Search results for "Asexual"
showing 10 items of 46 documents
Exceptional cryptic diversity and multiple origins of parthenogenesis in a freshwater ostracod.
2009
The persistence of asexual reproduction in many taxa depends on a balance between the origin of new asexual lineages and the extinction of old ones. This turnover determines the diversity of extant asexual populations and so influences the interaction between sexual and asexual modes of reproduction. Species with mixed reproduction, like the freshwater ostracod (Crustacea) morphospecies Eucypris virens, are a good model to examine these dynamics. This species is also a geographic parthenogen, in which sexual females and males co-exist with asexual females in the circum-Mediterranean area only, whereas asexual females occur all over Europe. A molecular phylogeny of E. virens based on the mit…
Intersexual competition among humans: prosocial towards the opposite sex and proself towards the same sex?
2017
In a research conducted on a sample of participants from three countries (N = 256): Poland, Ukraine and Denmark, a hypothesis of the moderating impact of other person sex on the level of social value orientation of men and women was tested. The study applied the now rarely used method of measuring social value orientation: the Warsaw Method, which was expected to reveal more subtle differences between men and women than those observed in the studies using the most popular social value orientation measurement tools, such as decomposed games. The direction of the observed relationship proved to be compatible with the predictions resulting from the phenomenon of intrasexual competition for a p…
(A)sexual reproduction - a review of life cycles of grape phylloxera,Daktulosphaira vitifoliae
2009
Since its emergence as a pest of grapevine about 150 years ago, studies on the life cycle and mode of reproduction of grape phylloxera (Daktulosphaira vitifoliae Fitch) (Homoptera: Phylloxeridae) have been of considerable scientific interest and importance for applied viticulture. The life cycle of grape phylloxera, as described in the mid to late nineteenth century, is still subject to discussion and confusion. In this article, we aim to provide for the first time an overview of the reported life cycle strategies of grape phylloxera by summarizing documented observations, the results of controlled field and laboratory assays, and the results of molecular genetic analyses. Thus, we present …
Pythium terrestris, a new species isolated from France, its ITS region, taxonomy and its comparison with related species
2002
Pythium terrestris (F-78) was isolated from soil samples taken in Lille in northern France. Its morphology resembles that of Pythium rostratum, and Pythium longandrum, a recently described species. However the antheridial and sporangial characteristics of this new species are unique. The fungus does not sporulate, the sporangium germinates directly into mycelium through germ tubes. The oogonia of P. terrestris are normally provided with hypogynous and monoclinous antheridia, at times the monoclinous antheridial branches wrap around the oogonia forming a complicated knot. Morphological features of this new species, together with the sequences of the internal transcribed spacer (ITS) region o…
Description of Dryocosmus destefanii new species (Hymenoptera: Cynipidae: Cynipini) from Quercus suber L. in Italy
2018
A new species, Dryocosmus destefanii Cerasa & Melika n. sp. associated with a Cerris section oak, Quercus suber L., is described from Italy. Description, diagnosis, host associations and biology for the new species and an illustrated identification key to the Western Palaearctic Dryocosmus species are given. The description is supported by morphological and molecular data.
Competición intrasexual en el trabajo: diferencias sexuales en celos y envidia en el trabajo
2012
ResumenDesde una perspectiva evolucionista, este articulo aborda las diferencias sexuales en las caracteristicas del rival que provocan celos y envidia en el trabajo, y como se relacionan con la competicion intrasexual. La muestra estuvo compuesta por 114 trabajadores de diferentes sectores profesionales. Los rivales provocaron mas celos y envidia en las mujeres que en los hombres cuando eran fisicamente atractivos. En ambos sexos, las habilidades sociales y el poder social y dominancia fueron las caracteristicas del rival que provocaron mas celos y envidia. En las mujeres, los celos provocados por el atractivo fisico del rival se relacionaron con la competicion intrasexual, mientras que en…
Regulation of mating in the budding yeast Saccharomyces cerevisiae by the zinc cluster proteins Sut1 and Sut2
2013
This article is made available through the Brunel Open Access Publishing Fund. Copyright @ The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The zinc cluster proteins Sut1 and Sut2 play a role in sterol uptake and filamentous growth in the budding yeast Saccharomyces cerevisiae. In this study, we show that they are also involved in mating. Cells that lack both SUT1 and SUT2 were defective in mating. The expression of the genes NCE102 and PRR2 was increased in the sut1 sut2 double deletion mutant…
Reproductive and developmental phenomena in annelids: a source of exemplary research problems
1999
Specific traits of reproduction, of early and postembryonic development and of sexual maturation in annelids are reported, and the existing and expected contributions to this field from the study of annelids are discussed. The study of early development, as in other spiralians, reveals the existence of canonical cleavage patterns and the combined action of antithetical principles, namely determination by stereotypic sorting-out of ‘determinants’ and determination depending upon the interactions between the blastomeres. A high potential of information about the processes of metameric trunk segment formation and of segment specification has only begun to be exploited in annelids. Epitoky, the…
Flower and fruit structure of the endangered species Petagnaea gussonei (Sprengel) Rauschert (Saniculoideae, Apiaceae) and implications for its repro…
2015
Petagnaea gussonei (Apiaceae) is an endangered species endemic to the Nebrodi mountains (north-eastern Sicily). Although an increasing number of studies have been performed on this species, its reproductive biology remains poorly understood. The aim of this study was to investigate in detail the structure of the flower and the fruit of Petagnaea, and the possible implications for its breeding system and seed dispersal mechanism. Results from fieldwork, light microscopy and scanning electron microscopy suggest (1) the presence of protandrous hermaphrodite flowers; (2) geitonogamy, autogamy, and allogamy as breeding system mechanisms of P. gussonei, even if asexual reproduction is preferred b…
Intrasexual competition at work: Sex differences in the jealousy-evoking effect of rival characteristics in work settings
2010
Sex differences in jealousy-evoking rival characteristics in the relationship with a supervisor at work were examined in a community sample of 188 individuals from Argentina. Among men, the rivals’ social dominance and communal attributes evoked the most jealousy, followed by physical dominance. Among women, the rival’s communal attributes evoked the most jealousy, followed by social dominance and physical attractiveness. For men physical dominance of the rival and for women physical attractiveness of the rival evoked relatively more jealousy, especially among those high in intrasexual competition and confronted with a same-sex supervisor. When confronted with an opposite-sex supervisor, s…