Phylogeny of the Botryosphaeriaceae reveals patterns of host association

Three anamorph genera of the Botryosphaeriaceae namely Diplodia, Lasiodiplodia and Dothiorella have typically dark, ovoid conidia with thick walls, and are consequently difficult to distinguish from each other. These genera are well-known pathogens of especially pine species. We generated a multiple gene genealogy to resolve the phylogenetic relationships of Botryosphaeriaceae with dark conidial anamorphs, and mapped host associations based on this phylogeny. The multiple gene genealogy separated Diplodia, Lasiodiplodia and Dothiorella and it revealed trends in the patterns of host association. The data set was expanded to include more lineages of the Botryosphaeriaceae, and included all isolates from different host species for which ITS sequence data are available. Results indicate that Diplodia species occur mainly on gymnosperms, with a few species on both gymnosperms and angiosperms. Lasiodiplodia species occur equally on both gymnosperms and angiosperms, Dothiorella species are restricted to angiosperms and Neofusicoccum species occur mainly on angiosperms with rare reports on Southern Hemisphere gymnosperms. Botryosphaeria species with Fusicoccum anamorphs occur mostly on angiosperms with rare reports on gymnosperms. Ancestral state reconstruction suggests that a putative ancestor of the Botryosphaeriaceae most likely evolved on the angiosperms. Another interesting observation was that both host generalist and specialist species were observed in all the lineages of the Botryosphaeriaceae, with little evidence of host associated co-evolution.     

中国裸子植物的物种多样性格局及其影响因子

物种多样性的大尺度空间格局是宏观生态学和生物地理学研究的核心问题之一。本文利用中国裸子植物分布数据, 结合气候、地形等环境信息, 分析了中国裸子植物物种多样性的大尺度格局及其影响因素, 比较了不同类群之间物种多样性格局和主导因子的差异, 并探讨了裸子植物在植物区系中所占比重的地理格局。结果表明, 中国裸子植物的物种多样性总体上呈现南高北低的趋势, 物种多样性在横断山区最高。在裸子植物的三个主要类群中, 松柏亚纲的物种多样性格局与整体相似, 买麻藤亚纲的多样性高值区则出现在中国西北部的干旱地区, 苏铁亚纲的分布区较为狭窄, 主要集中在南方地区。线性回归分析结果表明, 空间异质性和降水因子对中国裸子植物多样性格局的解释率最高, 末次冰期以来的气温变化、海拔高差和能量因子次之。这表明中国裸子植物物种多样性的格局受到了多种因素的影响, 其中空间异质性和降水因子影响最大。进一步分析发现, 物种多样性格局的主导因子在不同类群之间具有显著差异, 这可能反映了这些类群的进化历史以及生理适应的差异。裸子植物与被子植物的比例具有明显的空间格局: 在东部、南部气候环境优越的地区, 裸子植物与被子植物的比例低于0.06; 而在西部、北部等气候环境比较恶劣的地区, 裸子植物的比例则显著上升。回归分析表明, 能量和水分因子显著影响了裸子植物与被子植物的比例。随着能量的降低和降水的减少, 裸子植物与被子植物的比例会显著升高, 这可能是由于被子植物在温暖湿润地区具有较强竞争优势, 但裸子植物对极端环境具有更好的适应。     

Sexual systems in gymnosperms: A review

The aim of this study was to update figures for the presence of dioecy among the gymnosperms and investigate its correlation with climate, growth form, pollination and seed dispersal syndromes, and risk of extinction. Dioecy was found in almost 65% of contemporary gymnosperm species, a higher percentage than previous estimates. It dominates in 8 of the 12 families. As in angiosperms, dioecious gymnosperms are particularly common in climbers and are more commonly found in tropical climates. Analysis of the degree of threat using IUCN red list categories showed that the proportion of threatened species is higher in dioecious than in monoecious species only in temperate climate. The high sensitivity of dioecious species to environmental changes associated with human activity in temperate climate may explain this phenomenon. The monophyly of extant gymnosperms and the relatively small number of species (about 1000) create the possibility of treating them as a model group in investigating the evolution of sexual systems.     

Chilling rather than photoperiod controls budburst for gymnosperm species in subtropical China

低温而不是光周期调控中国亚热带裸子植物的出芽物候 摘要：被子植物春季物候的调控机制已经得到了广泛的研究。然而,裸子植物和被子植物在3亿年前就产生分化,裸子植物与被子植物的物候可能是受不同的因素所调控。亚热带植物物候的调节机制在很大程度上尚不明确,亚热带裸子植物物候是否由冷激需求和光照调控仍未得到验证。本研究在人工气候箱中设置了3个冷激处理和3 个光周期处理,并对切枝的出芽期进行了为期8周的研究。实验中我们测试了8种裸子植物：柳杉(Cryptomeria japonica)、杉木(Cunninghamia lanceolata)、柏树(Cupressus funebris)、银杏(Ginkgo biloba)、水杉(Metasequoia glyptostroboides)、马尾松(Pinus massoniana)、金钱 松(Pseudolarix amabilis)和罗汉松(Podocarpus macrophyllus),检验其出芽物候是否对光周期敏感或者是否具有较强的冷激需求,以及这两种因素哪个对促进出芽更为重要。研究结果表明,对于裸子植物,冷 激促进了出芽并提高了出芽率,而且裸子植物需要适度的低温天数来实现出芽。有趣的是,在同一森 林中裸子植物比被子植物对积温的需求更高。与德国温带裸子植物(194–600 d · °C)相比,亚热带裸子植 物(814–1150 d · °C)对积温的需求更高。光周期对裸子植物出芽的影响较小,说明冷激对裸子植物出芽的 促进作用大于光周期。这些结果表明,随着全球气候持续变暖,冬季气温的升高不仅会影响亚热带被子植物也会影响裸子植物的物候,从而可能导致春季出芽期的延迟。     

Nuclear DNA C-values Complete Familial Representation in Gymnosperms

The gymnosperms are a monophyletic yet diverse group of woodytrees with approx. 730 extant species in 17 families. A recentsurvey showed that DNA C-values were available for approx. 16%of species, but for only 12 of the 17 families. This paper completesfamilial representation reporting first C-values for the fiveremaining families: Boweniaceae, Stangeriaceae, Welwitschiaceae,Cephalotaxaceae and Sciadopityaceae. C-values for nine Ephedraand two Gnetum species are also reported. C-values are now availablefor 152 (21%) species. Analysis confirms that gymnosperms arecharacterized by larger C-values than angiosperms (modal 1Cof gymnosperms = 15.8 pg compared with 0.6 pg in angiosperms)although the range (1C = 2.25–32.20 pg) is smaller thanthat in angiosperms (1C = 0.05–127.4 pg). Given completefamilial coverage for C-values and increasing consensus in gymnospermphylogeny, the phylogenetic component of C-value variation wasalso investigated by comparing the two datasets. This analysisrevealed that ancestral gymnosperms (represented by cycads and/orGinkgo; mean genome size = 14.71 pg) probably had larger genomes thanancestral angiosperms. Copyright 2001 Annals of Botany Company Gymnosperm DNA amounts, C-values, phylogeny, ancestral genome size, Cycadales, Ginkgo, Gnetales, conifers, Pinaceae     

Seed size and shade-tolerance: a comparative analysis of North American temperate trees

Large seed size is a trait associated with plant species of mature, closed habitats, and is thought to supply an ample nutrient reserve necessary for seedling establishment. While this relationship has been shown for annuals and short-lived perennials, it is poorly documented for trees. A comparative method was used to determine whether North American temperate tree species which typically establish in shady conditions have larger seeds than those requiring more open conditions. Both angiosperms (hardwoods) and gymnosperms (conifers) were involved in the study. A significant relationship was found between large seed mass and shade-tolerance for angiosperms, but not for gymnosperms. These contrasting results seem to relate to unique evolutionary opportunities or constraints in different taxa. The absence of a relationship for gymnosperms is discussed in terms of character traits which might prevent seed size selection in response to shade. The finding for angiosperms underlines the importance of the regeneration niche in promoting coexistence among temperate hardwood species through seed size differentiation. Received: 18 March 1997 / Accepted: 26 November 1997     

Taxonomy of gymnospermae: multivariate analyses of leaf fatty acid composition

The fatty acid composition of photosynthetic tissues from 137 species of gymnosperms belonging to 14 families was determined by gas chromatography. Statistical analysis clearly discriminated four groups. Ginkgoaceae, Cycadaceae, Stangeriaceae, Zamiaceae, Sciadopityaceae, Podocarpaceae, Cephalotaxaceae, Taxaceae, Ephedraceae and Welwitschiaceae are in the first group, while Cupressaceae and Araucariaceae are mainly in the second one. The third and the fourth groups composed of Pinaceae species are characterized by the genera Larix, and Abies and Cedrus, respectively. Principal component and discriminant analyses and divisive hierarchical clustering analysis of the 43 Pinaceae species were also performed. A clear-cut separation of the genera Abies, Larix, and Cedrus from the other Pinaceae was evidenced. In addition, a mass analysis of the two main chloroplastic lipids from 14 gymnosperms was performed. The results point to a great originality in gymnosperms since in several species and contrary to the angiosperms, the amount of digalactosyldiacylglycerol exceeds that of monogalactosyldiacylglycerol.     

Variation in the psbC gene region of gymnosperms and angiosperms as detected by a single restriction site polymorphism

 This paper reports on a PCR-RFLP analysis in a chloroplast DNA region consisting of coding and intergenic spacer sequences of trnS and the adjacent psbC gene. This region was PCR-amplified in 62 woody plant species, predominantly tree species, that represent a broad systematic range in both gymnosperms and dicotyledonous angiosperms. The amplification products were digested by the restriction endonuclease HaeIII (GG↓CC). Fourteen different restriction patterns occurred, 5 of which characterised representatives of the gymnosperms, and 9 angiosperm representatives. A single restriction site polymorphism revealed most of the species to share restriction patterns. Groups formed which showed relationships to plant systematic units. This phenomenon is discussed with regard to the psbC gene and the GGCC motif for tracing species’ relationships on a high taxonomic level of gymnosperms and angiosperms. Received: 5 June 1996/Accepted: 20 September 1996     

Accessory costs of seed production and the evolution of angiosperms

Accessory costs of reproduction frequently equal or exceed direct investment in offspring, and can limit the evolution of small offspring sizes. Early angiosperms had minimum seed sizes, an order of magnitude smaller than their contemporaries. It has been proposed that changes to reproductive features at the base of the angiosperm clade reduced accessory costs thus removing the fitness disadvantage of small seeds. We measured accessory costs of reproduction in 25 extant gymnosperms and angiosperms, to test whether angiosperms can produce small seeds more economically than gymnosperms. Total accessory costs scaled isometrically to seed mass for angiosperms but less than isometrically for gymnosperms, so that smaller seeds were proportionally more expensive for gymnosperms to produce. In particular, costs of abortions and packaging structures were significantly higher in gymnosperms. Also, the relationship between seed:ovule ratio and seed size was negative in angiosperms but positive in gymnosperms. We argue that the carpel was a key evolutionary innovation reducing accessory costs in angiosperms by allowing sporophytic control of pre- and postzygotic mate selection and timing of resource allocation. The resulting reduction in costs of aborting unfertilized ovules or genetically inferior embryos would have lowered total reproductive costs enabling early angiosperms to evolve small seed sizes and short generation times.     

Molecular Data from the Chloroplast rpoC1 Gene Suggest a Deep and Distinct Dichotomy of Contemporary Spermatophytes into Two Monophyla: Gymnosperms (Including Gnetales) and Angiosperms

Partial sequences of the rpoC1 gene from two species of angiosperms and three species of gymnosperms (8330 base pairs) were determined and compared. The data obtained support the hypothesis that angiosperms and gymnosperms are monophyletic and none of the recent groups of the latter is sister to angiosperms. Received: 20 November 1998 / Accepted: 26 April 1999     

Adaptive Evolution in the GAF Domain of Phytochromes in Gymnosperms

The GAF domain of phytochrome is essential for photoconversion and signal transduction. In gymnosperms, it exists in all members of the phytochrome family that experience gene duplication. Maximum-likelihood models of codon substitution can provide a framework for constructing likelihood ratio tests of changes in selective pressure and make clear predictions about patterns of genetic change following gene duplication. In this study, 68 gymnosperm GAF sequences were analyzed to identify lineages and sites under positive selection. Our results indicate that (1) positive selection at a few sites (3.6%), rather than relaxation of selective constraints, has played a major role in the evolution of the gymnosperm GAF domain; (2) strong positive selective pressure tends to occur in the recent PHYP lineages of cogeneric species, but is absent in old lineages consisting of distantly related species; and (3) the selective pressure indicated by the ω ratio varies greatly among lineages and sites in the GAF domain.     

Xylem hydraulic and photosynthetic function of Gnetum (Gnetales) species from Papua New Guinea

Gnetum (Gnetales) species are suggested to be unique extant gymnosperms that have acquired high photosynthetic and transpiration capacities as well as greater xylem hydraulic capacity and efficiency compared with all other extant gymnosperms. This is because Gnetum is the only extant gymnosperm lineage that combines vessels, broad pinnate-veined leaves and an ecological distribution in wet, productive lowland tropical rainforest habitats. Yet, field-based observations on the group's ecophysiological performance are lacking. To test a hypothesis that Gnetum species are ecophysiologically analogous to light-demanding woody tropical angiosperms, stem xylem hydraulic performance, photosynthesis and stomatal conductance were investigated in Gnetum as compared with a diverse group of co-occurring woody plants in a lowland tropical rainforest. It was found that Gnetum species combined low photosynthetic capacity and low stomatal conductances with a low stem water transport ability. The physiological observations are consistent with the general occurrence of Gnetum species in shady, primary forest habitats. These results on Gnetum ecophysiology indicate that the coupling of vessels, broad pinnate-veined leaves and the liana habit do not signal the evolution of a highly opportunistic, light-demanding life history in gymnosperms.     

High universality of matK primers for barcoding gymnosperms

DNA barcoding is a tool to provide rapid and accurate taxonomic identification using a standard DNA region. A two-marker combination of rnatK+rbcL was formally proposed as the core barcode for land plants by the Consortium for the Barcode of Life Plant Working Group. However, there are currently no barcoding primers for matK showing high universality in gymnosperms. We used 57 gymnosperm species representing 40 genera, 11families and four subclasses to evaluate the universality of nine candidate matK primers and one rbcL primer in this study. Primer (1F/724R) of rbcL is proposed here as a universal primer for gymnosperms due to high universality. One of the nine candidate matK primers (Gym_F1A/Gym_R1A) is proposed as the best "universal" matK primer for gynnosperms because of high polymerase chain reaction success and routine generation of high quality bidirectional sequences. A specific matK primer for Ephedra was newly designed in this study, which performed well on the sampled species. The primers proposed here for rbcL and matK can be easily and successfully amplified for most gymnosperms.     

Application of the Serological Method for Evaluation of Relations between Gymnospermous and Dicotyledonous Plants

An attempt has been undertaken to evaluate interrelations of gymnospermous and dicotyledonous plants on the basis of immunochemical studies of seed proteins. For this purpose, 12 antisera were raised to proteins of taxa representing four gymnosperm classes: Ginkgoopsida, Cycadopsida, Coniferopsida, and Gnetopsida. Seed proteins of eight dicotyledonous subclasses (after Takhtadzhyan, 1987) were used. The representatives of all dicotyledonous subclasses gave immunochemical reactions with those of all gymnospermous classes. The data obtained suggest the presence of sufficiently close immunochemical relations between gymnosperms and dicotyledons. Samples were found among the representatives of subclasses Dilleniidae, Hamamelididae, and Rosidae, which gave satisfactory reactions with eight to ten antisera to proteins of dicotyledonous seeds. Analysis of the data we obtained suggests that gymnospermous and dicotyledonous plants took their origin from a common pragymnospermous ancestor and later evolved independently or that dicotyledons separated from gymnosperms at an early stage of their evolution before divergence of the latter into several phyletic lineages.     

裸子植物DNA条形码ITS2高通用性引物的筛选

DNA条形码技术是利用标准DNA片段进行准确快速鉴定物种的一种方法,理想的DNA条形码片段应具有高通用性。虽然核糖体DNA内部转录间隔区II（ITS2）被建议作为种子植物有效的DNA条形码,但目前裸子植物还没有通用性高的引物可用。为获得高通用性的ITS2引物,本研究基于裸子植物55个属的5．8S基因的保守序列区设计了3个正向引物,与已有的ITS反向引物组合,组成了7对ITS2引物进行通用性的评价。选取了裸子植物8目、12科和40属的56个种用于本文的研究。引物组合5．8SR／ITS4、5．8SRa／ITS4和5．8SF2／S3R因为在科水平评价中通用性低或者产生的PCR产物有双带,因而排除在全部物种水平上进一步评价。其余4对引物（GYM-5．8SF1／ITS4、GYM-5．8SFl／S3R、GYM-5．8SF2／ITS4和S2F／S3R）在56个物种的PCR检测中,均有100％的扩增率。基于PCR产物的亮度、序列质量和正反向引物覆盖率的综合评价,建议引物GYM_5．8SF2／ITS4作为裸子植物条形码片段ITS2最好的通用引物。     

Hydraulic design of leaves: insights from rehydration kinetics

We examined the leaf hydraulic design in 10 species based on their rehydration kinetics. In all cases, a biphasic response described the temporal pattern of water uptake, with time constants of approximately 30 to 800 s and approximately 800 to 8000 s. The time constants of the fast phase were significantly shorter in the six angiosperms (30 to 110 s) compared with the two single-veined conifer species (>400 s) examined, while the two multi-veined gymnosperm species, Gnetum gnemon and Ginkgo biloba, had time constants for the fast phase of approximately 150 s. Among angiosperm species, the fast phase constituted 50-90% of the total water absorbed, whereas in gymnosperms 70-90% of the water uptake could be assigned to the slow phase. In the four gymnosperms, the relative water uptake corresponding to the fast phase matched to a good degree the relative volume of the venation and bundle sheath extension; whereas in the angiosperm species, the relatively larger water influx during the fast phase was similar in relative volume to the combined venation, bundle sheath extension, epidermis and (in four species) the spongy mesophyll. This suggests a general trend from a design in which the epidermis is weakly connected to the veins (all four gymnosperms), to a design with good hydraulic connection between epidermis and veins that largely bypasses the mesophyll (four of six angiosperms), to a design in which almost the entire leaf appears to function as a single pool.     

The angiosperm radiation revisited, an ecological explanation for Darwin's 'abominable mystery'

One of the greatest terrestrial radiations is the diversification of the flowering plants (Angiospermae) in the Cretaceous period. Early angiosperms appear to have been limited to disturbed, aquatic or extremely dry sites, suggesting that they were suppressed in most other places by the gymnosperms that still dominated the plant world. However, fossil evidence suggests that by the end of the Cretaceous the angiosperms had spectacularly taken over the dominant position from the gymnosperms around the globe. Here, we suggest an ecological explanation for their escape from their subordinate position relative to gymnosperms and ferns. We propose that angiosperms due to their higher growth rates profit more rapidly from increased nutrient supply than gymnosperms, whereas at the same time angiosperms promote soil nutrient release by producing litter that is more easily decomposed. This positive feedback may have resulted in a runaway process once angiosperms had reached a certain abundance. Evidence for the possibility of such a critical transition to angiosperm dominance comes from recent work on large scale vegetation shifts, linking long-term field observations, large scale experiments and the use of simulation models.     

Energy–water and seasonal variations in climate underlie the spatial distribution patterns of gymnosperm species richness in China

Studying the pattern of species richness is crucial in understanding the diversity and distribution of organisms in the earth. Climate and human influences are the major driving factors that directly influence the large‐scale distributions of plant species, including gymnosperms. Understanding how gymnosperms respond to climate, topography, and human‐induced changes is useful in predicting the impacts of global change. Here, we attempt to evaluate how climatic and human‐induced processes could affect the spatial richness patterns of gymnosperms in China. Initially, we divided a map of the country into grid cells of 50 × 50 km² spatial resolution and plotted the geographical coordinate distribution occurrence of 236 native gymnosperm taxa. The gymnosperm taxa were separated into three response variables: (a) all species, (b) endemic species, and (c) nonendemic species, based on their distribution. The species richness patterns of these response variables to four predictor sets were also evaluated: (a) energy–water, (b) climatic seasonality, (c) habitat heterogeneity, and (d) human influences. We performed generalized linear models (GLMs) and variation partitioning analyses to determine the effect of predictors on spatial richness patterns. The results showed that the distribution pattern of species richness was highest in the southwestern mountainous area and Taiwan in China. We found a significant relationship between the predictor variable set and species richness pattern. Further, our findings provide evidence that climatic seasonality is the most important factor in explaining distinct fractions of variations in the species richness patterns of all studied response variables. Moreover, it was found that energy–water was the best predictor set to determine the richness pattern of all species and endemic species, while habitat heterogeneity has a better influence on nonendemic species. Therefore, we conclude that with the current climate fluctuations as a result of climate change and increasing human activities, gymnosperms might face a high risk of extinction.     

中国裸子植物红色名录评估(2021版)

定期开展物种红色名录评估, 了解植物濒危状态、致危因素变化, 对于物种保育有重要意义。本文报道了国产裸子植物的最新评估结果, 并与2013版红色名录进行了比较。本次评估了国产裸子植物274个种和种下分类群(隶属于8科37属)。与2013版红色名录相比, 本次评估减少了2科, 增加了3属和40个种和种下分类群。分类群变化是由于上次评估遗漏属种、新类群、新分布记录以及分类群名称和等级变化所致。本次评估有139个种和种下分类群被列入受威胁等级(包括极危、濒危和易危), 占总评估种类的50.7%, 与2013版的51.0%相比, 受威胁程度基本不变。物种自身进化属性、资源过度利用、生境丧失和全球变暖是国产裸子植物的主要致危因素。此外, 还有27种列为数据缺乏(DD), 占总种数的9.9%, 较2013版略有增加, 表明我国裸子植物需开展针对性野外调查和相关研究, 以摸清物种的野外生存现状, 为深入认识我国裸子植物濒危程度奠定数据基础。新的红色名录评估对濒危物种保育实践也有重要意义。     

通过遗传多样性探讨极小种群野生植物的致濒机理及保护策略: 以裸子植物为例

遗传多样性是生物多样性的重要组成部分, 然而由于资源的过度开发利用和生境的破碎化影响了物种的遗传多样性, 甚至威胁到物种的生存适应性和生物多样性。极小种群野生植物是亟待保护的国家重点保护濒危植物,遗传多样性研究对揭示极小种群致濒机理及保护策略具有重要意义。生境破碎化会造成物种遗传多样性降低、种群间分化增加、基因流减少等, 使种群濒危。但在某些物种中, 繁殖特征、进化历史等生物和生态因素的不同也可能造成近期生境破碎化后遗传效应的延迟。裸子植物进化历史悠久, 包含许多孑遗物种, 由于生活史周期长, 遭受生境破碎化后可能短期内显示不出遗传效应的改变, 但长期很难恢复。本文以裸子植物为例综述了濒危植物的遗传多样性研究的案例, 探讨了濒危裸子植物应对环境恶化的维持机制、致濒因素和保护方案, 旨在说明通过遗传多样性研究充分认识极小种群致濒机理对高效保护极小种群野生植物的重要性。