The influence of arbuscular mycorrhizae and light on Wisconsin (USA) sand savanna understories 2. Plant competition

Wisconsin (USA) oak savannas are endangered plant communities that have remarkably high plant species diversity. To investigate factors underlying this richness, we experimentally investigated the potentially interacting effects of light gradients and arbuscular mycorrhizal fungi (AMF) on plant competition in the greenhouse, using a fully randomized block design. We used four plant species, soil, and AMF from a remnant sand savanna, under two light and five AMF treatments. Plants were grown four per pot under two competition treatments (either one or four species per pot) for 20 weeks. Using ANOVA, we found that all species showed significant treatment effects on total and shoot biomass, primarily due to differences in competition and light, less to AMF. However, effects were the opposite of predictions. Putatively mycorrhizal plants showed neutral to negative responses to AMF, and a nonmycorrhizal species outcompeted AMF species in infected pots. We concluded that our experimental setup of small pots, sandy soil, and long growing period had induced parasitism by the AMF on susceptible hosts. This unexpected result is consistent with field data from the sand savanna, and may help explain how nonmycorrhizal plants can compete successfully with AMF species in established, species-rich communities.     

Colonization and emergence of midges (Chironomidae: Diptera) in slow sand filter beds

Colonization by midges, and temporal changes in their community structure, were examined in slow sand filter beds. The replicated beds allow the development of communities to be traced from a known starting point.The filter beds (rectangular concrete containers filled with water) have a substratum of sand on which a rich coating of organic particles develops during passage of the water through the bed. The containers (ponds) are drained from time to time and the organic layer is then scraped off the sand surface. This occurs on average, once a month. The length of time the ponds were filled with water (bed run) during the present study ranged from 16 to 77 days.In long bed runs small midges with a short aquatic phase (Cricotopus sylvestris, Psectrocladius limbatellus, Tanytarsus fimbriatus) produced adults after 16–20 days; other, larger midges,e.g. Psectrocladius barbimanus and the Tanypodinae required a longer aquatic phase. Of the Tanypodinae, the smallAblabesmyia phatta, had the shortest duration of the four species found, and was much the most numerous member of this subfamily. Some Chironomini only appeared when the organic coating had developed over the sand surface. Midges of this tribe frequently failed to complete their larval development within the duration of bed runs and were thus trapped on the substratum at the time of cleaning. When ponds were drained after short bed runs the succession in community structure observed in long runs was arrested.Three small midgesC. sylvestris, P. limbatellus andT. fimbriatus, were collected in high numbers throughout the life of all beds, except towards the end of the longest runs in the study. This suggests that small size, short life cycles, and the ability to colonize clean substrata, are important characteristics for the development of primary chironomid communities in short-lived temporary habitats.     

Ecological theories and Dutch nature conservation

This paper aims to achieve insight into various ecological theories in the Netherlands which have different, and sometimes opposing, views on the conservation of nature. Interviews, publications and archival research brought to light four separate theories: vitalistic/holistic, dynamic, cybernetic and chaos. Diversity is reached through stability according to vitalistic/holistic and cybernetic theories, but through change and instablility according to the dynamic and chaos theories. These two groups are working apart, and continue to have their own ideas. Prediction of the future is only possible with the vitalistic/holistic and cybernetic theories. Ecologists who adhere to these theories feel responsible and able in different ways to change ecological nature towards desirable end goals. The other two theories, dynamic and chaos, appear to be less activist.     

Snake communities of moist rainforest and derived savanna sites of Nigeria: biodiversity patterns and conservation priorities

The taxonomic composition and the abundance of two communities of snakes were studied in two different areas of southern Nigeria. One community was studied in a derived savanna area (environs of Ejule, 06°54N, 07°23E), and one community was studied in a moist rainforest area (environs of Eket, 04°50N, 07°59E). Both the specific diversity and the mean frequency of observation of snakes were significantly higher in the forest area than in the savanna area, and the dominance index was higher in the savanna than in the forest site. However, most of the species were found in only one of the two areas, depending on their habitat requirements (e.g. Gastropyxis smaragdina, Dispholidus typus, Thelotornis kirtlandii, Dendroaspis jamesoni, Bitis nasicornis, Causus maculatus, etc). The forest community housed a significant number of arboreal and semiaquatic taxa, but in both sites most of the species were terrestrial. The commonest species in the forest area was an oviparous, semiaquatic, batracophagous natricine snake (Afronatrix anoscopus), whereas the commonest species in the savanna area was an oviparous terrestrial lacertophagous psammophine snake (Psammophis phillipsi). Some conservation implications of our biodiversity analyses are presented. It is suggested that the moist rainforest represents a critically endangered habitat, and should deserve special attention by the international scientific community. Oil industry activity is especially dangerous for snake communities, especially in the southernmost regions of Nigeria.     

Immunofluorescence localization of the epidermolytic toxin target in mouse epidermal cells and tissue

Summary An epidermolytic toxin target was observed in keratohyalin granules of sectioned epidermis by a direct fluorescence procedure using FTC-toxin, but not by an indirect procedure using sequential reaction with toxin, anti-toxin and FTC-secondary antibody. The investigation of the two procedures was extended to keratinocytes. A dispase digestion procedure yielded three fractions which corresponded to basal, spinous and granular cells according to biochemical and morphological criteria. It was shown that the direct and indirect procedures both detected the toxin target in the keratohyalin granules of granular cells, but that the indirect procedure was very insensitive. In control experiments, the profilaggrin of keratohyalin granules was detected readily in cells by a direct procedure using FTC-antiprofilaggrin but only weakly by an indirect double antibody procedure. Insensitivity to indirect procedures thus appears to be a particular property of the keratohyalin granule site. It was shown that the toxin target was readily accessible in permeable (trypsin-isolated) granular cells but inaccessible in impermeable (dispase-isolated) cells.     

Convergent evolution masks extensive biodiversity among marine coccoid picoplankton

Coccoid picoplankters are minute unicellular algae that, when viewed with a light microscope, appear as little balls. They comprise an important component of open-ocean phytoplankton, and, except for colour differences (i.e. red, green, brown), many eukaryotic picoplankters are morphologically similar. To evaluate the biological diversity of the little brown ball subpopulation of little balls, we randomly selected nine undescribed algal strains and compared the nucleotide sequences of their nuclear 18S ribosomal RNA genes. The results indicate that little brown balls have evolved independently in three distinct eukaryotic lineages (heterokont algae, haptophyte algae, and green algae), and at least four taxonomic classes, and that, even within the four classes, considerable genetic diversity exists. These findings suggest that a tiny coccoid morphology confers some adaptive advantage in the open ocean, that repeated convergent evolution has occurred, and that molecular data may be necessary for taxonomic distinction of closely related coccoid picoplankters.     

The in vitro physiological phenotype of tomato resistance to Fusarium oxysporum f. sp. lycopersici

Summary With the aim of dissecting host-parasite interaction processes in the system Lycopersicon aesculentum-Fusarium oxysporum f. sp. lycopersici we have isolated plant cell mutants having single-step alterations in their defense response. A previous analysis of the physiological phenotypes of mutant cell clones suggested that recognition is the crucial event for active defence, and that polysaccharide content, fungal growth inhibition, peroxidase induction in in vitro dual culture and ion leakage induced by cultural filtrates of the pathogen can be markers of resistance. In this paper we present the results of a similar analysis carried out on cell cultures from one susceptible (Red River), one tolerant (UC 105) and three resistant (Davis UC 82, Heinz, UC 90) tomato cultivars. Our data confirm that the differences in the parameters considered are correlated with resistance versus susceptibility in vivo. Therefore, these parameters can be used for early screening in selection programmes. These data, together with those obtained on isolated cell mutants, suggest that the selection in vitro for altered fungal recognition and/or polysaccharide or callose content may lead to in vivo — resistant genotypes. The data are thoroughly discussed with particular attention paid to the importance of polysaccharides in active defense initiation.     

Effect of starvation on the content of free amino acids in plasma of different breeds of hen

Summary Leghorn, Cornish and White Rock hens were subjected to starvation. Free amino acids were determined in blood samples taken after 48, 72 and 96 h of starvation. A progressive decrease in concentration of the majority of amino acids was found. Changes in amino acid concentrations during starvation were dependent on the breed of hen.     

Arbuscular mycorrhizas in a valley-type savanna in southwest China

The arbuscular mycorrhizal (AM) status of 67 plant species in a savanna community in the hot, dry valley of Jinsha River, southwest China was surveyed. It was found that about 95% of the plant species formed AM and 5% possibly formed AM. The composition of AM fungi (AMF) in the rhizosphere soils was also investigated. The AMF spore density ranged from 5 to 6,400 per 100 g soil, with an average of 1,530, and these spores/sporocarps were identified as belonging to six genera. Fungi belonging to the genera Glomus and Acaulospora were the dominant AMF. High densities of AMF spores in the rhizosphere soils, and the intensive colonization of the plant roots, indicated that plants grown in this valley-type savanna may be highly dependent on AM.     

Cytological observations on some species and hybrids ofVaccinium

Summary Meiosis was studied inVaccinium myrtillus (n=12),V. vitis-idaea (n=12),V. myrtillus ×vitisidaea (n=12), colchicine-induced tetraploidV. myrtillus (n=24),V. uliginosum (n=24), the cultivated blueberry varieties Rancocas and Pemberton (n=24), and the hybridsV. uliginosum × Rancocas andV. uliginosum × Pemberton (n=24). Pairing was regular in the diploid species. Some multivalent formations occurred inV. uliginosum and in the cultivated blueberry varieties and to a considerable extent in the autotetraploidV. myrtillus. The spontaneous diploid hybridV. myrtillus ×vitis-idaea displayed numerous meiotic irregularities, whereas the artificial hybrids betweenV. uliginosum and cultivated blueberry showed relatively regular meiosis. Pairing relationships of the various genomes are discussed. Breeding programs for the use of North-European species with American cultivated blueberry varieties are discussed in the light of the cytological observations.

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Zusammenfassung Die diploiden (n=12) ArtenVaccinium myrtillus, V. vitis-idaea, V. myrtillus×vitis-idaea und die tetraploiden (n=24)V. myrtillus (Colchicin-induziert) undV. uliginosum sowie die kultivierten amerikanischen Blaubeersorten Rancocas und Pemberton (n=24) und die HybridenV. uliginosum×Rancocas undV. uliginosum×Pemberton wurden cytologisch untersucht. In den diploiden Arten war die meiotische Chromosomenpaarung regelmäßig. Multivalente traten in geringerem Umfange beiV. uliginosum und kultivierten Blaubeersorten, viel stärker aber in der autotetraploidenV. myrtillus auf. Die spontane diploide HybrideV. myrtillus×vitis-idaea zeigte zahlreiche meiotische Störungen, die künstlichen Hybriden zwischenV. uliginosum und der kultivierten amerikanischen Blaubeere hatten demgegenüber eine relativ regelmäßige Meiose. Die Paarungsverhältnisse der verschiedenen Genome werden diskutiert. Auf Grund der cytologischen Beobachtungen wird ein Züchtungsprogramm für nordeuropäischeVaccinium-Arten zusammen mit amerikanischen Kultursorten erörtert.

     

Puromycin enhances 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster

The effect of cycloheximide and puromycin on 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster has been studied by one-dimensional and two-dimensional SDS polyacrylamide electrophoresis. It is found that puromycin, but not cycloheximide, when applied simultaneously with the hormone enhanced the hormone-induced synthesis of the early and late proteins. However, when puromycin was applied after hormone treatment, only the late proteins were induced. The possible implication of these observations is discussed.     

Relationships of Agropyron intermedium chromosomes determined by chromosome pairing and alcohol dehydrogenase isozymes in common wheat background

Summary The relationships of Agropyron intermedium chromosomes in two wheat-Agropyron addition series were determined. Chromosome pairing behaviour revealed that the alien chromosome in lines TAF-2 and L7 of Vilmorin-A. intermedium set are homologous to the alien chromosomes in lines P and C of the Caribo-A. intermedium set respectively. Localization of alcohol dehydrogenase isozyme genes in Vilmorin-Agropyron addition line L4 and in Caribo-Agropyron line O indicated relationships with wheat chromosomes of homoeologous group 4.     

Secondary succession in Acacia nilotica (L.) savanna in the Hluhluwe Game Reserve,South Africa

Analysis of aerial photographs indicates that woody plant biomass has rapidly increased in Hluhluwe Game Reserve over the last 40 years. Open Acacia nilotica savanna is being replaced by broadleaf species, especially Euclea spp. We were interested in whether this secondary successional shift was due to high numbers of seedlings establishing and growing to maturity under acacias (facilitation) or due to the release of already established, but suppressed individuals (gullivers) of the resprouting broadleaf species. We examined the recruitment patterns and size-class distributions (height, basal diameter) of important species in this savanna.Densities of euclea seedlings (<0.6 cm basal diameter) under Acacia nilotica were low (median of 0 and mean of 0.06 m²) below adult canopies and effectively zero in adjacent interspaces. No differences in numbers of other broadleaf species were found between open sites and under Acacia nilotica sites. Few large eucleas or other broadleaf species occurred under Acacia nilotica. Few Acacia nilotica recruits were found either under adults or in the open whereas Acacia karroo recruits were more common.The overall size class distribution for eucleas was dominated by individuals in the intermediate size class, suggesting that recruitment is not the dominant demographic process. We propose that the escape of intermediate sized eucleas from the fire trap has caused the increase in woody plants.Analysis of a time sequence of aerial photographs shows that invasion occurred rapidly between 1954 and 1975. A common feature for sites where woody plant invasion has taken place, was the presence of barriers to fire (especially roads). We suggest that the recent and rapid increase in woody vegetation is due to a decrease in the frequency of intense fires, rather than the recent absence of megaherbivores which allowed Acacia nilotica establishment. Few intense fires allow suppressed tree or shrub individuals, ('gullivers'), to escape the grass/fire layer and thereby become tall and fire-resistant. This release may explain the rapid rate of invasion by inherently slow growing broad-leaf species.     

Fruiting studies in species ofCapronia (Herpotrichiellaceae)

A recently described protocol for thein vitro production of ascomata was employed to determine the sexual incompatibility systems of five species ofCapronia. The formation of mature ascomata in isolates derived from single ascospores demonstrated thatC. epimyces, C. mansonii, andC. munkii n. sp. are homothallic. In contrast, fertile ascomata were observed only in mass-ascospore isolates and pairwise crosses between specific single-ascospore isolates inC. dactylotricha n. sp. andC. moravica. TheExophiala anamorphs ofC. dactylotricha andC. munkii are described and aPhialophora-like synanamorph is reported for the former species. Germinating ascospores ofC. munkii formed conidiogenous cells directly, while the ascospores of the remaining species germinated to produce germ tubes and hyphae. The application of the terms microcyclic conidiation to secondary conidium production and sclerotial body and stroma to the multicellular structures produced by species ofCapronia andExophiala are discussed.     

Epigenetic Processes, when Natura Non Facit Saltum Becomes a Myth, and Alternative Ontogenies a Mechanism of Evolution

When I started the journal Environmental Biology of Fishes more than 25 years ago, it was designed to avoid any prejudices and scientific dogmas, to keep an open mind, and to allow publication of ideas that are irritating to followers of the so-called mainstream, ideas that few other journals dared to touch (Balon 1976, 1989d). While such articles in the journal were often ignored by the mainstream practitioners and the political establishment, none was ever opposed or proven wrong. As in many similar cases before, only time will show if these contributions were valid and of value to the advancement of knowledge.I have often wondered why it takes so long for some of the universal facts and ideas to be accepted or even to be known. I have come to believe that like with many textbooks some facts and conclusions are copied from one book to the next (as in the case of the origin of the common carp – Balon 1974, 1995a,b) without knowing or admitting that in the meantime new facts require new syntheses and conclusions. Even good scholars resist unknown facts or ideas. It is irritating that one's knowledge is inadequate or that others beat us to be first. I have wondered why wrong ideas persist for so long; but Bateson (1979, p. 206) already explained it to his daughter ... yes, your image of evolution is exact. And what Darwin called natural selection is the surfacing of the tautology or presupposition that what stays true longer does indeed stay true longer than what stays true not so long.After all it was Jean Baptiste Lamarckgrave, the founder of evolutionary theory, miserable, old, and blind, ... (Bateson 1972, p. xii) and/or Gottfried Treviranus who presented the truth long before the privileged Charles Darwin, alas in wrong languages. Over time, ignoring the truth became fashionable and the question which of the four theories of evolution (Løvtrup 1982) can be attributed to Darwin, if any, irrelevant. It is [exclaims Croizat 1977, transl. 1987, p. 137] a gross, very grave mistake to confuse Darwin as a historical figure with Darwin as an exalted figure of the thinking of biology (Croizat's italics).Nearly 30 years ago a BBC TV series and book on evolution glorified Darwin and molecular biology. Calder (1973, p. 9), the author of this book entitled The life game: evolution and the new biology felt that Darwin would [merely] need to know about the survival of the quickest, when it came to crossing the street. But the street was never crossed! Many TV viewers of the recent PBS series Evolution were again misled into believing that evolution was discovered by Darwin. Even Gould (2001) in the Introduction and the producer Hutton (2001) in the Foreword to the companion book of this series (Zimmer 2001) give the Darwinian evolution [sic] an exposé it hardly deserves. While such views have been repeatedly proven wrong, most scholars, with the exception of a few scientists, philosophers, and journalists, comfortably assume Darwin's priority in spite of numerous published evidences to the contrary. This myth is then fed to the general public. The following retrospective essay attempts to compile proofs in support of the evolutionary processes other than Darwin's natural selection and the gene-centric new synthesis, old by now as it is.     

Structure of the yolksac epithelium and gills in the early developmental stages of rainbow trout (Salmo gairdneri) maintained in different ambient salinities

Synopsis Small numbers of mitochondria-rich (chloride) cells were found in the yolksac epithelium of rainbow trout (Salmo gairdneri) embryos just before hatching and in eleuthero-embryos up to 14 days after hatching. This suggests that the yolksac epithelium may play a limited ionoregulatory role in this species.Mitochondria-rich cells were also present in small numbers in the branchial epithelium of embryos just before hatching and in increasing numbers in eleutheroembryos during the first two weeks after hatching. The cells in the branchial epithelium showed marked variations in appearance, particularly in the fine structure of the tubular (smooth) endoplasmic reticulum. Few of the mitochondria-rich cells examined here had the pitted apex which is characteristic of homologous cells in other species.There appeared to be no differences in the numbers or appearance of mitochondria-rich cells in embryos and eleutheroembryos reared in different ambient salinities (distilled water, 110/00 and 130/00 sea water), possibly indicating that the genesis of the ionoregulatory function of the gills has not occurred at that interval of development.     

Arbuscular mycorrhizal fungi (Glomeromycota) communities in tropical savannas of Roraima,Brazil

Savanna vegetation in the northern region of Brazil is jeopardized by several anthropogenic activities including cattle ranching and extensive agriculture, and soil biota of these ecosystems is virtually unknown. The soils in savannas are poor in nutrients, very acidic, and subject to drought, and under these conditions, arbuscular mycorrhizal fungi (AMF) are likely to play a key role on plant nutrition and improving soil structure. In this study, we surveyed AMF communities in five savanna locations in Roraima state, Northern Brazil. AMF species were identified using two approaches: field collected spores and trap cultures. Twenty-three AMF species were identified, including 21 species in field samples, 8 species in trap cultures, of which 15 and 2 were unique to field and trap culture samples, respectively. Gigaspora margarita, Dentiscutata heterogama, and Glomus sp1 were the most frequent species recovered from all locations. AMF communities were dominated by members of Gigasporaceae that accounted for 50 to 87% of the total species richness within each location. Spore numbers differed across locations and ranged from 5 to 25 spores 100 cm^?3 soil. Redundancy analysis indicated that soil organic matter was the only selected predictor among soil parameters and correlated positively with occurrence of Glomus heterosporum. We conclude that savannas in Roraima harbor a high sporulating AMF species richness with communities dominated by members of Gigasporaceae and that organic carbon is an important edaphic factor influencing AMF community composition in this ecosystem.     

Measuring the number of co-dominants in ecological communities

We suggest a concept that allows the objective determination of the number of co-dominants in a community. We define co-dominants as a subset of species that are more abundant and more uniformly distributed than other species in a given sample. We compare the sample with a model community and use Simpsons diversity index to estimate the apparent number of co-dominants. Dominant species determined in this way are responsible for 70–90% of the total measure of abundance in the sample. The statistical significance of the apparent number of co-dominants may be assessed by a randomization test.     

Genetic and environmental considerations for evaluating crown position of wheat

Summary Crown position affects winter survival of fallsown wheat (Triticum aestivum L.) Direct or indirect selection for crown depth has been little practiced. Reports have suggested that short subcrown internode length was closely related to semidwarf plant height and that semidwarfism was related to poor emergence. This study determined the relationships among crown depth, plant height, and emergence rate index in three wheat populations. The efficiency of evaluating crown placement in the field was examined and additional information was obtained on its genetic control. The F₂-derived F₄ and F₅ lines from the crosses of female parents Daws, Nugaines, and Stephens with male parent Selection 7952 were planted at Central Ferry and Pullman, Washington, respectively. Correlations from each population indicated that crown depth and subcrown internode length were not closely associated with plant height and emergence rate index. Crown depth was a more reliable indicator of crown placement than subcrown internode length. Adjustment of the data for seed depth differences was essential for evaluating subcrown internode length but less important for evaluating crown depth. After adjustment for seed depth, narrow-sense h ² values for subcrown internode length and crown depth were 0.25–0.41. Crown depth and subcrown internode length were inherited as quantitative traits in phenotypes that expressed variable dominance. Modest gains due to selection for crown depth were achieved.Contribution from USDA-ARS and College of Agriculture and Home Economics Research Center, Washington State University, Scientific Paper No. 7795     

Community diversity and invasion resistance: An experimental test in a grassland ecosystem and a review of comparable studies

The relationship between community diversity and invasion resistance in a grassland was examined using experimental plant assemblages that varied in species richness and composition. The assemblages were weeded for three seasons to remove unsown species and we used the number of weeded seedlings, their total biomass and the number of species removed as indicators of community resistance and susceptibility to invasion. In general, we found a positive relationship between invasion resistance and increasing community diversity. Similar patterns of establishment were observed at the end of the fourth field season after several months without weeding. Increased invasion resistance with higher diversity appears to come through reduced levels of several above- and belowground resources, although these did not fully explain the effects of species richness in the studys analyses. Experimental increases and reductions of litter biomass within the studys experimental plant assemblages did not modify these patterns significantly. A review of comparable studies of invasion across directly manipulated diversity gradients revealed similar patterns. Positive effects of species diversity on invasion resistance were found in experimental manipulations of plant diversity conducted in the field and in the glasshouse, from studies with aquatic microcosms and in a marine system. Although some exceptions to this pattern were found in both terrestrial plant systems and aquatic microcosms, it was concluded that in biodiversity manipulation experiments more diverse communities are generally more resistant to invasion.