Evolutionary games for spatially dispersed populations

An evolutionary game model is developed that incorporates both spatial dispersion and density effects in the evolutionary dynamic. It is shown that a stable equilibrium (e.g. an evolutionarily stable strategy) of the non-dispersed frequency dynamic becomes a stable equilibrium of the larger system if population density stabilizes at these fixed frequencies. It is also shown, by example, that other equilibria, whose frequencies change from one location to another, may appear when dispersal rates are relatively small.Research supported by Natural Sciences and Engineering Research Council of Canada Operating Grant A6187Research supported by Natural Sciences and Engineering Research Council of Canada Operating Grant A7822     

Predator-prey systems with group defence: The paradox of enrichment revisited

The main concern of this paper is with survival or extinction of predators in models of predator-prey systems exhibiting group defence of the prey. It is shown that if there is no mutual interference among predators, enrichment could result in their extinction. However, if there is mutual interference, the predator population survives (at least deterministically). Research partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A 4823. Research partially supported by a Natural Sciences and Engineering Research Council of Canada postdoctoral fellowship.     

Global analysis of a model of plasmid-bearing,plasmid-free competition in a chemostat

A model of competition between plasmid-bearing and plasmid-free organisms in a chemostat was proposed in a paper of Stephanopoulis and Lapidus. The model was in the form of a system of nonlinear ordinary differential equations. Such models are relevant to commercial production by genetically altered organisms in continuous culture. The analysis there was local (using index arguments). This paper provides a mathematically rigorous analysis of the global asymptotic behavior of the governing equations in the case of uninhibited specific growth rate.Research supported by the National Council of Science, Republic of ChinaResearch supported by National Science Foundation Grant, DMS-9204490Research supported by the Natural Science and Engineering Council of Canada. This author's contribution was made while on research leave visiting the Department of Ecology and Evolutionary Biology at Princeton University. She would especially like to thank Simon Levin for his guidance as well as for providing an exceptional working environment     

Global dynamics of a selection model for the growth of a population with genotypic fertility differences

A population growth model is considered for a one locus two allele problem with selection based entirely on fertility differences. A local stability analysis is carried out for the critical points — which include possible polymorphic states — of the resulting nonlinear differential equations. The methods of dynamical systems theory are applied to obtain limiting genotypic proportions for every initial state. Thus the results are global and there are no periodic solutions.Research for this paper was partially supported by the National Science and Engineering Research Council of Canada Grant NSERC A-8130Research for this paper was partially supported by the National Science and Engineering Research Council of Canada Grant NSERC A-4823Research supported by NSF Grant MCS 7901069. A portion of the work was carried out while the author was a Visiting Professor at the University of Utah, Salt Lake City, Utah     

Regulation of amylase activity in Drosophila melanogaster: Variation in the number of enzyme molecules produced by different amylase genotypes

Purified amylases from high- and low-activity variants of Drosophila melanogaster showed identical specific activities. Immunoelectrophoresis of crude larval homogenates showed severalfold differences between strains in the amounts of cross-reacting material. Control of amylase activity is trans-acting in heterozygotes between high- and low-activity variants. These results suggest the existence of polymorphic regulatory genes affecting the production levels of amylase protein in D. melanogaster.This work was supported by Grant GM-21279 from the Institute of General Medical Science of the NIH to R. C. Lewontin and by an Operating Grant from the Natural Sciences and Engineering Research Council Canada to D. A. Hickey.     

The Ultrastructure of Chaenea teres and an Analysis of the Phylogeny of the Haptorid Ciliates

Chaenea teres has typical haptorid ultrastructure. The somatic monokinetid has two transverse microtubular ribbons, an overlapping postciliary microtubular ribbon, and a laterally directed kinetodesmal fiber. The evered cytopharynx forms a dome at the apical end of the cell. The base of the dome is surrounded by oral dikinetids. The left, anterior kinetosome of the oral pair is not ciliated and has a transverse microtubular ribbon, a nematodesmata and a single postciliary microtubule. The right, posterior kinetosome is ciliated and has only postciliary microtubules. The kinetosomes at the anterior ends of the somatic kinetics are close together and their transverse microtubules and nematodesmata contribute to the support of the cytopharynx. The transverse microtubules of these oralized somatic kinetosomes, together with those from the oral dikinetids, line the cytopharynx. Accessory or bulge microtubules arise perpendicular to the transverse microtubules. A dorsal brush of three kineties of clavate cilia is found on the cell surface just posterior to the oral region. Mucocysts and a single type of toxicyst are present. The toxicysts are confined to the oral region. There are multiple ovoid macronuclei that stain weakly. Micronuclei were not observed. Cladistic analysis indicates the Chaenea may be most closely related to Fuscheria and Acropisthium. The cladistic analysis also suggests that existing taxonomies of the subclass Haptoria need to be revised. We propose some modifications to Foissner & Foissner's classification that include transferring Helicoprorodon, Actinobolina, the buetschiliids, and the balantidiids to the order Haptorida and recognizing the close relationship between pleurostomes and spathidiids.     

Allozyme and mitochondrial DNA analysis of a hybrid zone between white-tailed deer and mule deer (Odocoileus) in west texas

Thirty allozyme loci and 35 mitochondrial DNA (mtDNA) restriction sites were examined in 24 white-tailed deer and 46 mule deer from a hybrid zone in West Texas. A common mtDNA genotype is shared by all of the mule deer with 67% of the white-tailed deer. At the albumin locus, 13% of the white-tailed deer and 24% of the mule deer are heterozygous, sharing alleles that are otherwise species-specific in allopatric populations; 7% of the mule deer are homozygous for the allele that is characteristic of allopatric white-tailed deer. Gene flow appears to have been bidirectional, with greater genetic introgression into mule deer. The mtDNA data suggest that matings between white-tailed and mule deer have occurred in the past. Despite evidence of genetic introgression, analysis of multilocus genotypes indicates that none of the deer examined is an F₁ hybrid. Production of such hybrids appears to be generally uncommon in North American deer; management plans that assume otherwise should be reconsidered.This work was supported by an NIH Biomedical Research Support Grant, Texas Agricultural Experiment Station Program Development and Expanded Research Awards, the Caesar Kleberg Research Program in Wildlife Ecology, and a Natural Sciences and Engineering Research Council Operating Grant.     

Ultrastructural aspects of the somatic and buccal infraciliature ofColeps amphacanthus Ehrenberg 1833

Summary Somatic and buccal infraciliature ofColeps amphacanthus Ehrenberg 1833 were studied by light and electron microscopy. The somatic kineties are composed of monokinetids and 2 dikinetids at the anterior end of each kinety. The monokinetids are associated with postciliary microtubules at triplet 9, a kinetodesmal fiber at triplet 5 and 7 and nearly radially arranged transverse microtubules at triplet 4. The associated fibrillar systems of the posterior kinetosome of the dikinetids are like those of the monokinetids. The anterior kinetosome is associated with transverse microtubules at triplet 4 and one or few postciliary microtubules at triplet 9. The anterior kinetosome bears only a short cilium.The oral ciliature is composed of a kinety of nearly circumorally arranged paroral dikinetids and 3 adoral organelles at the ventral left side of the oral opening. Nematodesmata arising from the oral ciliature form the major component of the cytopharyngeal apparatus which is lined by microtubular ribbons of postciliary origin. The buccal cavity is surrounded by oral papillae which often contain toxicysts.     

The Ultrastructure of Zosterodasys agamalievi (Ciliophora: Synhymeniida)

ABSTRACT. The cell surface of the synhymeniid ciliate, Zosterodasys agamalievi , consists of shallow kinetal grooves separated by low cortical ridges. Numerous electron-opaque bodies are located in the cortical ridges, inside the kinetal grooves, and are distributed in parallel rows between adjacent kineties. Well-developed alveoli are present beneath the cell surface membrane. Zosterodasys agamalievi has a single micronucleus and a homomerous macronucleus. The infraciliature of the somatic monokinetid consists of an anteriorly-directed kinetodesmal fiber, a well-developed divergent postciliary microtubular ribbon, radially-oriented transverse microtubules, and a short striated rootlet, which extends anteriorly from the base of the kinetosome into the cell. Zosterodasys agamalievi has a perioral band of paired cilia, the synhymenium, that winds obliquely across the ventral surface of the body, just posterior to the cytostome. The infraciliature of the anterior kinetosome of the synhymenium consists of two postciliary microtubules; a well-developed, divergent post-ciliary ribbon of microtubules and a short kinetodesmal fiber are associated with the posterior kinetosome. The cytopharynx is supported by 14-16 nematodesmata which are capped distally by a capitulum. The cytopharynx is bound proximally by a fibrous sheath and is lined by radially-arranged microtubular ribbons. No obvious oral ciliature is present.     

Genetic variation in mouse salivary amylase rate of synthesis

Heterozygotes from matings of the mouse strains YBR/Cv and C3H/As have about 3 times more YBR-amylase than C3H-amylase in the saliva. The determinant for this quantitative effect is located on linkage group XVI close to or within the structural gene for salivary amylase. The quantitative effect is the result of an increase in the rate of synthesis of YBR-amylase, and the determinant is cis acting. Studies of other mouse strains suggest that regulatory genetic elements may modulate salivary amylase production.This work was supported by the Danish Natural Science Research Council and a grant from the United States Public Health Service (Grant GM-19521).     

The relationship between signal response selectivity and the functional structure of complex retinal neural networks

In this paper we simulate the simultaneous responses of 45 neurones within a hypothetical retina to a variety of spatio-temporal signals. Our results demonstrate how specific convergent and divergent excitatory and inhibitory connections are sufficient to determine signal response selectivity of specific ganglion cells and so delimit the known types of center-surround receptive fields.This work was partially supported by the Natural Sciences and Engineering Research Council of Canada under Grant A-4345 to M.N.O. and Grant A-4395 to T.M.C. through the University of Alberta     

Ultrastructure of the Somatic and Buccal Cortex of the Tetrahymenine Hymenostome Glaucoma chattoni

SYNOPSIS The membranes, epiplasm, and fiber systems are described in the somatic cortex of Glaucoma chattoni strain HZ-1. Kinetodesmal fibers, postciliary and transverse microtubular ribbons, basal microtubules, transverse fibers and transverse accessory material are associated with kinetosomes. Longitudinal microtubular ribbons and mitochondria occur interkinetally. In the buccal cortex, the membranes, epiplasm and fibers of the 3 membranelles, the paroral kinety, the ribbed wall, and the cytostome are described. Comparisons between G. chattoni and other ciliates reveal ultrastructural differences of possible systematic significance. In the somatic cortex of this and other tetrahymenines. Iongitudinal microtubular ribbons and basal microtubules occur concurrently. In the buccal cortex, alveoli are absent in tetrahymenine membranelles. A table is presented of the fiber systems associated with single somatic kinetosomes of various ciliates whose cortical ultrastructure has been studied to date.     

Models of competition in the chemostat with instantaneous and delayed nutrient recycling

Two models for competition of two populations in a chemostat environment with nutrient recycling are considered. In the first model, the recycling is instantaneous, whereas in the second, the recycling is delayed. For each model an equilibrium analysis is carried out, and persistence criteria are obtained. This paper extends the work done by Beretta et al. (1990) for a single species.Research partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant NSERC A4823Research carried out at the University of Alberta while on a Canada-China Scholarly Exchange Program     

A single,phosphate-repressible deoxyribonuclease,DNase A,secreted inAspergillus nidulans

High levels of nuclease activities were identified in filtrates ofAspergillus cultures after growth in low- but not in high-phosphate media. Deoxyribonuclease activities, characterized extensively by column chromatography, showed a coincident single peak for ss- and ds-DNase which was distinct from the peak for RNase. Both ss-DNase and ds-DNase are endonucleolytic and showed the highest activity in the presence of Ca²⁺ and Mn²⁺ (atpH 8.0). They also showed identical heat sensitivities suggesting that a single, phosphate-repressible DNase was secreted. This enzyme, therefore, corresponds to the well-characterized extracellular DNase A ofNeurospora. However, theAspergillus DNase A did not cross-react with antisera to secretedNeurospora nucleases and showed different chromatographic properties, and active peptides of different sizes were visualized on DNA activity gels. The increasing derepression ofAspergillus DNase A by decreasing phosphate levels was similar to that of secreted alkaline phosphatase and these increases were both abolished by the regulatory mutantpalcA. This investigation was supported by Grant A2564 from the Natural Science and Engineering Research Council of Canada.     

Predator-prey populations with parasitic infection

A predator-prey model, where both species are subjected to parasitism, is developed and analyzed. For the case where there is coexistence of the predator with the uninfected prey, an epidemic threshold theorem is proved. It is shown that in the case where the uninfected predator cannot survive only on uninfected prey, the parasitization could lead to persistence of the predator provided a certain threshold of transmission is surpassed.Support by the Central Research Fund of the University of Alberta is gratefully acknowledgedResearch partially supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A4823     

Optimal task performance of antagonistic muscles

Movements against a variety of loads are relatively invariant in form. These movements are controlled in general by antagonistic groups of muscles. In this paper optimal control strategies are computed for coupling antagonistic muscles so as to minimize deviations from a desired trajectory. Simulations are presented for linear and nonlinear decision functions linking control of the two muscles for a variety of movements in a way that may be compared with experimental observations.This work was partly supported by the Natural Sciences and Engineering Research Council of Canada Grant NSERC OGP-4345 and by the Medical Research Council of Canada Grant MRC PG-47 through the University of Alberta     

Historical effective size and the level of genetic diversity in Drosophila melanogaster and Drosophila pseudoobscura

We report the results of a sequential gel electrophoretic study of protein variation in Drosophila melanogaster and its comparison with D. pseudoobscura. The number of alleles and mean heterozygosity were lower in D. melanogaster than in D. pseudoobscura. On the other hand, geographical populations of Drosophila melanogaster have been shown to be much more differentiated than those of D. pseudoobscura. The results suggest that in D. melanogaster low-frequency alleles have been lost during the colonization process and that major alleles have become differentiated among populations. Population bottlenecks, due to various causes, appear to have played a significant role in the shaping of genetic variation in natural populations of many species. It is proposed that a comparison of genetic variation at homologous gene loci between related species can bring out effects of historical bottlenecks and provide an alternative approach for analyzing causes of genetic variation in natural populations.We thank the Natural Science and Engineering Research Council of Canada for financial support (Grant A0235 to R.S.S.).     

Competing predators for a prey in a chemostat model with periodic nutrient input

A system of ordinary differential equations is used to model the interactions of n competing predators on a single prey population in a chemostat environment with a periodic nutrient input. In the case of one or no predators, criteria for the existence of periodic solutions are given. In the general case, conditions for all populations to persist are derived.Research is in part based on a Ph.D. thesis submitted to the Faculty of Graduate Studies, University of AlbertaResearch is partly supported by the Natural Sciences and Engineering Research Council of Canada, Grant No. NSERC A4823     

The effect of variable mechanical impedance on the control of antagonistic muscles

Most models of muscle have assumed that the series elastic element has a constant stiffness, although experimentally this is not true, either at the level of individual cross-bridges or that of the whole muscle. In this paper elastic and viscous elements are introduced whose properties vary systematically with activity levels as has been found experimentally. The effects of these nonlinear variations on the methods for optimally controlling a pair of antagonistic muscles are calculated. Although the nonlinearities add some complexity to the derivation and are important to the mechanism of force generation in the muscle, they do not qualitatively change the overall control of movement.This work was partly supported by the Natural Sciences and Engineering Research Council of Canada NSERC OGP-4345 and by the Medical Research Council of Canada Grant PG-47 through the University of Alberta     

Ultrastructure of the flagellar apparatus inPleurochrysis (classPrymnesiophyceae)

Summary The ultrastructure of the flagellar apparatus of aPleurochrysis, a coccolithophorid was studied in detail. Three major fibrous connecting bands and several accessory fibrous bands link the basal bodies, haptonema and microtubular flagellar roots. The asymmetrical flagellar root system is composed of three different microtubular roots (referred to here as roots 1,2, and 3) and a fibrous root. Root 1, associated with one of the basal bodies, is of the compound type, constructed of two sets of microtubules,viz. a broad sheet consisting of up to twenty closely aligned microtubules, and a secondary bundle made up of 100–200 microtubules which arises at right angles to the former. A thin electron-dense plate occurs on the surface of the microtubular sheet opposite the secondary bundle. The fibrous root arises from the same basal body and passes along the plasmalemma together with the microtubular sheet of root 1. Root 2 is also of the compound type and arises from one of the major connecting bands (called a distal band) as a four-stranded microtubular root and extends in the opposite direction to the haptonema. From this stranded root a secondary bundle of microtubules arises at approximately right angle. Root 3 is a more simple type, composed of at least six microtubules which are associated with the basal body. The flagellar transition region was found to be unusual for the classPrymnesiophyceae. The phylogenetic significance of the flagellar apparatus in thePrymnesiophyceae is discussed.