Evolutionary genetics of arbuscular mycorrhizal fungi - causes and consequences of multiple genomes in Glomus intraradices

Résumé Les champignons endomycorhiziens arbusculaires (CEA) forment des symbioses avec la plupart des plantes terrestres. Les CEA influencent la croissance des plantes et la biodiversité. Ils sont supposés avoir évolué de manière asexuée pendant au moins 400 millions d'années et aucune diversification morphologique majeure n'a été constatée. Pour ces raisons, les CEA sont considérés comme d'anciens asexués. Très peu d'espèces sont connues actuellement. Les individus de ces champignons contiennent des noyaux génétiquement différents dans un cytoplasme continu. La signification évolutive, la variabilité et la maintenance des génomes multiples au sein des individus sont inconnues. Ce travail a démontré qu'une population du CEA Glomus intraradices est génétiquement très variable. Nous avons conclu que les plantes hôtes plutôt que la différenciation géographique devraient être responsables de cette grande diversité. Puis nous avons cherché l'existence de recombinaison entre génotypes dans une population. Nous avons détecté un groupe recombinant au sein de la population, ce qui met en doute l'état d'anciens asexués des CEA. Nous avons également détecté l'occurrence de fusions d'hyphes et l'échange de noyaux entre isolats génétiquement différents. La descendance hybride issue de cet échange était viable et distincte phénotypiquement des isolats parentaux. En résumé, ce travail identifie des événements cruciaux dans le cycle de vie des CEA qui ont le potentiel d'influencer l'évolution de génomes multiples. L'étude des conséquences de ces événements sur les interactions avec les plantes hôtes pourrait éclaircir significativement la compréhension de la symbiose entre plantes et CEA. Abstract Arbuscular mycorrhizal fungi (AMF) are important symbionts of most land plants. AMF influence plant growth and biodiversity. Very few extant species are described. AMF are thought to have evolved asexually for at least 400 million years and no major morphological diversification has occurred. Due to these reasons, they were termed `ancient asexuals'. Fungal individuals harbour genetically different nuclei in a continuous cytoplasm. The variability, maintenance and evolutionary significance of multiple genomes within individuals are unknown. This work showed that a population of the AMF Glomus intraradices harbours very high genetic diversity. We concluded that host plants rather than geographic differentiation were responsible for this diversity. Furthermore, we investigated whether recombination occurred among genotypes of a G. intraradices population. The identification of a core group of recombining genotypes in the population refutes the assumption of ancient asexuality in AMF. We found that genetically different isolates can form hyphal fusions and exchange nuclei. The hybrid progeny produced by the exchange was viable and phenotypically distinct from the parental isolates. Taken together, this work provided evidence for key events in the AMF life cycle, that influence the evolution of multiple genomes. Studying the consequences of these events on the interaction with host plants may significantly further the understanding of the AMF-plant symbiosis.

Taxonomy and morphology of Apsil Malloch (Diptera, Muscidae, Coenosiinae, Coenosiini) with new records, description of a new species and a key to identification

Taxonomy and morphology of Apsil Malloch (Diptera, Muscidae, Coenosiinae, Coenosiini) with new records, description of a new species and a key to identification. Apsil Malloch (Diptera, Muscidae, Coenosiinae, Coenosiini) includes 10 species, most of them described from Chile, but some also from Argentina. Five of them and one new species were found at the California Academy of Sciences collection (San Francisco, California) during the course of a project developed in that institution. Almost all material studied was collected in Chile, mainly by M. E. Irwin, during the year of 1966. Brief diagnosis of the known studied species (A. apicata Malloch, A. atripes Malloch, A. dilata Malloch, A. maculiventris Malloch (female described for the first time) and A. spatulata, Malloch), the description of A. mallochi, sp. nov. and a key for the identification of all known species are given. Color illustrations of some morphological characters make easier the recognition of the species. New geographic records were assigned.

Supermarket key attributes and location decisions: A comparative study between British and Spanish consumers

The Maximum Capture problem (MAXCAP) is a decision model that addresses the issue of location in a competitive environment. This paper presents a new approach to determine which store s attributes (other than distance) should be included in the newMarket Capture Models and how they ought to be reflected using the Multiplicative Competitive Interaction model. The methodology involves the design and development of a survey; and the application of factor analysis and ordinary least squares. Themethodology has been applied to the supermarket sector in two different scenarios: Milton Keynes (Great Britain) and Barcelona (Spain).

Ecology and evolution of multigenomic arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF) form extremely important mutualistic symbioses with most plants. Their role in nutrient acquisition, plant community structure, plant diversity, and ecosystem productivity and function has been demonstrated in recent years. New findings on the genetics and biology of AMF also give us a new picture of how these fungi exist in ecosystems. In this article, I bring together some recent findings that indicate that AMF have evolved to contain multiple genomes, that they connect plants together by a hyphal network, and that these different genomes may potentially move around in this network. These findings show the need for more intensive studies on AMF population biology and genetics in order to understand how they have evolved with plants, to better understand their ecological role, and for applying AMF in environmental management programs and in agriculture. A number of key features of AMF population biology have been identified for future studies and most of these concern the need to understand drift, selection, and genetic exchange in multigenomic organisms, a task that has not previously presented itself to evolutionary biologists.

RecA-mediated strand exchange traverses substitutional heterologies more easily than deletions or insertions.

RecA protein in bacteria and its eukaryotic homolog Rad51 protein are responsible for initiation of strand exchange between homologous DNA molecules. This process is crucial for homologous recombination, the repair of certain types of DNA damage and for the reinitiation of DNA replication on collapsed replication forks. We show here, using two different types of in vitro assays, that in the absence of ATP hydrolysis RecA-mediated strand exchange traverses small substitutional heterologies between the interacting DNAs, whereas small deletions or insertions block the ongoing strand exchange. We discuss evolutionary implications of RecA selectivity against insertions and deletions and propose a molecular mechanism by which RecA can exert this selectivity.

Redescription of Oropezella abdominalis Collin from Chile with description of the male and a key to the Neotropical genera of Ocydromiinae (Diptera, Hybotidae)

Oropezella abdominalis Collin, 1933 (Diptera, Hybotidae) is redescribed and the male is described for the first time. An identification key to the Neotropical genera of Ocydromiinae is also provided.

Key to the adults of the most common forensic species of Diptera in South America

Flies (Diptera, blow flies, house flies, flesh flies, horse flies, cattle flies, deer flies, midges and mosquitoes) are among the four megadiverse insect orders. Several species quickly colonize human cadavers and are potentially useful in forensic studies. One of the major problems with carrion fly identification is the lack of taxonomists or available keys that can identify even the most common species sometimes resulting in erroneous identification. Here we present a key to the adults of 12 families of Diptera whose species are found on carrion, including human corpses. Also, a summary for the most common families of forensic importance in South America, along with a key to the most common species of Calliphoridae, Muscidae, and Fanniidae and to the genera of Sarcophagidae are provided. Drawings of the most important characters for identification are also included.

Diagnosis and key of the main families and species of South American Coleoptera of forensic importance

The objective of this paper is to provide diagnosis and keys of the families and species, with illustrations of the main groups. A table of all related species recorded from South America is presented, including the substrate in which they were collected and their geographical distribution. The list comprises 221 species included in 15 families, of which 70% of the species are from Brazil. Scarabaeidae is the most diverse family with 121 species, followed by Staphylinidae with 68. Also we provide one database of Coleoptera species associated with carcasses in South America.

A new species of Seira Lubbock (Collembola, Entomobryidae), with a key to the species of Paraíba, Brazil

A new species of Entomobryidae of the genus Seira Lubbock, S. paraibensis sp. nov. is described and illustrated. The type locality of the species is the municipality of Areia, state of Paraíba, Brazil. The species was found inhabiting the Atlantic forest litter and top soil environment. S. paraibensis sp. nov. resembles S. pseudoannulata in many morphological features. This is the sixth species of the genus found and described in Paraiba so far. A key with the 11 species of Seira registered so far in Paraíba is provided. Also a list with all species of the genus from Brazil is presented.

Altruism, equity and reciprocity in a gift-exchange experiment: An encompassing approach

Considerable experimental evidence suggests that non-pecuniary motivesmust be addressed when modeling behavior in economic contexts. Recentmodels of non-pecuniary motives can be classified as either altruism-based, equity-based, or reciprocity-based. We estimate and compareleading approaches in these categories, using experimental data. Wethen offer a flexible approach that nests the above three approaches,thereby allowing for nested hypothesis testing and for determiningthe relative strength of each of the competing theories. In addition,the encompassing approach provides a functional form for utility in different settings without the restrictive nature of the approaches nested within it. Using this flexible form for nested tests, we findthat intentional reciprocity, distributive concerns, and altruisticconsiderations all play a significant role in players' decisions.

Responsibility-allevation and effort provision in a gift-exchange experiment

Previous indirect evidence suggests that impulses towards pro-socialbehavior are diminished when an external authority is responsiblefor an outcome. The responsibility-alleviation effect states that ashift of responsibility to an external authority dampens internalimpulses toward honesty, loyalty, or generosity. In a gift-exchangeexperiment, we find that subjects respond with more generosity(higher effort) when a wage is determined by a random process thanwhen it is assigned by a third party, indicating that even a slightshift in perceived responsibility for the final payoffs can changebehavior. Responsibility-alleviation is a factor in economicenvironments featuring substantial personal interaction.

Pseudopsis monica sp. nov. from the western Andes, Peru, with a key to the South American species of Pseudopsis Newman (Coleoptera, Staphylinidae, Pseudopsinae)

Pseudopsis Newman, 1834 is a genus of Pseudopsinae with about 46 species distributed worldwide, five of which have been reported for South America. In this paper P. monica sp. nov. is described and illustrated based on specimens collected in Lima, Peru. A key to South American species of Pseudopsis and a catalog are also provided.

Earnings management in Spain. Some evidence from companies quoted in the Spanish stock exchange

After the accounting scandals that have taken place mainly in the UnitedStates during the last years, some Spanish leading authorities havedefended the idea that this kind of accounting problems cannot happen inSpain. They argue that accounting regulation in Europe, and specificallyin Spain, make more difficult the use of creative accounting practices.The objective of this paper is to identify some evidence about thesituacion in Spain. The study tries to demonstrate that some accountingpractices of several of the companies quoted in the Spanish Stock Exchangecould be qualified as earnings management.To carry out this study, the authors have analysed the accounts of the 35companies included in the stock market index IBEX 35. This index iscalculated with the share prices variations of the most importantcompanies quoted in the Spanish Stock Exchange.