Sex dependent sexual reproduction strategies in a cyclic parthenogen—A case study from intermittent urban pond

Limnologica ◽  
2020 ◽  
Vol 83 ◽  
pp. 125795
Author(s):  
Andrzej Mikulski ◽  
Malgorzata Grzesiuk
2010 ◽  
Vol 13 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Katharina B. Budde ◽  
Leonardo Gallo ◽  
Paula Marchelli ◽  
Eva Mosner ◽  
Sascha Liepelt ◽  
...  

Author(s):  
Graciela Maria Preda

La expansión del capitalismo, a fines del siglo pasado, ha provocado profundas transformaciones en las estructuras sociales y en las relaciones de producción en el agro. En el norte de Córdoba, Argentina, lugar donde se realizó este estudio de caso, la ampliación de la frontera agraria con centralidad en la soja propició la inclusión de nuevos agentes productivos y la exclusión de otros. Así, coexistían diferentes formas de ocupación y modalidades de apropiación y puesta en producción de la tierra. Asimismo, la selección de lugares aptos para que el capital desplegara sus estrategias de reproducción generó la fragmentación del espacio geográfico. Este artículo se propone identificar a los productores que configuran la estructura social agraria y comprender cómo estos agentes –definidos por el volumen y la estructura de capital que poseen– generan el campo productivo y las relaciones de fuerza que lo caracterizan. La estrategia metodológica combina el análisis de datos secundarios y primarios provenientes de entrevistas en profundidad realizadas a productores, referentes técnicos y agentes institucionales de la región. Abstract The expansion of capitalism at the end of the last century has led to profound changes in social structures and in the relations of production in agriculture. In the north of Córdoba, Argentina, where this case study was carried out, the expansion of the agricultural frontier with centrality in soy allowed the inclusion of new productive agents and the exclusion of others. Thus, different forms of occupation and modalities of appropriation and putting into production of the land coexisted. Likewise, the selection of suitable places for capital to display its reproduction strategies generated the fragmentation of the geographical space. This article aims to identify the producers that shape the agrarian social structure, and understand how these agents, defined by the volume and structure of capital they possess,  generate the productive field and the relations of force that characterize it. The methodological strategy combines the analysis of secondary and primary data from in-depth interviews with producers, technical referents and institutional agents in the region.


2020 ◽  
Author(s):  
Delphine Paumier ◽  
Blandine Bammé ◽  
Annette Penaud ◽  
Romain Valade ◽  
Frédéric Suffert

AbstractWe performed a three-year field survey in France to characterize the dynamics of sexual reproduction in Mycosphaerella linicola, the causal agent of pasmo, during the interepidemic period. Cohorts of fruiting bodies were sampled from linseed straw during the autumn and winter and carefully observed, focusing on pseudothecia, asci and ascospores. A sequence of experimental steps corresponding to Koch’s postulates confirmed in July 2014, for the first time in France and continental Europe, the widespread presence of the sexual stage of M. linicola in plant host tissues. The developmental dynamics of pseudothecia on straw, expressed as the change over time in the percentage of mature pseudothecia, was similar in all three years. Pseudothecia appeared in late summer, with peak maturity reached in October. A temporal shift, thought to be due to early autumn rainfall, was highlighted in one of the three years. These observations suggest that sexual reproduction plays a significant role in the epidemiology of pasmo in France. A resurgence of M. linicola infections in spring flax is thought to have occurred in recent years, due to the increase in the area under flax. The presence of the sexual stage of this pathogen probably increased the quantitative impact of residues of winter linseed (used for oil) and flax straw (left on the soil for retting and used for fibers) as an interepidemic ‘brown bridge’. This case study highlights how certain parts of a disease cycle, in this case the sexual phase, can become crucial due to changes in production conditions.


2021 ◽  
Author(s):  
Manuel F. G. Weinkauf ◽  
Michael Siccha ◽  
Agnes K. M. Weiner

<p>Understanding the biology of reproduction is important for retracing key evolutionary processes (e.g. speciation and adaptation) in any group of organisms, yet gaining detailed insights often poses a major challenge. Planktonic Foraminifera are a group of globally distributed marine microbial eukaryotes that are important contributors to the global carbon cycle and, due to their fossil record, are widely used as model organisms to investigate the responses of plankton to past environmental changes. The extant biodiversity of planktonic Foraminifera shows restricted distribution patterns and local adaptations of some species, whereas others are cosmopolitan in the world ocean. Hypotheses on their diversification and population dynamics so far entirely rely on the assumption of a nearly exclusively sexual reproduction.</p><p>So far, reproduction in culture has not been successful under laboratory conditions, and thus details on their life cycle and its influence on the evolution of the group remain unknown. Only the production of flagellated gametes has been observed and is taken as an indication for sexual reproduction. Yet, sexual reproduction by spawning of gametes in the open ocean relies on sufficient gamete encounters to maintain viable populations. This represents a problem especially for unflagellated protists like planktonic Foraminifera, which lack the means of active propulsion and are characterized by low population densities in large areas of the world ocean.</p><p>To increase the sparse knowledge on the reproductive biology of planktonic Foraminifera, we applied a dynamic, individual-based modelling approach with parameters based on laboratory and field observations. We tested if random gamete encounters under commonly observed population densities are sufficient for maintaining viable populations or if alternative strategies, such as asexual reproduction or synchronization in depth and time, are indispensable to achieve reproduction success. Our results show that a strict synchronization of gamete release in time and/or space seems inevitable for a successful maintenance of populations. We further argue that planktonic Foraminifera optimized their individual reproductive success at the expense of community-wide gene flow, which may explain their high degree of diversity as well as hampered evolvability. Our modelling approach helps to illuminate the ecology and evolution of this important marine calcifier and to predict the existence of necessary reproduction strategies, which may be detectable in future field and laboratory experiments.</p>


2021 ◽  
Author(s):  
Jake Brown ◽  
Jared M Field

The Price equation provides a general partition of evolutionary change into two components. The first is usually thought to represent natural selection and the second, transmission bias. Here, we provide a new derivation of the generalised equation, which contains a largely ignored third term. Unlike the original Price equation, this extension can account for migration and mixed asexual and sexual reproduction. The derivation here expresses the generalised equation explicitly in terms of fitness, rendering this otherwise difficult third term more open to biological interpretation and use. This re-derivation also permits fundamental results, derived from the Price equation, to be more easily generalised. We take Hamilton's rule as a case study, and provide an exact, total expression that allows for population structures like haplodiploidy. Our analysis, more generally, makes clear the previously hidden assumptions in similar fundamental results, highlighting the caution that must be taken when interpreting them.


2016 ◽  
Author(s):  
J. Bradford Hubeny ◽  
◽  
Shelley Kielb ◽  
Francine M.G. McCarthy ◽  
Katrin Monecke ◽  
...  

2019 ◽  
Vol 83 (4) ◽  
pp. 357 ◽  
Author(s):  
Diogo Paulo ◽  
Onno Diekmann ◽  
Ana Alexandra Ramos ◽  
Filipe Alberto ◽  
Ester Alvares Serrão

Marine flowering plants can reproduce sexually and clonally, and the relative contribution of these two modes can be dependent on the environmental conditions. Zostera marina, a seagrass widely distributed in the northern hemisphere, can form annual and perennial meadows with different proportions of sexual versus clonal propagation depending on the environmental disturbance regime. We study the hypothesis that the contribution of sexual propagation varies during the recovery of a seagrass meadow. In this case study, we compare the proportion of sexual versus clonal propagation of a perennial Z. marina meadow before its disappearance due to winter storms and after recovery. Before disturbance, genotypic diversity was high, indicating frequent sexual reproduction events likely to create an abundant seed bank. Seedling germination allowed the population to recover after the extreme disturbance. As months passed, seedlings became rare and finally absent, giving place to adult shoots. In an advanced stage of colonization, the shoots colonized the area by vegetative growth, which lowered the genotypic diversity. Despite this reduction over time, the genotypic diversity of the new meadow is still high, demonstrating the importance of sexual reproduction in meadow recovery and persistence.


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