Unequal distribution of DNA-containing organelles in generative and sperm cells of Erythrina crista-galli (Fabaceae)

The generative cell at anthesis in the mature pollen grain of Erythrina crista-galli (Fabaceae) was examined by 4,6-diamidino-2-phenylindole(DAPI)-fluorescence microscopy using the squash method. An unequal, polarized distribution of DNA-containing organelles (plastids and/or mitochondria) within the generative cell was observed in every mature pollen grain examined. Polarization of DNA-containing organelles is obvious when generative cells are freed and assume a spherical shape soon after microspore mitosis, as revealed by fluorescence-microscopic observations of specimens embedded in Technovit 7100 resin and thin-sectioned at different developmental stages. Early establishment of polarized localization of organelles in young generative cells of E. crista-galli and maintenance of this unequal distribution until pollen maturation strongly suggests that the organelles may still be clustered at pollen mitosis. Production of a dimorphic pair of sperm cells, as has been reported in Plumbago zeylanica, was observed in some pollen tubes germinated in vitro. The differentiation of the two sperm cells is discussed in relation to possible preferential double fertilization in angiosperms. Received: 28 July 1999 / Revision accepted: 8 November 1999     

SYSTEMATIC SIGNIFICANCE OF POLLEN NUCLEAR NUMBER IN EUPHORBIACEAE,TRIBE EUPHORBIEAE

Pollen nuclear number is determined in 139 species of 5 genera in the Euphorbieae, subtribe Euphorbiinae. The 111 new determinations are tabulated along with previous reports, and the results indicate that the distribution of binucleate (II) and trinucleate (III) pollen is strongly associated with the taxonomic groupings within the Euphorbieae. Although binucleate pollen is probably primitive within the tribe Euphorbieae, as suggested by the nuclear condition in Neoguillauminia, the situation in Euphorbia still requires further elucidation. Within Euphorbia, the morphologically most primitive species studied have III pollen despite the fact that II pollen is presumably the original condition for the subtribe Euphorbiinae. In Euphorbia, II pollen only is reported from nine sections and III pollen only from ten sections, while in four sections (Esula, Goniostema, Aphyllis, and Deuterocalli) both II and III pollen have been found. The New World species of Euphorbia nearly all have III pollen, whereas the vast majority of the African succulents have II pollen. The genera of New World origin, Chamaesyce and Pedilanthus, have III pollen, while the African genera Monadenium and Synadenium have II pollen. Independent derivations of III pollen from II pollen appear to have occurred in sections Goniostema, Aphyllis, and Deuterocalli (all of subg. Euphorbia). There is no evidence that reversals from III to II pollen have occurred.     

Flower morphology and pollen germination in the genus Capsella (Brassicaceae)

Evolutive changes in mating systems are often accompanied by changes in flower morphology, such as the reduction in size or even loss of petals, changes in production of volatiles, pollen/ovule ratio, the position between anthers and stigma and the germination time of pollen after pollination. These changes have been merged under the term “selfing syndrome” and often result in new taxonomic species. The evolutionary shift frequently happens parallel within many families and genera, for example within the Brassicaceae family. Within the genus Capsella, which is closely related to the molecular model species pair Arabidopsis lyrata (SI)/A. thaliana (SC), we studied self-incompatible and self-compatible species. SC species C. rubella and C. bursa-pastoris produce in comparison with the SI species C. grandiflora (i) smaller petals as the result of decreased cell division and only less of decreasing cell volume, (ii) less production of pollen in one flower, (iii) show a lesser incision between the two valves of the fruits, in combination with a shorter style, and (iv) have a much quicker fertilization of SC pollen after pollination. Crossing success between the diploid species, between different provenances of the tetraploid C. bursa-pastoris, and between the two diploid species and particular individuals of the self-incompatible C. grandiflora has been proven.     

TWO-DIMENSIONAL POLLINATION IN HYDROPHILOUS PLANTS: CONVERGENT EVOLUTION IN THE GENERA HALODULE (CYMODOCEACEAE), HALOPHILA (HYDROCHARITACEAE), RUPPIA (RUPPIACEAE), AND LEPILAENA (ZANNICHELLIACEAE)

In most plant species with abiotic pollination systems, pollen is dispersed in three dimensions. Theoretical considerations suggest, however, that there are significant advantages for two-dimensional pollination systems over three-dimensional systems, especially if pollen is dispersed in conveyances or aggregations of large diameter. We report that two-dimensional pollination systems occur in the genera Halodule, Halophila, Lepilaena, and Ruppia, where pollen grains are not transported through the water singly, but in rafts or search vehicles. These genera possess unusual pollen morphologies which facilitate assemblage of pollen grains into search vehicles. These floating search vehicles have large diameters, thus greatly increasing probability of encountering a stigma. The grains have a hydrophobic surface that appears to mediate adhesion by an external coating of proteins and carbohydrates. Similar adaptations to two-dimensional pollination are found in the target organs, the stigmas. The long filamentous stigmas of the marine genera float, as do the indusiate stigmas of the freshwater genera, creating small depressions in the water surface. Pollination occurs through the collision of a moving search vehicle with a floating stigma. The existence of similar pollen search vehicles, stigma morphologies, and flowering phenologies in these unrelated hydrophilous genera evidences convergent evolution towards efficient search strategies in surface-pollinated aquatic plants.     

POLLEN MORPHOLOGY AND DETAILED STRUCTURE OF FAMILY COMPOSITAE,TRIBE CICHORIEAE. I. SUBTRIBE STEPHANOMERIINAE

A survey of pollen morphology in 20 species representing the 11 genera of the North American subtribe Stephanomeriinae by light, scanning electron, and transmission electron microscopy revealed 10 of the 11 genera to have echinate, tricolporate pollen grains, Lygodesmia being the only genus with echinolophate pollen. Sectioned exines of most of the species examined are similar, being composed of ektexine and endexine. The ektexine surface is composed of spines which typically have globose perforate bases. A cavus occurs as a separation between the basis (foot layer) and the columellae in all of the genera examined except Chaetadelpha. Pollen of the two species of Glyptopleura were found to be strikingly different in exomorphology. Pollen of the putatively self-fertile G. marginata has much shorter spines than the closely related G. setulosa. Atrichoseris, Anisocoma, Calycoseris, Glyptopleura, Pinaropappus, Prenanthella, and most species of Malacothrix have pollen which lack paraporal ridges. The remaining genera, Chaetadelpha, Lygodesmia, Rafinesquia, and Stephanomeria have well-developed ridges of fused spine bases around the apertures. Pollen characters, particularly those of the aperture region, have been found to be systematically useful in the subtribe, therefore acetolyzed material gives more useful information than untreated pollen.     

青藏高原东南部察隅河流域种子植物区系研究

在野外植被调查、标本采集和资料查询整理的基础上,汇总了察隅河流域种子植物名录,并对流域内植物物种的组成、优势科属、区系地理成分及性质进行分析。运用R语言在属水平上与其周边16个地区的植物区系进行聚类及主成分分析,探讨察隅河流域种子植物区系与其他区系之间的关系。结果表明：(1)察隅河流域共含种子植物138科、689属、2 771种(含变种),其中裸植子物4科12属56种,被子植物134科677属2 715种,被子植物中双子叶植物112科531属2 270种占绝对优势。(2)区内地理成分联系广泛,科的区系划分除世界分布类型外,热带分布型53科(55.21%),温带分布型43科(44.79%);属的区系划分中所有类型均有分布,温带分布型396属(62.07%),热带分布型230属(36.05%);属的分布型与科相比具有更明显的温带性质;植物种类丰富度高但特有成分低,无特有科,仅含12特有属。(3)流域内植被垂直地带性分布较为明显,保留了较多古老孑遗植物,如裸子植物的西藏红豆杉(Taxus wallichiana)、察隅冷杉(Abies chayuensis)和云南松(Pinus yunnanensis)等;由于青藏高原的上升运动,成为杜鹃花属(Rhododendron)、虎耳草属(Saxifraga)、龙胆属(Gentiana)和报春花属(Primula)等新生高山植物区系成分分化繁衍的摇篮。(4)察隅河植物区系属喜马拉雅山南侧热带成分向温带成分过渡的区系性质,与珠峰自然保护区植物区系更为相似。     

基于山地蜂蜜花粉组成的中华蜜蜂传粉多样性研究

中华蜜蜂为多种植物传粉,具有重要的生态服务价值。为进一步了解中华蜜蜂选择蜜粉源植物的多样性与特征,采用聚合酶链式反应(PCR)、DNA条形码、高通量测序等技术,研究了源自陕西宝鸡、贵州望谟和广西凤山蜂巢蜜中的花粉来源。通过对样品花粉rbcL基因片段扩增及测序、分析,发现各样本间可操作分类单元(OTU)水平上蜜粉源植物Alpha多样性指数无显著差异,同一地点样品不同重复间存在较高的相关性,而不同地区样本相关性较低。三地共鉴定出27目46科71属82种蜜粉源植物,其中宝鸡市、望谟县、凤山县样本中分别鉴定出57种、30种和40种,各地蜜粉源植物的物种组成存在较大差异。这些蜜粉源植物中,菊目植物种类最多,其次为毛茛目,分别有12种和7种。其中草本植物和木本植物(含乔木、灌木和木质藤本等)分别有44种和38种。研究对蜜粉源植物花序特点进行了分析,但并未发现相关性状对中华蜜蜂选择具有的影响。从属的区系成分分析,总体上温带分布区类型的植物属多于热带分布区类型的属,所占比例分别为46.5%和36.6%,但在凤山县样本中出现热带分布区类型多于温带分布区类型的情况。在不同样品中,红足蒿(Artemisia rubripes)、向日葵(Helianthus annuus)、芜青(Brassica rapa)、粗糠柴(Mallotus philippensis)、枇杷(Eriobotrya japonica)等分别占有一定优势,其与中华蜜蜂的关系值得进一步研究。根据蜜粉源植物的系统进化关系,中华蜜蜂访问的蜜粉源植物处于不同进化地位的分支,其中在菊类分支和蔷薇类分支比较集中。研究揭示了中华蜜蜂传粉植物组成特点,为进一步认知中华蜜蜂传粉服务功能的重要性提供依据。     

Floral resources and risk of exposure to pesticides for Melipona quadrifasciata anthidioides Lepeletier 1836 in a Cerrado of São Paulo (Brazil)

Honey and bee bread samples from storage pots of Melipona quadrifasciata anthidioides were collected monthly from April 2015 to May 2016 in the Mogi Guaçu Biological Reserve (22º 10? S, 47º 11? W). The flora in the site is characteristic of the Atlantic Forest with preserved areas of savanna-like vegetation surrounded by commercial forests, orchards and various crops of exotic and native plants. Samples were analysed with the use of melissopalynological methodology and 46 pollen types from 38 genera and 30 families were identified in 25 honey samples. Fabaceae, Asteraceae, Myrtaceae, Sapindaceae showed the greatest pollen richness in honey. Predominant nectariferous pollen types were Anadenanthera, Cordia, Eucalyptus, Mimosa scabrella, Schefflera, Sida, Serjania and Vernonia. Twenty-eight types of pollen from 21 genera and 19 families were identified in 22 bee bread samples. Fabaceae, Asteraceae and Myrtaceae showed the highest pollen richness. Anadenanthera, Cecropia, Eucalyptus, Melastomataceae, Mimosa scabrella, Mimosa verrucosa and Myrcia were the most frequent polliniferous pollen types. Principal component analysis (PCA) demonstrated that honey and pollen samples formed two main groups of similarity, mainly due to Eucalyptus’ nectar and pollen of Melastomataceae, respectively. Melipona quadrifasciata anthidioides collected nectar and pollen from the preserved areas as well as in the secondary and ‘ruderal’ vegetation and in cultivated forests/fields, suggesting their importance as pollinators both of native flora and exotic species. The use of trophic resources of plants grown with pesticides is a concern for the conservation of these species of bee and should be better studied.     

Upper Cretaceous sulcate pollen from the Timerdyakh Formation,Vilui Basin (Siberia)

One inaperturate and 16 monosulcate pollen types are described from the latest Campanian to earliest Maastrichtian sediments of the Vilui basin, Siberia, using both light and scanning electron microscopy, and assigned systematically when possible to modern families or subfamilies. Despite their scant occurrence, the pollen grains show considerable diversity. Two new genera have been erected. Lasioideaecidites with two species, Lasioideaecidites hessei and Lasioideaecidites bogneri, represents the earliest record of the subfamily Lasioideae (Araceae). Aristolochiacidites with one species, Aristolochiacidites viluiensis, is assigned to the subfamily Aristolochioideae (Aristolochiaceae) and represents the first fossil pollen record of the family. A new species of Liliacidites, Liliacidites goldblattii, is closely similar to pollen of Isophysioideae (Iridaceae) and/or Doryanthaceae and is the first fossil evidence of the clade that includes these closely related families. A further nine new fossil species are described (Clavatipollenites timerdyakhensis, Liliacidites palaeofritillaria, Retimonocolpites longosucatus, R. microreticulatus, R. microrugulatus, R. lysichitonoides, R. chapmaniae, Monosulcites parvus and Arecipites tyungensis) and assigned to Chloranthaceae, Araceae (Orontioideae, ?Pothoideae), Liliaceae, ?Hypoxidaceae and Arecaceae. The Hydatellaceae (Nymphaeales) may also be present in the palynoflora of the Vilui Basin, represented by pollen similar to M. rivularis Braman from the Santonian to Campanian (Upper Cretaceous) Milk River Formation, Canada.     

核酸碱基组分与毛霉目的分类

本文对毛霉目中6科16属40个种共60株真菌DNA的G+C含量与分布作了系统的研究。在提取DNA时选用了Storck等人在Marmur提取细菌DNA方法基础上发展起来的真菌DNA提取法,经过一些修改后成功地提取了毛霉目真菌的DNA。经该法提取的DNA片段长、纯度高,在热变性时DNA的增色效应一般都大于35%。各个种的GC含量大致有一固定值。根据所测毛霉目16属各属真菌的平均GC含量,可将它们分为明显的三组:Gongronella, Haplosporangium, Mortierella及Syncephalastrum为一组,GC含量最高为46.0-49.8%; Cunninghamella单独成一组,GC含量最低只有28.8%;其他各属包括Absidia, Mucor, Rhizopus等GC含量介乎这两组之间,分布于34.9-41.9%。这一次序除Helicostylum与Circinella的数值低于他人的报道外,其余和文献报道值一致。一般属内GC含量变化小于10%,种内变化小于2%。所测得的G+C mol%对分Syncephalastrum monosporum Zheng et al.和Mortierella ramanniana (Moeller) Linneman的合理归属提供了佐证。对某些所测结果与文献报道值有出入的原因作了讨论和分析。对采用Mandel等1970年建议的公式GC=(Tm 0.1×SSC/50.2)-0.990来计算GC含量的依据也作了讨论。     

Pollen analysis of honeys from Caatinga vegetation of the state of Bahia,Brazil

Based on pollen analysis, 17 honey samples collected in the Caatinga area from Nova Soure city were classified by botanical origin to identify the most important floral sources. Most of the honey samples were obtained in August and September. A total of 73 pollen types were identified belonging to 30 families, 64 genera and 30 species. The families best represented by their number of pollen types were Mimosaceae (11), Caesalpiniaceae (9), Rubiaceae and Fabaceae (5 each). Predominant pollen types were: Mimosa arenosa in four samples, M. sensitiva and M. tenuiflora in one sample. Pollen from Mimosa ursina was registered for the first time in the pollen spectrum of the Caatinga vegetation. The correspondence analysis showed a similarity among the honey samples based on pollen composition. The high representation of pollen from native species such as Chamaecrista nictitans, C. ramosa, C. swainsonii and Copaifera martii (Caesalpiniaceae); Aeschynomene martii and Zornia sericea (Fabaceae); Herissantia tiubae (Malvaceae); Mimosa arenosa, M. quadrivalvis, M. sensitiva, M. tenuiflora, M. ursina, Piptadenia moniliformis and Plathymenia reticulata (Mimosaceae), and Ziziphus joazeiro (Rhamnaceae) supports the origin of these honeys from Caatinga vegetation.     

PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. II. GENERA HAITIA THROUGH PEPLIS

Pollen morphology for 12 genera of the Lythraceae is described, using light microscopy (LM), scanning (SEM) and transmission electron microscopy (TEM). The genera surveyed are Haitia, Heimia, Hionanthera, Lafoensia, Lagerstroemia, Lawsonia, Lythrum, Nesaea, Orias (= Lagerstroemia), Pehria, Pemphis, and Peplis. Among results of taxonomic significance are 1) the similarity of pollen between Haitia and Ginoria, suggesting that future classifications reflect a close relationship between these genera, 2) a comparable similarity in pollen between Pehria and Adenaria, 3) the distinction of Hionanthera pollen from that of Ammannia, 4) an exine similar in certain ultrastructural characteristics between Orias and some species of Lagerstroemia, although in general aspect they appear quite different, 5) that within the Didiplis-Lythrum-Peplis complex, there are three palynologically distinct groups, with Didiplis standing apart from the somewhat more similar, but nevertheless, distinct Lythrum and Peplis, and 6) that considerable differences exist between pollen of Pemphis acidula and Pemphis madagascariensis, supporting removal of the latter species to a new genus. This pollen survey is part of a multi-disciplinary effort to clarify generic limits in the Lythraceae, and evaluate relationships within the family and among families of the Myrtales.     

Diverse fossil Onagraceae pollen from a Miocene palynoflora of north-east China: early steps in resolving the phytogeographic history of the family

The origin and evolution of angiosperms can be unravelled by using fossil records to determine first occurrences and phytogeographic histories of plant families and genera. Many angiosperm families, for example the Onagraceae, have a poor macrofossil record, but are more common in palynological records. Modern Onagraceae produce pollen clearly distinct from that of other angiosperms. Combined morphological features obtained by use of light and scanning electron microscopy have enabled assignment of fossil Onagraceae pollen to extant genera, and therefore tracing of the origin and past distributions of extant Onagraceae lineages. We studied a Miocene palynoflora from the Daotaiqiao Formation of north-east China. Using the single-grain technique, we examined individual Onagraceae pollen/tetrads using both light and scanning electron microscopy. Fossil Onagraceae pollen is more frequent than macrofossil remains, but is still rare, and usually represented by a single taxon in palynological samples. Remarkably, samples from the Miocene of north-east China contain five different species: two of Circaea, one of Epilobium, and two of Ludwigia. Such a large number of Onagraceae taxa from a single palynoflora is unknown elsewhere. Whereas Ludwigia pollen is known from Cenozoic sediments of the northern hemisphere, the Circaea pollen is the first fossil pollen assignable to this extant genus. This is also the first fossil record of Epilobium from China. Although the young geological age of this sample does not enable consideration of time of origin for the genera encountered, the co-occurrence of Circaea, Epilobium, and Ludwigia in the mid to late-Miocene of East Asia sheds some light on their phytogeographic histories.     

Phylogenetic implications of pollen nuclear number in theAraceae

Data on pollen nuclear number are presented for 74 of the 111 currently accepted genera of theAraceae — one of only three monocot families in which both bi- and trinucleate pollen are known to occur. Binucleate pollen, which characterizes 65% of aroid genera, is regarded as the primitive type inAraceae and monocots as a whole. The trend toward the trinucleate condition appears to be irreversible, and to have occurred many times within the family.Syngonium becomes the sixth angiosperm genus in which both character-states are known to occur; otherwise, the character is highly conservative at the generic level. Pollen nuclear number shows no evident correlation with pollen size, starch content or pollinator type.     

Pollen morphology and its taxonomic significance of the monotropoideae (Ericaceae)

A palynological survey, including LM, SEM and TEM is presented for eight genera, nine species and 76 samples of the Monotropoideae which is composed of 10 genera and 13 species. On the basis of the aperture number and shape, the following six pollen types are recognized: 1) 3-colp(oroid) ate—Allotropa, 2) 2-colpor(oid)ate—Monotropsis andHemitomes, 3) 4-colpor(oid)ate—Pterospora, Sarcodes andPleuricospora, 4) 2- and 3-colpor(oid)ate—Monotropa hypopitys, 5) 3-colporate and-porate —Monotropa uniflora, 6) 3- to 4- porate—Monotropastrum humile. Relationships among taxa within the Monotropoideae are illustrated on the palynological characters including the aperture type, exine sculpture and structure. Both pollen grains with two and four apertures have evolved independently from pollen grains with three apertures, according to the infraspecific variation of aperture numbers and the usual occurrence of three-aperturate pollen grains in the Ericaceae. 3-colp(oroid)ate pollen ofAllotropa is the most primitive and occupies an isolated position in the subfamily, on the other hand 3- to 4-porate pollen ofMonotropastrum humile is most advanced in the subfamily, probably even in the Ericaceae. A reduced sexine inMonotropastrum humile appears to be a specialized pollen character. Infraspecific geographical difference in palynological characters is revealed in two species ofMonotropa for the first time.M. hypopitys is basically characterized by pollen grains with two apertures in the New World vs. three apertures in the Old World.M. uniflora is basically characterized by 3-porate pollen in the New World vs. 3-colporate in the Old World. In both species pollen grains with more primitive characters usually occur in the Old World.     

Aquatic plants diversity in arid zones of Northwest China: patterns, threats and conservation

We investigated aquatic plant diversity by conducting the field investigation and collecting the published data in the arid regions of Northwest China. Two hundred and twenty four taxa of vascular aquatic plants representing 64 genera and 34 families occur in this area, 8.48% of which are endemic. Among these, 1 genus and 6 species were new state records and 1 family, 9 genera and 29 species were new area records. Typhaceae, Potamogetonaceae, Juncaginaceae and Haloragaceae were the most frequent families (considering relative frequency of occurrence), whereas Cyperaceae, Potamogetonaceae and Ranuncnlaceae are the most species-rich. The most frequent genera were Typha, Potamogeton, and Triglochin, and the most species-rich were Potamogeton, Eleocharis and Scirpus. The most frequent species are Triglochin palustre, Myriophyllum spicatum, Potamogeton pectinatus and Typha angustifolia. Aquatic plants diversity is distributed unevenly in the region. The maximum species occurs in Dzungarian basin while the least species in Hexi corridor. The aquatic flora in arid zone of China is not distinctive although some endemic species are found, most species are widely distributed. Local aquatic plants diversity can be influenced by many factors such as hydrological alteration, habitat loss, over-grazing, high human population pressure, global climate change, an inappropriate economic development policy. Among them, the largest threat to aquatic plants biodiversity may be habitat loss due to hydrological alteration. In order to conserve the aquatic plants biological resources and biodiversity in this region, some strategies and measures must be suggested including strengthening scientific research and biodiversity education in the local people, balancing economic development and ecological conservation, and enhancing governmental assistance and subsidy to the local residents.     

A farnesyl pyrophosphate synthase gene expressed in pollen functions in S‐RNase‐independent unilateral incompatibility

Multiple independent and overlapping pollen rejection pathways contribute to unilateral interspecific incompatibility (UI). In crosses between tomato species, pollen rejection usually occurs when the female parent is self‐incompatible (SI) and the male parent self‐compatible (SC) (the ‘SI × SC rule’). Additional, as yet unknown, UI mechanisms are independent of self‐incompatibility and contribute to UI between SC species or populations. We identified a major quantitative trait locus on chromosome 10 (ui10.1) which affects pollen‐side UI responses in crosses between cultivated tomato, Solanum lycopersicum, and Solanum pennelliiLA0716, both of which are SC and lack S‐RNase, the pistil determinant of S‐specificity in Solanaceae. Here we show that ui10.1 is a farnesyl pyrophosphate synthase gene (FPS2) expressed in pollen. Expression is about 18‐fold higher in pollen of S. pennellii than in S. lycopersicum. Pollen with the hypomorphic S. lycopersicum allele is selectively eliminated on pistils of the F₁ hybrid, leading to transmission ratio distortion in the F₂ progeny. CRISPR/Cas9‐generated knockout mutants (fps2) in S. pennelliiLA0716 are self‐sterile due to pollen rejection, but mutant pollen is fully functional on pistils of S. lycopersicum. F₂ progeny of S. lycopersicum × S. pennellii (fps2) show reversed transmission ratio distortion due to selective elimination of pollen bearing the knockout allele. Overexpression of FPS2 in S. lycopersicum pollen rescues the pollen elimination phenotype. FPS2‐based pollen selectivity does not involve S‐RNase and has not been previously linked to UI. Our results point to an entirely new mechanism of interspecific pollen rejection in plants.     

中国大陆北热带及亚热带地区樟科、壳斗科物种多样性及其生物地理格局分析

以中国大陆北热带及亚热带地区优势科樟科、壳斗科植物为研究对象,利用专著发表大量的样方数据和物种分布数据,分析樟科、壳斗科与群落构建的关系、它们各大属的地理分布格局,探讨影响其分布的可能历史原因。结果表明:中国大陆北热带及亚热带地区森林乔木层优势科为樟科、壳斗科、山茶科、杜鹃花科。樟科、壳斗科物种丰富度均与其所在群落的物种丰富度呈现一定的正相关,樟科对群落构建的贡献较大。樟科、壳斗科植物种的空间多样性分布中心均出现在我国亚热带中部偏南地区。樟科的厚壳桂属、琼楠属以及壳斗科的锥属物种多样性分布中心主要在南亚热带及北热带区域,以广西、云南省份的南部为主。樟科的樟属、新木姜子属、润楠属、木姜子属及壳斗科的柯属、青冈属主要分布在我国大陆北热带及亚热带中部偏南的地区,其多样性分布中心与樟科、壳斗科科水平的物种多样性分布中心极为相似。樟科的山胡椒属、楠属、黄肉楠属,壳斗科的栎属主要分布在研究区域中部以西的地区。研究结果佐证物种的生态学特性以及生物地理学历史综合作用导致目前樟科和壳斗科植物的生物多样性分布格局。     

ITS1: a DNA barcode better than ITS2 in eukaryotes?

A DNA barcode is a short piece of DNA sequence used for species determination and discovery. The internal transcribed spacer (ITS/ITS2) region has been proposed as the standard DNA barcode for fungi and seed plants and has been widely used in DNA barcoding analyses for other biological groups, for example algae, protists and animals. The ITS region consists of both ITS1 and ITS2 regions. Here, a large‐scale meta‐analysis was carried out to compare ITS1 and ITS2 from three aspects: PCR amplification, DNA sequencing and species discrimination, in terms of the presence of DNA barcoding gaps, species discrimination efficiency, sequence length distribution, GC content distribution and primer universality. In total, 85 345 sequence pairs in 10 major groups of eukaryotes, including ascomycetes, basidiomycetes, liverworts, mosses, ferns, gymnosperms, monocotyledons, eudicotyledons, insects and fishes, covering 611 families, 3694 genera, and 19 060 species, were analysed. Using similarity‐based methods, we calculated species discrimination efficiencies for ITS1 and ITS2 in all major groups, families and genera. Using Fisher's exact test, we found that ITS1 has significantly higher efficiencies than ITS2 in 17 of the 47 families and 20 of the 49 genera, which are sample‐rich. By in silico PCR amplification evaluation, primer universality of the extensively applied ITS1 primers was found superior to that of ITS2 primers. Additionally, shorter length of amplification product and lower GC content was discovered to be two other advantages of ITS1 for sequencing. In summary, ITS1 represents a better DNA barcode than ITS2 for eukaryotic species.     

Coloured Pollen in Cactaceae: a Mimetic Adaptation to Hummingbird-Pollination?

Pollen of 361 species from 71 genera of Cactaceae was investigated for this study of the correlation between pollen colour and the pollination syndrome. 11% of all species studied had red or brown pollen, and nearly all of these species were ornithophilous. This suggests that pollen colour probably is part of the bird-flower syndrome of Cactaceae. Possibly the red or brown pollen might be a crypto-mimetic adaptation to the dark coloured bill of the pollinating hummingbird (Trochilidae) and secures safe transport to a receptive stigma without being removed by the bird immediately. The results are discussed against a background of studies encompassing about 900 species from 77 families, which provide further evidence for the proposed adaptive significance of palynological characters.