Variation in Escape Behavior of Red and Green Clones of the Pea Aphid

Many insect species have evolved a number of antipredator tactics among which the animal can choose when attacked by a natural enemy. While it is known that individuals may differ in how the antipredator tactics are employed, quantitative studies are rare. In the pea aphid, it has been suggested that different clones differ in their propensity to escape from a predator and that this propensity is linked to the body color of the aphid. We tested clonal variation in the escape behavior in red and green clones of the pea aphid. In three experiments the responses of clones to artificial stimuli and a natural predator were quantified. The results indicate that (1) clones differ considerably in their propensity to show escape behavior, (2) red clones are more likely to drop off the host plant when subjected to an artificial stimulus than green clones are, and (3) the patterns of clonal variation in the escape behavior were not consistent through all three experiments, as clones did not differ in their behavior when attacked by a real predator. The differences in the responses of a clone toward different stimuli supposed to mimic predator attack suggest that extrapolating from laboratory experiments to a field situation may be difficul

Plasticity and Errors of a Robust Developmental System in Different Environments

SummaryMany developmental processes generate invariant phenotypes in a wide range of ecological conditions. Such robustness to environmental variation is a fundamental biological property, yet its extent, limits, and adaptive significance have rarely been assessed empirically. Here we tested how environmental variation affects vulval formation in Caenorhabditis nematodes. In different environments, a correct vulval pattern develops with high precision, but rare deviant patterns reveal the system's limits and how its mechanisms respond to environmental challenges. Key features of the apparent robustness are functional redundancy among vulval precursor cells and tolerance to quantitative variation in Ras, Notch, and Wnt pathway activities. The observed environmental responses and precision of vulval patterning vary within and between Caenorhabditis species. These results highlight the complex response of developmental systems to the environment and illustrate how a robust and invariant phenotype may result through cellular and molecular processes that are highly plastic—across environments and evolution

Sex Determination: Ways to Evolve a Hermaphrodite

Most species of the nematode genus Caenorhabditis reproduce through males and females; C. elegans and C. briggsae, however, produce self-fertile hermaphrodites instead of females. These transitions to hermaphroditism evolved convergently through distinct modifications of germline sex determination mechanisms

A role for genetic accommodation in evolution?

Whether evolutionary change can occur by genetic assimilation, or more generally by genetic accommodation, remains controversial. Here we examine some of the experimental evidence for both phenomena. Several experiments in Drosophila suggest that assimilation is possible, and a new paper1 shows that a color polyphenism in the tobacco hornworm, Manduca sexta, can evolve by genetic accommodation. We argue that genetic accommodation, including assimilation, is a plausible mechanism in evolution; however, more work is required to test how this mechanism acts and how often it is involved in evolutionary change

СТРУКТУРНАЯ НАДЕЖНОСТЬ ЭЛЕКТРИЧЕСКОГО БЛОКА ГИБРИДНОГО АВТОМОБИЛЯ

Проводится оценка структурной надежности электрического блока гибридного автомобиля в результате анализа возможных состояний системы, составляющих полную группу равновозможных, несовместных случайных событий

The genetic basis of natural variation in C. elegans telomere length [preprint]

Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligosaccharide/oligonucleotide-binding fold of POT-2, a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans

Species richness, distribution and genetic diversity of Caenorhabditis nematodes in a remote tropical rainforest

BACKGROUND: In stark contrast to the wealth of detail about C. elegans developmental biology and molecular genetics, biologists lack basic data for understanding the abundance and distribution of Caenorhabditis species in natural areas that are unperturbed by human influence. METHODS: Here we report the analysis of dense sampling from a small, remote site in the Amazonian rain forest of the Nouragues Natural Reserve in French Guiana. RESULTS: Sampling of rotting fruits and flowers revealed proliferating populations of Caenorhabditis, with up to three different species co-occurring within a single substrate sample, indicating remarkable overlap of local microhabitats. We isolated six species, representing the highest local species richness for Caenorhabditis encountered to date, including both tropically cosmopolitan and geographically restricted species not previously isolated elsewhere. We also documented the structure of within-species molecular diversity at multiple spatial scales, focusing on 57 C. briggsae isolates from French Guiana. Two distinct genetic subgroups co-occur even within a single fruit. However, the structure of C. briggsae population genetic diversity in French Guiana does not result from strong local patterning but instead presents a microcosm of global patterns of differentiation. We further integrate our observations with new data from nearly 50 additional recently collected C. briggsae isolates from both tropical and temperate regions of the world to re-evaluate local and global patterns of intraspecific diversity, providing the most comprehensive analysis to date for C. briggsae population structure across multiple spatial scales. CONCLUSIONS: The abundance and species richness of Caenorhabditis nematodes is high in a Neotropical rainforest habitat that is subject to minimal human interference. Microhabitat preferences overlap for different local species, although global distributions include both cosmopolitan and geographically restricted groups. Local samples for the cosmopolitan C. briggsae mirror its pan-tropical patterns of intraspecific polymorphism. It remains an important challenge to decipher what drives Caenorhabditis distributions and diversity within and between species

The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length

Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans

Legal determinants of external finance revisited : the inverse relationship between investor protection and societal well-being

This paper investigates relationships between corporate governance traditions and quality of life as measured by a number of widely reported indicators. It provides an empirical analysis of indicators of societal health in developed economies using a classification based on legal traditions. Arguably the most widely cited work in the corporate governance literature has been the collection of papers by La Porta et al. which has shown, inter alia, statistically significant relationships between legal traditions and various proxies for investor protection. We show statistically significant relationships between legal traditions and various proxies for societal health. Our comparative evidence suggests that the interests of investors may not be congruent with the interests of wider society, and that the criteria for judging the effectiveness of approaches to corporate governance should not be restricted to financial metrics