Hybridization processes in an introduced subpopulation of an endangered plant: Management strategies to guarantee the conservation of Helosciadium bermejoi (Apiaceae)

Abstract Translocations are a tool to restore populations of threatened plant species that are being widely used. However, these techniques are not without risks and require rigorous protocols to carry them out and for their subsequent monitoring. In translocation projects, hybridization with other species is one of the most important risks and may threaten the survival of the species we want to protect. Here we present the case of Helosciadium bermejoi (L. Llorens) Popper and M.F. Watson, a Critically Endangered plant from the island of Menorca (Western Mediterranean). It occurs only in one locality and has been introduced to three new locations during recent years according to its Recovery Plan (2008). Recently, intermediate forms between the endangered species and a native congener, Helosciadium nodiflorum (L.) Koch, have been detected. The aims of this study were (i) to elucidate whether these plants originated through a hybridization event and (ii) to provide information about the current conservation status of the species. Exhaustive monitoring of all subpopulations (number of patches and area of occupancy) was performed from September 2015 to June 2016, and the rDNA ITS region and cpDNA rps16-trnK intergenic spacer region were sequenced for several samples of the putative hybrid and its putative parental species. Overall, the entire population of H. bermejoi greatly increased from 2010 (last census with available data) to 2015 in terms of both number of patches and area of occupancy: from 110 to 277 patches and from 299.2 to 791.3 dm 2 . Molecular analysis confirmed the hybrid origin of Helosciadium × clandestinum Rita, Capo and Cursach and that both H. bermejoi and H. nodiflorum (L.) Koch can act as donors of pollen or ovules. We discuss the advantages and disadvantages of translocations, as well as the great importance of monitoring them for at least the next ten years, both to know if the actions have been successful and to prevent or mitigate risks. We also present this case as an example for the importance of fast decision and coordination between environmental managers.