Genetic and morphological evidence for introgression between three species of willows

BMC Evolutionary Biology

Research Article

Alexander I. Katyshev¹  Alla V. Verkhozina¹  Sofia Berlin²  Ann Christin Rönnberg-Wästljung²  Christina Dixelius²  Johan Fogelqvist²  Pascal Pucholt²  Martin Lascoux³ 

[1] Siberian Institute of Plant Physiology & Biochemistry, P.O. Box 317, Irkutsk-33, 664033, Irkutsk, Russia;Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, P.O. Box 7080, SE-75007, Uppsala, Sweden;Uppsala University, Department of Ecology and Genetics, Evolutionary Biology Centre, Science for Life Laboratory, Norbyvägen 18D, 752 36, Uppsala, Sweden;

关键词: Reproductive Isolation;    Hybrid Zone;    Single Nucleotide Polymorphism Marker;    Reproductive Barrier;    Incomplete Lineage Sorting;   

DOI  :  10.1186/s12862-015-0461-7

 received in 2015-03-18, accepted in 2015-08-20,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundHybridization and introgression are said to occur relatively frequently in plants, and in particular among different species of willows. However, data on the actual frequency of natural hybridization and introgression is rare. Here, we report the first fine-scale genetic analysis of a contact zone shared between the three basket willow species, Salix dasyclados, S. schwerinii and S. viminalis in the vicinity of the Lake Baikal in Southern Siberia. Individuals were sampled in fourteen populations and classified as pure species or hybrids based on a set of morphological characters. They were then genotyped at 384 nuclear SNP and four chloroplast SSR loci. The STRUCTURE and NewHybrids softwares were used to estimate the frequency and direction of hybridization using genotypic data at the nuclear SNP loci.ResultsAs many as 19 % of the genotyped individuals were classified as introgressed individuals and these were mainly encountered in the centre of the contact zone. All introgressed individuals were backcrosses to S. viminalis or S. schwerinii and no F1 or F2 hybrids were found. The rest of the genotyped individuals were classified as pure species and formed two clusters, one with S. schwerinii individuals and the other with S. viminalis and S. dasyclados individuals. The two clusters were significantly genetically differentiated, with FST = 0.333 (0.282–0.382, p < 0.001). In contrast, for the chloroplast haplotypes, no genetic differentiation was observed as they were completely shared between the species. Based on morphological classification only 5 % of the individuals were classified as introgressed individuals, which was much less than what was detected using genotypic data.ConclusionsWe have discovered a new willow hybrid zone with relatively high frequency of introgressed individuals. The low frequency of F1 hybrids indicates that ongoing hybridization is limited, which could be because of the presence of reproductive barriers or simply because the conditions are not favorable for hybridization. We further conclude that in order to get a complete picture of the species composition of a hybrid zone it is necessary to use a combination of morphological characters and genetic data from both nuclear and chloroplast markers.

【 授权许可】

CC BY   
© Fogelqvist et al. 2015