Population dynamics with a mixed type of sexual and asexual reproduction in a fluctuating environment

<p>Abstract</p> <p>Background</p> <p><it>Carassius gibelio</it>, a cyprinid fish from Eurasia, has the ability to reproduce both sexually and asexually. This fish is also known as an invasive species which colonized almost all continental Europe, most likely originating from Asia and Eastern Europe. Populations of both sexually and asexually reproducing individuals exist in sympatry. In this study we try to elucidate the advantages of such a mixed type of reproduction. We investigate the dynamics of two sympatric populations with sexual and asexual reproduction in a periodically fluctuating environment. We define an individual-based computational model in which genotypes are represented by <it>L </it>loci, and the environment is composed of <it>L </it>resources for which the two populations compete.</p> <p>Results</p> <p>Our model demonstrates advantageous population dynamics where the optimal percentage of asexual reproduction depends on selection strength, on the number of selected loci and on the timescale of environmental fluctuations. We show that the sexual reproduction is necessary for "generating" fit genotypes, while the asexual reproduction is suitable for "amplifying" them. The simulations show that the optimal percentage of asexual reproduction increases with the length of the environment stability period and decrease with the strength of the selection and the number of loci.</p> <p>Conclusions</p> <p>In this paper we addressed the advantages of a mixed type of sexual and asexual reproduction in a changing environment and explored the idea that a species that is able to adapt itself to environmental fluctuation can easily colonize a new habitat. Our results could provide a possible explanation for the rapid and efficient invasion of species with a variable ratio of sexual and asexual reproduction such as <it>Carassius gibelio</it>.</p

E. cyanostictus mtDNA Dloops

Sequences of E. cyanostictus, from all localities. Sequence names match isolate names in supplementary table S1

Data from: Water level fluctuations and metapopulation dynamics as drivers of genetic diversity in populations of three Tanganyikan cichlid fish species

Understanding how genetic variation is generated and maintained in natural populations, and how this process unfolds in a changing environment, remains a central issue in biological research. In this work, we analyzed patterns of genetic diversity from several populations of three cichlid species from Lake Tanganyika in parallel, using the mitochondrial DNA control region. We sampled populations inhabiting the littoral rocky habitats in both very deep, and very shallow areas of the lake. We hypothesized that the former would constitute relatively older, more stable and genetically more diverse populations, because they should have been less severely affected by the well-documented episodes of dramatic water level fluctuations. In agreement with our predictions, populations of all three species sampled in very shallow shorelines showed traces of stronger population growth than populations of the same species inhabiting deep shorelines. However, contrary to our working hypothesis, we found a significant trend towards increased genetic diversity in the younger, demographically less stable populations inhabiting shallow areas, in comparison to the older and more stable populations inhabiting the deep shorelines. We interpret this finding as the result of the establishment of metapopulation dynamics in the former shorelines, by the frequent perturbation and reshuffling of individuals between populations due to the lake level fluctuations. The repeated succession of periods of allopatric separation and secondary contact is likely to have further increased the rapid pace of speciation in lacustrine cichlids

V. moorii mtDNA Dloops

Sequences of V. morii, from all localities. Sequence names match isolate names in supplementary table S1

Tropheus sp. mtDNA Dloops

Sequences of Tropheus sp. from all localities. Sequence names match isolate names in supplementary table S1

Implementation status of morbidity and mortality conferences in Austrian hospitals-A cross-sectional national survey study.

INTRODUCTION Morbidity and mortality conferences (M&MCs) are an instrument for learning from past complications, unexpected follow-ups and deaths in hospitals and are important for improving patient safety. However, there are currently no quantitative data on the implementation of M&MCs in Austria. The aim of the study was to determine the status quo of the M&MCs in Austria. MATERIALS AND METHODS A national cross-sectional study was conducted by means of a survey of 982 chief physicians of surgical disciplines, internal medicine, anesthesiology, intensive care, gynecology/obstetrics and pediatrics. The questionnaire focused on overall goals, structure and procedures of hospital M&MCs. RESULTS Of the 982 contacted chief physicians, 314 (32.0%) completed the survey. Almost two thirds of the respondents, i.e. 203 (64.7%), had already implemented M&MCs. Of the 111 chief physicians who had not yet introduced M&MCs, 62 (55.9%) were interested in introducing such conferences in the future. Of the 203 respondents that had implemented M&MCs, 100 stated that their M&MC could be improved. They reported issues with "shame and blame" culture, hierarchical structures, too little knowledge about the capability of M&MC and, in particular, time constraints. Overall, the participating chief physicians showed that they are striving to improve their existing M&MCs. DISCUSSION/CONCLUSION While we found a relatively high number of already implemented M&MCs we also identified a large heterogeneity in the format of the M&MCs. A highly structured M&MC including guidelines, checklists or templates does not only considerably improve its outcome but can also alleviate the main limiting factor which is the lack of time

Foraging and impacts by benthic fish on the intertidal amphipod Corophium volutator

We studied feeding site selection and impacts by benthic fish (flounder and skates) on the amphipod Corophium volutator, an ecologically-important species in muddy intertidal communities. We determined that benthic fish foraged mainly in areas that had high densities of amphipods, on a mudflat in Nova Scotia, Canada. This observation was based on recording sediments displaced by benthic fish in areas where samples of amphipods also were taken. From gut-content analysis, we found that benthic fish fed almost entirely on C. volutator, and most consumed smaller amphipods than expected based on samples of amphipods collected from the substrate. Benthic fish also fed on male amphipods more than expected. We determined that daily foraging pressure by benthic fish on amphipods was low (about 0.3% per day) by measuring the new appearance of feeding traces made by fish. Nonetheless, fish are expected to have substantial impacts on demography of C. volutator due to the length of the fish foraging season and because fish appear to contribute to extreme female-biased sex ratios typically seen in this species

The functional significance of intersexes in the intertidal amphipod Corophium volutator

We investigated the functional significance of intersexuality in the amphipod Corophium volutator, a key species in soft-bottom intertidal communities. Intersexes in this species possess morphological and anatomical characters of both males and females. Two broad types of intersexes were identified: those with nonsetose oostegites and two penial papillae (Type I), and those with setose oostegites and one or two penial papillae (Type II). We found little evidence that intersexes function as females, but some females housed experimentally with intersexes became ovigerous, indicating that intersexes can function as males. Females that mated with Type II intersexes produced smaller broods than those that mated with Type I intersexes or males, suggesting that this form of intersexuality may be costly to amphipods (most Type II intersexes possessed only a single testis). Male function of intersexes may be important in populations of C. volutator because males are frequently the limiting sex due to extremely female-biased sex ratios

Determining the environmental fate of a filamentous fungus, Trichoderma reesei, in laboratory-contained intact soil-core microcosms using competitive PCR and viability plating

Trichoderma spp. are used extensively in industry and are routinely disposed of in landfill sites as sp