The production of hybrids with high ecological amplitude between exoticSpartina densifloraand nativeS. maritimain the Iberian Peninsula

Abstract

AbstractAim Hybridization is a common and potent mechanism of plant evolution that has the potential to be evolutionary significant in its own right, and hybrids are common between invasive and native congeneric species. Our aims were to document the existence and nature of newSpartinahybrids arising between introducedSpartina densifloraand nativeS. maritimain tidal marshes of the Iberian Peninsula, to examine the actual and potential range of hybrids in the intertidal zone, and to analyse the seed set of hybrids.Location South‐West Iberian Peninsula.Methods Hybrids were characterized using chloroplast and nuclear DNA, and ploidy assessments. The ecological tolerance of the hybrids was studied using vegetation surveys and transplant experiments.Results We found that both parental species have been seed parents to hybrids and that all hybrids had an additive pattern of species‐specific nuclear markers consistent with F1hybrids. Hybrid chromosome numbers varied between 2n = ca. 65 and 2n = ca. 94–97, whileS. maritimahad 2n = ca. 60 andS. densiflorahad 2n = ca. 70. Hybrids grew in three discrete locations along the intertidal zone but were capable of growing throughout the ranges of both parental species in transplanted gardens, and in most cases, grew better than the parental species. While the potential exists for the origination of another invasiveSpartinahybrid species, thus far hybrid plants are not fertile, limiting their ability to invade and spread.Main conclusions We recommend the eradication of all of the currently quite limited hybrid cordgrass and to fight theS. densiflorainvasion in the Iberian Peninsula to prevent the origination of a new invasive allopolyploidSpartinaspecies.