Genetic diversity and population structure of Commelina communis in China based on simple sequence repeat markers

Commelina communis（Asiatic dayflower） is a troublesome weed in China. Genetic variation of 46 C. communis populations from different collection sites in our country was investigated using 12 simple sequence repeat（SSR） primer pairs. Polymorphism analysis results showed high level of genetic diversity among these populations. The alleles（bands） were amplified by these primer pairs. The polymorphic proportion was 18.25%, and the average polymorphism information content was 0.1330. The highest effective number of alleles was 1.9915 at locus YP33, and the lowest value was 1.0000 at both loci YP25 and YP31. C. communis showed major average observed heterozygosity value（0.8655） than that of average expected heterozygosity（0.1330）. C. communis populations were divided into three groups on the basis of unweighted pair-group method with arithmetic mean cluster analysis（Dice genetic similarity coefficient=0.772） and genetic structure analysis（K=3）, and a principal coordinate analysis. The results of this study further illustrated that C. communis populations contained abundant genetic information, and the 12 SSR markers could detect the microsatellite loci of C. communis genomic DNA. These results might indicate that C. communis maintains high genetic diversity among different populations.

High ratio of illegitimate visitation by small bees severely weakens the potential function of heteranthery

Aims in heterantherous plants,‘division of labor’among structurally dif-ferent stamens,i.e.pollinating and feeding functions,has been thought to reduce the evolutionary conflict of relying on pollen both as the carrier of male gametes and as the food for pollinators.The key to successful division of labor among different sets of stamens is the size match between stamens and legitimate pollinators,which results in the precise deposition of pollen onto specific locations on pollinator’s body and facilitates cross pollination.However,the potential impact of small illegitimate insects that are ubiquitous dur-ing the pollination process on the plant reproduction in heteranth-erous species has been largely neglected in previous studies and never been demonstrated experimentally.Methods Here,we investigated the functions of three different types of sta-mens in Commelina communis.The pollinator visitation,pollen removal and deposition were compared among flowers with dif-ferent types of anthers emasculated at two natural populations.moreover,the mating systems of C.communis in wild populations were estimated using microsatellite markers.Important Findingsour data showed that the main floral visitors for C.communis at the two studied populations were small illegitimate bees rather than legitimate pollinators,accounting for 77.5 and 92.2%of total flower visits,respectively.Flower manipulations in C.communis demon-strated that the two types of brightly yellow stamens separately func-tioned as‘deceptive attraction’and‘feeding’functions.although the brown inconspicuous stamens of C.communis with the largest amount of fertile pollen had the potential function in offering pollen for cross pollination,the high ratio of illegitimate visitation by small bees significantly affected the dispersal and deposition of pollen from the pollinating anthers,and subsequently decreased the levels of outcrossing(tm=0.23-0.32)in wild populations.our work further confirmed that the size match between pollinators and the floral morphology is the prerequisite to successfully fulfill the functional differentiation among different sets of stamens in heterantherous plants.local high ratio of illegitimate visitation by size unmatched insects could significantly weaken the potential functions of heteranthery,affecting the dispersal and deposition of functional pollen in heterantherous plants and further the whole mating systems.