bluuebunny/crossref_metadata_2025_split huggingface dataset:
Manipulating the jasmonate response: How do methyl jasmonate additions mediate characteristics of aboveground and belowground mutualisms?
Authors: Toby Kiers E. , Adler Lynn S. , Grman Emily L. , Van Der Heijden Marcel G. A. 
Published: August 2009

Summary1. Plants use a range of sophisticated strategies to protect themselves against herbivores and pathogens, such as the production of jasmonates, a group of plant hormones that prime the plant’s defense system upon attack. However, defense‐related mechanisms, such as the jasmonate response, play a more diverse role than previously appreciated. Jasmonates also regulate key mutualist relationships, leading to a suit of potential conflicting selection pressures as a single response is employed to mediate multiple species interactions.2. Here, we experimentally manipulate the host’s jasmonate response and document the impact on two key plant mutualisms: (i) changes to arbuscular mycorrhizal symbionts belowground (ii) modifications to floral traits affecting pollinator mutualists aboveground. By exogenously applying a range of methyl jasmonate solutions to cucumber plant roots grown with and without mycorrhizal fungi, we are able to examine the potential costs of the jasmonate response to both above and belowground mutualists.3. We demonstrate that the negative effect of jasmonates on floral traits depends on whether the plant is mycorrhizal or nonmycorrhizal. Mycorrhization had a positive effect on floral traits, but benefits were lost with jasmonate application. While low levels of jasmonate decreased floral traits, these same jasmonate levels increased colonization by the mycorrhizal symbiont three‐fold, but only under high phosphorus conditions.4. Our results highlight potential conflicts for the host in the regulation of their mutualists under different conditions and suggest that the overall impact of the jasmonate response depends on the plant mycorrhizal status and its nutrient context.5. These findings suggest that increasing the jasmonate response may lead to differential costs and benefits for plants and their mutualists, and highlight potential conflictin planta, with mycorrhizal symbionts benefiting from intermediate levels of jasmonates while certain floral traits can be depressed at this same level.
Disturbance facilitates rapid range expansion of aspen into higher elevations of the Rocky Mountains under a warming climate
Authors: Landhäusser Simon M. , Deshaies Dominique , Lieffers Victor J. 
Published: August 2009

AbstractAim  Trembling aspen (Populus tremuloides Michx.) is absent in the upper foothills region of west‐central Alberta because of the cold conditions and short growing season at this high elevation. However, in recent years it appears that aspen has been establishing from seed in this zone and that it has been doing so mainly as a result of forest harvesting. The objectives of this study were to determine the frequency of and types of microsite required for the successful establishment of aspen seedlings at these higher elevations.Location  Rocky Mountains Upper Foothills Natural Subregion of west‐central Alberta, Canada.Methods  The current distribution of mature aspen and the presence and absence of aspen seedlings in harvested areas were determined in an area c. 300 km2 in size, using ground and aerial surveys. In an intensive study, 12 belt transects (180 m long and 5 m wide) were established in areas disturbed by forest harvesting at high elevations where no aspen was present prior to harvesting. Transects were surveyed seven growing seasons after disturbance and the microsites occupied by aspen seedlings were characterized according to their substrate and microtopography. Similarly, the availability of different substrates and microtopographic positions were assessed by systematic point sampling on these sites.Results  On level surfaces, aspen seedling regeneration was found up to 200 m higher in elevation than the mature aspen in the original undisturbed forests. Overall, there were 428 seedlings ha−1 established on these transects, and the age distribution indicates that aspen seedlings had established in each of the seven growing seasons since the disturbance. Nearly all of the seedlings (93%) were established on mineral soil microsites and virtually no seedlings were established on undisturbed forest floor layers. Significantly more seedlings were found in concave microtopographic positions.Main conclusions  This study indicates that aspen establishment from seed is currently not a stochastic event and demonstrates that aspen is rapidly expanding its range upslope in the Canadian Rocky Mountain region as a result of forest management practices that expose mineral soil substrates in conjunction with a warming climate. The change in canopy composition from conifer to deciduous forests at these higher elevations will have far‐reaching implications for ecosystem processes and functions.
Molecular clocks keep dispersal hypotheses afloat: evidence for trans‐Atlantic rafting by rodents
Authors: Rowe Diane L. , Dunn Katherine A. , Adkins Ronald M. , Honeycutt Rodney L. 
Published: August 2009

AbstractAim In order to resolve disputed biogeographical histories of biota with Gondwanan continental distributions, and to assess the null hypothesis of vicariance, it is imperative that a robust geological time‐frame be established. As an example, the sudden and coincident appearance of hystricognath rodents (Rodentia: Hystricognathi) on both the African and South American continents has been an irreconcilable controversy for evolutionary biologists, presenting enigmas for both Gondwanan vicariance and Late Eocene dispersal hypotheses. In an attempt to resolve this discordance, we aim to provide a more robust phylogenetic hypothesis and improve divergence‐date estimates, which are essential to assessing the null hypothesis of vicariance biogeography.Location The primary centres of distribution are in Africa and South America.Methods We implemented parsimony, maximum‐likelihood and Bayesian methods to generate a phylogeny of 37 hystricognath taxa, the most comprehensive taxonomic sampling of this group to date, on the basis of two nuclear gene regions. To increase phylogenetic resolution at the basal nodes, these data were combined with previously published data for six additional nuclear gene regions. Divergence dates were estimated using two relaxed‐molecular‐clock methods, Bayesianmultidivtimeand nonparametric rate smoothing.Results Our data do not support reciprocal monophyly of African and South American lineages. Indeed, Old World porcupines (i.e. Hystricomorpha) appear to be more closely related to New World lineages (i.e. Caviomorpha) than to other Old World families (i.e. Bathyergidae, Petromuridae and Thryonomyidae). The divergence between the monophyletic assemblage of South American lineages and its Old World ancestor was estimated to have occurredc. 50 Ma.Main conclusions Our phylogenetic hypothesis and divergence‐date estimates are strongly at odds with Gondwanan‐vicariance isolating mechanisms. In contrast, our data suggest that transoceanic dispersal has played a significant role in governing the contemporary distribution of hystricognath rodents. Molecular‐clock analyses imply a trans‐Tethys dispersal event, broadly confined to the Late Cretaceous, and trans‐Atlantic dispersal within the Early Eocene. Our analyses also imply that the use of the oldest known South American rodent fossil as a calibration point has biased molecular‐clock inferences.
The outer membrane of a heterocyst‐forming cyanobacterium is a permeability barrier for uptake of metabolites that are exchanged between cells
Authors: Nicolaisen Kerstin , Mariscal Vicente , Bredemeier Rolf , Pernil Rafael , Moslavac Sunčana , López‐Igual Rocío , Maldener Iris , Herrero Antonia , Schleiff Enrico , Flores Enrique 
Published: August 2009

SummaryThe multicellular Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can fix N2 in differentiated cells called heterocysts, which exchange nutritional and regulatory compounds with the neighbour photosynthetic vegetative cells. The outer membrane of this bacterium is continuous along the filament defining a continuous periplasmic space. The Anabaena alr0075, alr2269 and alr4893 gene products were characterized as Omp85‐like proteins, which are generally involved in outer membrane protein biogenesis. Open reading frame alr2269 is the first gene of an operon that also carries genes for lipopolysaccharide lipid A biosynthesis including alr2270 (an lpxC homologue). Strains carrying inactivating alr2269 or alr2270 constructs showed enhanced sensitivity to erythromycin, SDS, lysozyme and proteinase K suggesting that they produce an outer membrane with increased permeability. These strains further exhibited increased uptake of sucrose, glutamate and, to a lesser extent, a few other amino acids. Increased uptake of the same metabolites was obtained by mechanical fragmentation of wild‐type Anabaena filaments. These results document that the outer membrane is a permeability barrier for metabolites such as sucrose and glutamate, which are subjected to intercellular exchange in the diazotrophic filament of heterocyst‐forming cyanobacteria.
Small heat‐shock proteins and leaf cooling capacity account for the unusual heat tolerance of the central spike leaves inAgave tequilanavar. Weber
Authors: LUJÁN ROSARIO , LLEDÍAS FERNANDO , MARTÍNEZ LUZ MARÍA , BARRETO RITA , CASSAB GLADYS I. , NIETO‐SOTELO JORGE 
Published: August 2009

ABSTRACTAgaves are perennial crassulacean acid metabolism (CAM) plants distributed in tropical and subtropical arid environments, features that are attractive for studying the heat‐shock response. In agaves, the stress response can be analysed easily during leaf development, as they form a spirally shaped rosette, having the meristem surrounded by folded leaves in the centre (spike) and the unfolded and more mature leaves in the periphery. Here, we report that the spike ofAgave tequilanais the most thermotolerant part of the rosette withstanding shocks of up to 55 °C. This finding was inconsistent with the patterns of heat‐shock protein (Hsp) gene expression, as maximal accumulation ofHsptranscripts was at 44 °C in all sectors (spike, inner, middle and outer). However, levels of small HSP (sHSP)‐CI and sHSP‐CII proteins were conspicuously higher in spike leaves at all temperatures correlating with their thermotolerance. In addition, spike leaves showed a higher stomatal density and abated more efficiently their temperature several degrees below that of air. We propose that the greater capacity for leaf cooling during the day in response to heat stress, and the elevated levels of sHSPs, constitute part of a set of strategies that protect the SAM and folded leaves ofA. tequilanafrom high temperatures.
Phylogenetic systematics of the gondwanan Empis macrorrhyncha group (Diptera, Empididae, Empidinae)
Authors: DAUGERON CHRISTOPHE , D’HAESE CYRILLE A. , PLANT ADRIAN R. 
Published: August 2009

Abstract.The Empis macrorrhyncha group (Diptera: Empididae) from cool to warm temperate areas of South America and Australia is diagnosed and cladistically analysed, and five new species, Empis animosasp.n., E. austerasp.n., E. maculosasp.n., E. occidentalissp.n. and E. pedivillosulasp.n., are described. Cladistic analysis of 23 adult morphological characters for 14 species of the group generated a single tree of 28 steps (CI = 0.82; RI = 0.93). Monophyly was established on the basis of a single apomorphy, possession of a bilobed cercus of the male hypopygium. Three main clades were inferred: clade 1 included three Patagonian and a single southwestern Australian species; clade 2 included two species from southeastern Australia; clade 3 included a large Patagonian group of five species and a single southeastern Australian species. The E. fulvicollis complex (clade 1) is a sister‐group of the E. macrorrhyncha complex (clades 2 + 3). A provisional historical biogeographic hypothesis is advanced correlating the appearance of the South American and Australian sister lineages with the timing of the break‐up of Gondwana.
Systematic position of Triplosoba, hitherto the oldest mayfly, from Upper Carboniferous of Commentry in Central France (Insecta: Palaeodictyopterida)
Authors: PROKOP JAKUB , NEL ANDRÉ 
Published: August 2009

Abstract.A revision of the holotype of Triplosoba pulchella (Brongniart, 1883), the ‘oldest mayfly’, provides evidence for new attribution to Palaeodictyopterida sensu Bechly. New character states derived from the venation pattern, namely the basal connection of the median anterior with the radius and radius posterior in the forewing, the median anterior remote from the radius posterior and basally fused with the median posterior in the hindwing, and a strong costal margin formed by two connected or fused veins with a series of small spines (costa and subcosta anterior), support an ordinal placement of Triplosoba into Palaeodictyopterida (inclusive of Diphanopterodea sensu Bechly) versus Ephemeroptera as supposed by previous authors. It shares with Diaphanopterodea a potential synapomorphy in the presence of long curved connections between the three stems of the radius, media, and cubitus in the basal part of the forewing, a character not present in other groups of Palaeodictyopterida.
Diel and daily fluctuations in virioplankton production in coastal ecosystems
Authors: Winget Danielle M. , Wommack K. Eric 
Published: August 2009

SummaryViruses saturate the world around us, yet a basic understanding of how viral impacts on microbial host organisms vary over days to hours, which typify the replication cycles of aquatic viruses, remains elusive. Thus, diel patterns of viral production (VP) in Chesapeake Bay surface waters were examined on five sampling dates. Day‐to‐day variations in VP in the Chesapeake and coastal California surface waters were also investigated. Significant variations in VP were detected over 24 h cycles during four of five studies, but rates did not vary significantly over the course of a few days in either location. Diel patterns of VP displayed seasonality with shorter viral assemblage turnover times and shorter times to maximum viral abundance in summer, implying shorter replication cycles for virus–host systems in warmer months. No correlation was found between VP and time of day, likely due to seasonal changes in the diel patterns of VP. This analysis significantly increases our knowledge of the short‐term patterning of in situ VP, and thus viral impacts, and suggests that variations in viral biology in response to changes in host communities or physio‐chemical properties affect both diel and seasonal cycles and magnitudes of VP.
Using avatars and virtual environments in learning: What do they have to offer?
Authors: Falloon Garry 
Published: August 2009

AbstractThis paper explores and discusses arguments for the use of virtual environments and interactive avatars in supporting the achievement of student learning goals within conventional educational contexts. It describes and evaluates arguments promoted by some authors (eg,van den Brekel, 2007;Deuchar & Nodder, 2003;Dickey, 2003;Facer, 2004;de Freitas, 2006;de Freitas & Oliver, 2006;Garris, Ahlers & Driskell, 2002;JISC, 2007;Martino, 2007;Prensky, 2004;Prensky, 2007) relating to advantages from gaming and avatar use, ranging from enhanced engagement in learning activities, through to more purposeful and focussed communication, and, when used in group situations, better cooperation and collaboration between students. It explores the potential of avatar environments to act as powerful communication mediums for students to display knowledge and understanding, and engage in the development of ‘higher order thinking skills, such as interpreting, analysing, evaluating, synthesising and solving complex problems’.It also introduces and discusses the avatar‐based authoring program MARVIN, and identifies potential for its use as a digital storytelling tool to assist students in communicating outcomes from units of learning, and in supporting the development of a range of key learning competencies identified in the New Zealand Curriculum Framework (Ministry of Education, 2007). It profiles a successful example of the classroom‐based use of MARVIN within a community project undertaken by groups of year 7 and 8 students at two Hamilton intermediate schools, and identifies how the program supported studentthinkingandrelating to otherskey competencies (Ministry of Education, 2007).
Re‐Thinking Migrants’ Networks and Social Capital: A Case Study of Iranians in Turkey
Authors: Koser Akcapar Sebnem 
Published: August 2009

AbstractExisting research on international migration has focused on the importance of social networks and social capital in the countries of origin and destination. However, much less is known about the importance of social networks and associated social capital in transit countries. Drawing on ethnographic research on Iranian transit migrants in Turkey, this paper argues that migrant networks and social capital are equally important in transit countries. These networks, however, do not always generate positive social capital for Iranian migrants as there are scarce resources and there is no “enforceable trust”. Iranian migrant networks reorganized in a transit country like Turkey are not static structures and they are largely affected by macro‐variables such as current immigration and asylum policies of Turkey and Europe, transnationalism and globalization, and other place‐specific features like Turkey’s location bridging East and West, the existence of human smuggling networks, and its proximity to Iran. But Iranian migrant networks in Turkey are also affected by micro‐variables, such as gender, religion, and ethnicity of individual migrants.
Adaptation of Sudanese Refugees in an Australian Context: Investigating Helps and Hindrances
Authors: Shakespeare‐Finch Jane , Wickham Kylie 
Published: August 2009

AbstractThe present study investigates the experiences of Sudanese refugees by exploring the themes that characterize participants’ experiences in Sudan, en route, and at their Australian destination. In particular, the research identifies several factors that may be seen as ‘helps’ or ‘hindrances’ to Sudanese refugees’ adaptation. Participants were 12 Sudanese refugees aged between 19 and 40 years old who had been residing in Australia for five years or less. A qualitative phenomenological approach to data collection and analysis was employed. Examination of the interview transcripts revealed that all participants identified both ‘hindrances’ and ‘helps’ toward adaptation and indicated that positive adaptation is not only possible, but probable for Sudanese refugees in spite of their past experiences of trauma and present resettlement difficulties. Several practical implications were elicited from the research including a need for programs that actively promote refugees’ adaptation by encouraging the broadening of social networks.
Come Back or Stay? Spend Here or There? Return and Remittances: The Case of Moldova
Authors: Pinger Pia 
Published: August 2009

AbstractThis paper examines the determinants and consequences of temporary and permanent migration from the perspective of migrant source countries. Based on a large and detailed household dataset on migration in the Republic of Moldova, the most important factors that influence a respective migrant’s decision whether to return to the home country or to stay abroad for good are presented first. Second, the remittance behaviour of temporary and permanent migrants is analysed to investigate how developing countries benefit from either type of migration. The results indicate that the most important determinants of permanent migration relate to the economic conditions at home and abroad, as well as to the legal status of a migrant in the host country. Furthermore, economic and political frustration plays an important role in the decision of permanent migrants not to come back. On the contrary, family ties as measured by the number of close family members at home act as a pull factor for migrant return. Interestingly, permanent migrants use source country networks that differ from those of temporary migrants, indicating that the return decision of individuals is influenced by the decision of their migrant peers. Concerning remittances, the results reveal that, in absolute terms, temporary migrants remit around 30 per cent more than their permanent counterparts. This outcome is surprising, because temporary migrants often reside in countries where wages are much lower. Overall, the findings indicate that when compared to permanent migration, temporary migration is favourable for developing countries, as it fosters not only repatriation of skills, but also higher remittances, and home savings.
Moving Through Social Networks: The Case of Armenian Migrants in the Czech Republic
Authors: Klvaňová Radka 
Published: August 2009

AbstractThis paper brings attention to the role of social networks in the migration of asylum seekers and explores how the embeddedness of the migrants in social networks both facilitates and constrains their mobility in different phases of the migration process. It reconstructs the migration paths of eight Armenian migrant families who arrived in the Czech Republic as asylum seekers during the 1990s and the beginning of the twenty‐first century. By examining the narrated stories of the Armenian migrants it shows that social networks formed an important context for employing various migration strategies in all phases of the migration process, and that the meaning and character of migrants’ social networks changed over time. In the initial phase of decision‐making about migration as well as on their journey, it was mainly weak ties of random acquaintances that played a dominant role. The position of the migrants in those networks was rather insecure. They held a little control over the information they received, but in these vulnerable situations they had to rely on their weak ties, which strongly influenced their mobility. In the arrival and settlement phases the social context of the refugee camp hindered the cultivation of social ties outside the migrants’ circle on one hand, and facilitated development of bonding ties among the migrants on the other. Bonding social networks enabled inclusion of the Armenian migrants into various social spheres especially at the beginning of the settlement process. However, the bounded character of these networks was also recognized as excluding them from access to resources of the dominant society and preventing their social mobility in later phases of their settlement. Thus, bridging networks that provide access to certain resources of the dominant society were sought.