| To explore the coevolutionary relationship between plants and pollinators, the reproductive characters of several Pedicularis species were studied in northwest Yunnan, China. I examined the correlations between floral diversity and pollination patterns, the reproductive isolation mechanisms among the sympatric species, the evolutionary significance of corolla forms, the effects of pollinators on the reproductive success in 3 populations of P. densispica and the characteristics of seed germination in 4 Pedicularis species. The results are as following:The species which are toothless with nectar (P. densispica) are pollinated nototribic by bumblebees foraging for nectar and/or pollen or sternotribic for pollen. While the toothed species most of which have nectar (P. polyodonta) are pollinated nototribic by bumblebees. The species with a beak and short (P. gruina and P. rhinanthoides) or long corolla tube (P. longiflora P. siphonnantha and P. tricolor, these species endemic to Hengduan Mountains) are also buzz-pollinated sternotribic by bumblebees. The Pedicularis species are not quite strictly congruent with the bumblebees. One Pedicularis species may be visited by several Bombus species, and one Bombus pollinator may visit different plant species at different time, causing a complex plant-pollinator interaction.The reproductive isolation among sympatric Pedicularis species is influenced by the differences of pollinator behavior and floral form via ethological isolation and mechanical isolation.Floral sex allocation varied widely among 7 species, even those species with the same corolla form, pollen and ovule production per flower, P/O and pollen size werelargely different. However, increasing length of floral tube was companied with larger pollen size. In addition, the number of inflorescences, total flowers, opening flowers and the ratio of co-opening flowers of the long-tubed species are higher, while the blooming period of which is shorter. Compared to the species with shorter corolla tubes, the pattern of resource allocation and floral display in long-tubed Pedicularis species seems to take more advantages in enhancing pollen transfer. Meanwhile, the long-tubed species with longer style can lead to stronger pollen competition. The species with a beak can reduce pollen wastage, avoid autonomous self-pollination, benefit to develop mechanical isolation and elongate the style.A total of 4 species of bumblebees was observed visiting the flowers of P. densispica. The pollination patterns were nototribic or sternotribic. The bumblebees pollinated nototribic that could cause higher geitonogamy than those pollinated sternotribic, which might improve outcrossing. The insect visiting frequencies differed in species and populations. The percentage of stigmas with pollen deposition was higher than 76.58% in 3 populations, but the number of pollen grains per stigma was not enough to pollinate the ovules in each ovary. Hand-pollinated flowers yielded higher seed set than open-pollinated flowers. Seed production in this species is likely to be pollen limited. Seed set of the other 6 species ranged from 19.82% to 60%. Seed production in Pedicularis species seems to be pollen limited, indicating Pedicularis species may compete for bumblebee pollinators caused by unfavourable environment in Alpine habitats.The seed germination of P. densispica, P. polyodonta, P. gruina and P. siphonnantha was not affected by sand moisture content. No significant difference was found between the germinability of their seeds in light or in darkness. The optimal temperatures for germination in four species were 20 C ,15 C ,15C and 4C , respectively. Seeds of P. densispica could germinate immediately after ripen, while P. polyodonta seeds should be stratified for 60 days before germination, the percentages of germination were 95% and 84%, respectively. The percentage of seed germinationof P. gruina increased to 94% after stratified for 60 days. The percentage of seed germination of P. siphonnantha was 35 % in 60 days. Stratified at...
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