Sexual reproduction of the high mountain plant Saxifraga moschata Wulfen at varying lengths of the growing season

Flowering phenology, dynamics of seed development and reproductive success of Saxifraga moschata Wulfen, occurring from the alpine to the nival zone, was investigated in three climatically varying years on early- and late-thawing sites at 2340 m a.s.l. in the Austrian Alps. The growing season was particularly short in 2001, about normal in 2002 and exceptionally long and warm in 2003. S. moschata is a mid-season flowering species, which started to bloom about 1 month after snowmelt. From onset of anthesis until seed maturity an individual flower required 6–7 weeks, and all individuals of a site 9–11 weeks. In 2001, late flowering individuals lost about 40% of the seed crop because of too early snowfalls in autumn. No clear relationship could be found between thermal time and the length of different reproductive phases, which indicates that temperature was not a limiting factor for reproductive development in the growing seasons 2001–2003.

Plants from the earliest-thawing site produced about double the reproductive structures (reproductive shoots per individual, number of flowers per inflorescence, number of ovules per ovary), and had a significantly higher reproductive output (number of fruits and mature seeds per inflorescence) compared with individuals from the late-thawing site. Reproductive success was additionally affected by the seasonal climate and was lowest in the warm and dry summer of 2003. Fruit/flower ratio ranged between 0.6 and 0.8, seed/ovule ratio between 0.4 and 0.5 and relative reproductive success (RRS) between 0.3 and 0.4, depending on the site and year.

Different from our expectations, it took S. moschata relatively long to undergo reproductive development; however, its phenological plasticity and ability to continue seed maturation even under snow are most advantageous for a life at higher altitudes.     

同域分布的紫堇属三种植物的繁育系统和传粉差异

为研究近缘物种之间繁育系统分化对传粉环境的适应性意义,本文针对湖北地区的3种紫堇属植物（紫堇Corydalis edulis Maxim.、尖距紫堇C.shearer S.Moore.和小花黄堇C.racemosa（Thunb.） Pers.）进行了传粉生态学研究,对比分析了它们在花部特征、分布模式、花期、交配系统、传粉系统等方面的差异。3种紫堇属植物常见伴生现象,花期有一定重叠;花色、距长、花蜜量等方面均有显著差异;尖距紫堇交配系统为自交不亲和、依靠传粉者异花授粉;而紫堇和小花黄堇交配系统为自交亲和,兼有自交和异交的混合交配系统。3个物种均由蜂类传粉,且花部性器官与传粉者的接触部位一致,但访花频率差异较大。在混合群落中,传粉者访花具有较高的忠实性,花部特征差异可能是传粉者选择性访花的原因。对于紫堇属3个物种,花部特征和交配系统的分化有助于其避免传粉过程的相互干扰,交配系统与传粉环境具有一定相关性,混合交配系统可能有利于提高植物对不同生境和气候的适应性。     

山地虎耳草和棒腺虎耳草转录组SSR和SNP分析

利用Illumina HiSeqTM2000对山地虎耳草和棒腺虎耳草进行转录组测序,分析和比较其SSR和SNP特征。结果表明:山地虎耳草63 763条Unigene序列中含有4 622个SSR,发生频率为7.25%,有110种重复基元,平均每10.00kb出现一个SSR位点;棒腺虎耳草60 972条Unigene序列中含有4 542个SSR,发生频率为7.45%,有85种重复基元,平均每10.40kb出现一个SSR位点,略低于山地虎耳草。山地虎耳草和棒腺虎耳草转录组序列的SSR优势基元均为三核苷酸重复。2个物种的转录组SSR以5~10次的较低重复次数为主,长度主要集中于12~30bp,具有较高的多态性。山地虎耳草和棒腺虎耳草中分别获得118 424个和112 006个SNP位点,编码区的SNP位点分别占30.40%和28.59%,且在编码SNP中同义突变所占比例(30.27%、28.48%)远高于非同义突变(0.13%、0.11%)。比较发现,2个物种的各项检索结果基本一致,推测与选取的组织部位、组织的发育阶段以及物种的亲缘关系有关。     

Biomass production of the last remaining fen with Saxifraga hirculus in Switzerland is controlled by nitrogen availability

Olde Venterink H. and Vittoz P. 2008. Biomass production of the last remaining fen with Saxifraga hirculus in Switzerland is controlled by nitrogen availability. Bot. Helv. 118: 165 – 174. For conservation management of endangered plants it is important to know which nutrient(s) control growth of the vegetation, because maintenance of low nitrogen (N), phosphorus (P) or potassium (K) availability requires different management measures. The aim of this study was to determine the type of nutrient limitation for the vegetation in the last remaining site with Saxifraga hirculus in Switzerland, using nutrient ratios in the aboveground vegetation as an indicator. We made vegetation relevees, collected biomass of the vascular plants, and took soil samples in three plots at this site. The biomass was very low (152–231 g m ^-2), and all three plots were clearly N-limited with N:P ratios of 7– 8. Soil extractable N concentrations were generally low, and P and K concentrations were moderate to high, which was consistent with the indicated N limitation. Hence conservation management first of all needs to prevent N-enrichment, and needs to avoid increased mineralization rates through drainage, or the accumulation of N in the system from atmospheric deposition. Therefore N output seems required through for instance grazing or mowing. The current grazing management seems to function well, since total aboveground biomass is very low and S. hirculus has a high abundance in this last remnant. Submitted 5 June 2008; Accepted 14 October 2008 Subject editor: Sonja Wipf     

Reproductive ecology of blackbirds ( Turdus merula maximus) in a high-altitude location, Tibet

Reproductive data of high-altitude blackbirds (Turdus merula maximus) were collected at an alpine environment covered with scrub vegetation in Lhasa mountains, Tibet. The blackbird nests were found from 3,800 to 4,500 m at a breeding density of 0.07 pairs/ha. Egg-laying occurred from early May to late July, with a peak (73.0% of all nesting attempts) between mid-May and mid-June. Most (79.5%) of the nests were sited in six different plant species with Cotoneaster microphyllus being most preferred. A few (20.5%) nests were against rocky walls. Bushes used for nest sites were significantly higher. Compared with lowland blackbirds, montane blackbirds experienced a shorter breeding season (2.5 months), laid smaller clutches (2–4 eggs, averaging 2.86), but larger eggs (mean volume index 16,348), produced only one brood per year, had a slightly shorter incubation period (12–13 days), but a longer nestling period (16–18 days), and enjoyed a higher breeding success (59.0%). In the alpine environment where climate is harsh and food supply poor, the strategy of increased egg size with decreased clutch size suggests that the high-altitude blackbirds improve their breeding success by investing more reproductive energy in fewer offspring in response to the constraints of time and resources. However, the environmental constraints on reproduction result in a low annual reproductive output.This revised version was published online in December 2004. The german abstract has been included.     

The Peniophorella praetermissa species complex (Basidiomycota)

The corticioid basidiomycete Peniophorella praetermissa has long been regarded as a morphologically variable species complex. An ITS-based phylogenetic study based on a worldwide sampling was carried out using parsimony and Bayesian inference. The resulting trees feature three major clades, further divided into well-supported subclades. These could be considered as distinct species, a contention that is further supported by crossing test data. Only two out of the eight phylogenetic lineages identified can be distinctly morphologically characterized: P. odontiaeformis and P. subpraetermissa. P. odontiaeformis is an odontioid species with a paleotropical distribution whereas the taxa in the remaining subclades have smooth basidiomata and are distributed in temperate areas. P. subpraetermissa is known only from the type collection and is distinguished microscopically by its reddish brown apically encrustated cystidia. Taxa in the remaining subclades are impossible to distinguish from each other morphologically, and therefore, are viewed as a species complex, P. praetermissa s. lat. One of the subclades, which is widely distributed but restricted to the Northern hemisphere, is proposed to represent P. praetermissa s. str. An epitype is selected from the same area as the holotype, among the specimens studied here. However, the geographically most widespread clade with many representatives from both hemispheres is here referred to as P. pertenuis, a taxon that was previously considered a synonym to P. praetermissa.     

Seed ecology and germination treatments in Magnolia dealbata: An endangered species

Magnolia dealbata is a deciduous tree species in danger of extinction. Seed ecology data and successful germination treatments are important for conservation and species reintroduction programs. This study reports about seed ecology and germination treatments of M. dealbata Zucc. The results showed that the seeds, influence of vertebrates excluded, persisted viable after 1 year, suggesting the presence of a semi-persistent seed pool. There was no significant difference (p>0.05) in survival of seeds with or without sarcotesta after a year. Significant differences (p<0.05) were found in the number of seeds surviving after a year at different levels of burial. There was no significant interaction upon survival (p>0.05) between sarcotesta presence or absence in the seed and burial depth. If vertebrates were not excluded the seeds had a removal rate of 100% 8 months after being exposed. Seed survival curve was of Type II, that is, with constant mortality throughout the time. The most successful germination treatment (p<0.05) with 100% germination was soaking of seeds without sarcotesta for 24 h at room temperature (18–20 °C).     

山羊臭虎耳草的延迟自动自花授粉机制

通过对山羊臭虎耳草6个花形态及其发育阶段、授粉过程的连续观察和对花粉活性、柱头可授性的连续检测,报道了一种新的延迟自动自花授粉机制,即山羊臭虎耳草花丝运动引导的延迟自动自花授粉。利用电子显微镜研究了花粉囊的破裂方式和柱头结构,同时利用苏丹Ⅲ研究了花粉的组织化学性质。结果显示:(1)第四生长阶段,当花丝引导大部分花粉囊运动至柱头上方时,花粉和柱头的可授性才均达到峰值[可授性分别为(94±6)%和(96±13)%],这种运动消除了第三生长阶段花粉活性较高[(90±8)%]而柱头可授性较低[(6±17)%]的异花授粉特征,即消除了花粉与柱头的时空隔离;自动自花授粉发生于异花授粉特征消除之后,因此山羊臭虎耳草具有典型的延迟自动自交行为。(2)第四发育阶段柱头空腔的大量柱状突起和花粉鞘的油脂性特征,增加了花粉和柱头的接触表面,并且使花粉更好地互相堆积粘附在柱头上,提高授粉效率。(3)对山羊臭虎耳草的繁育系统研究表明,强制自花授粉和人工自花授粉产种量无明显差异,2007年和2008年的自交系数高达0.92和0.91,说明山羊臭虎耳草具有很好的自交能力并且不存在花粉数量限制;人工异花授粉的产种率显著高于人工自花授粉,说明自花花粉的质量显著低于异花花粉,虎耳草延迟自动自花授粉存在生殖衰退,生殖保障系数2007年为0.92,2008年为0.91,表明在极端环境下自动自花授粉为该植物提供了繁殖保障,但极端环境下,没有观察到有效的授粉昆虫。研究表明,作为高山冰缘植物的山羊臭虎耳草,保留了开花植物异花授粉的特征,在极端环境下利用延迟自动自花授粉机制完成授粉,保障生殖。     

The role of regional and local scale predictors for plant species richness in Mediterranean forests

Abstract

Both local and regional predictors play a role in determining plant community structure and composition. Climate, soil features as well as different local history and management affect forest understorey and tree species composition, but to date their specific role is relatively unknown. Few studies have addressed the importance of these predictors, especially in the Mediterranean area, where environmental conditions and human impacts have generated heterogeneous forest communities. In this study, the relationships between environmental variables and species richness of different groups of vascular plants (vascular species, woody species and open habitat species) and bryophytes were investigated in Tuscan forests. A total of 37 environmental variables were used by generalised linear model fitting in order to find parsimonious sub-sets of environmental factors (predictors) that are able to explain species diversity patterns at the local scale. Moreover, the role of regional and local variable groups on species richness of the considered plant groups was estimated by using the variance partitioning approach. We found that local variables, such as forest management and structure, explained more variance than regional variables for total species richness, open habitat species richness and bryophyte species richness. On the other hand, regional variables (such as elevation) played a central role for woody species richness.     

Germination behaviour of 14 Mediterranean species in relation to fire factors: smoke and heat

Fire is an ecological factor that has been present in the ecosystems of the Mediterranean region for thousands of years. Our study was undertaken to acquire knowledge of the effect of fire on the germination of Mediterranean species. We used high temperatures (up to 60°C) and smoke to determine the effect of these factors on the germination of species from the Mediterranean region. The species selected are characteristic of the central Mediterranean basin and are representative of both woody and herbaceous species: Rhamnus alaternus L., Cistus albidus L., Cistus monspeliensis L., Fumana ericoides (Cav.) Gand., Rosmarinus officinalis L., Melica ciliata L., Avena sterilis L., Bituminaria bituminosa (L.) C.H. Stirt., Anthyllis vulneraria L., Coronilla glauca L., Argyrolobium zanonii (Turra) P.W. Balland, Emerus major Mill., Genista scorpius (L.) D.C. and Spartium junceum L. The seeds were collected in Mediterranean shrubland (8) and woodland (6) ecosystems, around Montpellier, France (24°45′N and 3°50′E). Ten treatments were tested: a control, three smoke treatments and six heat treatments. The average germination level (germination percentage) and the average T₅₀ rates (time taken to reach 50% of germination) were calculated. The smoke and heat act in a different way on each of the species. The smoke enhanced the germination of two species, whilst moderate heat increased germination in all of the species excepting R. officinalis, F. ericoides, A. sterilis, A. vulneraria, and G. scorpius. Germination was fastest in M. ciliata and S. junceum and slowest in A. sterilis, E. major and C. albidus. The cues did not significantly affect the rate of germination. Fire modified the germination response of 12 of the 14 species studied.     

Seed germination responses of the Saharan plant species Ephedra alata ssp. alenda to fungicide seed treatments in the laboratory and the field

Given its importance in the functioning of arid ecosystems, Ephedra alata ssp. alenda has drawn some attention and appeared to be suitable for desert re-vegetation. An experimental study has been carried out on the germination properties of seeds of this strictly Saharan species. Analyses of temperature effects, and fungicide seed treatments in the laboratory and the field enabled to determine the optimum germination conditions.     

广西油茶人工林林下植物多样性区域变化规律

为揭示广西油茶林植物多样性的区域变化规律,以广西7个区域具代表性的油茶林为研究对象,采用典型抽样法,对油茶林林下植被进行了调查,并对比分析了群落物种组成、结构特征和物种多样性。结果表明:(1)油茶林林下植被灌草层科数、属数、种数最多的是三江县油茶林(SJ)、较少的是巴马县油茶林(BM)和来宾市油茶林(LB);除巴马县油茶林(BM)灌木层优势种为共有种,其他区域油茶林的灌木层、草本层优势种均为交叉种。(2)多样性指数方面灌木层仅Margalef指数差异显著,草本层Margalef指数、Simpson指数、Shannon-Wiener指数差异显著。(3)通过回归分析,纬度与灌木层(单一种数量)、草本层(科数、属数、种数、单一种数量)以及总数量(属数、种数)、年均温度与草本层(科数、属数、种数、单一种数量)、有效积温与草本层(属数、种数、单一种数量)、年均降雨量与灌木层单一种数量之间的趋势模拟呈二次曲线关系。(4)不同区域油茶林物种相似性不高,通过相似系数矩阵进行聚类分析三江县油茶林(SJ)、贺州市八步区油茶林(HZ)、岑溪市软枝油茶种子园油茶林(CX)、南宁市油茶林(NN)为一类,凤山县油...     

Changes between 1927 and 2004 and effect of rock climbing on occurrence of Saxifraga paniculata and Draba aizoides, two glacial relicts on limestone cliffs of the Swabian Jura, southern Germany

A number of glacial relicts can be found on limestone cliffs of the Swabian Jura in southern Germany. In general, they are rare and endangered, particular on cliffs where rock climbing is allowed. Two glacial relicts, Saxifraga paniculata Mill. and Draba aizoides L., were quantitatively surveyed on 28 cliffs in 2004 to investigate their occurrence compared to former surveys and to analyse the effect of rock climbing on species abundance. Number of cushions per cliff and number of rosettes per cushion were counted, smallest and largest diameter of cushions and rosettes, as well as aspect and inclination were also measured. S. paniculata was found on 75% and D. aizoides on 30% of the cliffs. Up to 150 S. paniculata and 370 D. aizoides cushions were noted per cliff, in total there were 696 S. paniculata and 705 D. aizoides cushions. In cliff areas where rock climbing takes place, S. paniculata was only located in relatively uninfluenced parts of the cliffs. In contrast, D. aizoides was found with at a significantly higher frequency on climbed cliffs, and surprisingly, also at the foot of the cliffs, which means that climbing activities even increased numbers of D. aizoides. Rosettes might have been cut of by trampling and climbing and fell to positions where they established new cushions at the base of the cliff. Compared to earlier studies in 1927 and 1966, a higher number of cliffs containing both glacial relicts were found. It can be assumed that not all cliffs had been surveyed in the past and that cliffs were not surveyed as completely as possible. The former locations were confirmed except for one cliff where D. aizoides did not exist anymore. From the cliffs studied, D. aizoides and S. paniculata do not seem to be directly in danger of disappearance in the near future. Nevertheless, rock climbing or visits of hikers on certain cliffs can be a threat, in particular to S. paniculata. This study provides the groundwork for future quantitative monitoring of these two glacial relicts.     

No inbreeding depression in an outcrossing alpine species: The breeding system of Campanula thyrsoides

Plants that live in fragmented landscapes, where populations are isolated from each other and in which long-distance dispersal is essential for colonization of empty sites, reproduction should be favoured by self-compatibility (Baker's law). Nevertheless, outcrossing mechanisms, such as self-incompatibility and dichogamy, are common in many species and are often maintained by inbreeding depression in the fitness of selfed progeny. Here, we studied the breeding system and the consequences of selfing and sister mating in Campanula thyrsoides, a short-lived perennial monocarp, which is found in the naturally fragmented landscape of the Alps. An experiment with controlled pollinations was set up in the common garden with plants grown from seeds originating from 14 seed families, collected in the siliceous Central Alps, where this plant is found on isolated carbonate bearing outcrops.Our results indicate that C. thyrsoides has a strong self-incompatibility system (SI) with no or low seed set in selfed flowers compared to outcrossed and sister-crossed flowers. Moreover, the SI system in C. thyrsoides did not break down with flower age as in some other Campanula species. Surprisingly, there was no significant difference in seed set, seed weight, germination percentage, seedling survival and size between outcrossed and sister-crossed offspring, which indicates no inbreeding depression.We suggest that the absence of inbreeding depression in this outcrossing species might be a result of frequent bottlenecks during colonization of the isolated habitats in the alpine landscape.     

Mating strategies and pollen limitation in a globally threatened perennial Polemonium vanbruntiae

Knowledge of the factors that limit reproduction is critical to an understanding of plant ecology, and is particularly important for predicting population viability for threatened species. Here, we investigated the pollination biology of a globally threatened plant, Polemonium vanbruntiae, using hand-pollination experiments in four natural populations to determine the degree of pollen limitation. In addition, we investigated the mating system and extent to which plants can self-fertilize by comparing geitonogamously and autonomously self-fertilized plants with purely outcrossed and open-pollinated plants. In contrast to several of the more common species of Polemonium, we found no pollen limitation in any of the four populations of P. vanbruntiae over two years. The lack of pollen limitation was best explained by the capacity for P. vanbruntiae to both geitonogamously and autonomously self-fertilize, unlike some of its more common congeners. Geitonogamously selfed flowers set equivalent numbers of seeds when compared to purely outcrossed and open-pollinated flowers. However, autonomously selfed flowers produced significantly fewer seeds, demonstrating that pollinators play an important role as inter- and intra-plant pollen vectors in this system. Our results support the reproductive assurance hypothesis, whereby the ability to self assures fertilization for plants in small populations. Self-compatibility in Polemonium vanbruntiae may decrease extinction risk of isolated populations experiencing a stochastic pollinator pool within a restricted geographic range. In addition, a mixed-mating strategy, including the ability for clonal reproduction, may explain the ability for this rare species to persist in small, fragmented populations.     

祁连山区特有物种黑虎耳草的居群遗传多样性研究

利用叶绿体基因(rbcL和trnS-G)及核糖体DNA内转录间隔区(ITS),对祁连山区狭域分布的特有物种黑虎耳草8个居群(115个个体)进行遗传多样性研究,旨在揭示黑虎耳草的居群遗传结构及其历史进化过程。结果表明:(1)所有取样个体共检测到4个cpDNA单倍型和9个ITS单倍型,其中祁连山东南部的居群固定较多的单倍型和特有单倍型,而西北部居群只固定少数几个广泛分布的单倍型,且遗传多样性普遍较低。(2)基于cpDNA数据和ITS数据的分子变异分析(AMOVA)显示,遗传变异主要来源于居群内。(3)基于cpDNA数据的中性检验表明,Tajima’s D(-1.012 30,P> 0.05)和Fu&Li’s D*(-2.066 77,P> 0.05)均为负值,均不显著;歧点分布分析结果显示,黑虎耳草居群经历过近期的扩张事件。根据物种现有遗传分布格局推测,黑虎耳草在第四纪冰期时退缩到祁连山东南部的边缘避难所,间冰期或冰期后回迁到祁连山西北部地区,在回迁过程中由于奠基者效应导致祁连山西北部的居群仅固定少数广泛分布的单倍型,并呈现出较低的遗传多样性;由于居群较小且相互隔离,该...     

Microsatellite markers for the palaeotropic pioneer tree genus Macaranga (Euphorbiaceae) and their cross‐species transferability

We developed primer sequences for five polymorphic microsatellite loci in the tropical ant‐plant genus Macaranga (Euphorbiaceae). Population genetic parameters were determined on the basis of 30 individuals from each of two Macaranga species in Borneo. Allele numbers per locus ranged from three to 13. Expected and observed heterozygosities ranged from 0.160 to 0.850 and from 0.130 to 0.700, respectively. Four of the five primer pairs cross‐amplify polymorphic PCR products in a wide range of Macaranga species.