The web and the structure of taxonomy

An easily accessible taxonomic knowledge base is critically important for all biodiversity-related sciences. At present, taxonomic information is organized and regulated by a system of rules and conventions that date back to the introduction of binomial nomenclature by Linnaeus. The taxonomy of any particular group of organisms comprises the sum information in the taxonomic literature, supported by designated type specimens in major collections. In this article, the way modern means of disseminating information will change the practice of taxonomy, in particular the Internet, is explored. Basic taxonomic information, such as specimen-level data, location of types, and name catalogues are already available, at least for some groups, on the Web. Specialist taxonomic databases, key-construction programs, and other software useful for systematists are also increasingly available. There has also been a move towards Web-publishing of taxonomic hypotheses, though as yet this is not fully permitted by the Codes of Nomenclature. A further and more radical move would be to transfer taxonomy completely to the Web. A possible model of this is discussed, as well as a pilot project, the "CATE" initiative, which seeks to explore the advantages and disadvantages of such a move. It is argued that taxonomy needs to forge better links with its user-communities to maintain its funding base, and that an important part of this is making the products of its research more accessible through the Internet.     

Seed survival and periodicity of seedling emergence in eight species of Cruciferae

Seeds of eight species of Cruciferae were collected, usually in each of 3 years, and mixed with the top 7-5 cm of sterilised soil confined in cylinders sunk in the ground outdoors and cultivated three times yearly. The seedlings emerging were recorded for 5 yr and the numbers of viable seeds remaining then determined. Emergence of Alliaria petiolata was almost entirely restricted to February and March. That of Erysimum cheiranthoides, Lepidium campestre, Sinapis arvensis and Raphanus raphanistrum took place mainly in March and April, but seedlings continued to appear until late autumn. Some seedlings of Arabidopsis thaliana, Cardamine hirsuta and Sisymbrium officinale appeared in spring, but most did so in summer (C. hirsuta and S. officinale) or early autumn (A. thaliana). Seed survival in A. petiolata was of short duration and there were few seedlings after the second year, whereas 18% of the seeds of R. raphanistrum were still present and viable after 5 yr. Seed survival at this time for the other six species ranged from 1 -6% (C. hirsuta) to 6-1% (S. arvensis).     

独行菜族8属(十字花科)植物果实及种子微形态研究

采用GMA(Glycol methacrylate,乙二醇甲基丙烯酸酯)半薄切片法,利用比较解剖学对独行菜族中代表植物8属25种果实及种子微形态结构进行观察分析。同时,以菥蓂属菥蓂为例详细介绍了假隔膜的形成过程。结果显示独行菜族果实及种子微形态特征明显,果实均为短角果,除厚壁荠属和沙芥属果实为背腹压扁外,其他属种均为两侧压扁;果实边缘有翅为独行菜族的典型特征,可分为周翅、微翅、宽翅及披针形翅;部分果皮细胞有纤维层,偶有木化,除菘蓝属、厚壁荠属、沙芥属无假隔膜结构外,其他属种均具有明显的假隔膜。种子大小为(0.8~10)mm×(0.5~2.8)mm,种皮纹饰丰富,遇水或潮湿环境可形成粘液种子。种皮通常由薄壁细胞构成,偶有木化,具内含物;除高河菜属和菥蓂属子叶与胚根的排列方式为子叶缘倚,其他属种均为子叶背倚。假隔膜为内果皮细胞向内延伸连接而成。本文完善了独行菜族果实及种子微形态结构信息,为分子系统学等其他相关研究提供基础资料。     

Oocyst structure and problem of coccidian taxonomy

A comparative ultrastructural study was made of both thin- and thick-walled oocysts of Cryptosporidium parvum. According to the authors' findings, all the oocysts in C. parvum should be considered as thin-walled, since their walls have been composed of a single membrane or of two, closely apposed membranes without any additional substance in between. Despite the presence of two types of wall-forming bodies (WFB) in the maturing macrogamete or zygote, there is no evidence of their involvement in oocyst wall formation. In this concern, the function and destiny of WFB in C. parvum oocysts still remain obscure. Similar structure of the oocysts wall was reported elsewhere for thin-walled oocysts of fish coccidia of the genera Goussia and Eimeria. In C. parvum, the "thick-walled" oocysts differ from oocysts with thin walls in the availability in the former of a single sporocyst. The sporocyst wall consists of two unequal layers: a thin outer layer and a thicker inner one, in which a characteristic suture line is occasionally seen. By this feature the thick-walled oocysts of C. parvum bear similarities with oocysts of the cyst-forming coccidia (Cystoisospora, Toxoplasma, Sarcocystis) and of the genus Goussia: in all these the valves making up the sporocyst wall are joint just along the suture line. The literary and the authors' own data make it possible to suppose that the suture detected in C. parvum oocysts is located in the sporocyst wall, joining its valves, rather than in the oocyst wall proper, known to be composed of one or two, closely apposed unit membranes. Again, the availability of a suture (or sutures) in the sporocyst hardly provides enough reason to relate C. parvum with either cyst-forming, or fish coccidia, since this structure itself may be of a convergency character, rather than of systematic value. This may be substantiated, at least in part, by the authors' previous findings (Beyer, Sidorenko, 1984) of a similar structure, originally referred to as a "slit channel", in the intraerythrocytic capsule around gamont stage of haemogregarines--the adeleid coccidia of the genus Karyolysus. The suture-like structure could have originated in the evolution independently in different groups of parasitic protozoa to serve eventually as a suitable mechanism for immediate separation of elements involved in protective formation harbouring different developmental stages, including, for example, sporozoites in the eimeriid coccidia, or gamonts in the adeleid coccidia.     

Global population structure and taxonomy of the wandering albatross species complex

A recent taxonomic revision of wandering albatross elevated each of the four subspecies to species. We used mitochondrial DNA and nine microsatellite markers to study the phylogenetic relationships of three species (Diomedea antipodensis, D. exulans and D. gibsoni) in the wandering albatross complex. A small number of samples from a fourth species, D. dabbenena, were analysed using mitochondrial DNA only. Mitochondrial DNA sequence analyses indicated the presence of three distinct groups within the wandering albatross complex: D. exulans, D. dabbenena and D. antipodensis/D. gibsoni. Although no fixed differences were found between D. antipodensis and D. gibsoni, a significant difference in the frequency of a single restriction site was detected using random fragment length polymorphism. Microsatellite analyses using nine variable loci, showed that D. exulans, D. antipodensis and D. gibsoni were genetically differentiated. Despite the widespread distribution of D. exulans, we did not detect any genetic differentiation among populations breeding on different island groups. The lower level of genetic differentiation between D. antipodensis and D. gibsoni should be reclassified as D. antipodensis. Within the context of the current taxonomy, these combined data support three species: D. dabbenena, D. exulans and D. antipodensis.     

The Characteristics of Low Temperature Tolerance during Seed Germination of the Ephemeral Plant Lepidium apetalum (Cruciferae)

Lepidium apetalum was used to explore the characteristics and mechanismes of low temperature tolerance during seed germination. The results showed that pre treatment the seeds at 4℃ would improve the seeds viability after stressed by low temperature at -5℃ and -10℃ and the capability of seeds tolerance to cold temperature became weaker along with germination development. Although the growth of radicle was inhibited significantly at 4℃ during germination, the seeds could still survive and grow. With appropriate time of stratified at 4℃, germination pace would be improved and germination rate would not change, while both of which decreased if stratification lasted too long. Moreover, Lapetalum seeds were very sensible to the temperature during germination. It showed no germination at 4℃, while if seeds were stratificated for 48 hours at 4℃ and subsequently treated with 25℃ for more than 6 hours, seeds would germinate at 4℃ and the germination rate increased with the time of 25℃ treatment prolonged. If treatment at 25℃ was less than 5 houes, it showed no germinating. In addition, seeds with stratification for 10 days following 1 h treatment at 25℃ could also germinated at 4℃. The present study indicated that some pivotal genes that related with a key physiological stage before the onset of radicle protrusion might inhibite at 4℃, which resulted in Lapetalum seed could not germinate at 4℃. Except that physiological stage, the Lapetalum seed had a strong tolerance to low temperature at other germination stages. This experiment provided a new way to explore the germination mechanism of ephemerals plants seeds at low temperature.     

Seed migration and the structure of plant populations

Summary We use chemical typing to compare sub-populations of thyme (Thymus vulgaris L.) growing in the channels of several ravines where seed migration is expected from sub-populations on the plateu to associated basin subpopulations. The results indicate that seed migration does occur. However, there is little effective gene flow between sub-populations. We discuss the implications of restricted gene flow for population dynamics and structure.     

短命植物独行菜种子萌发过程对低温的耐受特性

以独行菜（Lepidium apetalum）为材料,研究了其种子在萌发过程中耐受低温的特性,并对耐受低温的机制作了初步的探讨。结果表明：1.萌发至I、II、III期的独行菜种子经过冷诱导处理后,对零下低温-5℃、-10℃胁迫具有较强的耐受性,这种耐受性随萌发发展相对有所降低。2.独行菜种子萌发过程中胚根生长速度明显受到低温抑制,但也仍然能够生长。3.适当时间的低温层积能使独行菜萌发势显著提高,对终萌发率影响不大;过长时间的低温层积会使独行菜种子萌发势和最终萌发率降低。4.独行菜种子在4℃条件下不能萌发,但4℃层积2d的种子经25℃处理6h以上后,可耐受4℃低温而萌发,且萌发率随25℃处理时间增加而升高。如果25℃处理时间少于5h则不能在4℃低温下萌发。经4℃层积10d、再经25℃萌发处理1h的独行菜种子就能在4℃低温下萌发。综合分析认为独行菜种子不能耐受4℃低温萌发,原因可能是在露白前存在一个关键的生理阶段,在4℃胁迫逆境中不能越过这个阶段,该阶段之前与之后的萌发过程都能耐受4℃低温,因此对低温胁迫有良好的耐受性。这为探索早春短命植物耐受低温萌发的机制提供了新的思路。     

Seed coat structure and dormancy

An understanding of dormancy mechanisms is of ecological and economic importance. Identification of the level at which dormancy is imposed appears to be species specific. The variation brought about by this therefore requires that developmental studies be included in seed coat dormancy experiments. In most cases, a site of permeability can be identified during the developmental process, and this information can be utilized later to remove dormancy. Under natural conditions, the removal of seed coat dormancy requires the interaction of a number of ecological and physiological dormancy-breaking cues.     

Origin, taxonomy and population structure of the allopolyploid peat mossSphagnum majus

The polyploid peat mossSphagnum majus shows considerable phenotypic plasticity along ecological gradients in mires. It is considered taxonomically heterogeneous, and two subspecies have been described. Isozyme analyses were carried out on populations ofS. majus from Central Norway and from eastern coast of North America in order to assess the origin, taxonomy and population structure of this species. High levels of fixed heterozygosity in the populations demonstrate thatS. majus is a genetic allopolyploid. At all loci screened, extant populations ofS. cuspidatum shared enzyme bands withS. majus. The other most likely progenitor based on morphology,S. annulatum, was fixed for enzyme bands not found inS. majus. The progenitor genotype ofS. annulatum may have been missed because of inadequate sampling or extinction. Alternatively, another extinct or undetected taxon may constitute the second progenitor. The observed patterns of genetic variation and linkage disequilibria were uncorrelated with the previously proposed subspecific classification ofS. majus. Lack of genetic divergence between continents suggests that the origins ofS. majus in Europe and North America were not independent. Low mutation rates and large effective population sizes may be important causing populations to diverge slowly, and may explain the observed patterns without hypothesising frequent long-distance dispersal.     

Seed morphology and taxonomy of the North African species of Sideritis L. (Lamiaceae)

REJDALI, M., 1990. Seed morphology and taxonomy of the North African species of Sideritis L. (Lamiaceae). Seed morphology data are shown to support data from general morphology and palynology; they can be used for taxonomy at the sectional and specific levels. At times clear differences are apparent at the infraspecific level. Seed sculpturing was found to be of great value for separating taxa at all levels of the hierarchy.     

Taxonomical notes on the Chilean Cruciferae

The taxonomic status of some Chilean Cruciferae is elucidated, and new combinations in the genera Stenodraba Sch. and Hollermayera Sch. are established. Additionally a new section, Elatia , and two specific names to replace illegitimate binomials in Stenodraba are proposed.     

Seed image analysis and taxonomy of Diplotaxis DC. (Brassicaceae,Brassiceae)

West European Rock lizards, Lacerta (Iberolacerta) have small widely separated ranges in highland areas. Mitochondrial and nuclear DNA sequences corroborate the monophyly of the group and show it is not closely related to any of the other Rock lizards with which it was formerly placed in Archaeolacerta, an assemblage for which there is no evidence of clade status. L. (Iberolacerta) consists of four main units: L. (I.) horvathi of NW Croatia and neighbouring regions; the Pyrenees species, L. (I.) bonnali, L. (I.) aranica and L. (I.) aurelioi; L. (I.) cyreni of the Iberian Sistema Central, with distinctive populations in the Sierras de Bejar, Gredos and Guadarrama; and L. (I.) monticola of the Serra da Estrela of Central Portugal and NW Spain, this unit also contains L. (I.) cyrenimartinezricai of La Peña de Francia, W. Spain and a distinctive population in the Montañas de Sanabria. L. (Iberolacerta) has persisted in some mountain ranges for at least 4.2 ± 1.4 Ma and may have been restricted to mountains by competition from Wall lizards (Podarcis). Its clade status shows it has lost range extensively and has produced few external branches since its initial fragmentation. In contrast, Podarcis diversified about the time L. (Iberolacerta) fragmented, producing a series of widespread lineages that have persisted until the present time. The mainly European subfamily Lacertinae, to which both L. (Iberolacerta) and Podarcis belong, diversified rapidly 13–9 Ma ago, probably largely replacing other lacertid lizards of earlier origin. As another round of replacement started at approximately 9 Ma ago with the spread of Podarcis, this may be a recurrent phenomenon in the evolution of some lizard communities.     

A protein taxonomy based on secondary structure.

Does a protein's secondary structure determine its three-dimensional fold? This question is tested directly by analyzing proteins of known structure and constructing a taxonomy based solely on secondary structure. The taxonomy is generated automatically, and it takes the form of a tree in which proteins with similar secondary structure occupy neighboring leaves. Our tree is largely in agreement with results from the structural classification of proteins (SCOP), a multidimensional classification based on homologous sequences, full three-dimensional structure, information about chemistry and evolution, and human judgment. Our findings suggest a simple mechanism of protein evolution.     

Long-call structure and its relation to taxonomy in lion tamarins

Recent evidence on craniodental morphology suggests the acceptance of three species of lion tamarins (Leontopithecus). Confirmatory evidence is presented here using the morphology of long-call vocalizations recorded from several individuals of each type of lion tamarin. Recordings were made of Leontopicthecus rosalia, Leontopithecus chrysopygus, and Leontopithecus chrysomelas at the Centro de Primatologia do Rio de Janeiro (FEEMA) and of L. rosalia at Monkey Jungle in Florida. Thirty separate parameters were measured, and 17 of them differed significantly between populations. In general, L. chrysomelas had higher pitched calls with shorter note duration, while L. chrysopygus, the larger of the animals, had lower pitched calls with longer note duration. L. rosalia was either intermediate to the other two populations or resembled L. chrysopygus. Thus, the results from the analysis of vocal structures closely paralleled the results obtained with more traditional taxonomic methods and suggests that the quantitative analysis of vocal strucures can be a useful adjunct in taxonomy.     

Achene structure and taxonomy of North American Bolboschoenus (Cyperaceae)

Surface and transverse section achene structures ofBolboschoenus maritimus, B. robustus, B. fluviatilis, B. novae-angliae, B. glaucus, and the putative hybridsB. maritimus × B. rubustus andB. glaucus × B. maritimus from North America are described and illustrated with SEM micrographs. The same three type of pericarp structure reported by Browning and Gordon-Gray (1993) from southern Africa were found except that the “type 2” (B. glaucus) was not matched precisely. Intermediate achene structures and other evidence support both the hybrid origin ofB. novae-angliae (=B. fluviatilis × B. robustus) and hybridization betweenB. glaucus andB. maritimus. The new combinationBolboschoenus novae-angliae is made.