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Arthropods
Kinds of Arthropods Terms modified by Arthropods Selected AbstractsEffects of Shade-Tree Species and Crop Structure on the Winter Arthropod and Bird Communities in a Jamaican Shade Coffee Plantation,BIOTROPICA, Issue 1 2000Matthew D. Johnson ABSTRACT I examined the effects of two farm management variables, shade-tree species and crop structure, on the winter (dry season) arthropod and bird communities in a Jamaican shade coffee plantation. Birds and canopy arthropods were more abundant in areas of the plantation shaded by the tree Inga vera than by Pseudalbizia berteroana. The abundance of arthropods (potential pests) on the coffee crop, however, was unaffected by shade-tree species. Canopy arthropods, particularly psyllids (Homoptera), were especially abundant on Inga in late winter, when it was producing new leaves and nectar-rich flowers. Insectivorous and nectarivorous birds showed the strongest response to Inga; thus the concentration of birds in Inga may be a response to abundant food. Coffee-tree arthropod abundance was much lower than in the shade trees and was affected little by farm management variables, although arthropods tended to be more abundant in dense (unpruned) than open (recently pruned) areas of the plantation. Perhaps in response, leaf-gleaning insectivorous birds were more abundant in dense areas. These results underscore that although some shade coffee plantations may provide habitat for arthropod and bird communities, differences in farm management practices can significantly affect their abundances. Furthermore, this study provides evidence suggesting that bird communities in coffee respond to spatial variation in arthropod availability. I conclude that /. vera is a better shade tree than P. berteroana, but a choice in crop structures is less clear due to changing effects of prune management over time. [source] Effects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslandsECOGRAPHY, Issue 4 2005Jörg Perner Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source] High local species richness of parasitic wasps (Hymenoptera: Ichneumonidae; Pimplinae and Rhyssinae) from the lowland rainforests of Peruvian AmazoniaECOLOGICAL ENTOMOLOGY, Issue 6 2004Ilari E. Sääksjärvi Abstract., 1. The parasitic wasp family Ichneumonidae (Hymenoptera) is of great interest because it has been claimed that its species richness does not increase with decreasing latitude. 2. No extensive studies of the family have been conducted in South American localities. 3. Arthropods were sampled using 27 Malaise traps in the Allpahuayo,Mishana National Reserve (56 000 ha) in the north-eastern Peruvian Amazonian lowland rainforest. The total duration of the sampling programme was 185 Malaise trap months. 4. Altogether, 88 species were collected. This is one of the highest local pimpline and rhyssine species numbers ever recorded. A comparison with results from Mesoamerica revealed that at equal numbers of individuals sampled, the number of Pimplinae and Rhyssinae species in Peruvian Amazonia is at least twofold compared with lowland locations in Mesoamerica and somewhat higher than in the most species-rich Costa Rican higher altitude localities. 5. Non-parametric methods of estimating species richness were applied. These suggest that additional sampling would yield a considerable number of new Pimplinae and/or Rhyssinae species. [source] Arthropods and skin diseasesINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 9 2002Y. Isabel Zhu PhD First page of article [source] Arthropod responses to experimental fire regimes in an Australian tropical savannah: ordinal-level analysisAUSTRAL ECOLOGY, Issue 2 2000Alan N. Andersen Abstract Fire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long-term effect on ordinal-level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal-level resilience also occurs in Australia's tropical savannahs. The data are from a multidisciplinary, landscape-scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15,20 km2 compartments subjected to one of three fire regimes, each with three replicates: ,early' (annual fires lit early in the dry season), ,late' (annual fires lit late in the dry season), and ,unburnt' (fires absent during the five-year experimental period 1990,94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated-measures ANOVA. There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass-layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal-level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia. [source] New Bradoriid Arthropods from the Early Cambrian Balang Formation of Eastern Guizhou, South ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Jin PENG Abstract: The Early Cambrian Balang Formation is comprised of mudrock and shale, which was deposited in a shelf environment in the eastern part of Guizhou, south China. The Balang Fauna, which consists of seven phyla, occurs in the middle and upper parts of the Balang Formation. Arthropods are important constituents of the Balang Fauna and include a great number of trilobites, large bivalved arthropods, and newly-discovered well-preserved bradoriid fossils. The bradoriids present include three genera and four species: Comptaluta inflate (Cheng, 1974) emend Hou et al., 2002; Comptaluta kailiensis sp. nov, and Alutella elongeta sp. nov, Aluta sp. This faunal assemblage in the Balang Formation is distinguished from the Tsunyiella Chang, 1964, Songlinella Yin, 1978 and Kunmingella Hou, 1956 assemblage which occurs in the Niutitang and Mingxinsi formations of the Yangtze Platform in middle region of Guizhou and which is earlier than the Balang Formation in age. However, this assemblage resembles the ComptalutaÖpik, 1968 assemblage from the Early Cambrian Heilinpu Formation in Wuding County, Yuanan Province and from the Ordian Stage of the Cambrian of Australia. The great abundance of ComptalutaÖpik, 1968 and overall taxonomic diversity of the ComptalutaÖpik, 1968 assemblage set it distinctly apart from the Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 assemblages of the Balang Formation. Alutella Kobayashi et Kato, 1951 and Aluta Hou, 1956 also occur in the Early Cambrian Niutitang Formation of the Yangtze Platform of Guizhou. Individual Bradoriids from the Balang Formation are characterized by large size (>3 mm). The discovery of new Bradoriid assemblages not only expands the group's geographical range and assemblage affinities, but also indicates that Bradoriids migrated eastward from shallow-water to deeper-water environments during the Early Cambrian, indicating that they were capable of life in deeper-water, and adaptation to a new ecological setting. [source] Differing strategies for forming the arthropod body plan: Lessons from Dpp, Sog and Delta in the fly Drosophila and spider AchaearaneaDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2008Hiroki Oda In the insect Drosophila embryo, establishment of maternal transcription factor gradients, rather than cell,cell interactions, is fundamental to patterning the embryonic axes. In contrast, in the chelicerate spider embryo, cell,cell interactions are thought to play a crucial role in the development of the embryonic axes. A grafting experiment by Holm using spider eggs resulted in duplication of the embryonic axes, similar to the Spemann's organizer experiment using amphibian eggs. Recent work using the house spider Achaearanea tepidariorum has demonstrated that the homologs of decapentaplegic (dpp), short gastrulation (sog) and Delta, which encode a bone morphogenetic protein (BMP)-type ligand, its antagonist and a Notch ligand, respectively, are required in distinct aspects of axis formation. Achaearanea Dpp appears to function as a symmetry-breaking signal, which could account for Holm's results to some extent. Experimental findings concerning Achaearanea sog and Delta have highlighted differences in the mechanisms underlying ventral and posterior development between Drosophila and Achaearanea. Achaearanea ventral patterning essentially depends on sog function, in contrast to the Drosophila patterning mechanism, which is based on the nuclear gradient of Dorsal. Achaearanea posterior (or opisthosomal) patterning relies on the function of the caudal lobe, which develops from cells surrounding the blastopore through progressive activation of Delta-Notch signaling. In this review, we describe the differing strategies for forming the arthropod body plan in the fly and spider, and provide a perspective towards understanding the relationship between the arthropod and vertebrate body plans. [source] Herbivory patterns in mature sugar maple: variation with vertical canopy strata and tree ontogenyECOLOGICAL ENTOMOLOGY, Issue 1 2010SEAN C. THOMAS 1. Although leaf morphology and chemistry show profound changes as trees age, the consequences of such changes to herbivory have received little attention, particularly late in the ontogeny of canopy trees. 2. Using a mobile aerial lift for canopy access, patterns of leaf damage were evaluated in canopy-dominant mature sugar maple (Acer saccharum Marsh) trees ranging from ,20 to 70 cm in diameter, corresponding to an age range of ,40,180 years. 3. Herbivore damage patterns varied in relation to both vertical canopy position (among upper-, mid-, and lower-canopy positions) and with tree size. Damage types attributable to herbivores active on leaf surfaces, including leaf skeletonizers and leaf cutters (both principally Lepidoptera), and leaf stippling inducers (Hemiptera) showed decreases with tree size, and with increasing height in the canopy. In contrast, leaf damage from the most abundant gall-forming arthropod in the system, the eriophyid mite Vasates aceriscrumena, increased markedly with tree size. 4. The results indicate that herbivory patterns vary with both canopy stratum and with tree size in sugar maple, and that the relative strength of vertical stratification and tree ontogeny effects are similar in magnitude. The predominant patterns are of a decrease in herbivory with increasing height in the canopy and with tree size, but certain galling arthropods exhibit the reverse trends. [source] Temperature-dependent plasticity of segment number in an arthropod species: the centipede Strigamia maritimaEVOLUTION AND DEVELOPMENT, Issue 4 2008Vincent Vedel SUMMARY The evolution of arthropod segment number provides us with a paradox, because, whereas there is more than 20-fold variation in this character overall, most classes and orders of arthropods are composed of species that lack any variation in the number of segments. So, what is the origin of the higher-level variation? The centipede order Geophilomorpha is unusual because, with the exception of one of its families, all species exhibit intraspecific variation in segment number. Hence it provides an opportunity to investigate how segment number may change in a microevolutionary context. Here, we show that segment number can be directly altered by an environmental factor (temperature),this is the first such demonstration for any arthropod. The direction of the effect is such that higher temperature during embryogenesis produces more segments. This potentially explains an intraspecific cline in the species concerned, Strigamia maritima, but it does not explain how such a cline is translated into the parallel interspecific pattern of lower-latitude species having more segments. Given the plastic nature of the intraspecific variation, its link with interspecific differences may lie in selection acting on developmental reaction norms. [source] The fate of an intentional introduction of Formica lugubris to North America from EuropeJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2008A. J. Storer Abstract Red wood ants (Formica s.str.) are not prevalent in the forests of North America, but commonly occur in conifer and mixed conifer forests in northern Europe and Asia. In 1971, a European red wood ant species, Formica lugubris, was intentionally established in a 35-year-old predominantly mixed conifer plantation approximately 30 km north of QC, Canada. The purpose of its introduction was to evaluate the potential of this species as a biological control agent against conifer-defoliating Lepidoptera species. This red wood ant introduction was monitored periodically for about 5 years after establishment, but its long-term fate has not been reported. We visited this field site in 2005 and found that this species was well established, and we could locate some of the nests that resulted from the original release. We mapped and measured over 100 nests around the site of original release, which ranged from 5 cm in height to over 1 m. We estimated the population of introduced ants to have grown to over 8 million in the last 34 years. Significant clustering of nests suggests that these nests may be one supercolony. F. lugubris has become a dominant understory arthropod in this mixed forest, and is likely to have ecological impacts, including effects at the community and ecosystem level. [source] New arthropods from the Lower Devonian Hunsru¨ck Slate (Lower Emsian, Rhenish Massif, western Germany)PALAEONTOLOGY, Issue 2 2001Derek E. G. Briggs Four new genera and species of arthropod, Cambronatus brasseliWingertshellicus backesiEschenbachiellus wuttkensis and Magnoculus blindi, are described from the Hunsru¨ck Slate (Lower Emsian) of Germany. All four occur in the Wingertshell Member in the vicinity of Bundenbach. They preserve remarkable details of the ventral morphology, including the appendages, as a result of pyritization. In each case the body consists of just two tagmata, a cephalon and a large number of similar trunk somites. Both CambronatusWingertshellicus have fluke-like appendages making up a tail fan. The affinities of these arthropods lie with the Crustacea, apart from Magnoculus, which is an arachnomorph, but they do not fall within those clades with modern representatives. They show that morphologies other than those represented by trilobites and modern arthropod groups persisted long after the Cambrian, at least in muddy bottom marine settings. [source] Lack of discontinuous gas exchange in a tracheate arthropod, Leiobunum townsendi (Arachnida, Opiliones)PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2002John R. B. Lighton Abstract The discontinuous gas exchange cycle, characterized by stringent spiracular control and periods of near-zero external CO2 emission separated by ,bursts' of CO2 emission, has evolved independently in several taxa of tracheate arthropods. These include the hexapoda, diplopoda, and several arachnid taxa; ticks, pseudoscorpions and solphugids. This paper presents the first data on gas exchange kinetics in a harvestman (Arachnida; Opiliones). The experimental animal, Leiobunum townsendi Weed, from an arid area of the south-western United States, displayed a metabolic rate similar to those of other arthropods at 25 °C (129 ± 22 µW). Their CO2 emission kinetics showed, when the animals were motionless, only minor variations about a mean value of 0.0217 ± 0.0037 mL/h (n = 6, mean body mass 86 mg). Expressed on an intra-recording basis, the coefficient of variation of CO2 emission (= SD/MEAN), which is an index of short-term gas emission fluctuations and thus of spiracular control, had a mean value of only 0.082. In contrast, the coefficient of variation of animals employing a discontinuous gas exchange cycle is >,1.5. Gas exchange in opilionids, unlike the case with most other tracheate arthropods, may therefore be dominated by simple diffusion without a prominent role for wide modulations of spiracular conductance. Contributory to this conservative spiracular control strategy may be the weak degree of tracheation in opilionids, combined with circulating haemocyanin, which acts as both a transport medium and a buffering reservoir for respiratory gas exchange. [source] Mity model: Tetranychus urticae, a candidate for chelicerate model organismBIOESSAYS, Issue 5 2007Miodrag Grbic Chelicerates (scorpions, horseshoe crabs, spiders, mites and ticks) are the second largest group of arthropods and are of immense importance for fundamental and applied science. They occupy a basal phylogenetic position within the phylum Arthropoda, and are of crucial significance for understanding the evolution of various arthropod lineages. Chelicerates are vectors of human diseases, such as ticks, and major agricultural pests, such as spider mites, thus this group is also of importance for both medicine and agriculture. The developmental genetics of chelicerates is poorly understood and a challenge for the future progress for many aspects of chelicerate biology is the development of a model organism for this group. Toward this end, we are developing a chelicerate genetic model: the two-spotted spider mite Tetranychus urticae. T. urticae has the smallest genome of any arthropod determined so far (75 Mbp, 60% of the size of the Drosophila genome), undergoes rapid development and is easy to maintain in the laboratory. These features make T. urticae a promising reference organism for the economically important, poorly studied and species-rich chelicerate lineage. BioEssays 29:489,496, 2007. © 2007 Wiley Periodicals, Inc. [source] Effects of Shade-Tree Species and Crop Structure on the Winter Arthropod and Bird Communities in a Jamaican Shade Coffee Plantation,BIOTROPICA, Issue 1 2000Matthew D. Johnson ABSTRACT I examined the effects of two farm management variables, shade-tree species and crop structure, on the winter (dry season) arthropod and bird communities in a Jamaican shade coffee plantation. Birds and canopy arthropods were more abundant in areas of the plantation shaded by the tree Inga vera than by Pseudalbizia berteroana. The abundance of arthropods (potential pests) on the coffee crop, however, was unaffected by shade-tree species. Canopy arthropods, particularly psyllids (Homoptera), were especially abundant on Inga in late winter, when it was producing new leaves and nectar-rich flowers. Insectivorous and nectarivorous birds showed the strongest response to Inga; thus the concentration of birds in Inga may be a response to abundant food. Coffee-tree arthropod abundance was much lower than in the shade trees and was affected little by farm management variables, although arthropods tended to be more abundant in dense (unpruned) than open (recently pruned) areas of the plantation. Perhaps in response, leaf-gleaning insectivorous birds were more abundant in dense areas. These results underscore that although some shade coffee plantations may provide habitat for arthropod and bird communities, differences in farm management practices can significantly affect their abundances. Furthermore, this study provides evidence suggesting that bird communities in coffee respond to spatial variation in arthropod availability. I conclude that /. vera is a better shade tree than P. berteroana, but a choice in crop structures is less clear due to changing effects of prune management over time. [source] Emerging and poorly known viral inflammatory eye diseasesACTA OPHTHALMOLOGICA, Issue 2009M KHAIRALLAH Arthropod vector borne diseases are among the most important emergent infections. They include a wide variety of bacterial, viral, and parasitic diseases that are transmitted to humans by the bite of mosquito, tick, or other arthropod. Most of them are prevalent in tropical and subtropical areas, but they tend to spread into new regions mainly due to increasing temperatures worldwide, movement of people, increasing human population densities, wider dispersal of competent vectors, and transportation of goods and animals. Numerous arthropod vector borne diseases have been associated with uveitis. Among them, specific viral diseases recently emerged as important causes of uveitis in the developing and developed world. They include West Nile virus (WNV) infection, Rift Valley fever (RVF) , dengue fever (DF), and Chikungunya. These viral diseases have been recently associated with an array of ocular manifestations, including anterior uveitis, retinitis, chorioretinitis, retinal vaculitis, and optic nerve involvement. Proper clinical diagnosis of any of these infectious diseases is based on epidemiological data, history, systemic symptoms and signs, and the pattern of uveitis. The diagnosis is usually confirmed by detection of specific antibody in serum. A systematic ocular examination, showing fairly typical findings, can help establish an early clinical diagnosis of a specific systemic viral infection while serologic testing is pending. Prevention remains the mainstay for control of arthropod vector borne viral diseases. [source] The nematode,arthropod clade revisited: phylogenomic analyses from ribosomal protein genes misled by shared evolutionary biasesCLADISTICS, Issue 2 2007Stuart J. Longhorn Phylogenetic analysis of major groups of Metazoa using genomic data tends to recover the sister relationships of arthropods and chordates, contradicting the proposed Ecdysozoa (the molting animals), which group the arthropods together with nematodes and relatives. Ribosomal protein genes have been a major data source in phylogenomic studies because they are readily detected as Expressed Sequence Tags (ESTs) due to their high transcription rates. Here we address the debate about the recovery of Ecdysozoa in genomic data by building a new matrix of carefully curated EST and genome sequences for 25 ribosomal protein genes of the small subunit, with focus on new insect sequences in addition to the Diptera sequences generally used to represent the arthropods. Individually, each ribosomal protein gene showed low phylogenetic signal, but in simultaneous analysis strong support emerged for many expected groups, with support increasing linearly with increased gene number. In agreement with most studies of metazoan relationships from genomic data, our analyses contradicted the Ecdysozoa (the putative sister relationship of arthropods and nematodes), and instead supported the affinity of arthropods with chordates. In addition, relationships among holometabolan insects resulted in an unlikely basal position for Diptera. To test for biases in the data that might produce an erroneous arthropod,chordate affinity we simulated sequence data on tree topologies with the alternative arthropod,nematode sister relationships, applying a model of amino acid sequence evolution estimated from the real data. Tree searches on these simulated data still revealed an arthropod,chordate grouping, i.e., the topologies used to simulate the data were not recovered correctly. This suggests that the arthropod,chordate relationships may be obtained erroneously also from the real data even if the alternative topology (Ecdysozoa) represents the true phylogeny. Whereas denser taxon sampling in the future may recover the Ecdysozoa, our analyses demonstrate that recent phylogenomic studies may be affected by as yet unspecified biases in amino acid sequence composition in the model organisms with available genomic data. © The Willi Hennig Society 2007. [source] Use of Premontane Moist Forest and Shade Coffee Agroecosystems by Army Ants in Western PanamaCONSERVATION BIOLOGY, Issue 1 2000Dina 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] Evolutionary conservation and divergence of the segmentation process in arthropodsDEVELOPMENTAL DYNAMICS, Issue 6 2007Wim G. M. Damen Abstract A fundamental characteristic of the arthropod body plan is its organization in metameric units along the anterior,posterior axis. The segmental organization is laid down during early embryogenesis. Our view on arthropod segmentation is still strongly influenced by the huge amount of data available from the fruit fly Drosophila melanogaster (the Drosophila paradigm). However, the simultaneous formation of the segments in Drosophila is a derived mode of segmentation. Successive terminal addition of segments from a posteriorly localized presegmental zone is the ancestral mode of arthropod segmentation. This review focuses on the evolutionary conservation and divergence of the genetic mechanisms of segmentation within arthropods. The more downstream levels of the segmentation gene network (e.g., segment polarity genes) appear to be more conserved than the more upstream levels (gap genes, Notch/Delta signaling). Surprisingly, the basally branched arthropod groups also show similarities to mechanisms used in vertebrate somitogenesis. Furthermore, it has become clear that the activation of pair rule gene orthologs is a key step in the segmentation of all arthropods. Important findings of conserved and diverged aspects of segmentation from the last few years now allow us to draw an evolutionary scenario on how the mechanisms of segmentation could have evolved and led to the present mechanisms seen in various insect groups including dipterans like Drosophila. Developmental Dynamics 236:1379,1391, 2007. © 2007 Wiley-Liss, Inc. [source] The tritocerebrum and the clypeolabrum in mandibulate arthropods: segmental interpretationsACTA ZOOLOGICA, Issue 3 2010Jacques Bitsch Abstract Bitsch, J. and Bitsch, C. 2010. The tritocerebrum and the clypeolabrum in mandibulate arthropods: segmental interpretations. ,Acta Zoologica (Stockholm) 91: 249,266 Different interpretations of the segmental composition of the head in mandibulate arthropods are critically reviewed, with particular focus on three closely associated structures: the tritocerebrum, the stomatogastric nervous system and the clypeolabrum. The main conclusions arising from the different discussions are the following. (1) Each tritocerebral ganglion has a dual composition, clearly discernable in some crustacean and hexapod species, including a dorsal portion connected with the second antennae and a ventral portion connected with the stomatogastric nervous system via the frontal ganglion. (2) The suboesophageal commissure linking the tritocerebral lobes of the two sides, can be wholly ascribed to the tritocerebral segment. (3) The stomatogastric nervous system is a morphologically autonomous system that is not fundamentally affected by head metamerization. (4) The clypeolabrum, the epistome,labrum and the hypostome are regarded as homologous formations. The clypeolabrum represents a fundamental structure of the head probably present in the arthropod ground plan. Its close spatial and developmental association with the stomodeum and its derivative, the stomatogastric nervous system, suggests that it is an anterior outgrowth of the forehead arising from a preoral territory (presegmental acron or protocerebral,ocular region?) and secondarily connected with the tritocerebrum, rather than derived from a pair of reduced appendages. [source] The mushroom bodies , prominent brain centres of arthropods and annelids with enigmatic evolutionary originACTA ZOOLOGICA, Issue 1 2010Rudi Loesel Abstract Loesel, R. and Heuer, C.M. 2010. The mushroom bodies , prominent brain centres of arthropods and annelids with enigmatic evolutionary origin. ,Acta Zoologica (Stockholm) 91: 29,34 Mushroom bodies (MBs) are the most prominent and conspicuous neuropils in the brain of arthropods, onychophorans and vagile polychaete annelids but have not been described in any other animal group with complex brain architecture. Due to a number of unique neuroanatomical characters MBs can easily be identified and distinguished from other brain centres. However, their evolutionary origin and the question whether MBs are homologous structures is still under debate. This paper will briefly summarize the available morphological data and their implications with respect to the molecular evidence on early metazoan radiation. Unraveling the origin of MBs is an example of the challenges neurophylogenists will face in the future, especially so since it will signify a major step towards reconstructing early metazoan brain evolution. [source] Morpho-anatomy of the lobopod Magadictyon cf. haikouensis from the Early Cambrian Chengjiang Lagerstätte, South ChinaACTA ZOOLOGICA, Issue 4 2007Jianni Liu Abstract Magadictyon haikouensis (Luo and Hu, 1999) from the Early Cambrian Chengjiang Lagerstätte, an incomplete specimen of a large lobopod with strong appendages, has been regarded as related to the lobopods Microdictyon and Onychodictyon. Newly discovered complete specimens of Magadictyon cf. haikouensis (found by the Early Life Institute field team) show that the taxon, in addition to its strong appendages with appendicules, also had a head bearing similar caecum-like structures to those of the arthropod Naraoia and Chelicerate, ,Peytoia'-like mouthparts and frontal appendages. Because of their similarity, the caecum-like structures of Magadictyon cf. haikouensis are considered to be homologous with those of stem-group arthropods. The ,Peytoia'-like mouthparts and the frontal appendages are similar to those of the AOPK (Anomalocaris,Opabinia,Pambdelurion,Kerygmachela) group. In addition, the appendages with appendicules show that Magadictyon cf. haikouensis is closely related to Onychodictyon. Therefore, Magadictyon cf. haikouensis is regarded here as a rare transitional form between lobopods and arthropods. Besides, together with other lobopods, the morphology of Magadictyon cf. haikouensis demonstrates that the Cambrian lobopods appear to have been diverse and not particularly closely related to one another, and do not seem to represent a monophyletic clade. [source] Effects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslandsECOGRAPHY, Issue 4 2005Jörg Perner Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source] Corticolous arthropods under climatic fluctuations: compensation is more important than migrationECOGRAPHY, Issue 1 2005Andreas Prinzing Animals can cope with fluctuating climates by physiological tolerance, tracking of climatic fluctuations (migration) and compensatory redistribution among (micro)habitats (compensation). Compensation is less demanding and thus more important than migration at large geographic scales. It is not clear however which strategy is more important at the small scale of a microhabitat landscape. I investigated how six arthropod species (Collembola, Oribatei, Psocoptera, Isopoda) respond to microclimatic fluctuations at the surface of exposed tree trunks. Across a nine-month period I characterized the microclimatic zonation of 299 trunks, and focally sampled the arthropods from different microhabitat types (different cryptogam species and bark crevices) within different microclimatic zones. I found that compensatory microhabitat-use was a general phenomenon. The distribution of all species across microhabitats was influenced significantly by ambient microclimate. Also, the arthropods' microhabitat use changed throughout their ontogeny, and microhabitats were used even if they were rare. Most interestingly, the arthropods responded to microclimatic fluctuations primarily by redistribution among microhabitats and less by fluctuations of overall abundances across all microhabitats. Hence compensation was more important than migration. The animals moved for centimeters to decimeters rather than for decimeters to meters; they perceived and utilized their environment primarily at the finest, but also most complex scale. This has implications for the resilience of arthropod populations, their interactions with cryptogams and the turnover of species between macrohabitats. [source] Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus groveECOLOGICAL ENTOMOLOGY, Issue 3 2010JOSEP 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] Herbivory patterns in mature sugar maple: variation with vertical canopy strata and tree ontogenyECOLOGICAL ENTOMOLOGY, Issue 1 2010SEAN C. THOMAS 1. Although leaf morphology and chemistry show profound changes as trees age, the consequences of such changes to herbivory have received little attention, particularly late in the ontogeny of canopy trees. 2. Using a mobile aerial lift for canopy access, patterns of leaf damage were evaluated in canopy-dominant mature sugar maple (Acer saccharum Marsh) trees ranging from ,20 to 70 cm in diameter, corresponding to an age range of ,40,180 years. 3. Herbivore damage patterns varied in relation to both vertical canopy position (among upper-, mid-, and lower-canopy positions) and with tree size. Damage types attributable to herbivores active on leaf surfaces, including leaf skeletonizers and leaf cutters (both principally Lepidoptera), and leaf stippling inducers (Hemiptera) showed decreases with tree size, and with increasing height in the canopy. In contrast, leaf damage from the most abundant gall-forming arthropod in the system, the eriophyid mite Vasates aceriscrumena, increased markedly with tree size. 4. The results indicate that herbivory patterns vary with both canopy stratum and with tree size in sugar maple, and that the relative strength of vertical stratification and tree ontogeny effects are similar in magnitude. The predominant patterns are of a decrease in herbivory with increasing height in the canopy and with tree size, but certain galling arthropods exhibit the reverse trends. [source] Effects of aphids on foliar foraging by Argentine ants and the resulting effects on other arthropodsECOLOGICAL ENTOMOLOGY, Issue 1 2008CRYSTAL D. GROVER Abstract 1.,Although interactions between ants and honeydew-producing insects have received considerable study, relatively little is known about how these interactions alter the behaviour of ants in ways that affect other arthropods. In this study, field and greenhouse experiments were performed that examined how the presence of aphids (Aphis fabae solanella) on Solanum nigrum influenced the foraging behaviour of Argentine ants (Linepithema humile) and, in turn, modified the extent to which ants deter larval lacewings (Chrysoperla rufilabris), which are known aphid predators. 2.,A field experiment demonstrated that the level of foliar foraging by ants increased linearly with aphid abundance, whereas no relationship existed between the level of ground foraging by ants and aphid abundance. 3.,In the greenhouse, as in the field, foliar foraging by ants greatly increased when aphids were present. Higher levels of foliar foraging led to a twofold increase in the likelihood that ants contacted aphid predators. As a result of these increased encounters with ants, lacewing larvae were twice as likely to be removed from plants with aphids compared with plants without aphids. Once contact was made, however, the behaviour of ants towards lacewing larvae appeared similar between the two experimental groups. 4.,Argentine ants drive away or prey upon a diversity of arthropod predators and parasitoids, but they also exhibit aggression towards certain herbivores. Future work should attempt to quantify how the ecological effects that result from interactions between honeydew-producing insects and invasive ants, such as L. humile, differ from those that result from interactions between honeydew-producing insects and native ants. [source] Achieving high sexual size dimorphism in insects: females add instarsECOLOGICAL ENTOMOLOGY, Issue 3 2007TOOMAS ESPERK Abstract 1.,In arthropods, the evolution of sexual size dimorphism (SSD) may be constrained by a physiological limit on growth within each particular larval instar. A high SSD could, however, be attained if the larvae of the larger sex pass through a higher number of larval instars. 2.,Based on a survey of published case studies, the present review shows that sex-related difference in the number of instars is a widespread phenomenon among insects. In the great majority of species with a sexually dimorphic instar number, females develop through a higher number of instars than males. 3.,Female-biased sexual dimorphism in final sizes in species with sexually dimorphic instar number was found to considerably exceed a previously estimated median value of SSD for insects in general. This suggests a causal connection between high female-biased SSD, and additional instars in females. Adding an extra instar to larval development allows an insect to increase its adult size at the expense of prolonged larval development. 4.,As in the case of additional instars, SSD is fully formed late in ontogeny, larval growth schedules and imaginal sizes can be optimised independently. No conflict between selective pressures operating in juvenile and adult stages is therefore expected. 5.,In most species considered, the number of instars also varied within the sexes. Phenotypic plasticity in instar number may thus be a precondition for a sexual difference in instar number to evolve. [source] Horizontal transmission of Wolbachia in a Drosophila communityECOLOGICAL ENTOMOLOGY, Issue 4 2005Eleanor R. Haine Abstract., 1.,Wolbachia bacteria are reproductive parasites of arthropods and infect an estimated 20% of all insect species worldwide. In order to understand patterns of Wolbachia infection, it is necessary to determine how infections are gained or lost. Wolbachia transmission is mainly vertical, but horizontal transmission between different host species can result in new infections, although its ecological context is poorly understood. Horizontal transmission is often inferred from molecular phylogenies, but could be confounded by recombination between different Wolbachia strains. 2.,This study addressed these issues by using three genes: wsp, ftsZ, and groE, to study Wolbachia infections in fruit- and fungus-feeding Drosophila communities in Berkshire, U.K. 3.,Identical sequences were found for all three genes in Drosophila ambigua and Drosophila tristis. This suggests horizontal transmission of Wolbachia between these two previously unstudied Drosophila species, which may be the result of the two host species sharing the same food substrates or parasites. 4.,Wolbachia infections might be lost from species due to curing by naturally occurring antibiotics and the presence of these is likely to vary between larval food substrates. 5.,It was investigated whether Wolbachia incidence was lower in fungus-feeding than in fruit-feeding Drosophila species, but no significant difference based on food substrate was found. [source] Colonisation of pitcher plant leaves at several spatial scalesECOLOGICAL ENTOMOLOGY, Issue 4 2003M. Kurtis Trzcinski Abstract., 1.,The effect of meso-scale (zone within bog and local plant density) and fine-scale (leaf length and resource availability) factors on the colonisation of pitcher plant leaves by arthropods was examined in an eastern Canadian bog. 2.,In spring, the abundances of three arthropods, the mosquito Wyeomyia smithii, the midge Metriocnemus knabi, and the mite Sarraceniopus gibsoni, were determined for plots with low, moderate, and high densities of pitcher plants. All overwintering inhabitants were then removed from the plots. Newly opening leaves were colonised from outside the plots, and arthropod abundances were assessed again in autumn. 3.,Pitcher plant fauna varied in their response to the meso-scale factors. In autumn (soon after colonisation), midges were more abundant in areas with high densities of pitcher plants. The relationship between mosquito abundance and plant density, and the variation in abundance among zones within the bog in the spring, were probably due to overwintering mortality. 4.,All taxa responded to the fine-scale factors, leaf length, and capture rate, in the autumn, but the strength of the responses frequently depended on a meso-scale factor (plant density), in which responses were usually strongest where plants were sparse. Thus, the interaction between meso- and fine-scale processes needs to be considered when interpreting patterns of species abundance within arthropod assemblages in pitcher plant leaves. [source] Community effects of praying mantids: a meta-analysis of the influences of species identity and experimental designECOLOGICAL ENTOMOLOGY, Issue 4 2002William F. Fagan Abstract ,1. Generalist arthropod predators are ubiquitous in terrestrial ecosystems but experimental studies have yielded little agreement as to their effects on prey assemblages. Drawing on results from a suite of experimental field studies, a meta-analysis was conducted of the impact of praying mantids (Mantodea: Mantidae) on arthropod assemblages in order to identify predictable and unpredictable effects of these extremely generalised predators. 2. Results across different experiments were synthesised using the log response ratio framework, with a focus on quantifying net mantid impacts on arthropod density across taxonomic orders and trophic levels of arthropods, paying special attention to the contribution of mantid species identity and experimental design variables, such as the use of cages, length of experiment, and manipulated mantid density. 3. Calculated on a per mantid-day basis, the net impacts of Tenodera sinensis on arthropod density were generally weaker but more predictable than the effects of Mantis religiosa. Mantids in general had weak negative effects on density for most taxa but exhibited strong negative and positive effects on some taxa. Tenodera sinensis tended to have negative effects on Homoptera, Diptera, and Hemiptera and herbivores as a group, however M. religiosa exhibited greater variation in response of different taxa that appeared to be affected more strongly by experimental design. The effects of Stagmomantis carolina tended to be negative or non-significant. 4. Experimental cages had little influence on either the sign or magnitude of net community impacts for T. sinensis, however cage experiments reversed the sign of the mean effect for two of six taxonomic orders when the experimental predator was M. religiosa. Cages also increased the variability of effect size greatly for M. religiosa but not for T. sinensis. 5. It was concluded that it is possible to use log response ratios to determine general, predictable trends in a well-studied system. Similar meta-analyses of generalist predator effects in other systems should produce predictions of how these predators influence food webs, an important step towards defining more clearly the influences of generalist predators on community structure and dynamics. [source] | ||||||||||||||||||||||||||||||||||||||||||||||