Studies On Reproductive Traits And Seed Germination Of Pedicularis (Orobanchaceae) Species In The Eastern Edge Of Qinghai-Tibet Plateau

Pedicularis L.(Orobanchaceae), one of the largest genus in angiosperm in North Temperate Zone, has being focused on by numerous researchers due to so diverse species, rapid floral variation from a narrow genetic basis and their single and exclusive bumblebees pollinators. Many fruitful achievements have been acquired at the aspects of pollination biology, traditional taxonomy, floral adaptive evolution and so on in the genus, which offer basis for future study. However, until now, few studies focus on the studies of reproductive ecology and seed germination of the genus in special region, especially in Qinghai-Tibet Plateau.In this study, we had chosen many Pedicularis species from eastern edge of Qinghai-Tibet Plateau to focus on the questions as following:(1) the relationships between the patterns of sex allocation per flower and rewarding types for pollinator, elevation and plant size at the level of species; (2) the relationships between male/female reproductive success per plant and floral types, elevation, period of life history and plant size at the level of species; (3) Plasticity of reproductive traits responding to variation in light quantity at rosette stage of the first year in the strict biennials species, Pedicularis torta; and, (4) whether some primary environmental factors and life history characteristics have significant effect on seed germination of the genus interspecificlly. The results showed:(1) In this study, we investigated the variation in sex allocation per flower with respect to two distinct rewarding types for pollinators in 12 Pedicularis species (26 populations) in alpine regions, controlling for the effects of elevation, species and plant size simultaneously. We found that the rewarding types affected sex allocation significantly, and there was a female-biased sex allocation pattern in pure pollen rewarding species relative to nectar rewarding ones. The finding is inconsistent with traditional hypothesis, which predicted that the sex allocation in pollen rewarding species is expected to be male-biased for compensating the loss of pollen in pollination and attracting pollinators and provides a new insight into variation in sex allocation. It is reasonable relating with activities and foraging behavior of pollinators in the genus and with theory of sex allocation. Moreover, environmental conditions (elevation) may also play relatively important role in determining patterns of variation in sex allocation per flower, whereas plant size may not.(2) Male/female reproductive success per plant (i.e. indicated by the total number of flower per plant and the total seed weight per plant, respectively) is the most direct index measuring fitness of plant. In this experiment, we investigated the variation in male/female reproductive success per plant with respect to differences of basic floral types, elevation, period of life history and plant size in 12 Pedicularis species (30 populations) in alpine regions. We found that male/female reproductive success per plant belonging to primary floral types was less low than one of derived floral types. It means that these so-called advantages of floral characteristics in derived floral types in previous studies are not obvious in actual environments at the level of species. Although the differences of elevation had not obvious direct effect on variation in the two reproductive traits, it may affect them indirectly through its effect on plant size. It means that plants adjust the relationships between plant size and the two reproductive traits for adapting the variable environment. In addition, the two variables of period of life history (monocarpic plant vs. polycarpic plant) and plant size contributed greatly to variation in the two reproductive traits.(3) We performed a pot experiment to investigate the effect of light quantity at rosette stage of plants on following reproductive traits, plant size and its relationships for the strict biennials species (P. torta). The results showed that the light differences significantly affected variation in following reproductive traits at all stages of development except for mean individual seed mass, plant size and the relationship between total number of flowers per plant and plant size among treatments. To our knowledge, this is the first time to study effect of light quantity during specific rosette stage on reproductive traits using the approach like this.(4) In the study of seed germination among Pedicularis species in the region, we found that the two external factors of temperature and treatment of cold storage for seed (dry cold storage vs wet cold storage) gave little effect on difference of final germination percentage among species in the genus. In the specific conditions, seed size and elevation had significant effect on it. The two internal factors of period of life history and length of seed deposited significantly affected it in the two experiments, which may be adaptive mechanism of risk evenness under alpine environment.In addition, former published data was reanalyzed under the background of integrating previous studies and personal field observations. We found that there were significant relationships between some traits of primary sexual investments and basic floral types, length of pistil related with diverse floral forms directly at the level of species in the genus. It indicated that diverse floral forms do not only coadapt with pollination behaviors of bumblebees for prezygotic reproductive isolation interspecificaly as considered by pollination biologists, but have correlation with several components of the two primary sexual investments and may accelerate speciation in the Pedicularis genus.