探讨花的多样性及其生态和进化后果是植物进化生物学的核心主题。单花性（每个个体只开一朵花）是被子植物中的一个普遍现象，然而，很少有研究来探讨单花性的生态和进化意义。近期我们利用多年积累的数据研究发现，单花种植物在结实率和每株结籽率上显著低于花序种。本项目以两对单花种和花序种兰科植物为主要研究对象，在前期研究基础上，通过全因素试验设计和实验操纵法，对比分析单花种和花序种在不同微生境和开花密度条件下生殖分配和生殖代价；应用花粉染色法和分子标记法比较单花种和花序种植物的交配格局及其对微生境和密度的响应，从生活史适应策略和遗传后果方面探讨在数量上具有生殖劣势的单花种的可能补偿机制，为进一步理解花多样的适应和进化机制提供重要信息，并为作为植物保护中的“旗舰”类群的兰科植物的有效保护和合理利用提供有益的资料。

Understanding the diversification mechanisms of flower and its ecological and evolutionary consequences is a central theme in plant evolutionary ecology. Singleness, characterizing by producing a single flower or leaf, is common found in many taxa of angiosperm. However, the reproductive consequences of phenotype producing a single flower are poorly understood. Our recent study on many species over many years indicated that single-flowered species had significant lower proportion of fruit set and seed number per plant than multiple-flowered species. In order to investigate the potential compensatory mechanisms for such reproductive disadvantages in single-flowered species, a full factorial experiment manipulating microsite and floral density will be conducted in two populations of two species pairs producing either a single flower or multiple flowers per plant (Changnienia amoena vs Phaius delavayi, Cypripedium tibeticum vs Cypripedium henryi). Reproductive allotment will be estimated in two species pairs by comparing the relative dry weight of reproductive tissue in relation to total plant weight. Costs of natural investment in reproduction will be assessed by experimentally preventing fruit set by pollinator exclusions, whereas costs of increased reproductive investment are examined by the use of supplemental hand-pollination, maximizing fruit set under contrasting microsites and floral densities. Pollen flow within and between plants will be monitored by following the movement of the coloured pollen. Outcrossing rate in two species pairs will be estimated using a multilocus mixed model and selfing rate is compared the same species under contrasting microsites and floral densities. We discuss the possible compensatory mechanisms for reproductive disadvantages in single-flowered species by comparing cost of reproduction and mating pattern with multiple-flowered species. This project will not only enrich our understanding of life historical characteristics and mating pattern in different phenotypes producing a single flower or multiple flowers per plant, but also contribute to develop strategies for the conservation and sustainable utilization of these orchids in China.