A note on the structure of system state spaces and its implications on the existence of non-repeatable experiments

The implication of state space structure on the existence of a repeatable experimentE designed to determine if a states∈L has propertyP or notP is investigated. It is shown that if a state spaceL is connected, then no experimentE is repeatable. This formalism is used to demonstrate that if a propertyP has an associated set of points inL which is dense with dense complement inL, then there exists no repeatable experimentE which can be used to test whethers has propertyP or notP. Other consequences of this formalization are discussed.     

Genetic polymorphism for cyanogenesis and linkage at the linamarase locus in Trifolium nigrescens Viv. subsp. nigrescens

Polymorphisms at two genetic loci conditioning the cyanogenic glucoside linamarin (Ac) and the glucosidase linamarase (Li) are reported for the first time in Trifolium nigrescens Viv. subspecies nigrescens (2n=2x=16). T. nigrescens is one of several possible ancestral species that may have donated a genome to the allotetraploid species white clover (T. repens L., 2n=4x=32). T. nigrescens is a strong candidate because it is the only very close relative that, like white clover, is cyanogenic. Genetic analysis showed that in T. nigrescens, cyanogenesis was inherited as a two-locus genetic system in a similar way to that in white clover. Furthermore, Li, which is linked to the locus Sdh (shikimate dehydrogenase, SDH) at a distance of 6 cM in one genome of white clover, also showed linkage (12 cM) in T. nigrescens. It is concluded that one of the subspecies of T. nigrescens is a likely donor of a genome to white clover. Received: 27 December 2000 / Accepted: 12 April 2001     

The mathematical theory of group selection. I. Full solution of a nonlinear Levins E = E(x) model

The first complete overtime solution is obtained for a group selection model of Levins E = E(x) type with recolonization but no other gene flow between islands. Assuming a subdivided population at carrying capacity, the model describes selection at a biallelic locus (A, a) where a is opposed by Mendelian selection but is favored by a lower rate of extinction of demes having high a frequency. By contrast to the linear diffusion equations encountered in classical mathematical genetics, the PDE governing the dynamics is now nonlinear in the metapopulation gene frequency distribution φ(x, t); furthermore, the initial conditions now heavily influence the equilibrium distribution φ_∞(x). A fully explicit formula (20) expressing this dependence is derived. The results indicate that a fixation is never reached, but (A, a) polymorphism in the metapopulation will result if , where s 1 parametrizes the strength of Mendelian selection, E(x) is the Levins extinction operator, h (typically in the open interval (0, 1)) is the dominance of a, and B is a parameter measuring the flatness of the initial distribution f(x) in the x → 1 limit.     

The phylogenetic position of the bumble bee inquiline Bombus inexspectatus and implications for the evolution of social parasitism

The high alpine European bumble bee Bombus (Thoracobombus) inexspectatus is one of three taxa in which obligate social parasitism has evolved in bumble bees. Until now, the phylogenetic placement of this species has not been analyzed quantitatively because it is rare in nature. Here a specimen of B. inexspectatus is sequenced for five genes to assess its phylogenetic position relative to other bumble bee species. Phylogenetic estimation of B. inexspectatus places this species within the subgenus Thoracobombus, as expected based on morphology. This provides strong support for the acquisition of social parasitism in B. inexspectatus separate from that found in the bumble bees of the subgenus Psithyrus and B. (Alpinobombus) hyperboreus. Furthermore, B. inexspectatus is not the sister taxon of its host but is a near relative, suggesting a loose but not strict adherence to Emery’s rule. B. inexspectatus is a sister taxon to a clade including B. veteranus, a frequent nest usurper that has been suggested to be a facultative social parasite. The phylogenetic placement of all bumble bee social parasites relative to their hosts is discussed.     

Tests of Independence and Zero Correlations Among P Random Variables

Suppose it is desired to determine whether there is an association between any pair of p random variables. A common approach is to test H₀ : R = I, where R is the usual population correlation matrix. A closely related approach is to test H₀ : R_pb = I, where R_pb is the matrix of percentage bend correlations. In so far as type I errors are a concern, at a minimum any test of H₀ should have a type I error probability close to the nominal level when all pairs of random variables are independent. Currently, the Gupta-Rathie method is relatively successful at controlling the probability of a type I error when testing H₀: R = I, but as illustrated in this paper, it can fail when sampling from nonnormal distributions. The main goal in this paper is to describe a new test of H₀: R_pb = I that continues to give reasonable control over the probability of a type I error in the situations where the Gupta-Rathie method fails. Even under normality, the new method has advantages when the sample size is small relative to p. Moreover, when there is dependence, but all correlations are equal to zero, the new method continues to give good control over the probability of a type I error while the Gupta-Rathie method does not. The paper also reports simulation results on a bootstrap confidence interval for the percentage bend correlation.     

Revalidation of Phyllocaulis renschi (Mollusca: Gastropoda: Veronicellidae) based on radula and mandible structures of taxonomic significance for the genus

Exospermastix robustus Verhoeff, 1951 (Mato Grosso, nr Cuiaba) is regarded as a species of Urostreptus; the gonopods of the type specimen are illustrated and their structure discussed. The species is in many ways similar to U. camerani and U. paxillatus, but is much larger than either. The status of the generic and specific names Stenostreptus hassleri Carl is reviewed after a study of the type material, and the previous estimate of hassleri as a species of Urostreptus is reaffirmed. New drawings made from the lectotype of hassleri are given. The gonopods of a species identified as U. borelli by F. Silvestri, the author of that name, are illustrated, and the suggestion made that borelli may be found to be a senior synonym of hassleri.     

The genetic location of the self-incompatibility locus in white clover (Trifolium repens L.)

White clover (Trifolium repens L.) is a forage legume of considerable economic importance in temperate agricultural systems. It has a strong self-incompatibility system. The molecular basis of self-incompatibility in T. repens is unknown, but it is under the control of a single locus, which is expressed gametophytically. To locate the self-incompatibility locus (S locus) in T. repens, we carried out cross-pollination experiments in an F₁ mapping population and constructed a genetic linkage map using amplified fragment length polymorphism and simple sequence repeat markers. As the first step in a map-based cloning strategy, we locate for the first time the S locus in T. repens on a genetic linkage map, on the homoeologous linkage group pair 1 (E), which is broadly syntenic to Medicago truncatula L. chromosome 1. On the basis of this syntenic relationship, the possibility that the S locus may or may not possess an S-RNase gene is discussed.     

Paraspinibarbus,a new genus of cyprinid fishes from the Red River basin

Paraspinibarbus, a new and monotypic genus, is erected forSpinibarbus macracanthus Pellegrin et Chevey, 1936, a cyprinid from the Red River basin. It is characterized by a procumbent predorsal spine and a very thick lower lip with a continuous postlabial groove.Balantiocheilus hekouensis Wu, 1977 is a junior subjective synonym ofParaspinibarbus macracanthus. A lectotype is designated forS. macracanthus.     

The regulation of urease activity in Aspergillus nidulans

Aspergillus nidulans can utilize urea as a sole source of nitrogen but not as a carbon source. Urea is degraded by a urease. Mutation at any one of three genes, ureB, ureC, and ureD, may result in deficient urease activity. The ureB gene is closely linked to ureA, the structural gene for the urea transport protein. The heat lability of a ureB ^– revertant strain, intragenic complementation tests, and the linkage of ureB to ureA suggest that ureB is the urease structural gene. The ureD gene is probably involved in the synthesis or incorporation of a nickel cofactor essential for urease activity. The function of the ureC gene is not known. Urease is not induced but is subject to nitrogen regulation. The urease activities of ammonium-derepressed mutants show that the effector of nitrogen regulation is more likely to be glutamine than ammonium. When glutamine is present in the medium, urease appears to be inactivated by some means which does not involve a newly synthesized protease or a direct interaction between glutamine and urease.     

Phylogeny of the Myllaenini and related taxa (Coleoptera: Staphylinidae: Aleocharinae)

A cladistic analysis of the tribe Myllaenini Ganglbauer and related genera is presented. Monophyly of the Myllaenini is tested, and the tribe is hypothesized to be a monophyletic group consisting of nine genera (Myllaena Erichson, Amazonopora Pace, Dimonomera Cameron, Bryothinusa Casey, Philomina Blackwelder, Polypea Fauvel, Brachypronomaea Sawada, Rothium Moore and Legner, and Lautaea Sawada), based on the synapomorphy of antero‐lateral angles of mentum prolonged into spinose processes. A history of the classification of the Myllaenini is discussed. The data set for phylogenetic analysis comprised 99 characters representing 297 character states derived from adult morphology. The analysis agrees on the monophyly of the Myllaenini and the monophyly of the Pronomaeini Ganglbauer (Pronomaea Erichson, Pseudomniophila Pace, Nopromaea Cameron and Tomoxelia Bernhauer). The tribe Dimonomerini (Dimonomera Cameron) is confirmed to be a member of the Myllaenini. Masuriini is a possible sister group of the Myllaenini. Stylopalpus Cameron shows a sister group relationship to the Pronomaeini. Several other clades are also consistently recovered. However, the phylogenetic relationships of the genus Dysacrita are ambiguous. The rogue genus Diglotta Champion is not recovered as a member of the Myllaenini or Pronomaeini. On the contrary, it forms a monophyletic clade with the liparocephaline genera Halorhadinus Sawada and Amblopusa Casey. Evolution of the defensive gland on abdominal tergite VII among aleocharine lineages is reconsidered, and the origin of an intertidal habitat in the Myllaenini is discussed.     

Studies in the morphology and systematics of berberidaceae

The floral vasculature in three allied genera,Plagiorhegma, Jeffersoria andAchyls is investigated, and the results are compared with those ofEpimedium andVancouveria which are related closely toPlagiorhegma andJeffersonia. The vasculature in the receptacle ofPlagiorhegma andJeffersonia is similar, but that ofAchlys is much simpler. Slightly different trace patterns are observed in the sepals ofPlagiorhegma andJeffersonia. InJeffersonia, the 3-trace condition leaving 2 or 3 gaps is most frequently observed, but inPlagiorhegma traces of a double nature leaving a single gap are more frequent. The traces to the innermost sepals, petals and stamens are usually of a double nature leaving a single gap in both genera. Regular division and fusion are not observed in the receptacular stele. The vascular differentiation between sepals and petals is more advanced inPlagiorhegma andJeffersonia than inEpimedium andVancouveria. InAchlys, the traces are all staminal and single throughout their course. Two parts recognized in the pistils ofPlagiorhegma, Jeffersonia andAchlys are traversed by independent vasculature. The comparisons of pistil morphology including vasculature ofPlagiorhegma, Jeffersonia, Achlys, Epimedium andVancouveria lead to the interpretation that the pistils are based on the same morphological plan. The probable evolutionary trend in pistil is then suggested in these five genera.     

Anamylopsoraceae — a new family of lichenized ascomycetes with stipitate apothecia (Lecanorales: Agyriineae)

The anatomy, chemistry and developmental morphology ofAnamylopsora pulcherrima is investigated. Some characters, including the ascus structure, suggest a close affinity with theAgyriaceae. However, the chemistry and the pycnidial structure differ as well as the ascoma ontogeny.Anamylopsora has a gymnocarpous ascoma development and the ascogonia are produced in stipes.Trapelia coarctata, as a typical member of theAgyriaceae, shows a hemiangiocarpous ascoma ontogeny. The anatomical, chemical and ontogenetical characters of several families are compared withAnamylopsora and it is shown that the genus is best placed in a monotypic familyAnamylopsoraceae Lumbsch & Lunke, fam. nova, which is placed in theAgyriineae (Lecanorales).This paper is dedicated to Prof. DrAino Henssen (Marburg) on the occasion of the 70th birthday.     

Cloning by functional complementation, and inactivation, of theSchizosaccharomyces pombe homologue of theSaccharomyces cerevisiae geneABC1

TheSaccharomyces cerevisiae geneABC1 is required for the correct functioning of thebc ₁ complex of the mitochondrial respiratory chain. By functional complementation of aS. cerevisiae abc1 ^– mutant, we have cloned aSchizosaccharomyces pombe cDNA, whose predicted product is 50% identical to the Abc1 protein. Significant homology is also observed with bacterial, nematode, and even human amino acid sequences of unknown function, suggesting that the Abc1 protein is conserved through evolution. The cloned cDNA corresponds to a singleS. pombe geneabc1Sp, located on chromosome II, expression of which is not regulated by the carbon source. Inactivation of theabc1Sp gene by homologous gene replacement causes a respiratory deficiency which is efficiently rescued by the expression of theS. cerevisiae ABC1 gene. The inactivated strain shows a drastic decrease in thebc ₁ complex activity, a decrease in cytochromeaa3 and a slow growth phenotype. To our knowledge, this is the first example of the inactivation of a respiratory gene inS. pombe. Our results highlight the fact thatS. pombe growth is highly dependent upon respiration, and thatS. pombe could represent a valuable model for studying nucleo-mitochondrial interactions in higher eukaryotes.     

Evolution of <Emphasis Type="Italic">Hox3</Emphasis> and <Emphasis Type="Italic">ftz</Emphasis> in arthropods: insights from the crustacean <Emphasis Type="Italic">Daphnia pulex</Emphasis>

The Drosophila melanogaster genes zerknüllt (zen) and fushi tarazu (ftz) are members of the Hox gene family whose roles have changed significantly in the insect lineage and thus provide an opportunity to study the mechanisms underlying the functional evolution of Hox proteins. We have studied the expression of orthologs of zen (DpuHox3) and ftz (Dpuftz) in the crustacean Daphnia pulex (Branchiopoda), both of which show a dynamic expression pattern. DpuHox3 is expressed in a complex pattern in early embryogenesis, with the most anterior boundary of expression lying at the anterior limit of the second antennal segment as well as a ring of expression around the embryo. In later embryos, DpuHox3 expression is restricted to the mesoderm of mandibular limb buds. Dpuftz is first expressed in a ring around the embryo following the posterior limit of the mandibular segment. Later, Dpuftz is restricted to the posterior part of the mandibular segment. This is the first report of expression of a Hox3 ortholog in a crustacean, and together with Dpuftz data, the results presented here show that Hox3 and ftz have retained a Hox-like expression pattern in crustaceans. This is in accordance with the proposed model of Hox3 and ftz evolution in arthropods and allows a more precise pinpointing of the loss of ftz “Hox-like behaviour”: in the lineage between the Branchiopoda and the basal insect Thysanura.     

Approximate Michaelis-Menten kinetics displayed in a stochastic model of cell-mediated cytotoxicity

A nonlinear continuous-time Markov chain describing a two-step process of cytolytic cells binding to target and the subsequent lysis and release of label is shown to have kinetics which resemble standard enzyme-substrate kinetics. The Michaelis-Menten saturation function is found as a special case resulting when the target population is in excess. A comparison theorem for the pseudo-steady-state distribution Π is constructed to enable examination of that distribution whose expected value E and variance V satisfy - K_mE + (C_T − E)(T_T − E) + V = 0, where K_m is the Michaelis half-saturation constant and C_T and T_T are the initial populations of the two cell types. Using Π as an initial condition, the release of label process is examined. The main result is that the fraction of specific release, ƒ, has the approximate form when T_t is large, so that a nonlinear regression procedure is appropriate for the determination of the parameters.     

Ag,a novel protein secreted from Aplysia glia

We have isolated a cDNA (ag for Aplysia glial) corresponding to an mRNA specific to the nervous system of Aplysia californica. In this study, we characterized the ag cDNA sequence and the distribution of ag mRNA and protein in the Aplysia nervous system. The ag cDNA contains an open reading frame that encodes a novel 29 kD protein. In situ hybridizations demonstrate that ag mRNA is conspicuously absent from the cell bodies of the large neurons constituting the external layer of the ganglia. Instead, it is largely confined to a subset of small, apparently non-neuronal cells surrounding the neurons at the border of the neuropil, is sparsely scattered within the neuropil, and is widespread within the connective nerves, a pattern consistent with glial localization. Polyclonal anti-ag antiserum recognizes a protein between 27 and 29 kD that is more broadly distributed, especially within the neuropil. The distributions of ag mRNA and protein, together with the presence of a putative signal peptide, suggest that ag protein is secreted. Two findings support this hypothesis: first, ag protein is detectable by western blot in Aplysia hemolymph. Second, full length ag protein expressed in COS cells is secreted, but ag lacking the putative signal peptide is not. Secretion from glia raises the possibility that this abundant protein may affect neighboring neurons. © 1996 John Wiley & Sons, Inc.