Potential risk of interspecific hybridization in ex situ collections

Spontaneous hybridization in ex situ conservation facilities could potentially contaminate endangered plant species destined for the reintroduction into the wild. Despite the general recognition of the importance of such danger, studies exploring the consequences of hybridization including subsequent performance of the hybrids in comparison to the original species are rare. The aim of the present study was to assess the potential consequences of hybridization between the endangered endemic serpentinophyte species, Minuartia smejkalii, and its congener allopatric species, M. caespitosa. We performed controlled inter-specific crosses and compared seed production, germination, growth, seed morphology and dispersal ability between M. smejkalii and the hybrids. Our results showed that M. smejkalii and M. caespitosa can hybridize and produce viable seeds. Number of seeds per capsule produced by M. smejkalii and the hybrids did not differ but germination rates were higher in the hybrids. In addition, hybrids produced a higher number of flowers than M. smejkalii in open sites and serpentine soils, indicating that the hybrids perform better in the extreme serpentine conditions than the original serpentine species. Our simulation results showed a higher dispersal potential in hybrids compared to M. smejkalii despite their higher terminal velocity. Our results provide evidence that hybrid individuals from ex situ collections might outcompete the endemic M. smejkalii in the wild, if they are introduced by mistake. Therefore, for conservation and reintroduction purposes, ex situ hybridization events should be considered as a potential threat and treated carefully. We recommend establishing an adequate management of potentially crossable species and cautiously selecting individuals to be used for restoration.