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  • 1
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    The slow recovery of Opuntia megasperma on Española (2021)
    In:  http://aquaticcommons.org/id/eprint/5832 | 704 | 2011-09-29 14:30:13 | 5832 | Fundacion Charles Darwin Foundation
    Details
    Publication Date: 2021-07-12
    Keywords: Conservation ; Ecology ; Opuntia megasperma ; Isla Española ; Galápagos ; EI Niño ; goat eradication
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 13-15
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  • 2
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    Erythrina velutina and the colonization of remote islands (2021)
    In:  http://aquaticcommons.org/id/eprint/5954 | 704 | 2011-09-29 14:25:54 | 5954 | Fundacion Charles Darwin Foundation
    Details
    Publication Date: 2021-07-12
    Keywords: Biology ; Erythrina velutina ; Isla Wolf ; Isla Genovesa ; Galápagos ; floating ; seawater
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 3-5
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  • 3
    Electronic Resource
    Electronic Resource
    Sensitivity of Fusarium oxysporum f. sp. cubense to phosphonate (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 43 (1994), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Phosphonate (0.1 mM) significantly reduced growth of Fusarium oxysporum f. sp. cubense (Foc) race 4 grown at an optimal phosphate concentration of 0.3 mM in vitro. At higher phosphate concentrations, closer to physiological conditions within the plant, the sensitivity of Foc race 4 to phosphonate was greatly reduced, with 25 mM phosphonate required to reduce growth by 50% at 1 mM phosphate. Two isolates of Fusarium oxysporum f. sp. dianthi and another race of Foc, race 1, were shown to be similar to Foc race 4 in their sensitivity to phosphonate, while another species of Fusarium, F. avenaceum, was more sensitive to phosphonate in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3059.1994.tb00571.x
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  • 4
    Electronic Resource
    Electronic Resource
    The action of nitrite on NADP reduction by intact spinach chloroplasts (1972)
    Springer
    Planta 106 (1972), S. 181-184 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Isolated, intact spinach chloroplasts incubated in light in the presence of HCO 3 - and NO 2 - have the greater proportion of their NADP present in the reduced form. The steady state concentration of NADPH in light in these chloroplasts is significantly higher in the presence of NO2 than in its absence. These results invalidate earlier conclusions (Grant and Canvin, 1970) that NO 2 - inhibits photosynthesis by preventing NADP reduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383999
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  • 5
    Electronic Resource
    Electronic Resource
    Finch numbers, owl predation and plant dispersal on Isla Daphne Major, Galápagos (1975)
    Springer
    Oecologia 19 (1975), S. 239-257 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Populations of 4 geospizine finches were studied on Isla Daphne Major in April and December 1973. Finches were captured, banded, measured and released in both months, and censused in December. 1640±711 finches were estimated to be present in December, of which probably more than 1000 belonged to Geospiza fortis. G. fortis were 4 times more numerous than G. scandens. The overal density at this time was 27–54/ha. This is the first quantitative estimate of finch population sizes for a whole island in the Galápagos Archipelago. Some G. fuliginosa and magnirostris immigrated between study periods, but overall density remained nearly constant. There was no evidence of immigration of fortis and scandens. Survival rates of the two common species, fortis and scandens, from April to December were estimated, from banded birds, to be 86.9% and 91.3%. Up to 300 finches (fortis and scandens) disappeared between study periods. The amount of predation by owls (Asio flammeus), estimated from an analysis of 49 pellets, could account for more than 50% of the finch losses, but is likely to be less. The estimated loss due to predation was less than 10% of the populations in April. The discovery of the remains of house mice, Mus musculus, and black rats, Rattus rattus, in pellets indicates that owls hunt on one island (e.g. Santa Cruz or Baltra) and regurgitate on another (Daphne). Fruits of a Euphorb, Chamaesyce amplexicaulis (Hook. f.) Burch, that finches eat were found in two pellets that also contained finch remains. This suggests that seeds or fruits in the throat of a victim at the time of a kill may be transported unharmed inside an owl from one island to another. Indirect support to this suggestion is given by the results of flotation experiments with seeds and fruits of 22 species of plants. Most did not float, and are too heavy to be transported by normal winds. Many do not have hooks or sticky surfaces, and internal transport by birds (including owls) is therefore strongly suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345308
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  • 6
    Electronic Resource
    Electronic Resource
    Annual variation in Finch numbers, foraging and food supply on Isla Daphne Major, Galápagos (1980)
    Springer
    Oecologia 46 (1980), S. 55-62 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary (1) We report some effects of an annually variable and unpredictable rainfall upon Darwin's Finches on the Galápagos. Finch numbers, foraging and food supply were studied on I. Daphne Major in December of 1973 and 1977, and compared. 1973 was the second of two successive wet years and 1977 was a drought year. (2) Seed numbers and biomass were approximately one order of magnitude lower in the drought year than in the wet year. Small and soft seeds were absolutely and relatively rarer in the drought year than in the wet year. (3) Similarly finch numbers and biomass were approximately one order of magnitude lower in the drought year than in the wet year. Numbers of G. scandens declined less than did number of G. fortis. Both species exhibited unabalaced sex ratios, in favour of males, in the dry year in contrast to balanced sex ratios in the wet year. Male scandens were heavier on average in the wet year, but male fortis were heavier in the dry year. (4) The foraging of scandens, a cactus (Opuntia) specialist, was similar in the two years. The foraging of fortis in the dry year differed from foraging in the wet year in three important respects: fortis devoted a disproportionate amount of time to feeding on small seeds while tending to avoid seeds of Opuntia, they fed more on floral and extra-floral parts of Opuntia and they fed on Tribulus cistoides, a large and hard fruit which was absent from their diet in the wet year. As a consequence of feeding more on Opuntia, fortis foraging was more similar to scandens foraging in the dry year than in the wet year. (5) The results are discussed in relation to expectations from competition theory. The decline in numbers in relation to a decline in food supply was expected, but a convergence in diets was not. The convergence is attributed to the recent renewal of a single resource, Opuntia flowers, against a background of general resource scarcity. Diet overlap and limitation of numbers by food provide indirect evidence of interspecific competition; scandens, with an included niche, was competitively superior to fortis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346966
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  • 7
    Electronic Resource
    Electronic Resource
    Exploitation of Opuntia cactus by birds on the Galápagos (1981)
    Springer
    Oecologia 49 (1981), S. 179-187 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary (1) There is a close association between Opuntia helleri (cactus) and Geospiza conirostris (cactus finch) on Isla Genovesa, and between Opuntia echios and Geospiza scandens on Isla Daphne Major. The two finch species consume nectar and pollen, pollinate the obligatorily out-crossing flowers, consume the aril around the seeds, crack the seeds and occasionally disperse them. (2) In the dry season the two finch species open Opuntia flower buds, thereby gaining early access to pollen. But in the process, and at partially open flowers, they snip the style and destroy the stigmas in up to 78% of the flowers. (3) Stigma snipping prevents fertilization of the ovules and the development of seeds which are an important food item later in the year when food supply is likely to limit finch population sizes. Stigma snipping almost ceases in the main part of the wet season, corresponding with an increase in the density of Opuntia flowers and other food types, and a decrease in the proportion of feeding time spent on Opuntia flowers. Stigma snipping neither increased the time flowers remained open nor influenced nectar flow or the number and duration of subsequent visits to flowers by potential pollinators. This last result precludes the possibility that snipping is a means of marking the flower to signal a previous visit to the flower and pollen removal. (4) We conclude that the two finch species snip stigmas to facilitate removal of pollen from the central incurving stamens which are masked by the stigma in a closed or partially open flower. The finches gain a short-term benefit from the removal of stigmas in easy access to pollen and possibly nectar. They potentially suffer in the long term through diminished dry season food supply (seeds), particularly in drought years but we were unable to detect any fitness decrement suffered by the individual finches which do the snipping. (5) An important implication of these results and interpretations is that a behavioral trait which confers a short-term benefit to the individual may increase the chances of the population going extinct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349186
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  • 8
    Electronic Resource
    Electronic Resource
    Intracellular location of nitrate reductase and nitrite reductase in spinach and sunflower leaves (1970)
    Springer
    Planta 94 (1970), S. 60-72 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chloroplasts have been isolated from spinach and from sunflower which retain their outer membrane and their stroma protein as determined both by ability to fix CO2 and evolve O2 at high rates, and by appearance under the phase contrast microscope. Such chloroplasts contain both nitrate and nitrite reductase activity. However, calculations on the distribution of these enzymes, when compared with the distribution of pyruvate kinase and cytochrome c oxidase activity, demonstrate that the larger part of both nitrate and nitrite reductase is located outside of the chloroplast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386609
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of nitrate and nitrite on oxygen evolution and carbon-dioxide assimilation and the reduction of nitrate and nitrite by intact chloroplasts (1970)
    Springer
    Planta 95 (1970), S. 227-246 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Intact chloroplasts isolated from spinach reduced NO3 - and NO2 - in the light without the addition of either co-factors or added enzymes. The maximum rate observed, however, for the reduction of NO3 - was approximately 3μMoles hr-1 mg-1 (chlorophyll) and for NO2 - 6 μMoles hr-1 mg-1 (chlorophyll). These rates were consistent with the enzyme content of whole chloroplasts, but much lower than those found in whole leaf extracts. The addition of both NO3 - and NO2 - in low concentrations resulted in transient increases in both O2 evolution and CO2 fixation. The increases in oxygen evolution were not consistent in amount and bore no relation to the amount of substrate reduced. Similar transients were observed in a number of experiments when NaCl or NH4Cl were added. The addition of NO2 - at concentrations of 10-4 M and above resulted in marked inhibition of both O2 evolution and CO2 fixation. NO2 - appears to inhibit by blocking the reduction of NADP. NO3 - at similar concentrations had no such effect. An increase in the soluble amino nitrogen content of the chloroplasts was observed when NO3 - or NO2 - was reduced. There was, however, no increase in the incorporation of 14C from 14CO2 into amino acids under these conditions. Even with the addition of ammonia the amount of 14C incorporated into the amino acids was not changed from less than 5% of the total 14C fixed. We conclude that while intact chloroplasts do have the ability to reduce both NO3 - and NO2 - at low rates, they do not synthesize appreciable amounts of amino acid directly, and this fact must be considered when formulating any pathways for nitrogen metabolism during photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385090
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  • 10
    Electronic Resource
    Electronic Resource
    Fine structure study on the development of trabeculae in the siphonous green algaCaulerpa simpliciuscula C. Ag. (1981)
    Springer
    Protoplasma 107 (1981), S. 47-61 
    Details
    ISSN: 1615-6102
    Keywords: Caulerpa ; Fibre bundles ; Siphonous algae ; Trabeculae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Bundles of fibrils and tubular structures were found to be associated with growing trabeculae ofCaulerpa simpliciuscula. In the rhizome tips, the bundles had an average diameter of 0.1 to 0.3 μm, and a length greater than 10 μm. The fibrils in the bundles were oriented in a strictly parallel fashion, with an individual thickness of 3–8 nm. The development of trabeculae started with the apposition of material of low electron density onto the bundles, which in this way became the inner skeleton of the trabeculae. Although fibre bundles with the same internal structure also occurred in the frond tip, these rarely contributed to trabecula formation. In the frond tips a different type of bundle with paracrystalline structure was found associated with the trabecular surface, forming a temporary connection between adjacent trabeculae. Permanent connection was achieved by deposition of further layers of trabecular material. These bundles in the frond tip consisted of two layers of tubular elements with a wall thickness of 80 Å and an inner diameter of 20–25 nm. Both fibre bundles and tubular bundles appear to contribute to trabecula formation. The similarity of these structures to the vacuolar inclusions observed in other siphonous algae is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275606
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