【作者】 张龙冲；

【导师】 杜国祯；

【作者基本信息】 兰州大学 ， 生态学， 2010， 博士

【摘要】 马先蒿属是北温带被子植物中的大属之一,其在狭窄的遗传基础上演化出如此丰富的物种,多样化的花冠形式以及专一的传粉者等特点已经吸引了许多研究者的关注。他们在该属植物的传粉生物学,传统系统分类,花部适应性进化等方面取得了很多研究成果,为进一步深入研究奠定了基础。但截止目前,在物种水平上,对该属植物具体环境下的繁殖生态学和种子萌发研究却很少见,尤其在青藏高原这一独特的区域内。本研究以青藏高原东部地区为研究地点(甘南藏族自治州),着眼于以下几个问题：1.)马先蒿属植物种间的单花性分配与给予传粉者的报酬类型、海拔以及个体大小的关系；2.)该属植物的全株雌雄性繁殖成功率与花冠类型、海拔、生活史周期以及个体大小的关系；3.)该属两年生植物的繁殖性状是否会对其幼苗期所受的光照强度作出响应；4.)一些关键生态因子和生活史特征是否会对种间种子萌发变异产生影响。通过几年的研究,取得了一些初步成果,具体如下：1.)通过对该地区12个马先蒿物种26个种群种间单花性分配的研究分析,发现该属植物给予传粉者熊蜂的报酬类型对其单花性分配有显著影响,与花蜜花粉报酬并举型植物相比,纯花粉报酬类型植物的单花性分配明显偏雌。这和以前认为的纯花粉报酬型植物可能表现出偏雄倾向以补偿花粉散失,吸引传粉者这一猜想相悖,然而结合以前该属植物的传粉生物学研究和性分配理论,我们认为这一结果亦是合情合理的。海拔差异对该属植物的种间单花性分配差异也有显著影响而植株的个体大小则没有。2.)全株雌雄性繁殖成功率(每株总花数和每株种子总重量)是测量植物适合度最直接的指标。通过对该地区12个马先蒿物种30个种群全株雌雄性繁殖成功率的研究分析,发现该属植物中属于较原始花冠类型的植物的这两个适合度指标并不比属于较进化花冠类型的低,这意味着以前所测量的较进化花冠类型物种花期的那些所谓“进化特征”在具体环境下未必真正起作用。虽然海拔差异对这两个繁殖性状没有直接的显著效应,但可以作用于植物个体大小来间接影响它们,这说明马先蒿植物能通过调整其个体大小与这两个繁殖性状的关系来适应环境梯度的变化。在本研究中,植物的生活史周期差别(一年生植物和多年生多次开花结果植物)和个体大小对这两个适合度指标影响最大,从权衡(Trade-off)理论的角度来看,这也是理所当然的。3.)通过对两年生植物扭旋马先蒿苗期里的不同光照强度处理,我们发现这种差异对其以后大部分繁殖性状有显著影响,亦可以作用于个体大小间接影响植株总花数这一性状。据我们所知,这是第一次报道该现象。4.)在对该地区马先蒿植物的种子萌发种间变异研究中,我们发现,温度和冷藏处理(干冷和湿冷)这两个外部因素并不会对该属植物的种子萌发能力造成影响。种子大小这一生活史特征和海拔差异也仅在特定条件下对其有显著效应。而生活史周期和种子贮放时间则对其作用力显著,我们认为这可能是该属植物的种子在此环境下进化出的风险平摊机制。此外,我们对以前研究者公布的数据进行了再分析,发现基本花冠类型和雌蕊长度与一些基本性投资指标显著相关,而雌蕊长度在发育上与花冠管、喙的长度直接关联,这意味着马先蒿属植物多样化的花冠形式不仅仅导致了繁殖隔离,而且也直接作用于与适合度相关的性投资指标,从而丰富了马先蒿多样性花冠的适应意义。更多还原

【Abstract】 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.更多还原