Influence of Complexation on the Uptake by Plants of Iron, Manganese, Copper and Zinc: II. EFFECT OF DTPA IN A MULTI-METAL AND COMPUTER SIMULATION STUDY

Barley (Hordeum vulgare L.) plants were grown in nutrient solutionscontaining the chelating agent, DTPA. The experiments replicatedthose reported in the preceding paper in which EDTA was thechelating agent used. The concentrations of all the chemicalspecies of metals were stimulated using the program NUTRIENT.The concentrations of DTPA used were chosen to give a similarrange of complexation as used in the EDTA experiments. The effectof complexation by DTPA on the uptakes of the metal ions Fe³⁺,Mn²⁺, Cu²⁺, and Zn²⁺ and on plant growth were sufficiently differentfrom those with EDTA to indicate some dependence on the natureof the chelating agent used. The biggest difference betweenthe EDTA and DTPA experiments occurred in the solutions containingthe largest concentrations of these reagents. With DTPA, chlorosiswas seen only in the early stages; otherwise the plants showednormal growth. A simple chemical model for metal uptake is discussed. Key words: DTPA, EDTA, micronutrients, trace metals, computer simulation, plants, absorption, iron, manganese, copper, zinc     

Population limitation in Palaearctic-African migrant passerines

We report the results of key factor analyses for Sedge Warbler Acrocephalus schoenobaenus, Blackcap Sylvia atricapilla, Whitethroat Sylvia communis and Willow Warbler Pftylloscopus Irochilus based on extensive data from the United Kingdom gathered by the British Trust for Ornithology. These results are compared with those from published key factor analyses based on intensive studies of Swallows Hirundo ruslica, Redstarts Phoenicurus phoenicums and three populations of Pied Flycatchers Fiiedula hypoleuca. Variation in losses between fledging and the following breeding season lk₄ ) accounted for most of the variation in total losses (K_T) for all populations. Breeding performance was poorly correlated with population changes. Density-dependence was found mainly in 6₄, its strength decreasing as average rate of population change increased. There was also evidence of weak density-dependence in the clutch size of Swallows and in Willow Warbler egg losses. Fluctuations in k₄ were correlated with conditions on the wintering grounds in Sedge Warblers, Whitethroats and Swallows, for the first two species these relationships being confirmed by analyses of independent survival estimates based on mark-recapture data. Populations of Sedge Warblers and Whitethroats appear to be limited by competition for resources on the wintering grounds. Removal experiments suggest that Willow Warblers, Pied Flycatchers and perhaps Blackcaps are limited through recruitment to the breeding population, in the case of Pied Flycatchers this limitation being in relation to the availability of nest sites.     

The improbability of a muscular crinoid column

Donovan, Stephen K. 1989 07 15: The improbability of a muscular crirroid column. Lethaia , Vol. 22, pp. 307–315. Oslo. ISSN 0024–1164.
It has sometimes been assumed that the stems of ancient crinoids were muscular. However, the only contractile fibres found in the stems of extant crinoids are in the cirri of isocrinids and comatulids. On uniformitarian grounds, it is improbable that any ancient crinoid had tissues in the stem that would have aided active orientation, apart from the non-muscular catch connective tissue. This conclusion is supported by a detailed functional analysis of the various forms of column and cirrus articulation. The axial canal has been seen as the probable site of any column musculature, but this is functionally impossible with symplexial and synostosial articulations, both of which are poorly adapted for muscular flexure. Columns that articulate synarthrially are much more flexible, but modern bourgueticrinids lack any stem musculature, despite having such stalks. The only crinoid columns that were functionally adapted to utilize contractile fibres were those of certain coiled-stemmed taxa, where the axial canal was not in the plane of the synarthrial fulcra. However, it is unlikely that such stems, even if muscular, possessed any advantage over a non-muscular column. The only pelmatozoans with a probable muscular column were not crinoids, but the glyptocystitid rhombiferans. * Crinoids, stem, columnal, cirrus, catch connective tissue, contractile fibres, functional morphology .     

A taxonomic review of Iris L. series Unguiculares (Diels) Lawrence

DAVIS, A. P. & JURY, S. L., 1990. A review of Iris L. series Unguiculares (Diels) Lawrence (Iridaceae) . The morphology, pollen, chromosomes and distribution of these plants are discussed and a new systematic account of the series is given.     

History as a cause of area effects: an illustration from Cerion on Great Inagua, Bahamas

The two parts of this paper work towards the common aim of setting contexts for and documenting explanations based on historical contingencies. The first part is a review of area effects in Cepaea. We discuss the original definitions and explanations, emphasizing the debate of adaptationist vsstochastic approaches, but arguing that the contrast of historical contingency vs. selective fit to environment forms a more fruitful and fundamental context in discussing the origin of area effects. We argue that contingencies of bottlenecks and opening of formerly unsuited habitats may explain the classic area effects of Cepaea better than selectionist accounts originally proposed. The second part is a documentation of an area effect within Cerion columnaon the northern coast of Great Inagua, Bahamas. Historical explanations are often plagued by insufficiency of preserved information, but the Inagua example provides an unusual density of data, with several independent criteria all pointing to the same conclusion. Shells in the area effect are squat and flat-topped in contrast with typical populations of long, thin, tapering shells living both east and west of the area effect. The flat-topped area effect is a result of introgression with a propagule of the C. dimidiatum stock (living on nearby Cuba, and most apically flattened of all Cerion). Fossils of this propagule were found fully cemented into highly indurated fossil soil crusts within the region of the current area effect. Multivariate morphometry, based on complex patterns of covariation, not just intermediacy in single characters, identifies the area effect samples as hybrids between this propagule and typical C. columna. Genetic analysis has identified three unexpected alleles in area effect samples only, and in no other snails of any other Cerion taxon anywhere else on Inagua. We hypothesize that the flattopped area effect did not arise as a selective response to local environments within C. columna, but by introgression from a fortuitously introduced propagule of the C. dimidiaium complex. The unexpected alleles therefore represent genetic phantoms of C. dimidiatum's former presence or are hybrizymes—novel alleles produced by interspecific hybridization     

Nectar feeding by the early-spring mosquito Aedes provocans

Abstract. Nectar feeding by males and females of the mosquito Aedes provocans was studied at a site near Belleville, Ontario, Canada. Canada plum, Prunus nigra , and especially pin cherry, P. pensylvanica , bloomed contemporaneously with the emergence of Ae. provocans and were important nectar sources for adult mosquitoes during their first week of life. Blossoms of P. pensylvanica shielded for 24 h from foragers produced an average of 0.14 mg of sugar (≅ 2.3 J). This nectar was avidly sought by both sexes of Ae.provocans; > 97% of the blossoms were visited by mosquitoes in the first few days of blooming. Young adult mosquitoes were found on blossoms at all hours of the day and night; feeding on P. nigra was strongly eocrepuscular, whereas on P.pensylvanica feeding was much less strongly periodic. Adults foraged for nectar in an energy-conserving, pedestrian strategy, devoting 56% (females) and 68% (males) of their time on blossoms to nectar feeding during foraging bouts that lasted a median of 5.3min. Both sexes sought nectar soon after emergence - males before they had completed hypopygial rotation or swarmed, and females before mating or host seeking. Female Ae.provocans sought nectar in all stages of oogenesis, but primarily at the initiation of a gonotrophic cycle. Energy stores in the crop averaged 18 J per female, with a distribution that depended on gonotrophic age and parity.     

Phylogeny, classification, and biogeography of the cycloteline Therevinae (Insecta: Diptera: Thereavidae)

Twenty-one members of the Laurasian group of Therevinae (Diptera: Therevidae) are compared using 65 adult morphological characters. Cladistic analysis using parsimony on the 17 ingroup and 4 outgroup taxa provides a well-supported hypothesis of relationships among taxa within the Gyclotelini, tribe nov. The Cyclotelini is a monophyletic assemblage of mostly New World genera, including Anolinga , gen. nov. , Breviperna Irwin, Coleiana , gen. nov. , Crebraseta , gen. nov. , Cyclotelus Walker, Mesonana , gen.nov. , and Ozodiceromyia Bigot. In addition, three Old World genera, Ammothereva Lyneborg, Bugulaverpa , gen. nov. , and Procyclotelus Nagatomi & Lyneborg, are included in the tribe. These ten genera are divided into two monophyletic genus-groups, the Brevipema-group and the Cyclotelus-group. Keys are provided for the genera of Cyclotelini. The tribe, the two informal genus-groups, and all genera are diagnosed; five new genera and six new species are proposed. The biogeographical histories of the genera are discussed in terms of their cladistic relationships using methods of cladistic biogeography. Two major vicariant events account for the current distribution of the tribe. The first relates to the Beringian land bridge connecting western North America and eastern Asia. Second, New World cyclotelines were profoundly affected by the Early Eocene breakup of the archipelagic bridge between North and South America, and the distributions support the hypotheses favouring the continental origin of the Greater Antilles.     

Harvest Refugia in Marine Invertebrate Fisheries: Models and Applications to the Red Sea Urchin, Strongylocentrotus franciscanus

Benthic marine invertebrates with planktonic larvae may exhibitAllee effects in reproduction or recruitment. Hydrodynamic considerationsand experimental evidence suggest that species broadcastinggametes suffer greatly reduced fertilization efficiencies asdensities decline. There is also evidence for some species,including the red sea urchin, that post-dispersal recruitmentsuccess declines at low densities of adults, if adults provideshelter from predators or other sources of mortality. Speciesdisplaying strong Allee effects may be susceptible to catastrophicpopulation collapses with slight increases in mortality dueto harvesting or natural causes. A simple two patch logisticmodel suggests that the establishment of a harvest refuge isnecessary to prevent collapses and maintain sustainable catchesat high levels of harvesting effort. A more detailed, age structuredmodel based on the biology of the red sea urchin, Strongylocentrotusfranciscanus produces similar results. Effects of harvestingstrategies are sensitive to Allee effects caused by both fertilizationefficiency and the disruption of adult spine canopies. Theoreticalrequirements for the size and spacing of marine reserves dependsupon the dispersal abilities of the target species. Multiplereserves, spaced more closely than the average larval dispersaldistance, appear to be an effective and conservative strategyfor maintaining healthy populations and sustainable levels ofharvest.