A Study On Post-pollination Reproductive Isolations Of Sympatric Populations Between Primulina Eburnea And P. Mabaensis

Strong reproductive isolations are essential for sympatric populations of closely related species to maintain the entirety of species and to prevent gene introgression caused by hybridization. One population of Primulina eburnea shares the habitat with another closely related species P. mabaensis in Maba, Shaoguan, North Guangdong. Within the sympatric populations, their flowering seasons partially overlap, and natural hybrid have been identified in both morphological and molecular methods. However, the two species still kept their boundary from being disturbed by each other, suggesting that there must be forceful reproductive isolation mechanisms between them. In order to understand the importance of post-pollination reproductive isolations on preventing gene exchange between P. eburnea and P. mabaensis, we conducted manual pollination in greenhouse to examine those post-pollination isolation mechanisms as well as the strength of each mechanism, including pollen competition, fruit set, seed mass, seed germination and pollen viability of hybrid.The reproductive isolation strength of pollen competition, seed germination for P. eburnea and P. mabaensis are-0.321,-0.041 and-0.026,-0.199 respectively. Our results revealed that heterospecific pollen and hybrids have competitive advantage, indicating these two mechanisms would promote gene communication between species. However, the strength for other 3 mechanisms like fruit set, seed mass, and pollen viability are 0.005, 0.157, 0.264 and 0.003, 0.015, 0.333 for P. eburnea and P. mabaensis respectively. These mechanisms are weak, but they can somehow prevent the introgression.The total post-pollination isolation strength for P. eburnea and P. mabaensis is 0.33305 and 0.10968 respectively. They are obviously not strong enough to completely prevent the hybridization and introgression between P. eburnea and P. mabaensis and maintain their species entirety. It is probably that the existence of pre-pollination isolation mechanisms plays more important role in maintaining species boundaries between these two species.Based on transcriptome sequencing of 11 Primulina species, we developed 38,276 pairs of SSR primers. 1,296 SSRs are randomly selected to examine their polymorphism and universality in species level with 25 species. The result shows 28.09% SSRs can be successfully amplified on 80% species, and over 97.22% SSRs show polymorphism. These results suggest that transcriptome sequencing is an efficient method to achieve huge amounts of SSRs for genetic studies.