ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2000
Jonghoon Choi
Abstract Many polycyclic aromatic hydrocarbons (PAHs) are acutely toxic to fish and other aquatic organisms in the presence of solar ultraviolet radiation (SUVR) of environmentally realistic intensities. In the present study, the photoinduced toxicity of a PAH (anthracene; ANT) to topminnow hepatoma cell line (PLHC-1) was assessed. After the toxicity was characterized, the role of lipid peroxidation in PAH photoinduced toxicity was examined by measuring lipid peroxidation products and by assessing the effect of lipid peroxidation antagonist (Trolox) treatment. In cytotoxicity tests using two assays (MTT, neutral red), the SUVR/ANT treatment elicited toxicity to PLHC-1 cells in a concentration- and SUVR (exposure duration and intensity)-dependent pattern. As found in previous organism-level studies, no significant cytotoxicity was observed in the cells exposed either to fluorescent light/ANT or to SUVR only. The SUVR/ANT treatment elicited the lipid peroxidation process and Trolox pretreatment significantly reduced SUVR/ANT-induced cell mortality. Microscopic observation showed that Trolox pretreatment relieved the SUVR/ANT-inflicted damage, such as cell shrinkage and membrane disruption. Together with a recent finding in our lab that increased production of superoxide anion and a lipid peroxidation product (malondialdehyde) was found in SUVR/ANT-treated fish microsomes, the present study suggests that reactive oxygen radical-induced lipid peroxidation is an important factor in PAH photoinduced toxicity to fish. [source]

Evidence of oxidative stress in bluegill sunfish (Lepomis macrochirus) liver microsomes simultaneously exposed to solar ultraviolet radiation and anthracene

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2000
Jonghoon Choi
Abstract Many polycyclic aromatic hydrocarbons (PAHs) are acutely toxic to fish and other aquatic organisms in the presence of environmentally realistic intensities of solar ultraviolet radiation (SUVR). However, the biochemical mechanism of this toxicity is not well established. In this study, increased levels of both reactive oxygen species production and lipid peroxidation were hypothesized as a toxic mechanism. To test this hypothesis, the production of superoxide anion and of a lipid peroxidation product (malondialdehyde) was measured in bluegill sunfish (Lepomis machrochirus) liver microsomes. These microsomes were exposed to a representative phototoxic PAH (anthracene [ANT]) and to SUVR and normal laboratory fluorescent light (FLU) in four different combinations: FLU + no ANT, FLU + ANT, SUVR + no ANT, and SUVR + ANT. The highest mean levels of both superoxide anion and malondialdehyde production were observed in the SUVR + ANT group, and these levels were significantly different (p < 0.05) from those in all other treatment groups. We conclude that the photoinduced toxicity of ANT, and possibly of other phototoxic PAHs, manifests at least in part through lipid peroxidation after increased production of reactive oxygen species. [source]

PHYLOGENETIC PLACEMENT OF AN UNUSUAL CORAL MUSHROOM CHALLENGES THE CLASSIC HYPOTHESIS OF STRICT COEVOLUTION IN THE APTEROSTIGMA PILOSUM GROUP ANT,FUNGUS MUTUALISM

EVOLUTION, Issue 8 2009
Bryn T. M. Dentinger
The ,50 million-year-old fungus-farming ant mutualism is a classic example of coevolution, involving ants that subsist on asexual, fungal biomass, in turn propagating the fungus clonally through nest-to-nest transmission. Most mutualistic ants cultivate two closely related groups of gilled mushrooms, whereas one small group of ants in the genus Apterostigma cultivates a distantly related lineage comprised of the G2 and G4 groups. The G2 and G4 fungi were previously shown to form a monophyletic group sister to the thread-like coral mushroom family Pterulaceae. Here, we identify an enigmatic coral mushroom that produces both fertile and sterile fruiting structures as the closest free-living relative of the G4 fungi, challenging the monophyly of the Apterostigma -cultivated fungi for the first time. Both nonparametric bootstrap and Bayesian posterior probability support the node leading to the G4 cultivars and a free-living Pterula mushroom. These data suggest three scenarios that contradict the hypothesis of strict coevolution: (1) multiple domestications, (2) escape from domestication, (3) selection of single cultivar lineages from an ancestral mixed-fungus garden. These results illustrate how incomplete phylogenies for coevolved symbionts impede our understanding of the patterns and processes of coevolution. [source]

PLASTICITY IN QUEEN NUMBER AND SOCIAL STRUCTURE IN THE INVASIVE ARGENTINE ANT (LINEPITHEMA HUMILE)

EVOLUTION, Issue 10 2002
Krista K. Ingram
Abstract., In many polygynous social insect societies, ecological factors such as habitat saturation promote high queen numbers by increasing the cost of solitary breeding. If polygyny is associated with constrained environments, queen number in colonies of invasive social insects should increase as saturation of their new habitat increases. Here I describe the variation in queen number, nestmate relatedness, and nest size along a gradient of time since colonization in an invading population of Argentine ants (Linepithema humile) in Haleakala, Hawaii. Nest densities in this population increase with distance from the leading edge of the invasion, reaching a stable density plateau approximately 80 m from the edge (> 2 years after colonization). Although the number of queens per nest in Haleakala is generally lower than previously reported for Argentine ants, there is significant variation in queen number across this population. Both the observed and effective queen numbers increase across the density gradient, and nests in the center of the population contain queen numbers three to nine times higher than those on the edge of the invasion. The number of workers per nest is correlated with queen number, and nests in the center are six times larger than nests at the edge. Microsatellite analysis of relatedness among nestmates reveals that all nests in the Haleakala population are characterized by low relatedness and have evidence of multiple reproducing queens. Relatedness values are significantly lower in nests in the center of the population, indicating that the number of reproducing queens is greater in areas of high nest density. The variation in queen number and nestmate relatedness in this study is consistent with expectations based on changes in ecological constraints during the invasion of a new habitat, suggesting that the social structure of Argentine ant populations is strongly influenced by ecological factors. Flexibility in social structure may facilitate persistence in variable environments and may also confer significant advantages to a species when introduced into new areas. [source]

Stabilizing flows in the legal field: illusions of permanence, intellectual property rights and the transnationalization of law

GLOBAL NETWORKS, Issue 1 2003
Paul Street
In this article I examine some of the problems that ,modern' legal theory poses for a consideration of the extended reach of social actors and institutions in time and space. While jurisprudence has begun to engage with the concept of globalization, it has done so in a relatively limited manner. Thus legal theory's encounters with highly visible transnational practices have, for the most part, resulted not in challenging the prevailing formal legal paradigm, but in a renewed if slightly modified search for a general jurisprudence that ultimately takes little account of the manner in which the work of law is carried out transnationally. In the first part of this article I examine how legal theory's concern to maintain its own integrity places limitations on its ability to examine the permeability of social boundaries. In the latter part I draw on critical human geography, post,structuralism and actor,network theory (ANT), to examine the manner in which transnational actors have been able to mobilize law, and in particular intellectual property rights (IPRs), as a necessary strategy for both maintaining the meanings of bio,technologies through time and space, and enrolling farmers into particular social networks. [source]

New Directions in Natural Resource Management The Offer of Actor-Network Theory

IDS BULLETIN, Issue 4 2001
Nathalie A. Steins
Summaries The article offers theoretical insights from Actor-Network Theory (ANT) as to how natural resource management (NRM) perspectives might be enhanced. ANT asks us to abolish the conventional sociological practice of studying phenomena in terms of predefined categories and principles, as they hinder our analysis of how the stakeholders involved construct resource management processes and the way these constructions are used. In this analytical process, any (uncertain) outcome of NRM is regarded as an effect of the interplay amongst the different stakes in the resource and the way stakeholders continuously mobilise social and material resources in order to achieve their goals. Only by analysing how certain outcomes have been achieved can we develop our understanding of the dynamics and uncertainties involved in NRM. The article uses empirical examples from coastal management scenarios to illustrate these theoretical points. [source]

Measurement of varus,valgus and internal,external rotational knee laxities in vivo,Part II: relationship with anterior,posterior and general joint laxity in males and females

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2007
Sandra J. Shultz
Abstract We examined sex differences in general joint laxity (GJL), and anterior,posterior displacement (ANT,POST), varus,valgus rotation (VR,VL), and internal,external rotation (INT,EXT) knee laxities, and determined whether greater ANT and GJL predicted greater VR,VL and INT,EXT. Twenty subjects were measured for GJL, and scored on a scale of 0,9. ANT and POST were measured using a standard knee arthrometer at 133 N. VR,VL and INT,EXT were measured using a custom joint laxity testing device, defined as the angular displacements (deg) of the tibia relative to the femur produced by 0,10 Nm of varus,valgus torques, and 0,5 Nm of internal,external torques, respectively. INT,EXT were measured during both non-weight-bearing (NWB) and weight-bearing (WB,=,40% body weight) conditions while VR,VL were measured NWB. All laxity measures were greater for females compared to males except for POST. ANT and GJL positively predicted 62.5% of the variance in VR,VL and 41.8% of the variance in WB INT,EXT. ANT was the sole predictor of INT,EXT in NWB, explaining 42.3% of the variance. These findings suggest that subjects who score higher on clinical measures of GJL and ANT are also likely to have greater VR,VL and INT,EXT knee laxities. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:989,996, 2007 [source]

1,1-bis(3,-indolyl)-1-(p- substituted phenyl)methanes decrease mitochondrial membrane potential and induce apoptosis in endometrial and other cancer cell lines

MOLECULAR CARCINOGENESIS, Issue 7 2008
Jun Hong
Abstract 1,1-Bis(3,-indolyl)-1-(p -substituted phenyl)methanes, containing p-t- butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC6H5) substituents, are peroxisome proliferator-activated receptor , (PPAR,) agonists; however, DIM-C-pPhtBu-induced growth inhibition and cell death in human HEC1A endometrial cancer cells is PPAR,-independent. DIM-C-pPhtBu decreased mitochondrial membrane potential (MMP) and promoted the release of cytochrome c and caspase activation and nuclear uptake of endonuclease G leading to apoptosis of HEC1A cells. DIM-C-pPhtBu specifically targeted the mitochondrial permeability transition pore complex (PTPC) because the DIM-C-pPhtBu-induced pro-apoptotic responses were inhibited by atractyloside (Atra), a compound that specifically interacts with the inner mitochondrial membrane adenine nucleotide transport (ANT) proteins. At the dose of Atra used in this study (300 µM), this compound alone did not alter the PTPC but inhibited the mitochondriotoxic effects of DIM-C-pPhtBu. DIM-C-pPhtBu/DIM-C-pPhC6H5 and Atra also differentially affected the ability of eosin-5-maleimide (EMA) to alkylate Cys160 in the ANT protein and Atra, but not DIM-C-pPhtBu, inhibited the exchange of ATP/ADP in isolated mitochondria suggesting that these pharmacophores act on different sites on the ANT protein. Results of this study show that the receptor-independent proapoptotic activity of DIM-C-pPhtBu and DIM-C-pPhC6H5 were related to novel mitochondriotoxic activities involving inner mitochondrial ANT proteins. © 2007 Wiley-Liss, Inc. [source]

Impaired conflict resolution and alerting in children with ADHD: evidence from the Attention Network Task (ANT)

THE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 12 2008
Katherine A. Johnson
Background:, An important theory of attention suggests that there are three separate networks that execute discrete cognitive functions. The ,alerting' network acquires and maintains an alert state, the ,orienting' network selects information from sensory input and the ,conflict' network resolves conflict that arises between potential responses. This theory holds promise for dissociating discrete patterns of cognitive impairment in disorders where attentional deficits may often be subtle, such as in attention deficit hyperactivity disorder (ADHD). Methods:, The Attentional Network Test (ANT), a behavioural assay of the functional integrity of attention networks, was used to examine the performance of 73 children with ADHD and 73 controls. Results:, Performance on the ANT clearly differentiated the children with and without ADHD in terms of mean and standard deviation (SD) of reaction time (RT), the number of incorrect responses made and the number of omission errors made. The ADHD group demonstrated deficits in the conflict network in terms of slower RT and a higher number of incorrect responses. The ADHD group showed deficits in the alerting network in terms of the number of omission errors made. There was no demonstration of a deficit in the orienting network in ADHD on this task. Conclusions:, The children with ADHD demonstrated deficits in the alerting and conflict attention networks but normal functioning of the orienting network. [source]

Actor-Network Theory as a Critical Approach to Environmental Justice: A Case against Synthesis with Urban Political Ecology

ANTIPODE, Issue 4 2009
Ryan Holifield
Abstract:, Recent critiques of environmental justice research emphasize its disengagement from theory and its political focus on liberal conceptions of distributional and procedural justice. Marxian urban political ecology has been proposed as an approach that can both contextualize environmental inequalities more productively and provide a basis for a more radical politics of environmental justice. Although this work takes its primary inspiration from historical materialism, it also adapts key concepts from actor-network theory (ANT),in particular, the agency of nonhumans,while dismissing the rest of ANT as insufficiently critical and explanatory. This paper argues that ANT,specifically, the version articulated by Bruno Latour,provides a basis for an alternative critical approach to environmental justice research and politics. Instead of arguing for a synthesis of ANT and Marxism, I contend that ANT gives us a distinctive conception of the,social,and opens up new questions about the production and justification of environmental inequalities. [source]

Assembling Justice Spaces: The Scalar Politics of Environmental Justice in North-east England

ANTIPODE, Issue 4 2009
Karen Bickerstaff
Abstract:, In contrast to the US environmental justice movement, which has been successful in building a networked environmentalism that recognises,and has impacted upon,national patterns of distributional (in)equalities, campaigns in the UK have rarely developed beyond the local or articulated a coherent programme of action that links to wider socio-spatial justice issues or effects real changes in the regulatory or political environment. Our purpose in this paper is to extend research which explores the spatial politics of mobilisation, by attending to the multi-scalar dynamics embedded in the enactment of environmental justice (EJ) in north-east England. It is an approach that is indebted to recent work on the scalar politics of EJ, and also to the network ideas associated with actor-network theory (ANT)-inspired research on human,nature relations. Our account provides preliminary reflections on the potential for an "assemblage" perspective which draws together people, texts, machines, animals, devices and discourses in relations that collectively constitute,and scale,EJ. To conclude, and building upon this approach, we suggest future research avenues that we believe present a promising agenda for critical engagement with the production, scaling and politics of environmental (in)justice. [source]

Anthropogenic warming of central England temperature

ATMOSPHERIC SCIENCE LETTERS, Issue 4 2006
David J. Karoly
Abstract The variability of central England temperature (CET) at inter annual, decadal and 50-year time scales, as simulated by the HadCM3 model, agrees well with its observed variability over the period 1700,1900. The observed warming in annual-mean CET of about 1.0 °C since 1950 is very unlikely to be due to natural climate variations and is consistent with the response to anthropogenic (ANT) forcing, demonstrating a significant human influence on this warming. © Crown Copyright 2006. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd. [source]

ALTERNATE NUCLEAR TRANSFER IS NO ALTERNATIVE FOR EMBRYONIC STEM CELL RESEARCH

BIOETHICS, Issue 2 2008
JOHN A. FENNEL
ABSTRACT Recent developments allow for the creation of human stem cells without the creation of human embryos, a process called alternate nuclear transfer (,ANT'). Pursuing this method of stem cell research makes sense for pro-lifers if arguments for the sanctity of the human embryo do not apply to ANT. However, the technology that makes ANT possible undermines the erstwhile technical barrier between human embryos and somatic cell DNA. These advances bring home the force of hypothetical arguments about the potential of the DNA in somatic cells, showing that there is not a morally relevant difference between the potential of an embryo and the potential of the DNA in a somatic cell. Therefore, the supposed distinction between entities that are potential human life and entities that are human life does not give any support to arguments for the sanctity of the human embryo because those arguments extend value to too many entities. [source]

ANTIMICROBIAL DEFENSE SHOWS AN ABRUPT EVOLUTIONARY TRANSITION IN THE FUNGUS-GROWING ANTS

EVOLUTION, Issue 5 2008
William O. H. Hughes
Understanding the relative evolutionary importance of parasites to different host taxa is problematic because the expression of disease and resistance are often confounded by factors such as host age and condition. The antibiotic-producing metapleural glands of ants are a potentially useful exception to this rule because they are a key first-line defense that are fixed in size in adults. Here we conduct a comparative analysis of the size of the gland reservoir across the fungus-growing ants (tribe Attini). Most attines have singly mated queens, but in two derived genera, the leaf-cutting ants, the queens are multiply mated, which is hypothesized to have evolved to improve colony-level disease resistance. We found that, relative to body size, the gland reservoirs of most attines are similar in size but that those of the leaf-cutting ants are significantly larger. In contrast, the size of the reservoir did not relate with the evolutionary transition from lower to higher attines and correlated at most only slightly with colony size. The results thus suggest that the relationship between leaf-cutting ants and their parasites is distinctly different from that for other attine ants, in accord with the hypothesis that multiple mating by queens evolved to improve colony-level disease resistance. [source]

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

ECOLOGICAL ENTOMOLOGY, Issue 3 2010
JOSEP PIÑOL
1. Predation-exclusion experiments have highlighted that top-down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1-year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant-excluded than in control trees, whereas only dermapterans were more abundant in bird-excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator,prey system. [source]

Induced biotic responses to herbivory and associated cues in the Amazonian ant-plant Maieta poeppigii

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2004
Alexander V. Christianini
Abstract Ants inhabiting ant-plants can respond to cues of herbivory, such as the presence of herbivores, leaf damage, and plant sap, but experimental attempts to quantify the dynamic nature of biotic defenses have been restricted to a few associations between plants and ants. We studied the relationship between certain features of the ant-shrub Maieta poeppigii Cogn. (Melastomataceae) and the presence or absence of ant patrolling on the leaf surface in plants occupied by the ant Pheidole minutula Mayr (Hymenoptera: Formicidae). We also carried out field experiments to examine ant behavior following plant damage, and the potential cues that induce ant recruitment. These experiments included clipping of the leaf apex, as well as the presentation of a potential herbivore (live termite worker) and a foliar extract from Maieta on treatment leaves. The presence of ants patrolling the leaves of M. poeppigii is influenced by the number of domatia on the plant. Ant patrolling on the leaves of M. poeppigii was constant throughout a 24 h cycle, but the mean number of patrolling ants decreased from young to mature leaves, and from leaves with domatia to those without domatia. There was an overall increase in the number of ants on experimental leaves following all treatments, compared to control leaves. Visual and chemical cues associated with herbivory are involved in the induction of ant recruitment in the Maieta,Pheidole system. The continuous patrolling behavior of ants, associated with their ability to respond rapidly to foliar damage, may result in the detection and repellence/capture of most insect herbivores before they can inflict significant damage to the leaves. [source]

Entropy-based metrics in swarm clustering

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 9 2009
Bo Liu
Ant-based clustering methods have received significant attention as robust methods for clustering. Most ant-based algorithms use local density as a metric for determining the ants' propensities to pick up or deposit a data item; however, a number of authors in classical clustering methods have pointed out the advantages of entropy-based metrics for clustering. We introduced an entropy metric into an ant-based clustering algorithm and compared it with other closely related algorithms using local density. The results strongly support the value of entropy metrics, obtaining faster and more accurate results. Entropy governs the pickup and drop behaviors, while movement is guided by the density gradient. Entropy measures also require fewer training parameters than density-based clustering. The remaining parameters are subjected to robustness studies, and a detailed analysis is performed. In the second phase of the study, we further investigated Ramos and Abraham's (In: Proc 2003 IEEE Congr Evol Comput, Hoboken, NJ: IEEE Press; 2003. pp 1370,1375) contention that ant-based methods are particularly suited to incremental clustering. Contrary to expectations, we did not find substantial differences between the efficiencies of incremental and nonincremental approaches to data clustering. © 2009 Wiley Periodicals, Inc. [source]

Spatial distribution of ants (Hymenoptera: Formicidae), vine mealybugs and mealybug parasitoids in vineyards

JOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2010
N. Mgocheki
Abstract The mutualistic association between some ant species and honeydew-producing Hemiptera has been shown to influence the distribution patterns and abundance of these hemipterans and their natural enemies. We studied the spatial distribution patterns of three ant species, mealybugs and mealybug parasitoids for two consecutive growing seasons on three wine grape farms in the Western Cape, South Africa. During the study period, no ant or mealybug controls were applied. Ant and mealybug monitoring was conducted on a total of 21 ha using a presence/absence sampling system, while parasitoids were collected from infested mealybug females. Spatial analysis by distance indices was used to analyse spatial distribution of insects and ArcViewÔ was used to map the gap, patch and local association indices where significant association and disassociation occurred. Significant associations were found between some ants and parasitoids, while significant disassociations between the ants Crematogaster peringueyi and Linepithema humile; and also between Crematogaster peringueyi and Anoplolepis steingroeveri were found. Interspecific competition between ant species could play a role in the distribution of parasitoids and mealybugs. Our results stress the importance of monitoring for ants and mealybugs and further highlight the importance of restricted chemical applications against ants during the growing season. [source]

Mutualism, hybrid inviability and speciation in a tropical ant,plant

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008
G. LÉOTARD
Abstract Although biotic interactions are particularly intricate in the tropics, few studies have examined whether divergent adaptations to biotic interactions lead to speciation in tropical organisms. Ant,plant mutualisms are widespread in the tropics. Within Leonardoxa africana, two subspecies present contrasting defences against herbivores. Young leaves of subsp. africana are defended by mutualistic ants, whereas subsp. gracilicaulis satiates herbivores by synchronized leaf production. Subsp. africana possesses hollow internodes and many large foliar nectaries, housing and feeding ants. We detected no genetic introgression between the two subspecies in the contact zone between them. F1 hybrids were present. They were intermediate in phenotype, expressing reduced, nonfunctional but costly myrmecophilic traits. However, they suffered more herbivory than their parents. Hybrids remained small, failing to reach reproductive size, probably due to their maladapted defence phenotype. Hence, there could be a direct link between adaptation to mutualism and reproductive isolation: biotic interactions could be a driver of tropical diversity. [source]

Three nuclear genes for phylogenetic, SNP and population genetic studies of molluscs and other invertebrates

MOLECULAR ECOLOGY RESOURCES, Issue 1 2010
A. AUDZIJONYTE
Abstract The study reports new primers capable of amplifying fragments from three nuclear protein-coding genes in a variety of deep-sea molluscs and annelids , adenine nucleotide translocase (Ant), calmodulin (Cal) and cyclophilin A (CycA). The Ant primers appear to be restricted to bivalve molluscs, whereas the Cal and CycA primers also amplified appropriate gene fragments from Lepetodrilus gastropod molluscs and Osedax polychaete worms. The amplified fragment of Cal contains an intron in the molluscs, but no intron was detected in the Ant and CycA fragments from any of the tested animals. DNA sequences generated by the three primer sets exhibited one to 15 single nucleotide polymorphism sites in deep-sea vesicomyid clams and Osedax boneworms. The observed levels of polymorphism indicate that the genes are likely to be useful in both population genetic and phylogenetic analyses of different invertebrate taxa. [source]

The Ecology and Evolution of Ant,plant Interactions

AUSTRAL ECOLOGY, Issue 1 2010
DUNCAN MACKAY
No abstract is available for this article. [source]

Use of Premontane Moist Forest and Shade Coffee Agroecosystems by Army Ants in Western Panama

CONSERVATION BIOLOGY, Issue 1 2000
Dina L. Roberts
Behavioral and distributional studies of these two species have been confined largely to humid lowland forest. We conducted intensive systematic area searches at elevations between 1200 and 1800 m in western Panama to assess the distribution of both species in intact premontane moist forest, shade coffee plantations, and sun coffee plantations. Both species were repeatedly observed in forest, shade coffee plantations close to forest, and shade coffee plantations distant from forest. Neither species was observed in sun coffee plantations. We believe that retention of certain forest-like characteristics in the traditional shade coffee farm contributes to the persistence of these forest organisms in modified landscapes. Large canopy trees not only provide shade that buffers temperature extremes but also supply the ground layer with regular inputs of leaf litter and coarse woody debris from fallen trunks. Both E. burchelli and L. praedator hunt in leaf litter, and E. burchelli uses coarse woody debris as nesting sites ( bivouacs). There were significantly fewer potential bivouacs available in sun coffee plantations than in forest and shade coffee habitats. Also, litter depth was less in sun coffee than in forest and shade coffee. Our results provide the first evidence that shade coffee plantations can provide additional habitat for E. burchelli and L. praedator, top predators of the leaf litter arthropod community. E. burchelli and L. praedator act as critical links between swarm-attendant bird species and leaf-litter arthropods, providing an easily exploited food resource that would otherwise be unavailable for many birds. Continued conversion of shade coffee plantations to sun coffee plantations could have negative effects on army ants and associated biodiversity. Resumen: Las hormigas arrierras Neotropicales, Eciton burchelli y Labidus praedator ( Hymenoptera: Formicidae: Ecitoninae) son especies que requieren de extensas áreas de hábitat para cazar. Los estudios conductuales y de la distribución de estas especies se han realizado principalmente en bosques húmedos en tierras bajas. Desarrollamos búsquedas sistemáticas intensivas en elevaciones entre 1200 y 1800 msnm en Panama occidental para determinar la distribución de ambas especies en bosque húmedo premontano intacto, en plantaciones de café con y sin sombra. Las dos especies fueron observadas recurrentemente en bosque y en plantaciones de café de sombra cercanos y lejanos al bosque. Consideramos que la retención de ciertas características del bosque en las plantaciones de café de sombra contribuye a la persistencia de estos organismos de bosque en ambientes modificados. Los árboles no solo proporcionan sombra que amortigua la temperatura, sino que proporcionan hojarasca y restos leñosos de troncos caídos. Tanto E. burchelli como L. praedator cazan en la hojarasca, E. burchelli utiliza restos leñosos para anidar (vivaques). Encontramos significativamente menos vivaques en plantaciones de café sin sombra al compararlos con bosque y plantaciones de café con sombra. Asimismo, la profundidad de la capa de hojarasca fue menor en plantaciones de café sin sombra en comparación con bosque y plantaciones de café con sombra. Nuestros resultados proporcionan la primera evidencia de que las plantaciones con sombra proporcionan hábitat adicional para E. burchelli y L. praedator, depredadores de la comunidad de artrópodos en la hojarasca. E. burchelli y L. praedator actúan como eslabones críticos entre especies de aves que se alimentan de hormigas y los artrópodos de la hojarasca, proporcionando un recurso alimenticio fácilmente explotado que de otra manera no estaría disponible para muchas aves. La continua transformación de plantaciones de café con sombra a plantaciones sin sombra pudiera tener efectos negativos sobre las hormigas arrieras y la biodiversidad asociada. [source]

Visual experience and age affect synaptic organization in the mushroom bodies of the desert ant Cataglyphis fortis

DEVELOPMENTAL NEUROBIOLOGY, Issue 6 2010
Sara Mae Stieb
Abstract Desert ants of the genus Cataglyphis undergo an age-related polyethism from interior workers involved in brood care and food processing to short-lived outdoor foragers with remarkable visual navigation capabilities. The quick transition from dark to light suggests that visual centers in the ant's brain express a high degree of plasticity. To investigate structural synaptic plasticity in the mushroom bodies (MBs),sensory integration centers supposed to be involved in learning and memory,we immunolabeled and quantified pre- and postsynaptic profiles of synaptic complexes (microglomeruli, MG) in the visual (collar) and olfactory (lip) input regions of the MB calyx. The results show that a volume increase of the MB calyx during behavioral transition is associated with a decrease in MG numbers in the collar and, less pronounced, in the lip. Analysis of tubulin-positive profiles indicates that presynaptic pruning of projection neurons and dendritic expansion in intrinsic Kenyon cells are involved. Light-exposure of dark-reared ants of different age classes revealed similar effects. The results indicate that this structural synaptic plasticity in the MB calyx is primarily driven by visual experience rather than by an internal program. This is supported by the fact that dark-reared ants age-matched to foragers had MG numbers comparable to those of interior workers. Ants aged artificially for up to 1 year expressed a similar plasticity. These results suggest that the high degree of neuronal plasticity in visual input regions of the MB calyx may be an important factor related to behavior transitions associated with division of labor. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 408,423, 2010 [source]

Distribution of myrmecochorous species over the landscape and their potential long-distance dispersal by emus and kangaroos

DIVERSITY AND DISTRIBUTIONS, Issue 1 2008
María Calviño-Cancela
ABSTRACT Topographical heterogeneity can create a mosaic of substrate types leading to the formation of isolated plant populations. Seed dispersal then becomes crucial for the colonization of such suitable but remote substrate types. We surveyed the distribution of seven elaiosome-bearing species (myrmecochores) over 5 km2 of natural heathland in southwestern Australia. Ants are the standard means of dispersal of these species, which provide limited dispersal (usually of a few metres). Six species were associated with particular substrate types (dune or swale) and all occurred as discrete populations, on average 270,500 m apart, with closest dune edges 280 m apart. We evaluated the possible roles of emus and kangaroos as alternative agents of long-distance seed dispersal between substrate types. Their droppings contained viable seeds of three of the target species, as well as other myrmecochores, and were evenly distributed over the substrate types. While migration of these plant species between preferred substrate types seems unlikely when considering only their standard dispersal agents (ants), it is highly likely in the presence of emus (in particular) and kangaroos that act as non-standard dispersers. This may have important consequences for plant species conservation by increasing habitat connectivity and favouring regional persistence. [source]

Resource discovery in ant communities: do food type and quantity matter?

ECOLOGICAL ENTOMOLOGY, Issue 5 2010
JESSICA M. C. PEARCE-DUVET
1. Omnivorous woodland ant species trade off between the ability to find and behaviourally control food resources. Dominant species can limit the ability of subordinates to harvest certain food items. However, subordinate species, by being faster discoverers, could gain access to such food items by arriving at them first. 2. In this study, we tested the hypothesis that resource-directed discovery occurs in ant communities and that good discoverers preferentially discover high value resources. We did this by measuring time to discovery and the number of discoveries of high and low levels of two resource types, crickets and honey, for species occurring in Texas and Arizona woodland ant communities. 3. Ants discovered resources roughly 10 times faster in Texas than in Arizona. They discovered crickets more rapidly than honey in both communities, but there was no difference in the discovery of different resource levels. We also found that species were not biased in their discovery of different resource types or levels. 4. These results provide indirect evidence that discovery is directed by resource stimuli but that such directedness does not impact interspecific exploitative competition. [source]

Arboreal substrates influence foraging in tropical ants

ECOLOGICAL ENTOMOLOGY, Issue 4 2010
NATALIE A. CLAY
1. Physically complex substrates impart significant costs on cursorial central-place foragers in terms of time spent outside the nest and total distance travelled. Ants foraging in trees navigate varied surfaces to access patchy resources, thus providing an appropriate model system for examining interactions between foraging efficiency and substrates. 2. We expected that the speed of recruitment, body size distribution and species richness of foraging arboreal ants would differ predictably among common substrate types occurring on tropical tree trunks. We measured changes in ant abundance and species composition over time at baits placed on bare tree bark, moss-covered bark, and vine-like vegetation appressed to bark. We also measured average body size and body size frequency on the three substrate types. Ants discovered baits sooner and accumulated at baits relatively faster when using vine substrates as the primary foraging trail. Average body size was smaller on vine substrates than on bark. Experimental removal of vine and moss substrates nullified these differences. Contrary to our predictions, species richness and body size distributions did not differ among the three substrate types, due in part to the frequent presence of a few common ground-nesting species at baits on bare bark. 3. Our results collectively indicate that linear substrates facilitate access of foraging ants to patchy resources. Ant use of vine-like substrates appears to be opportunistic; vine use is not confined to certain species nor constrained by body size. [source]

Avoidance responses of an aphidophagous ladybird, Adalia bipunctata, to aphid-tending ants

ECOLOGICAL ENTOMOLOGY, Issue 4 2008
THOMAS H. OLIVER
Abstract 1.,Insect predators often aggregrate to patches of high prey density and use prey chemicals as cues for oviposition. If prey have mutualistic guardians such as ants, however, then these patches may be less suitable for predators. 2.,Ants often tend aphids and defend them against predators such as ladybirds. Here, we show that ants can reduce ladybird performance by destroying eggs and physically attacking larvae and adults. 3.,Unless ladybirds are able to defend against ant attacks they are likely to have adaptations to avoid ants. We show that Adalia bipunctata ladybirds not only move away from patches with Lasius niger ants, but also avoid laying eggs in these patches. Furthermore, ladybirds not only respond to ant presence, but also detect ant semiochemicals and alter oviposition strategy accordingly. 4.,Ant semiochemicals may signal the extent of ant territories allowing aphid predators to effectively navigate a mosaic landscape of sub-optimal patches in search of less well-defended prey. Such avoidance probably benefits both ants and ladybirds, and the semiochemicals could be regarded as a means of cooperative communication between enemies. 5.,Overall, ladybirds respond to a wide range of positive and negative oviposition cues that may trade-off with each other and internal motivation to determine the overall oviposition strategy. [source]

New role for majors in Atta leafcutter ants

ECOLOGICAL ENTOMOLOGY, Issue 5 2007
SOPHIE E. F. EVISON
Abstract 1.,Atta (Hymenoptera: Formicidae) leafcutter ants display the most polymorphic worker caste system in ants, with different sizes specialising in different tasks. The largest workers (majors) have large, powerful mandibles and are mainly associated with colony defence. 2.,Majors were observed cutting fallen fruit and this phenomenon was investigated in the field by placing mango fruit near natural Atta laevigata and Atta sexdens colonies in São Paulo State, Brazil. 3.,Ants cutting the fruit were significantly heavier (mean = 49.1 mg, SD = 11.1 mg, n= 90) than the ants carrying the fruit back to the nest (mean = 20.9 mg, SD = 9.2 mg, n= 90). 4.,Fruit pieces cut by majors were small (mean = 15.9 mg), approximately half the weight of leaf pieces (mean = 28.5 mg) cut and carried by media foragers. It is hypothesised that it is more difficult to cut large pieces from three-dimensional objects, like fruit, compared to two-dimensional objects, like leaves, and that majors, with their longer mandibles, can cut fruit into larger pieces than medias. 5.,The study shows both a new role for Atta majors in foraging and a new example of task partitioning in the organisation of foraging. [source]

Biodiversity in tropical agroforests and the ecological role of ants and ant diversity in predatory function

ECOLOGICAL ENTOMOLOGY, Issue 4 2006
STACY M. PHILPOTT
Abstract 1.,Intensive agricultural practices drive biodiversity loss with potentially drastic consequences for ecosystem services. To advance conservation and production goals, agricultural practices should be compatible with biodiversity. Traditional or less intensive systems (i.e. with fewer agrochemicals, less mechanisation, more crop species) such as shaded coffee and cacao agroforests are highlighted for their ability to provide a refuge for biodiversity and may also enhance certain ecosystem functions (i.e. predation). 2.,Ants are an important predator group in tropical agroforestry systems. Generally, ant biodiversity declines with coffee and cacao intensification yet the literature lacks a summary of the known mechanisms for ant declines and how this diversity loss may affect the role of ants as predators. 3.,Here, how shaded coffee and cacao agroforestry systems protect biodiversity and may preserve related ecosystem functions is discussed in the context of ants as predators. Specifically, the relationships between biodiversity and predation, links between agriculture and conservation, patterns and mechanisms for ant diversity loss with agricultural intensification, importance of ants as control agents of pests and fungal diseases, and whether ant diversity may influence the functional role of ants as predators are addressed. Furthermore, because of the importance of homopteran-tending by ants in the ecological and agricultural literature, as well as to the success of ants as predators, the costs and benefits of promoting ants in agroforests are discussed. 4.,Especially where the diversity of ants and other predators is high, as in traditional agroforestry systems, both agroecosystem function and conservation goals will be advanced by biodiversity protection. [source]