【作者】 李群；

【导师】 王学英； 阮成江；

【作者基本信息】 沈阳农业大学 ， 农学， 2011， 博士

【摘要】 开花植物性器官分离的进化及适应意义一直令进化生物学家所着迷,如雌雄异熟(时间上的分离)和雌雄异位(空间上的分离)。一直以来雌雄异熟和雌雄异位的适应意义是避免自交,然而最近越来越多的证据表明是为了避免雌雄干扰。多种多样的花部特征和花部构造影响植物的传粉和交配系统,自从达尔文指出兰科植物花部行为的适应意义为避免自交以来,最近又提出了许多关于花部行为适应意义的假说,其中包括降低雌雄干扰、避免自交和促进异交、延迟自交和应对不良环境。然而,一些物种花部行为的适应意义仍未被完全解释。蜀葵(Althaea rosea),锦葵科二年生或多年生草本植物,雌雄同花,雄蕊先熟,单体雄蕊紧抱花柱,其上被多轮小雄蕊,花柱被包围在单体雄蕊管内,柱头从雄蕊柱中伸出,形成雌雄异位,其柱头分枝能发生弯曲,最终与自身花药毗邻或接触。本文以大连地区蜀葵的自然居群为研究对象,首次从开花物候、花部特征、开花动态、繁育系统、传粉生物学、交配系统及锦葵科部分物种花柱弯曲的进化机制进行系统研究,得出以下结论：1.蜀葵花期在6月下旬至10月初,自然居群内的开花过程呈单峰曲线,群体内开花模式属于“集中开花模式”,开花同步性指数为0.81±0.06。单株每日开放0～40朵花,平均每株6±1.21朵。每日单株上的花总数平均为23±3.45朵,盛花期,最高可达108朵。蜀葵的这种开花方式对交配系统的影响是双亲近交不可避免。2.自然状态下,绝大多数花朵都集中在上午7：00左右开放,阴雨天则延迟开放或者不开放。蜀葵单花持续时间为3.57±0.14d,雄性先熟,持续时间为2.45±0.16d,雌性期持续时间为1.55±0.16d；花表现出柱头探出式雌雄异位,5.18±0.03mm。柱头于花后第2d早约7：00左右从单体雄蕊柱中钻出,2-4h后开始弯曲且弯曲速度较慢,11：00-13：00间,花柱弯曲的速度加快,之后花柱弯曲速度减慢,至花冠闭合前,花柱停止运动,与花药接触；当柱头与自身花药接触时,其柱头可授性为89.7%,花粉生活力为42.33%；蜀葵的不完全雌雄异熟、雌雄异位和花柱运动的进化机制综合了促进异交、避免雌雄干扰和延迟自交几种进化机制。3.花粉—胚珠(P/O)比为744.55,属兼性异交；而杂交指数(OCI)为5,属异交,部分自交亲和,需要传粉者。本研究认为OCI在判断蜀葵的繁育系统上可能比P/O比更合适。4.套袋实验结果表明,蜀葵不存在无融合生殖,自交亲和,并能够通过花柱运动完成延迟自交。去雄和授粉处理不影响蜀葵的座果率,人工自花授粉与去雄后异花授粉间座果率无差异(P=0.058),二者间单果种子数基本相同,分别为30.63±0.57和30.37±0.38,表明蜀葵有很强的自交亲和能力。蜀葵的自动自交能力很强(AF=0.86),对照(Flo)与去雄后自然授粉(FEo)之间单果种子数无差异(P=0.765),表明发生在蜀葵上的延迟自交不能在传粉者缺少的情况下为繁殖提供保障(RA=0.005)。5.自交后代种子百粒重明显低于杂交种子(P<0.01),自动自交与去雄后人工异花授粉间种子发芽率差异显著(P<0.05),杂交子代生物量明显高于自交后代(P<0.05),即自交后代适合度明显低于杂交后代。6.花期内蜀葵花蜜分泌量呈单峰曲线,花蜜常备量在花后4h内急剧下降,表明花蜜是吸引访花昆虫的主要报酬。蜀葵花蜜含糖量为8.41%,其中葡萄糖占77.52%(64.5mg/mL),果糖占22.48%(18.7 mg/mL);蜀葵花蜜中氨基酸含量为0.017%,共检测到14种氨基酸,其中半胱氨酸含量最高,占氨基酸总量的36.13%。7.共观察到蜀葵的访花昆虫13种,隶属4目(膜翅目,双翅目,鞘翅目和螳螂目)。意大利蜂(Apis mellifera)是蜀葵的主要传粉昆虫,其平均访花频率为3.07朵/min±0.20；花蜜分泌速率与访花频率间并无相关性(r=0.262,P=0.411)；意大利蜂在一天内的访花频率间也存在极显著性差异(one-way ANOVA,F11,24=2.33,P=0.04)；意大利蜂的取食时间与花蜜分泌速率无相关性(r=-0.193,P=0.549),取食时间在一天内的差异不显著(one-way ANOVA,F11,24=1.63,P=0.15)；意大利蜂的访花频率与取食时间之间存在着负相关(r=-0.849,P<0.000)；意大利蜂在一个植株上的访花数目不等,访问1朵花的比例最大(33.96%),访问2朵以上的比例是66.04%,表明蜀葵同株异花传粉发生的可能性极大。8.共1015个子代DNA,16个ISSR引物用于检测蜀葵交配系统参数,结果表明蜀葵是以异交为主的物种,3个居群多位点异交率在0.972～0.981之间,平均为0.977±0.003,其中SY居群的异交率最大(tm=0.981±0.007),DL居群异交率次之(tm=0.979±0.003),AS居群异交率最小(tm=0.972±0.000)；3个居群存在明显的双亲近交且变化较大,tm—ts值在0.281(SY)～0.465(AS)之间,3个居群双亲近交程度也许与其居群内植物密度有关；3个居群中均存在亚结构,其rps—rpm值在1.552±0.012(AS)～0.720±0.009(DL)之间；3个居群的期望指数均小于固定指数,即F>Fe,表明子代有不同程度的近交衰退；11个ISSR引物所产生的所有标记位点是研究蜀葵交配系统的最小数目。9.为了探讨花柱运动的适应性进化机制,用叶绿体DNA的ndhF序列和rpL16内含子序列绘制进化树,包括锦葵科13个属52个种,其中8个属的23个种表现柱头弯曲,其结果首次证明远古时锦葵科中雌雄异位花的柱头是没有弯曲的,这种柱头弯曲的进化至少有8次。柱头弯曲转换1次与一年生或多年生草本的转换相关联。一个不可预期的传粉环境可能是柱头弯曲进化的重要因素,因为发生柱头弯曲的种类有相同的生态分布却有不同的传粉方式。柱头弯曲进化作为一种传粉模式出现,使之具有在异交失败的情况下为了达到繁殖成功而发生自交的能力,提供一种混合的交配系统并且也反映了功能特性转变与生态环境之间的普遍的对应关系。更多还原

【Abstract】 The evolution and functional significance of sexual diversity in flowering plants have long intrigued evolutionary botanists. These include dichogamy (the temporal separation of male and female function within hermaphroditic flowers) and herkogamy (the spatial separation of male and female within a flower). Although dichogamy and herkogamy have been interpreted as mechanisms for reducing self-fertilization, increasing evidence suggests that they may act as mechanisms to reduce intrafloral male-female interference.Variations in floral traits and floral structures influence plant pollination and mating systems. Since Darwin noted that reconfiguration of pollinia in orchids avoids self-pollination, various hypotheses have been proposed to explain the adaptive significance of floral movements. These include reduction in intrafloral male-female interference, avoidance of self-pollination and promotion of outcrossing, delayed autonomous pollination and tolerance to harsh environments. However, the adaptive significance of floral movement in some species has yet to be fully explained. Althaea rosea (Malvaceae) is a biennial or perennial dicot herb species. Its flowers are hermaphrodite, protandrous, with a monadelphous androecium in which filaments are united to form one tube, the anthers forming part of the tube. The stigmas are exserted beyond the anthers, forming approach herkogamy. Previous observations indicate that the style branches of A. rosea can curve at anthesis, and eventually bring some stigmas down or in contact with the anthers. In this thesis, the research about A. rosea is studied, as the first time, in details by using naturalize populations in Da Lian. This focuses on flowering phenology, floral traits, flower opening process, breeding system, pollination biology, mating system and adaptive evolution of context-edpendent style curvature in the Malvaceae. Main conclusions are presented as follows.1. The florescenece in large scale of Althaea rosea is between late June to beginning of October. The flower opening process are a single-peak curve in naturalized population and in similar model of "Mass-flowering pattern". The synchronous index is 0.81±0.06. Each individual plant has an average of 23±3.45 flowers in different developmental stages ranging from 0 to 40 and an average 6±1.21 per plant. There are 108 flowers in one plant in full flowering. The effects of floral display on mating system is the biparental inbreeding.2. Most flowers opened about 7:00 AM in sunny days and delayed or non-flowering in cloudy or rainy days. The single florescence can last 3.57±0.14d. Protandrous and the male phase is 2.45±0.16d, and the female phase is 1.55±0.16d. The distance is about 5.18±0.03mm between the stigmas and the anther, it is the approach herkogamy, the stigmas exserted from the column about 7:00AM after 1 day and began to curve after 2-4h. The speed was slow at beginning and then it was faster about 11:00-13:00, subsequently the speed was slower, and the stigmas can contact to the anther later in flowering. The stigma receptivity and pollen viability was 89.7 and 42.33%, respectively when stigmas were in contact with anthers via style curvature. The adaptive significance of protandrous, approach herkogamy and style curvature in A. rosea may be simultaneously involved in three functions, including reduction of intrafloral male-female interference, promotion of outcrossing, and achievement of delayed selfing.3. The pollen-ovule ratio is 744.55, these indicate that breeding system of A. rosea belongs to facultative xenogamy, but the outcrossing index suggested the breeding system is outcrossing and partial self-compatibility and a pollinator is needed because the OCI was 5. The outcrossing index is more suitable than P/O in breeding system of A. rosea.4. A. rosea is not agamospermy, it is self-compatibility and has the self-pollination of delayed selfing by stylar movements. There are no significant differences in fruit set between intact hand self-pollinated flowers and emasculated hand cross-pollinated flowers (P= 0.058). Intact hand self-pollinated flowers have the same seed set as emasculated cross-pollinated flowers, indicating that A. rosea has a high level of self-compatibility. A. rosea has a potentially strong auto fertility capacity (AF=0.86), although there is no significant difference in seed set between intact and emasculated open flowers (P=0.765), indicating that delayed selfing in A. rosea does not provide reproductive assurance (RA=0.005) when pollinators are scarce.5. The 100-seed weight of the self-pollinated progenies is lighter than the out-crossing (P < 0.01). There are significant differences in germination rate between autonomous self pollination flowers and emasculated hand cross-pollinated flowers (P= 0.058). The weight of seedlings of the self-pollinated progenies is lighter than the out-crossing (P< 0.01). These results indicated that the fintess of self-pollinated progenies is lighter than the out-crossing.6. The nectar was secreted before flower opening and has a single-peak curve in anthesis. The nectar volume of standing crop decreased sharply after 4h of anthesis, indecating the nectar was the main rewards. The content of sugar is 8.41% in nectars, the glucose and fructose are 77.52%(64.5 mg/mL) and 22.48% (18.7 mg/mL) respectivily, The content of amino acids is 0.017% and 14 amino acids are detected in the nectar, the content of cysteines is 36.13% among the amino acids.7. There were 13 flowering-visiting species belonging to 4 orders (Hemenoptera, Diptera, Coleoptera and Mantodea). The Apis mellifera is the main pollinator and the average visiting frequency was 3.07flowers/min±0.20. The visiting frequency of A. mellifera is no correlated with the nectar volume of secretion in A. rosea (r=0.262, P=0.411). There are significant differences in diurnal changes of flower-visiting frequency of A. mellifera. There is no correlation between foraging time and nectar secretion rate (r=-0.193, P=0.549). It is no obvious difference in foraging time in one day (one-way ANOVA, F11,24=1.63, P= 0.15); There is a negative correlation between visiting frequency and foraging time (r=-0.849, P <0.000); Among the pollinators’, the proportion of visiting one and more than two flowers was 33.96% and 66.04% respectivily, these indicated the geitonogamous was unavoidable.8. A total 1015 seedlings and 16 ISSR primers were used to estimate mating system parameters, this suggests that this species is predominantly outcrossing. The multilocus outcrossing rates were 0.972 to 0.981 in different populations with a mean of 0.977. The multilocus outcrossing rates of SY population was the highest (tm= 0.979±0.003), DL population took second place (tm=0.979±0.003) and AS population was 0.972±0.000. The rates of biparental inbreeding (tm—ts) were significantly variable and it was ranged from 0.281(SY) to 0.465 (AS). Biparental inbreeding in A rosea is possibly associated with plant density and the product of flower size and number The correlation of paternity for the multilocus significantly differed from the correlation of paternity for the single-locus, with rpsrpm ranged from 1.552±0.012 in population AS to 0.720±0.009 in population DL, which suggested there are substructure for every sampled population. Inbreeding depression was observed in the three populations because expected fixation index (Fe) was lower than estimated F. An empirical analysis suggests that 11 ISSR markers is the minimum number of dominant marker loci necessary to achieve robust estimates of Mating system parameters of A. rosea.9. To investigate the adaptive evolution of this curvature, we mapped the trait state of styles and correlated characters on the molecular phylogenetic trees of 52 species of 13 genera of this family reconstructed using chloroplast DNA sequences of ndhF and rp116 intron, in which 23 species belonging to eight genera present style curvature. The results first showed that the ancestral state of styles is no curvature, and thant style curvature evolved at least eight times in species with herkogamous flowers of the Malvaceae. A shift to use style curvature is associated with a shift to annual or perennial herbs. An unpredictable pollinator environment is likely an important trigger for the evolution of style curvature, because species with style curvature have similar ecological distributions with variable pollination. The evolution of style curvature as one mode of pollination appears to have coevolved an ability to self in order to achieve reproductive success if outcrossing fails, offering a mixed mating system and also reflecting the widespread correspondence between functional trait state transitions and ecological conditions.更多还原