Data from: Fitness of reciprocal F1 hybrids between Rhinanthus minor and Rhinanthus major under controlled conditions and in the field

The performance of first‐generation hybrids determines to a large extent the long‐term outcome of hybridization in natural populations. F1 hybrids can facilitate further gene flow between the two parental species, especially in animal‐pollinated flowering plants. We studied the performance of reciprocal F1 hybrids between Rhinanthus minor and R. major, two hemiparasitic, annual, self‐compatible plant species, from seed germination to seed production under controlled conditions and in the field. We sowed seeds with known ancestry outdoors before winter and followed the complete life cycle until plant death in July the following season. Germination under laboratory conditions was much lower for the F1 hybrid formed on R. major compared to the reciprocal hybrid formed on R. minor, and this confirmed previous results from similar experiments. However, this difference was not found under field conditions, which seems to indicate that the experimental conditions used for germination in the lab are not representative for the germination behaviour of the hybrids under more natural conditions. The earlier interpretation that F1 hybrid seeds formed on R. major face intrinsic genetic incompatibilities therefore appears to be incorrect. Both F1 hybrids performed as well as or sometimes better than R. minor, which had a higher fitness than R. major in one of the two years in the greenhouse and in the field transplant experiment. The high fitness of the F1 hybrids confirm findings from naturally mixed populations, where F1 hybrids appear in the first year after the two species meet and which leads to extensive advanced‐hybrid formation and introgression in subsequent generations.Wesselingh_2019_Rhinanthus_germination_labresults of germination trial in laboratoryWesselingh_2019_Rhinanthus_hybrids_field_emergence_survivalresults of field transplant experiment: emergence of seedlings and survival until floweringWesselingh_2019_Rhinanthus_hybrids_field_flowers_seedsfield transplant: flower and seed production of surviving plantsWesselingh_2019_Rhinanthus_hybrids_greenhouse_flowersflower production of plants in the greenhouse in 2013Wesselingh_2019_Rhinanthus_hybrids_greenhouse_2013_flowers.csvWesselingh_2019_Rhinanthus_hybrids_greenhouse_2014_flowersflower production by plants in the greenhouse in 201