Pollination Ecology Of Two Sympatric Primula Specie (Primulceae)

Reproduction by most plant species occurs in a community of other flowering species and a diverse fauna of potential pollinators.This community context shapes both pollinator behavior and ecology and the outcome and evolution of plant reproduction.When the co-occurring plants are close related species,the fact that they could easily hybridize with another make the situation more intriguing,because hybridization is one of the most important evolution force.Distylous plant Primula secundiflora and P.poissonii are sympatric distributed at Shangri-La County, Yunnan,China,and some curious individuals with intermediate morphology occasionally happened in the field.To understand the pollination ecology of the two sympatric distributed distylous plants,we explored the true nature of these individuals with intermediate morphology,measured the reproductive isolation mechanisms between P.secundiflora and P.poissonii,and evaluated the effect of nectar robbing on reproductive fitness of P.secundiflora.Most morphological characters of these curious individuals were found to be intermediate between parental species,but plant height and corolla tube length were significantly transgressive.Molecular analyses based on nuclear internal transcribed spacer(ITS) additivity and/or two types of cloned sequences(corresponding respectively to those of two parental species) clearly suggested that these individuals have hybrid origin between P.poissonii and P.secundiflora.We further used maternally inherited chloroplast DNA fragment(rpl16 intron) to trace maternal composition of the hybrids.Among 26 hybrids,16(ten thrums,six pins) possessed the P.poissonii haplotype,while ten(two thrums,eight pins) had the P.secundiflora haplotype.These results suggest that both species had together served as the mother donors of the hybrids and reciprocal hybridization between two species seems to be symmetrical,rather than unidirectional. Empirical estimates of the relative importance of different barriers to gene flow between recently diverged species are important for understanding processes of speciation.I investigated the factors contributing to reproductive isolation between the sympatric distributed P.poissonii and P.secundiflora.The studied reproductive isolation mechanism included flowering phenology,pollinator fidelity,pollen competition,and relative hybrid fitness.Except floweing phenology,We found substantial reproductive barriers at multiple stages in the life history of P. secunfiflora and P.poiisonii.For P.secundiflora,pollinator fidelity,pollen competition,and relative hybrid fitness are 0.37063,0.61507 and 0.01418, respectively.For P.poissonii,they are 0.41558,0.41422and 0.15110,respectively. Our result suggested that although there were some hybrids in the field,the reproductive isolation mechanisms between P.secundiflora and P.poissonii were almost completely intact;and the fact that the total reproductive isolation index of P. poisonii was smaller than P.secundiflora's(0.98090＜0.99988),are consistent with P. poissonii devoted more mother donor than P.secundiflora.