Asymmetric Reproductive Barriers and Gene Flow Promote the Rise of a Stable Hybrid Zone in the Mediterranean High Mountain Abdelaziz Mohamed, Mohamed Muñoz Pajares, Antonio Jesús Berbel, Modesto García Muñoz, Ana Gómez, José M. Perfectti Álvarez, Francisco Hybridization Erysimum mediohispanicum Erysimum nevadense Sierra Nevada Phenotype Reproductive isolation This research has been supported by a grant from the Spanish Ministry of Economy and Competitiveness (CGL2014-59886JIN), the Organismo Autonomo de Parques Nacionales (Ref: 2415/2017), and the Ministry of Science and Innovation (PID2019-111294GB-I00/SRA/10.13039/501100011033). FP acknowledges the projects A.RNM.505.UGR18 (FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento) and the Spanish Ministry of Science and Competitiveness (CGL201679950-R; CGL2017-86626-C2-2-P), including FEDER funds. MA was supported by the TransSpeciation project (CGL2014-59886JIN). AJM-P was funded by the European Commission under the Marie Sklodowska-Curie Action Cofund 2016 EU agreement 754446 and the UGR Research and knowledge TransferAthenea3i. MB was supported by global Hybrids project (Ref: 2415/2017) and AG-M was supported by OUTevolution project (PID2019-111294GB-I00/SRA/10.13039/501100011033). Hybrid zones have the potential to shed light on evolutionary processes driving adaptation and speciation. Secondary contact hybrid zones are particularly powerful natural systems for studying the interaction between divergent genomes to understand the mode and rate at which reproductive isolation accumulates during speciation. We have studied a total of 720 plants belonging to five populations from two Erysimum (Brassicaceae) species presenting a contact zone in the Sierra Nevada mountains (SE Spain). The plants were phenotyped in 2007 and 2017, and most of them were genotyped the first year using 10 microsatellite markers. Plants coming from natural populations were grown in a common garden to evaluate the reproductive barriers between both species bymeans of controlled crosses. All the plants used for the field and greenhouse study were characterized by measuring traits related to plant size and flower size. We estimated the genetic molecular variances, the genetic differentiation, and the genetic structure by means of the F-statistic and Bayesian inference. We also estimated the amount of recent gene flow between populations.We found a narrow unimodal hybrid zone where the hybrid genotypes appear to have been maintained by significant levels of a unidirectional gene flow coming from parental populations and from weak reproductive isolation between them. Hybrid plants exhibited intermediate or vigorous phenotypes depending on the analyzed trait. The phenotypic differences between the hybrid and the parental plants were highly coherent between the field and controlled cross experiments and through time. The highly coherent results obtained by combining field, experimental, and genetic data demonstrate the existence of a stable and narrow unimodal hybrid zone between Erysimum mediohispanicum and Erysimum nevadense at the high elevation of the Sierra Nevada mountains. 2021-10-18T11:30:30Z 2021-10-18T11:30:30Z 2021-08-25 journal article Abdelaziz M... [et al.] (2021) Asymmetric Reproductive Barriers and Gene Flow Promote the Rise of a Stable Hybrid Zone in the Mediterranean High Mountain. Front. Plant Sci. 12:687094. doi: [10.3389/fpls.2021.687094] http://hdl.handle.net/10481/70936 10.3389/fpls.2021.687094 eng info:eu-repo/grantAgreement/EC/H2020/754446 http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España Frontiers Research Foundation