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  • 1
    ISSN: 1572-9710
    Keywords: ants ; Amazonia ; invertebrate conservation ; forest clearing ; forest regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study evaluates biotic responses, using ants as bio-indicators, to relatively recent anthropogenic disturbances to mature forest in central Amazonia. The structure of the ground-foraging ant community was compared in four habitats that represented a gradient of disturbance associated with differences in land use. Ants were collected in undisturbed, mature forest, in an abandoned pasture, in a young regrowth forest (situated in a former pasture area), and in an old regrowth forest (established where mature forest was just cleared and abandoned). More ant species were found in mature and old regrowth forest than in the abandoned pasture. By contrast, ant abundance tended to decrease with forest maturity. Both pasture and young regrowth forest exhibited a distinct ant species composition compared to mature forest, whereas species composition in the old regrowth forest showed greater similarity to that of mature forest. In spite of differences in fallow time between former pasture areas and non-pasture areas, there is evidence that different land-management practices do result in different rates of recovery of the ant forest fauna after land abandonment. In any case, recuperation of the ground-foraging ant fauna appears to be faster than regeneration of the woody-plant community. In this sense, regrowth forests may be valuable for the conservation of ground-foraging ants and perhaps for other components of mature-forest leaf-litter fauna within the context of a fragmented landscape.
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In tropical forests, large canopy and emergent trees are crucial sources of fruits, flowers and shelter for animal populations. They are also reproductively dominant and strongly influence forest structure, composition, gap dynamics, hydrology and carbon storage. Here we show that forest ...
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  • 3
    ISSN: 1432-1939
    Keywords: Ant-plant interactions ; Mutualism ; Herbivory ; Maieta guianensis ; Pheidole minutula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hypothesis that ants (Pheidole minutula) associated with the myrmecophytic melastome Maieta guianensis defend their host-plant against herbivores was investigated in a site near Manaus, Amazonas, Brazil. M. guianensis is a small shrub that produces leaf pouches as ant domatia. Plants whose ants were experimentally removed suffered a significant increase in leaf damage compared with control plants (ants maintained). Ants patrol the young and mature leaves of Maieta with the same intensity, presumably since leaves of both ages are equally susceptible to herbivore attack. The elimination of the associated ant colony, and consequent increase in herbivory, resulted in reduced plant fitness. Fruit production was 45 times greater in plants with ants than in plants without ants 1 year after ant removal.
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  • 4
    ISSN: 1432-1939
    Keywords: Key words Amazonia ; Stable isotope ; Savanna ; Trophic level ; Carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (x¯ = −30.8, SD = 1.2), vines (x¯ = −30.7, SD = 0.46) and trees (x¯ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (x¯ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (x¯ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing, the frogs and lizards generally had higher values of δ13C (x¯ = −21.7, SD = 1.6; x¯ = −21.9, SD = 1.8, respectively) than the birds (x¯ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (x¯ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
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  • 5
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    Springer
    Oecologia 95 (1993), S. 439-443 
    ISSN: 1432-1939
    Keywords: Ants ; Colony founding ; Maieta guianensis ; Mutualism ; Myrmecophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ants Pheidole minutula and Crematogaster sp. are obligate inhabitants of the ant-plant Maieta guianensis. They nest and reproduce exclusively in this and a few other Amazon melastome ant-plants. Experimental transplants of uncolonized M. guianensis seedlings to sites at different distances from established colonies of these two ant species, which are sources of founding queens, have shown that distance is an important factor affecting seedling colonization by ants. The proportion of colonized seedlings and the average number of colonizations per seedling, both by Crematogaster sp. and P. minutula, decreased as distance from established colonies increased. Seedling colonization was also affected by rainfall and fewer seedlings were colonized during the dry season, especially by P. minutula, than during the rainy season. P. minutula queens usually cooperate with each other during colony foundation, a behaviour not observed among founding queens of Crematogaster sp. Competition between these two ant species for host-plants appears to be strong as 63.6% of the seedlings colonized by Crematogaster sp. were also colonized by P. minutula during a 15-month observational period. However, there was generally an interval of a few months between colonizations, possibly giving the first species to colonize the plant a better chance of domination on this plant.
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