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  • 1
    Electronic Resource
    Electronic Resource
    An experimental demonstration of density-dependent reproduction in a natural population of Diamorpha smallii, a rare annual (1981)
    Springer
    Oecologia 51 (1981), S. 1-6 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a North Carolina population of Diamorpha smallii, densities were artificially manipulated by thinning stands to predetermined densities. Individuals in areas of high density produce fewer seeds than individuals at low density in the same habitat. Three components of fecundity, the number of flowers per plant, the number of fruits per plant, and the number of seeds per fruit, were negatively correlated with density. The relationship of components of fecundity to density were used to develop a model of population regulation for this species. These results and predictions from the model are discussed in relation to other density studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00344643
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  • 2
    Electronic Resource
    Electronic Resource
    The differential establishment of seedlings from chasmogamous and cleistogamous flowers in natural populations of the grass Danthonia spicata (L.) Beauv (1983)
    Springer
    Oecologia 57 (1983), S. 183-188 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The grass Danthonia spicata produces dimorphic seeds from chasmogamous and cleistogamous flowers. The seed remains attached to seedlings so one can identify the reproductive origin of seedlings. The proportion of chasmogamous and cleistogamous seedlings becoming established varies widely between populations. The types of seedlings becoming established was generally consistent from year to year and correlated with the proportion of flower types produced. Mown populations showed especially high levels of cleistogamous seedling establishment. Germination and seedling survival were experimentally investigated. Chasmogamous and cleistogamous seeds had different germination behaviors. Cleistogamous seedlings had higher survival rates than chasmogamous seedlings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379579
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  • 3
    Electronic Resource
    Electronic Resource
    Environmental heterogeneity, fungal parasitism and the demography of the grass Stipa leucotricha (1995)
    Springer
    Oecologia 103 (1995), S. 55-62 
    Details
    ISSN: 1432-1939
    Keywords: Demography ; Environmental heterogeneity ; Fungal parasitism ; Reciprocal transplant ; Stipa leucotricha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study investigated the demographic consequences of fungal infection of a perennial grass, Stipa leucotricha. The rate of parasitism of this grass by the host-specific, systemic fungus Atkinsonella texensis varies over short distances. Infection was frequent (57% of plants) in “mottes” (clusters of woody plants) but rarer in adjacent open grasslands (9%). To test the hypothesis that the relative performance of infected and uninfected plants differed in the two habitats, infected and uninfected genotypes were collected from mottes in a central Texas population, propagated in the green-house and then transplanted into the same site in replicate plots within mottes, at the edges of mottes, and in open grassy areas. Demographic data were recorded for 30 months over three growing seasons. Plants were observed to lose and gain infection. Infection had no significant effect on plant survival, tiller number or dry mass although infected plants tended to be larger. Uninfected plants had a significantly higher probability of setting seed but there were no differences in seed production by reproductive plants. There were significant effects of planting environment on all of these measures. Motte edges were most favorable for S. leucotricha transplants while motte interiors were least favorable and open areas were intermediate. There was no evidence of habitat x infection interactions; therefore the fungal infection had similar effects in different habitats. The high frequency of infection in motte habitats is best explained by more efficient contagious spread there. The favorability of motte edges for plant growth is substantially offset by higher infection rates at the edges of mottes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328425
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  • 4
    Electronic Resource
    Electronic Resource
    Impact of the fungus Balansia henningsiana on Panicum agrostoides: frequency of infection, plant growth and reproduction, and resistance to pests (1989)
    Springer
    Oecologia 80 (1989), S. 374-380 
    Details
    ISSN: 1432-1939
    Keywords: Panicum agrostoides ; Balansia henningsiana ; Fungal endophyte ; Growth ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The impact of the systemic fungus Balansia henningsiana (Clavicipitaceae) on the grass Panicum agrostoides was examined in field and greenhouse studies comparing infected and uninfected plants. Approximately one-half of all plants in three populations located in southern Indiana were infected. In field samples and greenhouse studies infected plants were significantly heavier than uninfected plants and produced significantly more tillers. Infection tended to suppress flowering but occasional asymptomatic tillers on infected plants produced healthy inflorescences. Although infected plants produced fewer inflorescences than uninfected plants as a proportion of total tillers, absolute numbers of inflorescences were similar in the two groups. Because other grasses infected by different species of Balansia and related fungi often are more resistant to insect damage, pest damage was quantified in one population. No differences between infected and uninfected plants were detected in levels of herbivory but infected plants had significantly less damage by the common leaf spot fungus Alternaria triticina. The results suggest that there is no selective disadvantage for plants infected by B. henningsiana.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379039
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of CO2 enrichment, nutrient addition, and fungal endophyte-infection on the growth of two grasses (1990)
    Springer
    Oecologia 84 (1990), S. 207-214 
    Details
    ISSN: 1432-1939
    Keywords: Grasses ; Fungal infection ; Growth ; CO2 ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Increasing atmospheric carbon dioxide (CO2) concentration is expected to increase plant productivity and alter plant/plant interactions, but little is known about its effects on symbiotic interactions with microorganisms. Interactions between perennial ryegrass, Lolium perenne (a C3 plant), and purpletop grass, Tridens flavus (a C4 plant), and their clavicipitaceous fungal endophytes (Acremonium lolii and Balansia epichloe, respectively) were investigated by growing the grasses under 350 and 650 μl l− 1 CO2 at two nutrient levels. Infected and uninfected perennial ryegrass responded with increased growth to both CO2 enrichment and nutrient addition. Biomass and leaf area of infected and uninfected plants responded similarly to CO2 enrichment. When growth analysis parameters were calculated, there were significant increases in relative growth rate and net assimilation rate of infected plants compared to uninfected plants, although the differences remained constant across CO2 and nutrient treatments. Growth of purpletop grass did not increase with CO2 enrichment or nutrient addition and there were no significant differences between infected and uninfected plants. CO2 enrichment did not alter the interactions between these two host grasses and their endophytic-fungal symbionts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318273
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  • 6
    Electronic Resource
    Electronic Resource
    Fungal endophytes of grasses and their effects on an insect herbivore (1985)
    Springer
    Oecologia 66 (1985), S. 1-5 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of endophytic fungi (Tribe Balansiae, Clavicipitaceae, Ascomycetes) of grasses on an insect herbivore were studied by feeding paired groups of larvae of the fall armyworm (Spodoptera frugiperda, Noctuidae, Lepidoptera) leaves from either infected or uninfected individuals. Perennial ryegrass infected by “the Lolium endophyte”, tall fescue infected by Epichloe typhina, dallisgrass infected by Myriogenospora atramentosa, Texas wintergrass infected by Atkinsonella hypoxylon, and sandbur infected by Balansia obtecta were utilized. The endophytes of ryegrass and fescue previously have been shown to be toxic to mammalian herbivores and to deter feeding of some insect herbivores. In this study we extend the antiherbivore properties of those endophytes to the fall armyworm and demonstrate that fungal endophytes in three other genera have similar antiherbivore properties. For most grasses, survival and weights of fall armyworm larvae fed infected leaves were significantly lower and larval duration was significantly longer compared to larvae fed uninfected leaves. Resistance to herbivores may provide a selective advantage to endophyte-infected grasses in natural populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378545
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  • 7
    Electronic Resource
    Electronic Resource
    Avian seed preference and weight loss experiments: the effect of fungal endophyte-infected tall fescue seeds (1991)
    Springer
    Oecologia 88 (1991), S. 296-302 
    Details
    ISSN: 1432-1939
    Keywords: Passerines ; Fungal endophyte ; Seed preference ; Weight loss ; Foraging behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The impact of endophytic fungus-infected seeds on seed predators is poorly understood. In this multiple trophic level investigation, seed preference experiments were conducted to determine whether five species of passerines (dark-eyed juncos, Junco hyemalis; American tree sparrows, Spizella arborea; song sparrows, Melospiza melodia; chipping sparrows, Spizella pusilla; and house sparrows, Passer domesticus) recognize and preferentially consume noninfected (NI) over infected (I) seeds of tall fescue (Festuca arundinacea). We predicted that the birds would refrain from eating I seeds because those seeds contain high concentrations of fungal alkaloids. When given a choice of NI fescue seeds and control seeds (millet), all bird species showed a significant preference for millet. However, individuals of all species consumed some NI seeds. When given a choice of NI and I fescue seeds, all species except the chippig sparrow ate significatly more NI than I fescue seed and the chipping sparrow showed the same trend. Thus, birds were able to distinguish between the two seed types and preferred NI seeds in choice tests. Additional experiments investigated weight changes in dark-eyed juncos fed diets containing different proportions of millet, NI, and I fescue seed. Significant differences in weight loss were observed for the various diets. Juncos showed greater weight loss when the proportion of fescue seed, especially the proportion of I seed, in their diet was greater. The potential significance of the finding that abundant grass seeds are made unavailable to predators by fungal infection is discussed in relation to foraging and competition in avian communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320825
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of ergot alkaloids from fungal endophyte-infected grasses on fall armyworm (Spodoptera frugiperda) (1989)
    Springer
    Journal of chemical ecology 15 (1989), S. 169-182 
    Details
    ISSN: 1573-1561
    Keywords: Balansiae ; Clavicipitaceae ; ergot alkaloids ; fall armyworm ; feeding deterrents ; acquired chemical defense ; fungal endophytes ; grasses ; Lepidoptera ; Noctuidae ; Spodoptera frugiperda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ergot alkaloids produced by endophytic fungi in the tribe Balansiae (Clavicipitaceae, Ascomycetes), which infect grasses, may provide plant defense against herbivores. This study examined the effects of six ergot alkaloids on survivorship, feeding, and growth of larvae of the fall armyworm (Spodoptera frugiperda, Lepidoptera: Noctuidae), a generalist herbivore of grasses. Corn leaf disks were soaked in solutions of individual ergot alkaloids at different concentrations and presented to neonate larvae. At the highest concentrations (77–100 mg/liter) of ergonovine, ergotamine, ergocryptine, agroclavine, and elymoclavine, larval weights and/or leaf area consumed after eight days were reduced relative to controls. Lysergol had no effect on larval weights and leaf consumption at any concentration. Although active concentrations were higher than those reported from two host grasses, in vivo levels of ergot alkaloids have not been quantified for most endophyte-infected grasses. The detrimental effects on fall armyworm observed in this study suggest that ergot alkaloids could be responsible, at least in part, for the greater insect resistance of endophyte-infected grasses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02027781
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