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Community Consisting (community + consisting)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Importance of species interactions to community heritability: a genetic basis to trophic-level interactions

ECOLOGY LETTERS, Issue 1 2006
Joseph K. Bailey
Abstract Recent community genetics studies have shown that specific genotypes of a host plant support distinct arthropod communities. Building upon these findings, we examined the hypothesis that a trophic community consisting of cottonwood trees, a galling herbivore and avian predators could also be related to the genetics of the host tree. We found genetic correlations among phytochemistry of individual tree genotypes, the density of a galling herbivore, and the intensity of avian predation on these herbivores. We detected significant broad-sense heritability of these interactions that range from H = 0.70 to 0.83. The genetic basis of these interactions tended to increase across trophic levels suggesting that small genetic changes in the cottonwood phenotype could have major consequences at higher trophic levels affecting species interactions and energy flow. These findings show a heritable basis to trophic-level interactions indicating that there is a significant genetic basis to community composition and energy flow that is predictable by plant genotype. Our data clearly link plant genetics to patterns of avian foraging and show that species interactions are important components of community heritability and ecosystem processes. Overall, these data support the hypothesis that evolution of plant traits can alter trophic-level interactions and community composition. [source]

Localization of processes involved in methanogenic degradation of rice straw in anoxic paddy soil

ENVIRONMENTAL MICROBIOLOGY, Issue 8 2001
Kristin Glissmann
In anoxic paddy soil, rice straw is decomposed to CH4 and CO2 by a complex microbial community consisting of hydrolytic, fermenting, syntrophic and methanogenic microorganisms. Here, we investigated which of these microbial groups colonized the rice straw and which were localized in the soil. After incubation of rice straw in anoxic soil slurries for different periods, the straw pieces were removed from the soil, and both slurry and straw were studied separately. Although the potential activities of polysaccharolytic enzymes were higher in the soil slurry than in the straw incubations, the actual release of reducing sugars was higher in the straw incubations. The concentrations of fermentation products, mainly acetate and propionate, increased steadily in the straw incubations, whereas only a little CH4 was formed. In the soil slurries, on the other hand, fermentation products were low, whereas CH4 production was more pronounced. The production of CH4 or of fermentation products in the separated straw and soil incubations accounted in sum for 54,82% of the CH4 formed when straw was not removed from the soil. Syntrophic propionate degradation to acetate, CO2 and H2 was thermodynamically more favourable in the soil than in the straw fraction. These results show that hydrolysis and primary fermentation reactions were mainly localized on the straw pieces, whereas the syntrophic and methanogenic reactions were mainly localized in the soil. The percentage of bacterial relative to total microbial 16S rRNA content was higher on the straw than in the soil, whereas it was the opposite for the archaeal 16S rRNA content. It appears that rice straw is mainly colonized by hydrolytic and fermenting bacteria that release their fermentation products into the soil pore water where they are further degraded to CH4. Hence, complete methanogenic degradation of straw in rice soil seems to involve compartmentalization. [source]

Allochtonous input and trophic level heterogeneity: impact on an aquatic food web

OIKOS, Issue 1 2006
J. Lövgren
The impact of food web complexity in open and closed food webs was explored experimentally under controlled laboratory conditions. We used an aquatic model community consisting of two forms of primary producers, phytoplankton (Scenedesmus obtusiuscusculus) and periphyton (Nitzschia perminuta) and two types of consumers, Daphnia pulex feeding on phytoplankton and Chydorous sphaericus feeding on both periphyton and phytoplankton. Three different food webs all having the phytoplankton and periphyton, but having either one of the consumers or both were set up. These food webs were studied in an open and closed treatment. In the open treatment, phytoplankton was continuously flowing through the aquaria whereas in the closed system all the phytoplankton was delivered at the start of the experiment. D. pulex had a positive effect on the density of C. sphaericus in both the open and closed treatments. In the open treatment C. sphaericus increased to very high numbers and was able to depress phytoplankton and thereby negatively affect D. pulex. Our study shows that the explicit handling of the population dynamics of both grazers allowed us to show how a compensatory increase in one primary producer due to increased grazing on another primary producer creates a negative feedback between consumers: C. sphaericus increased and negatively affected D. pulex. [source]

Nectarivory by Endemic Malagasy Fruit Bats During the Dry Season,

BIOTROPICA, Issue 1 2006
Daudet Andriafidison
ABSTRACT Madagascar has a distinctive fruit bat community consisting of Pteropus rufus, Eidolon dupreanum, and Rousettus madagascariensis. In this study, we observed fruit bat visits to flowering baobabs (Adansonia suarezensis and Adansonia grandidieri) and kapok trees (Ceiba pentandra) during the austral winter. Eidolon dupreanum was recorded feeding on the nectar of baobabs and kapok, P. rufus was observed feeding on kapok only and no R. madagascariensis were seen. Three mammals species, two small lemurs (Phaner furcifer and Mirza coquereli) and E. dupreanum, made nondestructive visits to flowering A. grandidieri and are therefore all potential pollinators of this endangered baobab. This is the first evidence to show that A. grandidieri is bat-pollinated and further demonstrates the close link between fruit bats and some of Madagascar's endemic plants. Eidolon dupreanum was the only mammal species recorded visiting A. suarezensis and visits peaked at the reported times of maximum nectar concentration. Pteropus rufus visited kapok mostly before midnight when most nectar was available, but E. dupreanum visited later in the night. These differences in timing of foraging on kapok can be explained either by differing distances from the roost sites of each species or by resource partitioning. We advocate increased levels of protection, education awareness, and applied research on both mammal-pollinated baobab species and fruit bats, and suggest that both baobabs and bats are candidate "flagship species" for the threatened dry forests of Madagascar. RESUME Madagascar a une remarquable communauté de chauves-souris frugivores comprenant Pteropus rufus, Eidolon dupreanum et Rousettus madagascariensis. Dans le cadre de la présente étude, nous avons observé les visites que les chauves-souris effectuent sur les baobabs (Adansonia suarezensis et Adansonia grandidieri) et les kapokiers (Ceiba pentandra) en floraison durant l'hiver austral. Eidolon dupreanum a été observé se nourrissant du nectar des baobabs et des kapokiers, Pteropus rufus a été observé en train de se nourrir des kapokiers uniquement, et aucun Rousettus madagascariensis n'a pu être recensé. Trois espèces de mammifères, deux lémuriens (Phaner furcifer, Mirza coquereli) et Eidolon dupreanum, effectuent des visites non destructives des fleurs d' A. grandidieri et sont, de ce fait, des pollinisateurs potentiels de cette espèce de baobab en danger. Il s'agit de la première preuve qu' A. grandidieri est pollinisé par les chauves-souris. Cette observation démontre aussi le lien étroit qui existe entre les chauves-souris frugivores et quelques-unes des plantes endémiques de Madagascar. Eidolon dupreanum est la seule espèce observée sur Adansonia suarezensis et les visites sont plus fréquentes aux heures de concentration maximale de nectar. Pteropus rufus visite les kapokiers, surtout avant minuit, lorsque les nectars sont encore disponibles. En revanche, la visite effectuée par Eidolon dupreanum a lieu plus tard dans la nuit. Cette différence d'heures de fourrage sur les kapokiers pourrait être justifiée par l'inégalité de la distance des gîtes de chaque espèce ou par le partage des ressources. Aussi recommandons-nous le renforcement des mesures de protection, des activités d'IEC et de la recherche appliquée aux espèces de baobab pollinisées par des mammifères et les chauves-souris frugivores. Nous suggérons l'intégration des baobabs et des chauves-souris dans la liste des espèces " flagship" pour les forêts caducifoliées en danger à Madagascar. [source]