Competition for nutrients between Calluna vulgaris (L.) Hull and Molinia caerulea (L.) Moench

Summary A combination of a removal and fertilization experiment in the field and a replacement experiment in containers in a cold frame was carried out to investigate the role of nutrient supply in the interactions between Calluna vulgaris and Molinia caerulea. It is concluded that the growth of Calluna as well as that of Molinia increased with increasing nutrient availability. However, the increase in biomass of Molinia was much larger than that of Calluna. It is also concluded that increased nutrient availability favours the competitive vigour of Molinia in interaction with Calluna.     

Eutherian mammals from the Early Cretaceous of Mongolia

A collection of eutherian mammals consisting of 39 specimens (teeth and jaw fragments) from the ?Aptian or Albian Khoboor Beds in the Gobi Desert, Mongolia, is described. It contains 3 taxa: Prokenna1estes gen.n., assigned to the Otlestidae Nessov, new rank, with 2 shrew size species; P. trofimovi sp.n. and P. minor sp.n.; a heavily worn larger lower molar which will be described elsewhere. It cannot be excluded that P. trofimovi and P. minor are only sexual morphs within the same species. Prokennalestes and Bobolestes Nessov are possibly the oldest known eutherian mammals, but Prokennalestes is morphologically more primitive than Bobolestes. It has a labial mandibular foramen, 5 premolars and 3 molars, 3 cusps in parastylur region, paracone larger than metacone, unwinged conules, no pre- and posteingula, and lower molars with a 3-cusped talonid, which is narrower than the trigonid, Otlestes and Kennalestes may be derived with little modification from Prokennalestes. Prokennalestes gen.n. is congeneric with Prokennalestes Trofimov and Prozalambdalestes Trofimov, which are both nomina nuda.     

CYTOGENETIC STUDIES OF CARTHAMUS DIVARICATUS WITH ELEVEN PAIRS OF CHROMOSOMES AND ITS RELATIONSHIP TO OTHER CARTHAMUS SPECIES (COMPOSITAE)

Carthamus divaricatus (Beg. et Vacc.) Pamp., found only in Libya, has 11 pairs of chromosomes, a new chromosome number in the genus. The species is distinct morphologically. It has yellow, purple, and white corollas, yellow pollen, dark-purple striped anthers, horizontal branches, and strongly divaricate outer involucral bracts. The terminal portion of the middle involucral bracts is dentate and reddish brown. It is self-incompatible. Meiosis is regular in the different corolla-color types of C. divaricatus and their intraspecific hybrids. C. divaricatus was crossed to six species with n = 12, to three species with n = 10, to C. lanatus with n = 22, and to two species with n = 32 chromosomes. The morphological characteristics and cross-ability of the parental species plus the pollen viability, seed-set, and meiotic behavior of the hybrids involving C. divaricatus and other Carthamus species indicated that C. divaricatus is very closely related to species with n = 10, closely related to C. lanatus with n = 22, and less closely related to C. tinctorius with n = 12 chromosomes. C. divaricatus seems to be distantly related to C. nitidus (n = 12). It is proposed that C. divaricatus be included provisionally with 10-chromosome species in Section II. Alternative hypotheses for the development of the three basic chromosome numbers are discussed.     

New species of <Emphasis Type="Italic">Euphorbia</Emphasis> (Euphorbiaceae) from eastern Ethiopia

The new species Solanum pronum Thulin, from Acacia-Commiphora bushland in eastern Ethiopia and central Somalia, is described and illustrated. It is a member of Solanum sect. Somalanum and is compared with S. benadirense, S. jubae and S. pampaninii.     

Serological Relationships of Bromus L. and Boissiera Hochst. ex Steud

Serological techniques have been used to compare the seed albumin and globulin fractions of species of Bromus L. and Boissiera squarrosa (Soland.) Nevski. Compared with other grass genera, Boissiera squarrosa gives a very strong reaction with Bromus antisera, resembling the reactions of Bromus section Bromus species. It is considered that this evidence of serological relationship, together with evident morphological resemblance and the same basic chromosome number, require the transference of the species to the genus Bromus. It is therefore included in that genus under the name Bromus pumilio (Trin.) P. Smith, comb. nov. The significance of reactions with Bromus antisera by seed extracts of species in the tribe Hordeae is discussed.     

Jimpy, a new totally sex-linked gene in the house mouse

Summary A new recessive mutant jimpy, jp, is described. It is situated on the differential segment of the sex chromosome and is lethal in the hemizygous condition. The jimpy mice show a behaviour disorder distinguished by an intention tremor first visible at about 11 days; after about three weeks they are liable to go into a convulsion if disturbed; death occurs usually between twenty-five and thirty-two days. jp shows about 21% recombination with Ta and 36% with Bn. It has not been tested directly against Br and Mo, but they both have been shown to be about four units beyond Ta with respect to Bn (Falconer 1954). The presumed order is therefore Bn, Ta, Br and Mo, jp.Member of the Scientific Staff, Medical Research Council.     

A Bryophyte Flora of Hertfordshire

Abstract

A new species, Bruchia queenslandica, collected in tropical Australia, is described. It is similar to B. carolinae in spore features but differs in the smooth calyptra and in vegetative characters. It is compared with B. carolinae and B. brevipes     

A cladistic phylogeny of the genus Littorina (Gastropoda): implications for evolution of reproductive strategies and for classification

Gross anatomical characters of all 18 species of Littorina are used to construct a phylogenetic hypothesis for the genus, by the method of cladistic analysis. The resulting cladogram suggests that of the four subgenera of Littorina, one (Littorina) is paraphyletic. It is uncertain whether the genus Mainwaringia should be included in Littorina. It is shown that the non-planktotrophic Littorina species in the northern Atlantic comprise a monophyletic group, with the sister-species L. kurila and/or L. subrotundata in the northern Pacific. Invasion of the Atlantic by a minimum of two Pacific species, across the Arctic migration route established during the late Cenozoic, is sufficient to account for the modern distribution of the subgenera Littorina and Neritrema. The importance of the cladogram as a basis for hypotheses of adaptation is illustrated by a discussion of spawn and development in Littorina.     

A new species of <Emphasis Type="Italic">Zamia</Emphasis> from Chocó, Colombia (Cycadales,Zamiaceae)

Zamia pyrophylla, a new species from Chocó, Colombia, is described and illustrated. It is compared to Z. amazonum, Z. cunaria, and Z. ipetiensis. It is distinguished by its bright orange and red emerging leaves with leaflets that progressively turn green from the apex to the base as they mature, petioles with branched prickles and with ferruginous pubescence when immature, villous strobilar axes, and adaxial microsporangia.     

A field theory of neural nets: I: Derivation of field equations

A model is described in which neural activity is represented by a field quantity ϕ, with the neurons as the sources of ϕ. It is shown that, with certain physically realistic assumptions, ϕ satisfies a moderately nonlinear differential equation. It is also found that this equation is isotropic and of second order if and only if the neuronal connectivity has a dependence on distance,p, of the formp ⁻¹ e ^−1/2βp .     

Indirect effect of IGF2 intron3 g.3072G>A mutation on prolificacy in sows

A QTL located in the paternally expressed insulin-like growth factor 2 (IGF2) gene is known to increase muscle growth and reduce fat deposition in pigs. This makes the QTL in IGF2 a good marker for use in pig breeding programmes. However, care has to be taken as it is postulated that increased leanness and lowered fat deposition may have a negative effect on the prolificacy and longevity of sows. Selection of sire and dam lines for different alleles of the mutation in the paternally imprinted IGF2 gene could actually provide a solution to this problem. Therefore, in this study, the effect of the IGF2 QTL on prolificacy-related traits in sows was investigated. It was found that the paternal IGF2 wild-type allele was associated with higher reproduction performance in the sow. Moreover, it was also examined whether the difference in prolificacy in sows could be a consequence of differential IGF2 expression in the ovarian follicles of the sow or whether it is mainly a secondary effect caused by differences in fatness traits. Therefore, IGF2 expression was measured in follicles of different sizes from sows with different genotypes for the paternal IGF2 allele. It was observed that, however, while the size of the follicles was associated with follicular IGF2 expression level, the IGF2 genotype was not. It could be concluded that the difference in prolificacy of sows with a different paternal IGF2 genotype could be a secondary effect, resulting from differences in fat deposition.     

Genetic homeostasis and developmental stability in natural populations of bisexual (<Emphasis Type="Italic">Carassius auratus</Emphasis>) and unisexual (<Emphasis Type="Italic">C. gibelio</Emphasis>) goldfishes

One amphymictic diploid Carassius auratus, three apomictic triploids C. gibbelio, and a hybrid triploid Carassius auratus forms of goldfish were compared with respect to a set of characteristics of developmental stability: morphological variation, fluctuating asymmetry, and phenodeviations. It was found that C. gibbelio forms are characterized by lower levels both of morphological variation and fluctuating symmetry and more rare morphological abnormalties. A hybrid form Carassius auratus-gibelio was characterized by the intermediate values of the above-listed features. It is emphasized that phenotypic stabilization of apomictic forms is caused by two factors: its clone structure and actual developmental canalization. It is specified that promoted genetic homeostasis of the C. gibelio form does not give obvious adaptive advantages, as in the basic river basins of East and Central Europe. they are everywhere ousted by an amphimictic C. auratus.     

Sedimentation coefficients of DNA topoisomers: the helical wormlike chain

The sedimentation coefficient s_N of the DNA topoisomer with the linking number N is evaluated as a function of N and chain length on the basis of a (circular) twisted wormlike chain, i.e., a special case of the helical wormlike chain. Evaluation is carried out by an application of the Oseen–Burgers procedure of hydrodynamics to the cylinder model with the preaveraged Oseen tensor. The necessary mean reciprocal distance between two contour points is obtained by a Monte Carlo method. It is shown that s_N increases as |ΔN| is increased from 0 in the range of small |ΔN|, where ΔN = N ? N , with N the number of helix turns in the linear DNA chain in the undeformed state. It is found that there is semiquantitative agreement between the Monte Carlo values and the experimental data obtained by Wang for s_N.     

Temperature Drop as a Tool for Cold Tolerance Increment in Plants

The experiments were conducted with Cucumis sativus L., Triticum aestivum L., Brassica capitata, Solanum tuberosum, Zea mays L. and Pisum sativum L. Temperature drop increased cold resistance in all studied species. Level of cold resistance under the drop treatments was much higher than under the constant low temperature. It remained at a higher level for a longer period during de-acclimation. It is concluded that DROP technology is a good way for successful transplantation of greenhouse agricultural and bedding plants in early spring.     

Shoreline algal wash as a factor in reed decline in Lake Constance-Untersee

This paper assesses the chemical and mechanical impact of algal wash (Cladophora, Spirogyra, Chara) upon the lakeside reed belt (Phragmites australis) using field mapping methods, bioassays with Scenedesmus acutus in batch culture, and field experiments. Heavy mats of filamentous algae are correlated with a reduction in number of the outermost reed stalks. The water pressed from decaying heaps of Cladophora and Spirogyra reduced the growth rate of Scenedesmus significantly, but mats from Chara did not. It is assumed that the toxic substance is an organic compound. In field experiments the detrimental effect could not be clearly evidenced. The reasons for this are discussed. It is concluded that mechanical impact is of major importance.     

Morphological and molecular investigations of Paramecium schewiakoffi sp. nov. (Ciliophora, Oligohymenophorea) and current status of distribution and taxonomy of Paramecium spp.

Paramecium schewiakoffi sp. nov. is described from a pond in Shanghai, China. It is a freshwater species belonging to the “aurelia” subgroup of the genus. It is of similar size and shape to P. jenningsi, but has a single large micronucleus of the “chromosomal” morphological type, while P. jenningsi has two smaller micronuclei. The general morphology, morphometric characteristics and nuclear reorganization pattern, a random amplified polymorphic DNA (RAPD) fingerprint pattern, and the small subunit rRNA gene sequence are presented for the species. Comparison of P. schewiakoffi with the other species of Paramecium indicates that it is a valid new species of the genus. Geographical locations reported for many Paramecium species do not support the theory that all ciliates have a cosmopolitan distribution. It is proposed that, in an extension of Jankowski's earlier suggestion, the genus Paramecium should be subdivided into four subgenera: Chloroparamecium, Helianter, Cypriostomum and Paramecium, on the basis of morphometric, biological and molecular differences.     

阳西静容卫矛(卫矛科)——华南一新变种

报道了中国广东省阳西县沟谷雨林内1新变种——阳西静容卫矛(Euonymus chengii var.yangxiensis Y.S.Ye&L.F.Wu),并提供简要描述和照片。阳西静容卫矛隶属于卫矛科(Celastraceae)浅裂卫矛组(Euonymus),蒴果顶端浅裂,与原变种静容卫矛(E.chengii J.S.Ma)和中华卫矛(E.nitidus Benth.)相似,主要区别是该变种叶缘顶部2/3以上具锯齿,侧脉明显,花少且大,蒴果大,萼片伸展。     

Myxine formosana, a new species of hagfish (Myxiniformes: Myxinidae) from the southwestern waters of Taiwan

Myxine formosana, a new hagfish species, is described on the basis of the specimens from the Pacific Ocean southwest of Taiwan at depths 588–1500 m. It is five-gilled and white-headed with a three-cusp multicusp on the anterior set of cusps and a two-cusp multicusp on the posterior set. Myxine formosana, M. circifrons, M. mccoskeri, and M. robinsi are superficially rather similar, but M. formosana has low to vestigal caudal finfolds. It is the first record of the genus Myxine from Taiwan. Received: October 25, 2000 / Revised: March 17, 2001 / Accepted: April 21, 2001