Analysis of cardiac motion using MRI and nonrigid image registration

Imperial Users onl

Behavioural castes, dominance and division of labour in a primitively eusocial wasp

Female wasps of the primitively eusocial species Ropalidia marginata may be classified, by a statistical analysis of their time-activity budgets, into three behavioural castes namely Sitters, Fighters and Foragers. We show that Foragers are primarily responsible for the risky task of foraging for food and have very poorly developed ovaries. Sitters and Fighters forage rarely if at all but share the bulk of the intra-nidal tasks such as feeding larvae and building the nest. Both Sitters and Fighters have better developed ovaries than Foragers. Queens of most colonies belong to the Sitter caste. There are no obvious morphological differences between queens and workers or between the behavioural castes. Queens are not necessarily the most dominant individuals in their colonies. Instead, most dominance behaviour is performed by a group of workers (the Fighters). Division of labour and social organization are achieved through behavioural caste differentiation and not, as in many other species studied, through a dominance hierarchy led by a despotic queen suppressing all her nestmates into worker roles. This suggests that behaviour patterns in such primitively eusocial insects are likely to be moulded by a complex interaction between selection at the individual and colony levels

Insect species diversity in Tropics: sampling methods and a case study

The tropical regions of the world generally have a richer store of biological diversity than other regions of the globe. But most tropical habitats face a significant threat of destruction. Yet, little is known about tropical biotic communities. Suspecting that at least part of the reason for the poor documentation of tropical insect communities is the lack of appropriate research methodology, we have endeavoured to standardize a package of methods for quantitative sampling of insects, suitable for tropical ecologists with modest research budgets. This methodology includes the use of a small light trap as well as net sweeps, pitfall traps and scented traps. The methods have been used to sample insect species diversity patterns in three replicate one hectare plots each in twelve selected sites in the Uttara Kannada district of Kamataka, India. During this case study, we have encountered 16,852 adult individuals belooging to 1,789 species. 219 families and 19 orders of insects. Here, we provide evidence that this methodology is adequate for sampling insects and differentiating habitats on the basis of the distribution of insect species. Some interesting biological problems that tropical ecologists can study with the data generated from the application of these methods are also briefIy illustrated

Serial polygyny in Ropalidia marginata: implications for the evolution of eusociality

This article does not have an abstract

Ant species richness and diversity in some selected localities of Western Ghats

We have sampled ants from twelve different localities in the Uttara Kannada district of Karnataka, India using both a package of standardized trapping methods as well as by intensive all-out-search. The relative efficacies of trapping versus all-out-search are compared. Different methods of trapping are also compared among themselves. A check list of all ants seen by all methods put together, identified up to the genus level is provided. Different localities are compared by the similarity and diversity 'of their ant fauna. A weak but statistically significant positive correlation between ant species diversity. and plant species diversity is demonstrated. This report provides the first estimates of the diversity and abundance of ants for any forest habitat of India

Analysis of cardiac motion using MRI and nonrigid image registration

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Queen succession in the primitively eusocial tropical wasp Ropalidia marginata (Lep.) (Hymenoptera: Vespidae)

Females of the primitively eusocial wasp Ropalidia marginata can be classified into three behavioral groups: Sitters, Fighters, and Foragers. It has been speculated that both Sitters and Fighters may be hopeful queens and that the Foragers may have little or no opportunities for direct reproduction. Here we show that in 9 of 12 queen-removal experiments where such a behavioral differentiation could be discerned, the individual that became a queen (the potential queen) was a Sitter in 6 cases, a Fighter in 2 cases, and a Forager in only 1 case. Although potential queens spent significantly more time absent from the nest and showed significantly higher rates of dominance behavior compared to the mean values for nonqueens in their colonies, they were intermediate with respect to all behaviors and age when compared to the range of values for nonqueens in their colonies. Potential queens were not necessarily the highest-ranking individuals among the nonqueens. The pattern of queen succession in this species appears to be quite different from the temperate pattern, where an old and active forager of high dominance rank is the potential queen. Although somewhat similar to the tropical pattern of a relatively younger female that has performed relatively little foraging being the potential queen, it is perhaps more accurate to describe the potential queens of R. marginata as "unspecialized intermediates"

Evolution of Eusociality: Lessons from Social Organization in Ropalidia Marginata (Lep.) (Hymenoptera:Vespidae)

In the primitively eusocial wasp Ropalidia marginata which lacks morphological caste differentiation, all adult females on a nest can be assigned to one of the three behavioural castes namely, Sitters, Fighters and Foragers (1). Here we explore the manner in which social organization and division of labour are achieved through such a behavioural caste differentiation. To do this, we examine the behavioural, morphological and anatomical correlates of behavioural castes in 12 post-emergence colonies of R. marginata from Bangalore and Mysore, India. Our sampling methodology and the variables used in the study are described elsewhere (1,2). Analysis of time activity budgets of wasps as described before (1) showed the presence of three behavioural castes namely Sitters, Fighters and Foragers in all colonies. Logistic regression analysis revealed that the risky task of foraging for food is performed largely by Foragers. Having very poorly developed ovaries, Foragers have the least chance of becoming queens in the future. On the other hand intra-nidal tasks such as feeding larvae and nest building are shared by Sitters and Fighters. Fighters also showed dominance signficantly more often than either Sitters or Foragers. Both Sitters and Fighters have equally well developed ovaries and can be treated as hopeful queens. No morphological differences were seen between the three behavioural castes. A complex network of dominancesubordinate relationships rather than a simple linear hierarchy was evident in most colonies. The queens were not necessarily the most dominant animals in their colonies; in fact the queens did not show any dominance behaviour in three colonies. The frequency of dominance behaviour was correlated with the frequency of such behaviours as Feed larva, Extend walls of cells, and Build new cells, suggesting that individuals showing dominance behaviour also perform several intra-nidal tasks

Behavioural Castes and their Correlates in the Primitively Eusocial Wasp, Ropalidia Marginata (Lep.)Hymenoptera:Vespidae)

Insects living in groups comprising of individuals from more than one generation, most of whom give up reproduction in favour of one or a few members of their group, but cooperate in rearing the resulting brood are termed eusocial (Michener, 1969; Wilson, 1971). In the highly eusocial insects such as all termites, most ants and some bees and wasps the non-reproductives are morphologically distinct castes who have little or no reproductive opportunities. Such morphological differences often extend to subcastes among workers as well. This leads to efficient division of labour and stable social organization. Such morphologically distinct castes are however absent in most primitively eusocial bees and wasps. Here adult wasps or bees are considered totipotent because the social roles, including that of the egg layer, that members of a colony can undertake are flexible. In the absence of morphological castes why do certain individuals accept the role of workers and how are the division of labour and social organization achieved