Limitation of gene flow by distance in the common yellow jasmine (Chrysojasminum fruticans, Oleaceae): implications for the study of its mating strategies

The common yellow jasmine (Chrysojasminum fruticans, Oleaceae) is a distylous shrub occurring in the wild in south-western Europe and the Mediterranean Basin. Little is known about the genetics of its populations and such information would be necessary to investigate its spread and mating strategies. Here, the organization of its genetic diversity was investigated among and between 13 populations from southern France, including a 35-year-old experimental plot ('CEFE', CNRS Montpellier). Markers (microsatellites and indels) were developed to screen polymorphisms in nuclear, chloroplast, and mitochondrial genomes. Low linkage disequilibrium was observed between chloroplast and mitochondrial haplotypes probably resulting from paternal leaks in their inheritance as reported in other species of tribe Jasmineae. Yet, analyses of 36 progenies issued from parents with distinct chloroplast and/or mitochondrial DNA haplotypes only revealed a maternal contribution. Natural populations of C. fruticans are moderately to highly differentiated at the regional scale with a strong isolation-by-distance pattern detected on nuclear data, indicating limited gene flow. An isolated site ('Moulis'), located on the marginal distribution area, was remarkably genetically depauperate and highly differentiated from other populations. Further studies on the variation of mating strategies in C. fruticans should consider populations with contrasting patterns of genetic diversity. The artificial 'CEFE' population also offers opportunities for experiments in a closed system.