黑腹果蝇种组五种核型的报道

通过传统的敲片、Giemsa染色的方法, 本文首次对果蝇属黑腹果蝇种组的5种果蝇 （D. constricta、D. ohnishii、D. ogumai、D. pseudobaimaii、D. tani）染色体的数目和形态进行了分析报道。分析发现：这5个种具有相同的染色体数目（2n=8）和不同的形态。D. pseudobaimaii和D. tani 为2V,1R,1D型;D. constricta染色为2V,1R,1D型且其点状染色体难以辨认;D. ohnishii和D. ogumai 具有相同形态为2V,2R。另外,还发现核型与亲缘关系之间有一定的对应性。     

Arabidopsis Species Hybrids-Emerging Model Systems for the Analysis of Species Differences

   apd: 9 March 2001     

Species Delimitation and Analysis of Cryptic Species Diversity in the XXI Century

The potentials and limitations of different approaches to revealing species boundaries and describing cryptic species are discussed. Both the traditional methods of species delimitation, mostly based on morphological analysis, and the approaches using molecular markers are considered. Besides, the prospects of species identification using digital image recognition and machine learning are briefly considered. It is concluded that molecular markers provide very important material for species delimitation; the value of these data increases manifold if they can be compared with information on morphology, geographic distribution, and ecological preferences of the studied taxa. In many cases, only a practicing taxonomist who knows his or her group thoroughly can correctly interpret the molecular data and incorporate them into the existing knowledge system in order to make a taxonomic decision.

     

果蝇亚群中六个种的求爱歌的研究：对ipi作用的探究

据认为果蝇求爱歌的脉冲间隔(ipi)在种特异性配偶认识系统(SMRS)中起着重要的作用。果蝇D.takahashii亚群中各物种求爱歌的ipi值和种间亲缘关系的相关性如何?迄今尚未见报道。我们测定了此亚群中能饲养存活的6个种的ipi,并用O’Farrell双向电泳方法及杂交实验研究了它们之间的亲缘关系。在近缘种D.takahashii和D.lutescens之间,D.takahashii和D.paralutea之间,D.lutescens和D.paralutea之间,其求爱歌的ipi值,不论平均数或众数都相差甚远。而D.paralutea和D.prostipennis是2个亲缘关系较远的种,两者不能杂交,但其ipi的平均数在统计学上无差异,众数亦很相近。本实验可导出这样的见解:ipi值在不同果蝇种群或亚群的SMRS中的作用可能并不相同。在D.takahashii亚群中ipi值对于杂交成败似乎不起支配性作用。     

入侵种小管福寿螺对本土物种梨形环棱螺的生态挤压作用

在世界范围内,物种入侵正成为一个影响经济发展、公众健康的重大生态事件.为了探究入侵物种小管福寿螺(Pomacea canaliculata)对本土近生态位物种的生态挤压作用,选择了梨形环棱螺(Bellamya purificata)作为受试动物,设置直接生态竞争实验和间接分泌物胁迫实验两类实验.直接生态竞争实验中两种螺...     

Species of the coccidian genus Alveocystis

Publications on the coccidia of certain invertebrates are reviewed and two new taxonomic-nomenclatural combinations are introduced: Alveocystis macrocoronata (Lüling, 1942) n. comb., in hosts Priapulus caudatus and Halicryptus spinulosus (Priapuloidea); and A. gugleri (Wacha, 1981) n. comb., in Triodopsis albolabris (Mollusca).     

On the Chinese Species of Passifloraceae

The present paper is an outcome of taxonomic study of Chinese passifloraceous plants. It contains 2 genera, 23 species, 2 varieties and 7 cultivarieties, of which one species is described as new and two are first recorded from China. The Chinese passifloraceous plants are mainly distributed in Yunnan (2 gen. 16 sp.), Guangdong (2 gen. 9sp.) and Guangxi (2 gen. 8 sp.).     

The Biosemiotic Concept of the Species

Any biological species of biparental organisms necessarily includes, and is fundamentally dependent on, sign processes between individuals. In this case, the natural category of the species is based on family resemblances (in the Wittgensteinian sense), which is why a species is not a natural kind. We describe the mechanism that generates the family resemblance. An individual recognition window and biparental reproduction almost suffice as conditions to produce species naturally. This is due to assortativity of mating which is not based on certain individual traits, but on the difference between individuals. The biosemiotic model described here explains what holds a species together. It also implies that boundaries of a species are fundamentally fuzzy, and that character displacement occurs in case of sympatry. Speciation is a special case of discretisation that is an inevitable result of any communication system in work. The biosemiotic mechanism provides the conditions and communicative restrictions for the origin and persistence of diversity in the realm of living (communicative and semiotic) systems.     

Shoot-Level Flammability of Species Mixtures is Driven by the Most Flammable Species: Implications for Vegetation-Fire Feedbacks Favouring Invasive Species

Invasive species can cause shifts in vegetation composition and fire regimes by initiating positive vegetation-fire feedbacks. To understand the mechanisms underpinning these shifts, we need to determine how invasive species interact with other species when burned in combination and thus how they may influence net flammability in the communities they invade. Previous studies using litter and ground fuels suggest that flammability of a species mixture is nonadditive and is driven largely by the more-flammable species. However, this nonadditivity has not been investigated in the context of plant invasions nor for canopy fuels. Using whole shoots, we measured the flammability of indigenous-invasive species pairs for six New Zealand indigenous and four globally invasive plant species, along with single-species control burns. Our integrated measure of flammability was clearly nonadditive, and the more-flammable species per pairing had the stronger influence on flammability in 83% of combinations. The degree of nonadditivity was significantly positively correlated with the flammability difference between the species in a pairing. The strength of nonadditivity differed among individual flammability components. Ignitability and combustibility were strongly determined by the more-flammable species per pair, yet both species contributed more equally to consumability and sustainability. Our results suggest mechanisms by which invasive species entrain positive vegetation-fire feedbacks that alter ecosystem flammability, enhancing their invasion. Of the species tested, Hakea sericea and Ulex europaeus are those most likely to increase the flammability of New Zealand ecosystems and should be priorities for management.     

On the Physiology of Rhizopus Species

Part. V. The preliminary research on the occurrence of zymase and carboxylase in Rhizopus species.

Part. VI. The verification of the occurrence of zymase in Rhizopus species.

Part. VII. On the formation of ethyl alcohol from acetic acid by acetone-Rhizopus (Rhizopus treated by acetone.)

Part. VIII. On the formation of ethyl alcohol from malic acid by Rhizopus species.

Part. IX. On the formation of ethyl alcohol from malic acid by ace’one-Rhizopus.     

Species relationships in the avenae

In order to assess the genome homologies of a number of diploid and tetraploid species of Avena, two meiotic characters — mean chiasmata per cell and frequency of types of pairing configurations — have been studied in the species and in a number of diploid, triploid and tetraploid hybrids. The results indicate extensive structural differentiation of the genome of A. longiglumis from that which is common to the other diploids A. strigosa, A. brevis, A. hirtula, A. glabrata and A. wiestii. Structural differentiation is found also between the genomes of the three tetraploids A. vaviloviana, A. abyssinica and A. barbata. Chromosome pairing in triploid hybrids indicates the similarity of the genome in the A. strigosa group to one of those in the tetraploids and a partial but significant affinity with the other. These data, though derived from a very limited range of genotypes, lead to the conclusions that (a) structural differentiation of chromosomes may be common in the genus and important in its evolution, and (b) that current ideas on evolution of the polyploid species through simple allopolyploidy are unlikely to be true. The polyploids probably have a more complex origin in which autopolyploids or near autopolyploids and structural change of chromosomes have played a part.