species. Along with these, others are also frequent although their presence is not restricted to gypsum; they show a clear preference for them (gypsocline). While this phenomenon (gypsophily) has been studied regionally, and various hypotheses put forward to explain it, there has been little global synthesis. We present a preliminary check-list on the gypsophile and gypsocline flora of the Palaearctic and Australian areas as a part of a project to develop a global checklist of the World's gypsophytes, which can broaden our ecological and biogeographical understanding of these unique environments. The database contains 935 taxa spanning 54 countries. The Irano-Turanian region -and to a lesser extent the Mediterranean region-emerged as the richest territories in terms of gypsophile species; this richness was much reduced in the SaharoArabian and, especially in the Eurosiberian regions. The factors that can modulate the richness of gypsophytes in a region are discussed and have been distributed into four groups: a) geological and edaphic factors; b) factors linked to the insular nature of outcrops; c) climatic variables and their interaction with the soil; d) biogeographical factors. The importance of those factors linked to insularity and, especially, to water availability is emphasized. Because the soil structure of many gypsum outcrops reduces water ability to plants, such outcrops can be regarded as "dry-islands" surrounded by less xeric substrates. The fact that gypsophytes can be grouped within a few major flowering plant clades across continents, confirms their pre-adaptations to these harsh and unique environments. Our work provides a preliminary database for exploring ecological and biogeographic issues relating to gypsophily, and we hope it will stimulate global interest in these valuable ecosystems. Keywords: edaphism; global check-list; gypsicolous; gypsophile; gypsophyte; gypsophily. Un primer inventario de la flora gipsícola del Paleártico y de AustraliaResumen. Los sustratos yesíferos son sobradamente conocidos por presentar cortejos florísticos peculiares y exclusivos, lo que incluye a numerosos endemismos (especies gipsófilas). Junto a estas especies, aparecen otras también muy frecuentes cuya presencia no se restringe al yeso, pero hacia el que muestran una clara preferencia (gipsoclinas). Mientras que este fenómeno (gipsofilia) ha sido estudiado regionalmente, y se han sugerido varias hipótesis para explicarlo, apenas existen síntesis globales sobre el mismo. Aquí se ofrece un inventario preliminar de la flora gipsófila y gipsoclina de los territorios paleártico y australiano como parte de un proyecto que pretende desarrollar una checklist mundial, de manera que se contribuya a ampliar el conocimiento ecológico y biogeográfico de este ambiente único. Este inventario incluye 935 taxa distribuidos por 54 países. La región irano-turaniana -y en meno...

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