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

Abstract

Aim 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 new Spartina hybrids arising between introduced Spartina densiflora and native S. maritima in 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 F1 hybrids. Hybrid chromosome numbers varied between 2n = ca. 65 and 2n = ca. 94–97, while S. maritima had 2n = ca. 60 and S. densiflora had 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 invasive Spartina hybrid 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 the S. densiflora invasion in the Iberian Peninsula to prevent the origination of a new invasive allopolyploid Spartina species.

The chloroplast genome of the hexaploid Spartina maritima (Poaceae, Chloridoideae): Comparative analyses and molecular dating

“…The latter hybrid has given rise to the above-mentioned allododecaploid S. anglica by genome doubling (Baumel et al, 2003;Ferris et al, 1997). In Spain, bidirectional hybridization occurred between S. maritima and the introduced heptaploid S. densiflora resulting in individuals that inherited alternatively the plastome of S. maritima or of S. densiflora (Castillo et al, 2010).…”

Hybridization between native and invasive alien plants: an overlooked threat to the biodiversity of Sri Lanka

“…Identification of these hybrid taxa from the parent taxa is important as eradication of such taxa in the early stage is an achievable goal (Castillo, 2010). Studies highlight the identification of the hybrid taxa as the base for studying the invasion ecology of congeneric species.…”

Control and consequences of Spartina spp. invasions with focus upon San Francisco Bay

“…The first known introduction was S. densiflora from South America to the Gulf of Cadiz, Spain early in European exploration of the New World (Castillo et al 2000). The first interspecific Spartina hybridization likely occurred there between S. densiflora and S. maritima which produced several hundred sterile hybrids in three estuaries by 2008 (Castillo et al 2010). All of the known introductions to Pacific shores occurred in the twentieth century.…”