Two reproductively isolated cytotypes and a swarm of highly inbred, disconnected populations: a glimpse into Salicornia's evolutionary history and challenging taxonomy

The main factor of differentiation at six nuclear microsatellite and seven cpDNA loci in Salicornia from the Mediterranean and Atlantic coasts of France is cytotypic identity, suggesting the presence of a strong reproductive barrier among sympatric cytotypes. Within cytotypes, a substantial proportion of the differentiation between species is due to confounded phylogeographic signal. Conspecific individuals tend to be significantly more related than individuals from different species at the population scale, but mean kinship coefficients among pairs of conspecific and nonconspecific individuals from different populations are not significantly different, suggesting the absence of reproductive isolation among species of the same cytotype. The observed association between morphology and genetic variation within populations would thus result from the selfing mating system (F-is = 0.70) generating substantial linkage within the genome, linkage that would quickly disappear among unrelated individuals from different populations. Salicornia species thus function as a network of inbred populations, strongly challenging taxonomic concepts.