Big thistle eats the little thistle: does unidirectional introgressive hybridization endanger the conservation of Onopordum hinojense?
Hybridization is known to have a creative role in plant evolution. However, it can also have negative effects on parental species. Onopordum is a large genus whose species frequently hybridize. In the Southwest Iberian Peninsula, the rare O. hinojense co-occurs with the widely distributed O. nervosum, and hybrids between these two taxa have been described as O. × onubense. In this study we determine the extinction risk in a hybrid zone, both for hybrids and parentals, using analyses of morphological and cytogenetic traits as well as genetic markers and demographic models. To investigate the introgression process we used amplified fragment length polymorphism (AFLP) markers, Bayesian analyses and genome scan methods. Morphology, genome size and molecular markers confirmed homoploid hybridization and also indicated unidirectional backcrossing of F₁ hybrids with O. nervosum, which is likely to swamp O. hinojense, the parental with lower pollen size and a very low fruit set (8%). Genome scan methods revealed several loci significantly deviating from neutrality. Finally, our demographic modeling indicated that the higher fitness of O. nervosum threats the survival of O. hinojense by demographic swamping. Our study provides strong new evidence for a scenario of rapid extinction by unidirectional introgression and demographic swamping. The multifaceted approach used here sheds new light on the role of introgression in plant extinctions.
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain.|Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030, Austria.
Francisco
F
Balao
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain.|Departmento de Biología, CASEM, Universidad de Cádiz, Campus Río San Pedro, E-11510, Puerto Real, Spain.
Ramón
R
Casimiro-Soriguer
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain.
Juan Luis
JL
García-Castaño
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain.|Department of Systematic and Evolutionary Botany, University of Vienna, Rennweg 14, 1030, Austria.
Anass
A
Terrab
Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain.
Salvador
S
Talavera
D054458:Amplified Fragment Length Polymorphism Analysis; D001499:Bayes Theorem; D003247:Conservation of Natural Resources; D003710:Demography; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D006824:Hybridization, Genetic; D031183:Onopordum / Q000235:genetics*; D010641:Phenotype; D011110:Polymorphism, Genetic; D013045:Species Specificity
D005819:Genetic Markers
Onopordum; amplified fragment length polymorphism (AFLP); extinction; genome scan; hybridization; morphology; outlier loci; unidirectional introgression