Reproductive biology and habitat characterization of Euphorbia fontqueriana Greuter, an endangered endemism from Mallorca

[eng] Euphorbia fontqueriana is an endangered species (BOIB no. 131, 26/10/2017) endemic from Mallorca (Balearic Islands) that occurs in only one natural location in Serra de Tramuntana. Until now, many basic aspects related to the biology of the species were still unknown. Thus, in this work we aimed to describe several aspects about its reproductive biology and improve the knowledge about the habitat of the species. Concretely, we addressed the flowering and fruiting phenology, cyathia functionality, mating system, reproductive output, and germination traits. Also, soil nutrients and organic matter content as well as its texture composition were analysed, and data of air temperature and humidity were recorded during a whole year. Finally, vegetation was characterized through linear transects and plant abundance studies to obtain plant richness and diversity indexes. All fieldwork was performed in the natural population during the reproductive season of 2018 and 2019. Results showed a clear andromonoecious character of the species. It blooms during a few weeks (April-May) and depends on insects to set seeds, mainly Diptera. In natural conditions, fruit abortion was high (~50%) but we did not find evidence of pollen limitation. Seed production is ~5 seeds per individual, which present photoinhibtion and dormancy. Regarding its habitat, soil is characterised by a dolomitic character and a highly rocky and sandy composition, highly exposed to erosion, and very poor in nutrients. The plant community of E. fontqueriana consists of 36 taxa, with high levels of endemicity (41.67%). Shannon index was 3.03 and 2.09 for 2018 and 2018, respectively, but plant density was very low (mostly