Functional monoecy due to delayed anther dehiscence : a novel mechanism in pseuduvaria mulgraveana (annonaceae)

Unlike most genera in the early-divergent angiosperm family Annonaceae, Pseuduvaria exhibits a diversity of floral sex expression. Most species are structurally andromonoecious (or possibly androdioecious), although the hermaphroditic flowers have been inferred to be functionally pistillate, with sterile staminodes. Pseuduvaria presents an ideal model for investigating the evolution of floral sex in early-divergent angiosperms, although detailed empirical studies are currently lacking. The phenology and pollination ecology of the Australian endemic species Pseuduvaria mulgraveana are studied in detail, including evaluations of floral scent chemistry, pollen viability, and floral visitors. Results showed that the flowers are pollinated by small diurnal nitidulid beetles and are protogynous. Pollen from both hermaphroditic and staminate flowers are shown to be equally viable. The structurally hermaphroditic flowers are nevertheless functionally pistillate as anther dehiscence is delayed until after petal abscission and hence after the departure of pollinators. This mechanism to achieve functional unisexuality of flowers has not previously been reported in angiosperms. It is known that protogyny is widespread amongst early-divergent angiosperms, including the Annonaceae, and is effective in preventing autogamy. Delayed anther dehiscence represents a further elaboration of this, and is effective in preventing geitonogamy since very few sexually mature flowers occur simultaneously in an individual. We highlight the necessity for field-based empirical interpretations of functional floral sex expression prior to evaluations of evolutionary processes.

Reproductive Biology of Corymbia citriodora subsp. variegata and Effective Pollination across its Native Range.

The spotted gum species complex represents a group of four eucalypt hardwood taxa that have a native range that spans the east coast of Australia, with a morphological cline from Victoria to northern Queensland. Of this group, Corymbia citriodora subsp. variegata (CCV) is widespread in south-eastern Queensland and northern New South Wales. It is currently the most commonly harvested native hardwood in Queensland. However, little basic knowledge of the reproductive biology of the species is available to inform genetic improvement and resource management programmes. Here we take an integrative approach, using both field and molecular data, to identify ecological factors important to mating patterns in native populations of CCV. Field observation of pollinator visitation and flowering phenology of 20 trees showed that foraging behaviour of pollinator guilds varies depending on flowering phenology and canopy structure. A positive effect of tree mean flowering effort was found on insect visitation, while bat visitation was predicted by tree height and by the number of trees simultaneously bearing flowers. Moreover, introduced honeybees were observed frequently, performing 73% of detected flower visits. Conversely, nectar-feeding birds and mammals were observed sporadically with lorikeets and honeyeaters each contributing to 11% of visits. Fruit bats, represented solely by the grey-headed flying fox, performed less than 2% of visits. Genotyping at six microsatellite markers in 301 seeds from 17 families sampled from four of Queensland's native forests showed that CCV displays a mixed-mating system that is mostly outcrossing (tm = 0.899 ± 0.021). Preferential effective pollination from near-neighbours was detected by means of maximum-likelihood paternity analysis with up to 16% of reproduction events resulting from selfing. Forty to 48% of fertilising pollen was also carried from longer distance (>60 m). Marked differences in foraging behaviour and visitation frequency between observed pollinator guilds suggests that the observed dichotomy of effective pollen movement in spotted gums may be due to frequent visit from introduced honeybees favouring geitonogamy and sporadic visits from honeyeaters and fruit bats resulting in potential long-distance pollinations.

同域分布两种兰科植物的传粉生物学及其防止同株异花授粉机制

兰科植物是被子植物中物种最丰富和最进化的类群之一，具有精巧、多样化的花部结构以及独特的吸引传粉者方式。开展兰科植物传粉生物学的研究对理解自然选择机制和异花授粉优势学说具有重要的理论意义。广西雅长兰科植物自然保护区是我国第一个以兰科植物命名的保护区，本文通过对保护区内同域分布的流苏贝母兰（Coelogyne fimbriata）和兔耳兰(Cymbidium lancifolium )传粉过程观察和繁殖成功等方面的研究，探讨兰科植物传粉机制和防止同株异花授粉的机制。同时结合传粉生物学研究的结果，对兰科植物多样性保护提出相关建议。主要研究结果如下： 1．流苏贝母兰的传粉生物学 在保护区2 个居群内对流苏贝母兰花期物候、传粉者种类和行为进行了连续3 年（2005-2007）的观察，对花和传粉者形态学指标进行了测量，对两个居群内所选取实验样地的花粉移走率、花粉接收率和结实率进行了详细的统计，通过动物行为学实验检测了花香对传粉者吸引方面的影响。并通过人工繁育系统实验检测流苏贝母兰的繁殖特征。结果显示，流苏贝母兰为具有特殊气味且无花蜜的兰科植物，由一种黄胡蜂属（Vespula）昆虫的雌性个体专性传粉，此为第二例由胡蜂专性传粉的具有食源性欺骗机制的兰科植物，且在传粉者行为和吸引机制与第一例存在很大差异。行为学实验显示花香对传粉者具有吸引作用。流苏贝母兰的花期与实验地黄胡蜂的繁殖季节和种群扩张期相吻合，在此期间，为了满足自身和幼虫的需求，黄胡蜂对碳水化合物需求大大增加。推测流苏贝母兰利用了黄胡蜂在繁殖和种群扩张期间需要大量摄取碳水化合物类物质，通过模拟碳水化合物来源（如果实或有花蜜、汁液分泌的植物）的气味，吸引传粉者。居群内花粉移走率、花粉接收率和结实率分别为0.069-0.918，0.025-0.695和0.014-0.069。结实率较低的原因可能与流苏贝母兰的自交不亲和特性和传粉者连续访问造成的同克隆授粉有关。其自交不亲和特性能有效地阻止自交，促进异交，同时蕊喙在接收花粉24 h 内与柱头愈合也能够减少花粉浪费，提高雄性适合度。 2．兔耳兰的传粉生物学 在保护区1 个居群内对兔耳兰进行了连续2 年（2005-2006）的观察和实验。观察发现兔耳兰唯一的传粉者为膜翅目蜜蜂科的中华蜜蜂(Apis cerana cerana)。中华蜜蜂在花内的停留时间为8-71 s。根据观察我们推测兔耳兰可能是通过其唇瓣上无规则的紫栗色小斑点(假蜜导)来吸引中华蜜蜂为其传粉, 属于食源性欺骗方式。在传粉过程中兔耳兰的药帽与花粉团和粘盘一起粘在中华蜜蜂胸背部。药帽的存在能够阻止下一朵被拜访的花实现雌性功能。兔耳兰药帽高度加上传粉昆虫胸高大于传粉通道入口的高度, 支持兔耳兰可能通过药帽来减少同株异花授粉现象的推测。蕊喙会在花粉接受72 h 内逐渐下弯并与柱头愈合，将接受的花粉包裹，且有些花的花萼片和侧面的两个花瓣会环抱住唇瓣侧裂片及蕊柱形成的入口，即传粉通道，避免继续接收花粉，增加花粉输出，提高雄性适合度。2005 和2006 年该兔耳兰居群的自然繁殖成功率分别为0.211 和0.213。繁育系统实验证明兔耳兰是高度自交亲和物种，不存在无融合生殖和自动自花授粉的现象, 其结实依赖传粉者。TTC 法检测结果显示兔耳兰种子活力达85.78%因此推断种子活力不是制约兔耳兰种子萌发的主要原因。而传粉者的密度和访问频率可能是影响兔耳兰结实的重要因素, 并最终影响兔耳兰种群的维持和扩张。 3．兰科植物促进繁殖成功的机制 植物通过各种方式吸引传粉者的最终目的是实现繁殖成功，是植物生活史的重要环节。兰科植物具有雌雄同体的合蕊柱的特殊结构，为了避免花粉-柱头间的干扰，其进化出一系列特殊的花部结构和适应机制，如欺骗性吸引机制、花粉块柄弯曲、花粉干缩等等。流苏贝母兰作为大量开花的克隆植物，其自交不亲和特性是促进异交的重要机制，另外蕊喙在花粉接收24 h 内与柱头发生愈合也是减少同株异花授粉机率的重要花部适应特征。兔耳兰为聚丛状生长的兰科植物，总状花序具多朵花，在传粉过程中通过药帽的阻挡和机械隔离，使携带于昆虫背部的花粉不能进入花内与柱头发生接触，避免同株异花授粉的发生。另外兔耳兰也存在花部适应的机制，蕊喙在花粉接收72 h 内逐渐下弯与柱头愈合，同时有些花的花萼片和侧面的两个花瓣环抱传粉通道入口，避免继续接收花粉，提高雄性适合度。 4. 兰科植物传粉系统和多样性保护 传粉生物学的研究为兰科植物的保护生物学提供了坚固的理论基础和重要的科学依据。绝大部分的兰科植物繁殖成功受到传粉者数量的限制。由于其精巧的花部结构，约67%已知传粉系统的兰科植物仅由唯一的传粉者专性传粉。另外，在某些区域内，还存在着较高程度的传粉者共享。传粉者数量的减少已经威胁到兰科植物的繁殖生存。因此，对兰科植物的保护应不仅仅关注于植物的保护，同时还应致力于传粉系统的保护。

Reproductive ecology of the Qinghai-Tibet Plateau endemic Gentiana straminea (Gentianaceae), a hermaphrodite perennial characterized by herkogamy and dichogamy

The combined occurrence of both herkogamy and dichogamy in a hermaphrodite species has been considered to strongly favour outcrossing. In this study, we investigated in detail the reproductive ecology of Gentiana straminea Maxim. (Gentianaceae), a hermaphrodite perennial endemic to the Qinghai-Tibet Plateau. In a series of observations and experiments over four consecutive years, we examined whether the combination of dichogamy and herkogamy in individual flowers completely prevents geitonogamous pollen transfer in this species. The mode of floral development clearly indicates that autonomous self-pollination is completely avoided through herkogamy and dichogamy in individual flowers. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Many flowers opened simultaneously on individual plants, the ratio of male to female phase flowers was close to 2:1 in each inflorescence, at the full anthesis phase, and they were randomly distributed amongst the upper, middle and lower parts of each stem's inflorescence. On average, Bombus sushikini Skorikov, the most frequent visitor and only legitimate pollinator of G. straminea, visited nearly two flowers per inflorescence, and four flowers per plant. Among the pollinators' foraging bouts, the proportions of geitonogamous visits to inflorescences or flowers within an individual plant were 29% and 37%, respectively. Therefore, despite the strict dichogamous and herkogamous characteristics of the individual flowers, geitonogamous selfing might still prevail in G. straininea because of the size of its floral displays and the continuous visiting behavior of B. sushkini. (C) 2005 Elsevier SAS. All rights reserved.

Entomofauna visitante de Stenolobium stans (Juss.) Seem (Bignoniaceae), durante seu período de floração

Realizaram-se estudos sobre as formas de reprodução de Stenolobium stans (Juss.) Seem e determinou-se a diversidade, freqüência e constância dos insetos visitantes nas flores em diferentes horas, durante quatro anos. As flores de S. stans começam a se abrir nas primeiras horas do dia entre 5 e 6h, com duração de 3 a 8h. Quando o estigma está receptivo, o pólen tem 90% de viabilidade. Além do pólen, a flor possui outros atrativos para os insetos visitantes, ou seja, os osmóforos responsáveis pelo odor adocicado, luz ultravioleta refletida e néctar com 25% de açúcar. A planta é autocompatível, reproduzindo-se por autogamia, geitonogamia ou xenogamia o que determina a necessidade de polinizadores externos e justifica ser a espécie vegetal em estudo uma séria invasora de campos e pastagens. Grande diversidade de insetos foi verificada visitando as flores, com predominância das abelhas. Os polinizadores foram Centris collaris Lepeletier, Bombus morio (Swederus), Eulaema nigrita Lepeletier e Epicharis sp. No meio rural houve menor incidência das espécies nativas do que no ambiente urbano, com predominância da abelha introduzida Apis mellifera L. Fatores ambientais, principalmente a temperatura, luminosidade, umidade relativa do ar e velocidade do vento, influenciaram a atividade forrageadora dos insetos.

caracterização in situ e estrutura genética de populações de Gossypium mustelinum

Gossypium mustelinum Miers ex Watt is the only cotton species native from Brazil. It is endemic of the semi-arid region from North-east of the country, where it occur near from resilient water sources. The threats to the in situ conservation of the populations are caused by human interference in its habitat, mainly by excessive cattle graze and deforestation. Establish efficient strategies of in situ conservation depend on the accomplishment of a diagnosis of how the specie is found in its natural environment, and the knowledge about the genetic structure of the populations. The objectives of this work were i) to determine the in situ conditions of two populations present in rivers from basin of Rio Paraguaçu at the Bahia State, ii) to evaluate the structure and genetic variability presented in both populations, iii) to establish in situ and ex situ conservation strategies. It were realized collection in november 2007, when was realized in situ characterization of G. mustelinum. SSR markers were used for analyze 218 genotypes deriving from two populations of the G. mustelinum, localized at Tocó river and the Capivara river. The allelic frequencies, the heterozigosity and the F statics were estimated. All the plants were classified as wild and natives, and there was no evidence of the use the plants or its parts. The populations showed different conservation conditions in situ. Few plantlets were found in sites with excessive cattle feed, an indication that the damages in young plants should be high enough to compromise the renovation of the populations. On the other hand, populations were well preserved when the anthropic damages was low or inexistent. The 14 SSR primer pairs amplified 17 loci with a medium number of 5 alleles per locus (a total of 85 alleles). The high level of endogamy estimated (FIS=0,808) and the low observed heterozygosity (H0=0,093) were indicatives that the populations reproduce mainly by selfing, geitonogamy and crosses between related individuals. The genetic diversity was high (HE=0,482) and the differentiation between the populations was very high (FST=0,328). At least two sites from both populations of G. mustelinum must be preserved to achieve suitable in situ conservation. Actions that preserve the gallery forest and keep the cattle away should implemented, and could be as simple as erecting a fence. It is not possible anticipated if the in situ preservation will be possible. Therefore collections and ex situ preservation of representative specimens are essential to conserve the genetic diversity of native G. mustelinum

The reproductive biology of Cybistax antisyphilitica (Bignoniaceae), a characteristic tree of the South American savannah-like "Cerrado" vegetation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Selection and Floral Evolution in Platanthera bifolia and P. chlorantha (Orchidaceae)

Natural selection mediated by pollinators has influenced the evolution of floral diversity of the flowering plants (angiosperms). The scope of this thesis was to study: 1) phenotypic selection, 2) mating systems, and 3) floral shifts involved in plant speciation. Model plant species were Platanthera bifolia and P. chlorantha (Orchidaceae). These orchids are moth-pollinated, strictly co-sexual (bisexual flowers), and produce a spike that displays 10-20 white flowers. I explored the influence of characters on plant fitness by using multiple linear regressions. Pollen removal (male fitness) and fruit set (female fitness) increased with more flowers per plant in three P. bifolia populations. There was selection towards longer spurs in a dry year when average spur length was shorter than in normal-wet years. Female function was sensitive to drought, which enabled an application of the male function hypothesis of floral evolution (Bateman's principle). The results show that selection may vary between populations, years, and sex-functions. I examined inbreeding by estimating levels of geitonogamy (self-pollination between flowers of an individual) with an emasculation method in two P. bifolia populations. Geitonogamy did not vary with inflorescence size. Levels of geitonogamy was 20-40% in the smaller, but non-significant in the larger population. This may relate to lower number of possible mates and pollinator activity in the smaller population. Platanthera bifolia exhibits the ancestral character state of tongue-attachment of pollinia on the pollinator. Its close relative P. chlorantha attaches its pollinia onto the pollinator's eyes. To explore the mechanism of a floral shift, pollination efficiency and speed was compared between the two species. The results showed no differences in pollination efficiency, but P. chlorantha had faster pollen export and import. Efficiency of pollination in terms of speed may cause floral shifts, and thus speciation.