Additivity of ISSR Markers in Natural Hybrids of Related Forest Species Bromus benekenii and B. ramosus (Poaceae)

Abstract

AbstractThe co-occurrence of hybrids and parental species in similar ecological niches poses a question on the role of traits additivity and overdispersion (emergence of new traits) in microevolutionary processes. We analysed genetic polymorphism ofBromus benekenii,B. ramosusand the spontaneous hybridB. benekenii×B. ramosusin sympatric and allopatric parts of the species distribution in Europe, based on non-coding regions of the taxon genomes (ISSR genetic fingerprinting). We tested 68 individuals in 7 populations, including a hybrid population in N France. Altogether 233 polymorphic ISSR bands (loci) were obtained. We found that the parent species were genetically distinct and the hybrids had an additive pattern of ISSR bands found in the putative parental species (NMDS, STRUCTURE); however, there was evidence of introgression towardsB. ramosus(NEWHYBRIDS, UPGMA classifications, Nei's D genetic distance).Bromus benekeniihad 72,B. ramosus21 and the hybrids 9 private bands (genetic overdispersion), probably resulting from the rearranged genomes. Based on its low genetic divergence index DW, the hybrid population seems to be at a young age. We argue that in the face of anthropogenic landscape transformations favouring secondary contacts, the hybrids may competitively replace the parental species in sympatric areas.