The mechanism of caste differentiation in a social aphid Tuberaphis styraci, which has a sterile soldier caste in the 2nd instar, was investigated using an artificial diet rearing system. High aphid density induced soldier production. Combinatorial prenatal and postnatal density treatments revealed that (1) either prenatal high density or postnatal high density is sufficient for soldier induction; (2) thus, embryos in the maternal body and newborn 1st instar nymphs are both responsive to high density; (3) the combination of prenatal high density and postnatal high density enhances soldier differentiation in a synergistic manner; and (4) the final determination of soldier differentiation occurs postnatally, probably at a late 1st instar stage. This study first throws light on the developmental aspects of caste differentiation in a social aphid.
"Very little is known about the molecular mechanisms by which aphid developmental paths diverge to produce different morphologies. Some aphid phenotypes are conditioned very early in the development of the aphid (Hardie & Lees, 1985; Shibao et al., 2003), perhaps during embryogenesis. Beyond gross morphological and behavioural differences, the aphid life-style, particularly that of apterous viviparae, requires that individuals adapt to a dynamic environment, which may include changes in host plant metabolism, photoperiod, temperature, population density and the presence of predators and parasites. "
[Show abstract][Hide abstract] ABSTRACT: Aphids display extraordinary developmental plasticity in response to environmental cues. These differential responses to environmental changes may be due in part to changes in gene expression patterns. To understand the molecular basis for aphid developmental plasticity, we attempted to identify the chromatin-remodelling machinery in the recently sequenced pea aphid genome. We find that the pea aphid possesses a complement of metazoan histone modifying enzymes with greater gene family diversity than that seen in a number of other arthropods. Several genes appear to have undergone recent duplication and divergence, potentially enabling greater combinatorial diversity among the chromatin-remodelling complexes. The abundant aphid chromatin modifying enzymes may facilitate the phenotypic plasticity necessary to maintain the complex life cycle of the aphid.
"This finding was consolidated by examination of soldier proportions in field-collected colonies at high population density. The timing of this density-induced defense investment has also been investigated (Shibao et al. 2003). High aphid density was found to have a prenatal influence on embryos still within the ovarioles of their mothers, which resulted in increased soldier production. "
[Show abstract][Hide abstract] ABSTRACT: Social aphids are an ideal animal group in which to demonstrate the relative importance of ecological versus genetic factors
in the evolution of sociality for several reasons: (1) Since aphids are clonal, the genetics of a colony is starkly simple
(the aphids are either from the same clone or they are not) and, in principle, easy to measure; (2) Because good phylogeni
es are available for several aphid taxa and there is clear evidence that there have been more independent origins of sociality
in aphids than in any other social clade, it is possible to test for associations between ecological factors and the evolution
of sociality; (3) Recent developments, in the understanding of the mechanism of the proximate control of soldier development,
in the genetic basis of sociality, and in models of social evolution, make the social aphids an ideal group for experimental
work on the evolution of social behavior; (4) The social aphids are of special ecological interest because they include the
only organisms that have evolved sterile castes in societies that do not occupy some kind of nest (the secondary-host generations
of the Hormaphidinae).
The ecological context of altruism in social aphids has been shown to be quite intricate since it is now clear that colony
defense is not the only costly behavior that they perform: they also have vital roles in keeping the colony clean, migrating
to new colonies, and repairing their nest. Numerous ecological factors are highly pertinent in aphid social evolution including
(1) the fact that all social aphids have at some stage in their life cycle a valuable and defensive fortress in the form of
a plant gall, (2) population size and density, (3) birth rate, (4) the level of exposure to specialized predation, and (5)
variation in the level of tending provided by ants. Kin selection in social aphids has given rise not only to a range of elaborate
adaptations in behavior and morphology but also to impressive short-term flexibility in social investment. For example, in
species that have specialized defenders that can mature to make a direct contribution to their colony’s fitness, defense investment
can be increased both through heightened production of defenders at birth and prolongation of the defender stage.
We demonstrate that ecological factors are essential in any attempt to understand the role of kin selection in the evolution
of social behavior in a group of organisms: ecology determines the extent to which groups consist of related individuals and
the context in which these individuals can give and receive help.
Ecology of Social Evolution, 02/2008: pages 37-56;
[Show abstract][Hide abstract] ABSTRACT: Although the study of adaptation is central to biology, two types of adaptation are recognized in the biological field: physiological
adaptation (accommodation or acclimation; an individual organism’s phenotype is adjusted to its environment) and evolutionary–biological
adaptation (adaptation is shaped by natural selection acting on genetic variation). The history of the former concept dates
to the late nineteenth and early twentieth centuries, and has more recently been systemized in the twenty-first century. Approaches
to the understanding of phenotypic plasticity and learning behavior have only recently been developed, based on cellular–histological
and behavioral–neurobiological techniques as well as traditional molecular biology. New developments of the former concepts
in phenotypic plasticity are discussed in bacterial persistence, wing di-/polymorphism with transgenerational effects, polyphenism
in social insects, and defense traits for predator avoidance, including molecular biology analyses. We also discuss new studies
on the concept of genetic accommodation resulting in evolution of phenotypic plasticity through a transgenerational change
in the reaction norm based on a threshold model. Learning behavior can also be understood as physiological phenotypic plasticity,
associating with the brain–nervous system, and it drives the accelerated evolutionary change in behavioral response (the Baldwin
effect) with memory stock. Furthermore, choice behaviors are widely seen in decision-making of animal foragers. Incorporating
flexible phenotypic plasticity and learning behavior into modeling can drastically change dynamical behavior of the system.
Unification of biological sciences will be facilitated and integrated, such as behavioral ecology and behavioral neurobiology
in the area of learning, and evolutionary ecology and molecular developmental biology in the theme of phenotypic plasticity.
Population Ecology 01/2009; 52(1):5-14. DOI:10.1007/s10144-009-0187-8 · 1.57 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.