花粉限制诱导的性表达变化是植物适应环境的重要方式，花粉限制强度越大植物相关繁育性状受到的自然选择就越强烈，但花粉限制对植物性系统进化的作用近年来才被真正重视。依赖专一性传粉者的植物被证实往往遭受更强烈的花粉限制，榕属物种与其传粉小蜂是目前已知的专一性最强的传粉共生体系之一，传粉小蜂的传粉行为对宿主榕的性表达有极强的选择作用，主动与被动传粉榕进化出不同的传粉综合征。地果为主动传粉榕，却呈现出不同于其他主动传粉榕的性系统特征，且在不同地域连续变化。我们拟比较不同类型地果的典型和交错带种群，评价其性表达的时空格局；野外调查和人工补充授粉相结合评价地果自然种群的花粉限制强度、传粉小蜂的传粉效率；野外调查和遗传分析相结合探究传粉小蜂的分化及种群统计动态；以厘清地果性表达格局转换的进化机理，解读强制异交物种对花粉限制强度、传粉者种群大小和行为波动的响应，深化对被子植物繁育系统进化的认识。

It is adaptively important for plants to adjust their sex expression in response to pollen limitation. Stronger pollen limitation usually imposes stronger natural selections on traits important for reproduction. However, the idea that pollen limitation might be important in the plant sex system evolution was not took seriously until recent years. It is demonstrated the plants relying on specific pollinators are more prone to pollen limitation. Ficus species and their pollinating fig wasps are among the most specific mutualisms. The sex expressions of Ficus species underwent strong selection by the pollination behavior and pollination efficiency of their species-specific pollinating fig wasps. Divergence in the anther-to-ovule ratios (A/O ratios) and distribution patterns of male flowers were demonstrated significant between actively- and passively-pollinated Ficus species. The Chinese endemic Ficus tikoua has an apparently-active pollinator, but atypical high variation of A/O ratios were detected among its natural populations in Southwest China. The distribution patterns of male flower showed continuous transitions along geographic clines. The high A/O ratios and scattered distribution pattern of male flowers deviated from the expectation of the active pollination mode. We plan to further investigate variations in A/O ratios among different natural populations of F. tikoua in order to map the distribution of pollination modes in relation to environmental variables; to estimate the level of pollen limitation of focal populations through a comparison of seed production under open pollination and artificial pollination; to assess the genetic divergence and population sizes of the pollinating fig wasps using both ecological and molecular methods and to compare behavior of the wasps in different areas. We thereby aim to explore evolutionary and ecological adaptations to pollen limitation in F. tikoua. This will aid interpretation of the responses of obligate-outcrossing species to pollinator population declines and changes in pollinator behavior, and contribute to a better understanding of the evolution of the plant breeding systems.