Reproductive Strategies Of Three Common Species Of Ranunculaceae At Alpine Meadow In Qinghai Tibetan Plateau

Reproductive strategies, especially resource allocation are central of study of plant life history. In the pollinating process, many pollinators are attracted by visual cues. Outcrossers at different altitudes can obtain more visitations through different strategies to release the absence of pollinators. Increasing the resources investment to their attractants and rewards of insect-pollinated plants in high arctic and alpine areas is regarded as an adaption to low pollinator abundance and consequent pollen limitation. There are a lot of unique plants in Alpine Meadow at Eastern QinghaiTibetan Plateau. How to adapt the especial environment of Alpine, and what reproductive strategies appear for these species, which provide a special chance for ecologists and evolutionists. Therefore, we selected 3 common species of Ranunculaceae, comparative primordial plants in Alpine Meadow at Eastern QinghaiTibetan Plateau, and studied the reproductive strategies, such as reproductive allocation, especially sex allocation, to understand how the plants adapt the environmental conditions. The results showed:(1) The results showed that relationship between scape length and male, female function vared with speices with different mating systems and with attitudes, In Trollius ranunculoides Hemsl. (self-incompatible) plants, the relationship between scape length and stamina:pistils number (the ratio of stamina number to pistils number of a flower) and stamina:pistils weight (the ratio of stamina weight to pistils weight of a flower) vried with altitude. Stamina:pistils number was negatively related to scape length at all attitudes (2900m,3400m,3700m and 3900m). Stamina:pistils weight was positively related with scape length at the lowest elevation (2900m) but negatively related at the other three higher elevations (3400m,3700m and 3900m). In Anemone obtusiloba D. Don (facultatively self-pollinated), stamina:pistils number was positively related to scape length at two lower elevations (2200m and 2900m), but negatively related to scape length at a higher elevation (3400m). In contrast, stamina:pistils weight was negatively at the two lower elevations (2200m and 2900m) but positively related at the higher elevation (3400m) with scape length. (2) In Trollius ranunculoides plants, conspicuous yellow sepals is a visual attractive structure of this species) while degenerate petals can be evaluated as reward to pollinators i.e. nectar output, because each petal has a nectary at the base and the number of petals has a positive relationship with visiting maintenance Pollen limitation and resources allocation to sepals and petals was studied in Trollius ranunculoides at four altitudes. Female fitness was more pollen limited at the higher altitudes. The plants invested more resources to sepals and less to petals at higher than at the lower altitues.(3) Both the number of pistil and seed size of Aconitum gymnandrum plants did not vary with flower position within inflorescence or with different genotypes. The seed size, but not the number of pistil was affected by different resource availability. From bottom to top flower within inflorescence floral sex allocation tends to be male-biased: more anther number and pollen, less carpel number and ovule, lower seed set at top flower. It was caused by "constructure effect" and "resource limitation"(4) Floral longevity and male phase duration of Aconitum gymnandrum increased and the female phase duration was invariable from bottom to top flowers. Shading plants starting from the seedling stage maintained reproduction success, which was attributable to strategies like less investment to vegetative growth and male function; less flowers and larger flower display size. Shaded plants also had shorter floral longevity and male phase duration.In summary, our studies showed that, generally alpine plant species were pollen limited. To overcme pollen limitatation, resources allocation to different parts of reproduction functions (floral display, floral longivtiy and male and femal function) was related with each other. They also varied with many interal and external factors related to reproduction, such as mating system, altitudes and flowers postions within inflorescence. The alpine plant species at high altitudes would increase floral display to increase the opportunity of pollinators' visitation. These results indicated the three species had evolved complex reproduction systems to well adapt to the alpine envionments.