Home | [11–20] << 21 22 23 24 25 26 27 28 29 30 >> [31–40] |
Orivel, J., & Leroy, C. (2011). The diversity and ecology of ant gardens (Hymenoptera: Formicidae; Spermatophyta: Angiospermae). Myrmecol. News, 14, 73–85.
Abstract: Mutualistic interactions between ants and plants are important features of many ecosystems, and they can be divided into three main categories: dispersal and protective mutualisms and myrmecotrophy. In both the Neotropics and the Southeastern Asian Paleotropics, ant gardens (AGs), a particular type of ant-plant interaction, are frequent. To initiate AGs, ants integrate the seeds of certain epiphyte species into the carton of their nest. The development of the plants leads to the formation of a cluster of epiphytes rooted in the carton. They have been defined as one of the most complex associations between ants and plants known because of the plurispecific, but also specialized nature of the association involving several phylogenetically-distant ant and plant species. The aim of this review is to provide a synthesis of the diversity and ecology of AGs, including the outcomes experienced by the partners in the interaction and the direct and indirect impacts ant-garden ants have on the plant and arthropod communities.
Keywords: Ant-plant interactions; epiphytes; mutualisms; Neotropics; Paleotropics; phytotelm; parabiosis; seed dispersal; review
|
Rutishauser, E., Barthelemy, D., Blanc, L., & Nicolini, E. A. (2011). Crown fragmentation assessment in tropical trees: Method, insights and perspectives. For. Ecol. Manage., 261(3), 400–407.
Abstract: Decreasing growth rate (Feeley et al., 2007) and large die-back due to drought (Phillips et al., 2009) suggest that tropical forests are suffering recent climate changes. Forest vulnerability to external factors (e.g. air pollution, acid rain) is widely studied in northern countries, while only a few attempts have investigated crown integrity in the Tropics. The method needs to be generic enough to account for the large number of species and crown shapes encountered in tropical forests. In the present study, we developed and tested a novel field method that estimates crown fragmentation (main branch mortality (MB) and secondary branch mortality (SB)), liana infestation (LI) and crown position (CP) in the canopy. The relationship between crown fragmentation and annual growth rate (agr) was investigated through multiple regression. Six out of eight canopy tree species showed significant growth decline with increasing crown fragmentation. Higher probability of death was also found in trees with severe crown fragmentation. The capacity of such crown assessment to depict tree vitality in a forest stand is discussed along with potential applications in both forest science and management. (C) 2010 Elsevier B.V. All rights reserved.
Keywords: Crown assessment; Crown fragmentation; Tree mortality; Forest dynamics
|
Le Lann, C., Roux, O., Serain, N., Van Alphen, J. J. M., Vernon, P., & Van Baaren, J. (2011). Thermal tolerance of sympatric hymenopteran parasitoid species: does it match seasonal activity? Physiol. Entomol., 36(1), 21–28.
Abstract: Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely-related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.
Keywords: Climate change; critical thermal limits; CTmax; CTmin; dry mass; guild; hind tibia length; seasonal activities; surface to volume ratio
|
Orivel, J., Lambs, L., Male, P. J. G., Leroy, C., Grangier, J., Otto, T., et al. (2011). Dynamics of the association between a long-lived understory myrmecophyte and its specific associated ants. Oecologia, 165(2), 369–376.
Abstract: Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant-plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant-ant species. In exchange, plant-ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients. Although most studies to date have highlighted a similar global pattern of interactions in these systems, little is known about the temporal structuring and dynamics of most of these associations. In this study we focused on the association between the understory myrmecophyte Hirtella physophora (Chrysobalanaceae) and its obligate ant partner Allomerus decemarticulatus (Myrmicinae). An examination of the life histories and growth rates of both partners demonstrated that this plant species has a much longer lifespan (up to about 350 years) than its associated ant colonies (up to about 21 years). The size of the ant colonies and their reproductive success were strongly limited by the available nesting space provided by the host plants. Moreover, the resident ants positively affected the vegetative growth of their host plant, but had a negative effect on its reproduction by reducing the number of flowers and fruits by more than 50%. Altogether our results are important to understanding the evolutionary dynamics of ant-plant symbioses. The highly specialized interaction between long-lived plants and ants with a shorter lifespan produces an asymmetry in the evolutionary rates of the interaction which, in return, can affect the degree to which the interests of the two partners converge.
Keywords: Allomerus decemarticulatus; Hirtella physophora; Lifespan; Mutualism; Myrmecophyte
|
Haettenschwiler, S., Coq, S., Barantal, S., & Handa, I. T. (2011). Leaf traits and decomposition in tropical rainforests: revisiting some commonly held views and towards a new hypothesis. New Phytol., 189(4), 950–965.
Abstract: Proper estimates of decomposition are essential for tropical forests, given their key role in the global carbon (C) cycle. However, the current paradigm for litter decomposition is insufficient to account for recent observations and may limit model predictions for highly diverse tropical ecosystems. In light of recent findings from a nutrient-poor Amazonian rainforest, we revisit the commonly held views that: litter traits are a mere legacy of live leaf traits; nitrogen (N) and lignin are the key litter traits controlling decomposition; and favourable climatic conditions result in rapid decomposition in tropical forests. Substantial interspecific variation in litter phosphorus (P) was found to be unrelated to variation in green leaves. Litter nutrients explained no variation in decomposition, which instead was controlled primarily by nonlignin litter C compounds at low concentrations with important soil fauna effects. Despite near-optimal climatic conditions, tropical litter decomposition proceeded more slowly than in a climatically less favourable temperate forest. We suggest that slow decomposition in the studied rainforest results from a syndrome of poor litter C quality beyond a simple lignin control, enforcing energy starvation of decomposers. We hypothesize that the litter trait syndrome in nutrient-poor tropical rainforests may have evolved to increase plant access to limiting nutrients via mycorrhizal associations.
Keywords: energy starvation; French Guiana; litter quality; mycorrhizas; nutrient cycling; nutrient limitation; phosphorus; soil fauna
|
Leroy, C., Sejalon-Delmas, N., Jauneau, A., Ruiz-Gonzalez, M. X., Gryta, H., Jargeat, P., et al. (2011). Trophic mediation by a fungus in an ant-plant mutualism. J. Ecol., 99(2), 583–590.
Abstract: 1. Plants often rely on external, mutualistic partners to survive and reproduce in resource-limited environments or for protection from enemies. Such interactions, including mycorrhizal symbioses and ant plant associations, are widespread and play an important role at the ecosystem and community levels. In ant-plant mutualisms, the plants may benefit from both the protection provided by the presence of ants and from the nutrients absorbed from insect debris. However, the role of third partners in plant nutrition, particularly ant-associated fungi, has never before been demonstrated. 2. We investigate this issue in the ant-plant Hirtella physophora. In this model system, Allomerus decemarticulatus ants are involved in two, highly specific interactions: first, with their host plant, and, secondly, with a fungus that they actively manipulate. Moreover, the ants combine both plant trichomes and fungal hyphae to make a trap to capture prey. 3. We empirically demonstrate the existence of a third type of interaction between the fungus and the plant through the use of both experimental enrichments with stable isotopes (N-15) and histological approaches. The fungus growing in the galleries plays a role in providing nutrients to the host plant, in addition to the structural role it plays for the ants. Fungus-facilitated nitrogen uptake occurs mainly in old domatia, where abundant hyphae are in close contact with the plant cells. Whether the fungi inside the domatia and those in the galleries are the same is still uncertain. 4. Synthesis. Together, our results show that a fungal partner in an ant-plant mutualism can benefit the plant by improving its nutrient uptake, and they demonstrate the existence of a true tripartite mutualism in this system. Our results add further evidence to the notion that interpretations of some ant plant symbioses as purely protective mutualisms have overlooked these nutritional aspects.
Keywords: delta N-15; Allomerus decemarticulatus; ant-plant-fungus interactions; Ascomycete; fungal mediation; Hirtella physophora; mutualisms; myrmecophytes; nutrient provisioning; stable isotopes
|
Lebrini, M., Robert, F., & Roos, C. (2011). Alkaloids Extract from Palicourea guianensis Plant as Corrosion Inhibitor for C38 Steel in 1 M Hydrochloric Acid Medium. Int. J. Electrochem. Sci., 6(3), 847–859.
Abstract: Corrosion inhibition effect of alkaloids extract from Palicourea guianensis plant (AEPG) on C38 tell in 1 M HCl medium has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The polarization studies that AEPG acts as mixed-type inhibitor. The electrochemical impedance spectroscopy showed that the charge transfer resistance increases and the double layer capacitance decreases on increasing plant extract concentration. The inhibition efficiency of the extract obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of the extract. Inhibition efficiency of 89% was achieved with 100 mg L-1 of AEPG at 25 degrees C. The obtained results showed that, the Palicourea guianensis extract could serve as an effective inhibitor for the corrosion of steel in acid media. The adsorption of AEPG obeys the Langmuir adsorption isotherm.
Keywords: Palicourea guianensis; corrosion inhibitors; C38 steel; acidic media; adsorption
|
Lebrini, M., Robert, F., Lecante, A., & Roos, C. (2011). Corrosion inhibition of C38 steel in 1 M hydrochloric acid medium by alkaloids extract from Oxandra asbeckii plant. Corrosion Sci., 53(2), 687–695.
Abstract: The inhibition effect of alkaloids extract from Oxandra asbeckii plant (OAPE) on the corrosion of C38 steel in 1 M hydrochloric acid solution has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases on increasing plant extracts concentration. Cathodic and anodic polarization curves show that OAPE is a mixed-type inhibitor. The effect of temperature on the corrosion behavior of C38 steel in 1 M HCl with and without addition of plant extract was studied in the temperature range 25-55 degrees C. The thermodynamic functions of dissolution and adsorption processes were calculated from experimental polarization data and the interpretation of the results are given. The adsorption of this plant extract on the C38 steel surface obeys the Langmuir adsorption isotherm. Surface analysis (Raman) was also carried out to establish the corrosion inhibitive property of this plant extract in HCl solution. (C) 2010 Elsevier Ltd. All rights reserved.
Keywords: Steel; EIS; Polarization; Raman spectroscopy; Acid inhibition
|
Lecante, A., Robert, F., Blandinieres, P. A., & Roos, C. (2011). Anti-corrosive properties of S. tinctoria and G. ouregou alkaloid extracts on low carbon steel. Curr. Appl. Phys., 11(3), 714–724.
Abstract: The effect of alkaloid extracts from two Amazonian trees (Guatteria ouregou and Simira tinctoria) on low carbon steel corrosion was investigated in acidic solutions by using electrochemical techniques. All of these plant extracts inhibit the corrosion of low carbon steel in 0.1 M HCl solutions. As their concentration increases to 250 mg/L, the inhibition efficiencies of S. tinctoria and G. ouregou alkaloid extracts reach approximately 92% in 0.1 M HCl solutions. The adsorption of the inhibitor molecules was in accordance with the Langmuir adsorption isotherm. The results obtained show that these plant extracts could be serve as an effective inhibitor for the corrosion of low carbon steel in hydrochloric acid media. Furthermore, harmane was identified as the main component of S. tinctoria extract and that suggests that it is the active ingredient against corrosion of low carbon steel. (C) 2010 Elsevier B.V. All rights reserved.
Keywords: Low carbon steel; Acidic media; Corrosion inhibitor; Plant extract; EIS
|
Dejean, A., & Lachaud, J. P. (2011). The hunting behavior of the African ponerine ant Pachycondyla pachyderma. Behav. Processes, 86(2), 169–173.
Abstract: The hunting behavior of the African ponerine ant Pachycondyla pachyderma, a semi-specialized centipede predator, appears well adapted to this kind of prey and shows a graded complexity according to the difficulty it has in overwhelming prey. Small prey (5-to-8-mm-long termites) were detected by contact and seized by the thorax while larger prey (>= 30-mm-long centipedes) were frequently detected from a distance and seized by the anterior-most part of their body. Termites and 30-mm-long lithobiomorph centipedes were not always stung, whereas stinging and even repeated stinging was needed for 50-mm-long geophilomorphs and scolopendromorphs. Moreover, overwhelming wide and heavy scolopendromorphs, which have better defensive abilities, involved the use of additional behaviors allowing the workers to capture them safely: venom spreading, and a peculiar stinging posture, the “fatal embrace”. Here the workers seize scolopendromorphs by an antenna or by one of their first legs, wrap themselves around the prey while maintaining their grip with their mandibles and legs, and slowly inject venom into the prey's ventral surface. Workers retrieve small prey solitarily while, for large geophilomorphs and scolopendromorphs, nestmates can be recruited at short range or even at long range through tandem running. (C) 2010 Elsevier B.V. All rights reserved.
Keywords: Hunting behavior; Feeding specialization; Behavioral flexibility; Ponerine ants; Pachycondyla; Myriapoda
|