Unraveling cryptic reticulate relationships and the origin of orphan hybrid disjunct population in Narcissus

Abstract

Evolutionary consequences of natural hybridization between species may vary so drastically depending on spatial, genetic, and ecological factors that multiple approaches are required to uncover them. To unravel the evolutionary history of a controversial hybrid (Narcissus ×perezlarae), here we use four approaches: DNA sequences from five regions (four organellar, one nuclear), cytological studies (chromosome counts and genome size), crossing experiments, and niche modeling. We conclude that (1) it actually consists of two different hybrid taxa, N. ×perezlarae s.s. (N. cavanillesii × N. miniatus) and N. ×alentejanus (N. cavanillesii × N. serotinus); (2) both have been formed several times independently, that is, polytopically; (3) N. cavanillesii was the mother progenitor in most hybridization events. We also address the origin of orphan hybrid populations of N. ×perezlarae in eastern Spain, hundreds of kilometers away from N. cavanillesii. Although long-distance dispersal of already formed hybrids cannot be completely rejected, extirpation of N. cavanillesii via demographic competition is a more likely explanation. Lowreproductive barriers to fertilization by foreign pollen in N. cavanillesii, molecular footprints of the former presence of this species in the area, active asexual propagation by bulbs in N. ×perezlarae, and overlapping ecological niches are consistent with the extirpation scenario.