Shedding light through the smoke on the germination of Mediterranean Basin flora

Natural and anthropogenic fires have historically been part of the Mediterranean Basin (MB). As a result of this long exposure to fires, MB flora has developed various strategies to persist under recurrent fires. One of these strategies is to survive and regenerate by resprouting and another is through post-fire seedling recruitment. For species that recruit seedlings after a fire there is evidence that fire-related germination cues are implicated in the process of triggering seedling emergence from soil-stored seeds. In some species, particularly in Cistaceae and Fabaceae, germination is stimulated by heat. Fire-related chemical germination cues, such as smoke, charcoal, and nitrogenous compounds (collectively termed ‘smoke’), have also been recognised as promoting seed germination in MB flora. However, the role of smoke in the germination of MB plant species has received less attention and recognition than the role of heat-shock and is generally seen as having a relatively limited role as a post-fire germination cue in MB flora. Our hypothesis is that this is due to the fact that research on smoke-stimulated germination in the MB region has been limited and poorly addressed, and this is biasing our view on the role of smoke in MB flora. Using available literature, we first analyse the role of smoke in the germination of MB flora and discuss some of the issues that limit our understanding of its role on the flora of the region. We point to gaps in the literature and provide suggestions for further research. We conclude that differences in evidence of smoke-stimulated germination in MB flora when compared with other Mediterranean regions may not reflect real ecological or evolutionary differences among these regions but are likely the consequence of the limited number of well-designed studies in the MB.BM was supported by the Fundação para a Ciência e a Tecnologia [grant number SFRH/BPD/90277/2012]. This work was performed under the framework of the TREVOL and FILAS projects (CGL2012-39938-C02-01, CGL2015-64086-P) from the Spanish Government and the PROMETEO/2016/021 project from the Valencia government (Generalitat Valenciana). CIDE is supported by CSIC, Generalitat Valenciana and the University of Valencia.Peer reviewe