Variations with altitude in reproductive traits and resource allocation of three Tibetan species of Ranunculaceae

We investigated the adaptive response of alpine plants to elevational gradients by examining reproductive traits and resource allocation of three species of Ranunculaceae with contrasting mating systems in alpine and subalpine populations on the eastern QinhaiTibetan Plateu. The results showed that ( i) at alpine sites, the self-incompatible Trollius ranunculoides Hemsley tended to become limited by pollination rather than by nutrient availability, although the self-compatible Anemone rivularis var. flore-minore Maxim. Fl. Tang. and A. obtusiloba D. Don. seemed not to be limited by pollen availability; ( ii) influences on the reproduction of these three species induced by high altitude were seen in different reproductive characters, and the influences were, to some extent, dependent on the plant. Female investment in the self-compatible A. rivularis and A. obtusiloba was influenced by altitude and plant size; with a much lower carpel number per flower and larger mean seed size in A. rivularis, and a much higher carpel number per flower and smaller mean seed size in A. obtusiloba, at a higher altitude. Floral investment in the self-incompatible T. ranunculoides was also influenced by altitude and plant size, with a smaller single-flower size and larger seed at the higher altitude. Results also showed that ( iii) reproductive allocation to flowering and fruiting did not always decrease with altitude as predicted. This may be due to higher nutrient availability in soil at alpine sites. ( iv) Although self-pollination may be an assurance mechanism alleviating pollination limitation, changes in allocation pattern, ( i. e. the male-biased. oral sexual allocation in A. rivularis and the higher allocation to attractive structure in A. obtusiloba) seem to promote pollinator visits at the high altitude.