63 resultados para frog decline


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Background: Studies of mate choice in anuran amphibians have shown female preference for a wide range of male traits despite females gaining no direct resources from males (i.e. non-resource based mating system). Nevertheless, theoretical and empirical studies have shown that females may still gain indirect genetic benefits from choosing males of higher genetic quality and thereby increase their reproductive success.
Methodology/Principal Findings: We investigated two components of sexual selection in the Moor frog (Rana arvalis), precopulatory female choice between two males of different size (‘large’ vs. ‘small’), and their fertilization success in sperm competition and in isolation. Females’ showed no significant preference for male size (13 small and six large male preferences) but associated preferentially with the male that subsequently was the most successful at fertilizing her eggs in isolation. Siring success of males in competitive fertilizations was unrelated to genetic similarity with the female and we detected no effect of sperm viability on fertilization success. There was, however, a strong positive association between a male’s innate fertilization ability with a female and his siring success in sperm competition. We also detected a strong negative effect of a male’s thumb length on his competitive siring success.
Conclusions/Significance: Our results show that females show no preference for male size but are still able to choose males which have greater fertilization success. Genetic similarity and differences in the proportion of viable sperm within a males ejaculate do not appear to affect siring success. These results could be explained through pre- and/or postcopulatory choice for genetic benefits and suggest that females are able to perceive the genetic quality of males, possibly basing their choice on multiple phenotypic male traits.

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Enrolments in Australian Year 11 and year 12 chemistry are declining. In 1992, 23% of Australian year 12 students studied chemistry, decreasing to 18% in 2010. For science as a whole, the decrease is even more dramatic, from 94% to 51%. The decrease is slowing, but is continuing.
How should we respond to the report? Firstly, we should realise that it is not all gloom and doom. Secondly, education is not solely the responsibility of curriculum authorities and teachers. Each RACI member can communicate, inform and generally educate the wider community about the excitement and value of chemical science. Just a couple of hours of your time is not a panacea, but it can still make long-lasting impacts and affect career choices: even the largest beach consists of tiny individual grains of sand.

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Stimulated by the increasing demand for qualified personnel for business ventures that employ the Internet in their operations, electronic commerce (e-commerce) emerged as an academic discipline at the eve of the twenty first century. This paper presents a study on the changing status of e-commerce as an academic discipline in Australia in the second half of the 2000s. The findings of the study show that e-commerce is losing its status as a distinctive academic discipline in Australia. The number of e-commerce educational programs is declining and full-fledged e-commerce programs are now offered at a limited number of Australian universities only. E-commerce is diminishing into a niche area of business education rather than prospering as a significant academic discipline.

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Radiotherapy is administered to most patients with low-grade glioma. A well-designed, retrospective study assessed neurocognitive function in patients who had received radiotherapy for low-grade gliomas versus those who had not. Cognitive function did not differ markedly between groups after 6 years, but by 12 years this feature was worse in the group that received radiotherapy.

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In this paper, we show that aggregate illiquidity is a priced risk factor on the Shanghai Stock Exchange (SHSE). We develop the relationship between the illiquidity factor, asymmetric information, and market decline. Our empirical results show that while the illiquidity factor is a source of asymmetric information on the SHSE, asymmetric information does not trigger market decline.

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While field and laboratory based studies have provided significant insights into the parental care and courtship behaviour of dendrobatoid frogs, a comprehensive assessment of their genetic mating systems and population genetic parameters has been precluded because ofthe lack of highly variable DNA markers. Here we document the development of nine novel polymorphic microsatellite markers for the dyeing poison frog Dendrobates tinct or ius (Dendrobatidae ). We found between three and 16 alleles per locus in 60 individuals (30 males, 30 females) from the field site Saut Parare, French Guiana, with an average observed heterozygosity of 0. 75. None of the loci deviated significantly from Hardy-Weinberg equilibrium or showed linkage disequilibrium. We also report successful cross-species amplification of the nine markers in two other dendrobatoid species (Allobates femora/is and Oophaga pumilio). These markers have the potential to aid in determining the genetic structure of local populations, identifying small-scale phylogenies such as parent-offspring relationships and will allow for cross-species comparisons within dendrobatoid species. Therefore, these markers can be applied to a wide range of scientific fields, such as conservation, behavioural ecology and evolutionary biology.

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The Dirichlet is one of the most important theoretical achievements of marketing science. It provides insights into the distribution of consumer loyalties and is used widely in industry for benchmarking and interpreting brand performance. The Dirichlet’s implications run counter to some well-entrenched marketing pedagogy and so, unsurprisingly, it has attracted criticism arguing that it cannot adequately reflect the dynamic nature of consumer choice. The authors address these criticisms by discussing how consumer loyalties are manifested and examining whether changes in consumer loyalties do, in fact, disrupt Dirichlet buying patterns. To the best of our discipline’s knowledge, based on extensive empirical and theoretical work, brands compete in a Dirichlet world.