Colony Clustering Research Articles

Intra and inter-specific relationships in a cluster of stenogastrine wasp colonies (Hymenoptera Vespidae)

The behaviour of females belonging to various colonies of Parischnogaster alternata of a nest cluster recently completely destroyed and reconstructed, was observed and described. Behaviours included fights during attempts to land on alien nests and foundations and the stealing of abdominal secretion placed on eggs, of the eggs themselves and of nest material. Egg deposition by females of Liostenogaster flavolineata in P. alternata nests and interspecific duels are described for the first time.

Animal-plant defense association: the soft coral Sinularia sp. (Cnidaria, Alcyonacea) protects Halimeda spp. from herbivory

An associationsl refuge occurs when an organism escapes predation by being closely associated with another organism. We describe a refuge provided by the soft coral Sinularia sp. for algae of the genus Halimeda growing at its bases. Total algal biomass was significantly greater in the 0–10 cm zone than in zones 10–20 and 20–30 cm around individual soft coral colonies. Total algal biomass was also significantly greater within clusters of colonies than in zones 0–10, 10–20, and 20–30 cm around the perimeter of the clusters. Halimeda incrassata (Ellis) and Halimeda opuntia (Linnaeus) Lamouroux comprised the bulk of the total algal biomass and were the only species that showed a pattern of growth similar to the total biomass. Fishes consistently grazed less algae ( Halimeda incrassata and Acanthophora spicifera (Vahl) Boergesen and seagrass ( Halodule uninervis Ascherson) strands placed next to soft corals than farther away. Fishes grazed indiscriminately around objects (rocks or outcrops of dead hard coral), whereas differential grazing occurred around soft corals. This suggested that the presence of an object alone is not responsible for reduced grazing next to the soft coral. When soft corals were removed, the pattern of grazing was disrupted, whereas around intact colonies the pattern persisted. Subsequently, funnel-shaped carrageenan models, that resembled the arborescent shape of Sinularia sp., produced a similar grazing pattern. Removing soft corals did not appear to encourage grazing of exposed Halimeda spp. by fishes. This may be explained by the chemically deterrent or heavily calcified nature of Halimeda spp. (the dominant algae around soft corals) which would prohibit vigorous consumption by herbivorous fishes. Algal species richness did not appear to be enhanced by the presence of Sinularia sp. We found no evidence for chemical defense in experiments with soft coral extracts, carrageenan models, and rehydrated Sinularia sp. colonies. Just as much seagrass was grazed around models and colonies with added extracts as around controls, suggesting that terpenes and other metabolites present in the extracts were not responsible for the protective refuge provided by the soft coral. However, a significant effect of distance was consistently obtained in experiments with funnel-shaped models and rehydrated soft corals, whereas, no effect of distance occurred with beaker-shaped models. These results suggest that the arborescent shape of Sinularia sp. provides a refuge for young recruits of Halimeda spp., and allows the algae to mature until they are not preferred by herbivorous fishes. This study is the first to directly test whether morphological features or chemical properties of a benthic marine organism are responsible for protecting closely associated algae.

Factors Affecting the Distribution and Size of Pygoscelid Penguin Colonies in the Antarctic

Using census data on three species of pygoscelid penguins, we tested the hypothesis that competition for food during the chick-provisioning stage of reproduction limits the number of conspecific seabirds in a region. This prey-depletion hypothesis predicts that a negative correlation should exist between colony population size and the total number of breeding pairs from other colonies within parental foraging range. We also tested whether or not a negative correlation exists between colony size and the population size of, or distance to, the nearest neighboring colony. Suitable data were available for Adélie, Chinstrap, and Gentoo penguins (Pygoscelis adeliae, P. antarctica, P. papua) along the coasts of Victoria Land and the Antarctic Peninsula, where major portions of these species' world populations nest. Results indicated that colonies were highly clustered, with small colonies grouped around one or two large ones, in turn spaced widely. Depending on species, two different patterns of geographic structuring were observed. For the Adélie and Gentoo penguins, no significant negative correlation existed between colony size and the total number of pairs breeding within parental foraging range of the reference colony; however, a significant negative correlation occurred at 150 and 200 km, well beyond foraging range. We found no relationship between colony size and size of or distance to the nearest neighboring colony. In contrast, for the Chinstrap Penguin, a significant positive correlation existed between colony size and total breeding population within the foraging range (50 km) but, as with the other two species, the correlations became more negative at greater distances. Moreover, a significant positive correlation existed between colony size and size of, but not distance to, the nearest colony in this species. We confirmed the hypothesis previously put forward that prey depletion by parents feeding chicks cannot explain size structuring of seabird colonies where breeding-season food supply is superabundant, as in polar regions. However, we also showed that prey depletion is not a necessary condition for negative size structuring. We suggest that if prey depletion occurs (by exploitative or interference competition), any manifestation in terms of colony distribution is overridden near to the colony by aggregating factors that originally led penguins to be colonial and philopatric, for example, social facilitation or predator avoidance. We further propose that geographic structuring is better explained by factors affecting the metapopulation (all breeders and nonbreeders associated with the colony cluster), especially during the prebreeding period, than by factors affecting chick-provisioning parents alone.

Genetic relatedness and incipient eusociality in stenogastrine wasps

Abstract. Social wasps of the subfamily Stenogastrinae represent an incipient stage of eusociality characterized by slight behavioural and morphological differences between egg-layers and non-egg-layers, and the preservation of several reproductive options in all adult females. Females may remain as helpers on the colony where they emerge, join a non-relative on another nest as egg-layer or helper, or begin a new nest. To explore eusociality in this group, a sample was collected from colonies of two of the best-studied species, Liostenogaster flavolineata and Parischnogaster alternata. Because females move between nests, and mother/daughter overlap in generations is slight, relatedness by pedigree is difficult to assess. Therefore, inbreeding and relatedness among colony members was estimated from allozyme variation. Inbreeding or population viscosity might elevate relatedness between colony members from the same cluster of colonies, but there was no evidence for this in either species. Among 57 female colony members from 22 colonies of P. alternata relatedness was 0·56 (se = 0·19) and among 95 female colony members from 38 colonies of L. flavolineata relatedness was 0·22 (se = 0·10), the lowest reported thus far for any primitively eusocial insect. Although a minority of females actually become egg-layers on their own colonies (a key factor in assessing the eusocial status of the group), females exhibit continual efforts to maximize their direct reproductive success in ways more reminiscent of vertebrate communal groups than of eusocial insects.

Aggregation of Colletotrichum acutatum in Response to Simulated Rain Episodes

AbstractThe influence of rain splash dispersal on the aggregation and variability of spores of Colletotrichum acutatum, the causal agent of strawberry anthracnose, was studied with simulated rain over a soil surface. In the first experiment, rains with intensities of 15 and 30 mm/h were generated and sampling plates, with a selective medium for Colletotrichum, were positioned under rainshields at both 20 and 60 cm from an inoculum point source (five infected fruit) for 1‐min exposure periods. Number of colonies growing in plates were used to measure spore density. For each distance, time, rain intensity, and replication, the mean (m), variance (v), and Lloyd's index of patchiness (LIP) were calculated. Estimated (LIP) exceeded 1, indicating the high variability and clustering of colonies, and hence spores, resulting from splash dispersal. LIP increased with distance from the source and with rain intensity at the greater distance. Aggregation was further quantified by Taylor's power law describing the linear relation between ln (v) and ln (m). The slope (b) of the relation for all data points was 1·67, which was significantly (P < 0·01) greater than 1, a further indication of clustering. Distance form the source had a slight positive effect on b. Colony means (Y) were transformed to Y*=Y1/5 based on an approximate b of 1·6. Analysis of Y* indicated an expected significant main effect of rain duration and a significant interaction of distance and rain intensity. In another experiment, six infected fruit and the sampling plates were uniformly placed over the surface. LIP again exceeded 1, and Taylor's b equaled 1·63. In a final study, the inoculum source and sampling plates were raised 46 cm above the soil surface. There was a drastic reduction in Y* compared to surface values, supporting the prior hypothesis that surface topography strongly affects splash dispersal. Results indicate that the physical process of splash dispersal produces a degree of aggregation similar to that produced by population dynamic and other ecological processes.

A Different Kind of Independence: The Postwar Restructuring of the Historical Study of Early America

FS OR Americans, writing and teaching the history of their own country represents a special intellectual enterprise, different from that of studying Germany or China or Nigeria. Like all histories, national history springs from the human fascination with self-discovery, from persistent concerns about the nature of social existence and our engagement with it, but with American history, a relatively open-ended search about the past collides with the vigilant censors of patriotic pride and national self-imaging. Through the years, these censors have been most invested in the proposition that the United States marks out the political path of the future, leaving historians to scour the past for evidence of this role. Since American progress had first become manifest with the nationbuilding acts of Revolution and constitution writing, the seventeenth and eighteenth centuries were turned into a prologue to the history of the United States, the pathbreaking republic and exemplary society. Declaring their independence from this whiggish historiography, early American historians of the last generation have attached themselves to a European frame of reference that, perversely, has had a liberating effect on their scholarship. The liberation early American scholars have sought is from that patriotic narrative that insistently accorded the United States an exceptional destiny even when, as with the Progressives, that destiny was used as a standard for calibrating shortcomings. With roots reaching deep into the pasts of ancient Greece and medieval England, American institutions stood forth, in this account, as both climax and new beginning. As the organic metaphor suggests, seeds once planted-be they town meetings or the practice of religious toleration-require only a favorable setting to come to fruition. And for many years historical scholarship on early America drew on this image of potent plantings in a uniquely favored environment to explain how a great nation emerged from a cluster of British colonies growing on the Atlantic shelf of North America. Trapped

Direct plasmid transfer from replica-plated E. coli colonies to competent B. subtilis cells. Identification of an E. coli clone carrying the hisH and tyrA genes of B. subtilis.

We have cloned the hisH tyrA wild-type genes of Bacillus subtilis with the aid of the chimeric plasmid pBJ194, which replicates both in B. subtilis and Escherichia coli. Primary cloning was done in E. coli. The original E. coli clone, carrying the recombinant plasmid (pGR1) which complements hisH tyrA mutants of B. subtilis, was selected directly from a mixture of plated E. coli clones by replicaplating these clones onto minimal agar plates without tyrosine, spread just before with competent B. subtilis cells. After overnight incubation clusters of small colonies had developed exclusively in the E. coli [pGR1] colony prints. The Tyr+ minicolonies were shown to be B. subtilis carrying pGR1 because (i) their appearance depended linearly on the number of B. subtilis cells plated, (ii) they produced extracellular protease and amylase and (iii) plasmids could be reisolated from the minicolonies and used to transform B. subtilis recE4 tyrA1 both to Cmr and Tyr+. Plasmid pGR1 transfer through replica plating was compared with plasmid transfer in liquid. Both systems depended on transformable B. subtilis strains and were sensitive to DNAseI. However, whereas integration of the tyrA+ gene into the chromosome and concomitant loss of plasmids occurred frequently during regular plasmid transformation of Rec+ B. subtilis, this was a rare event during plasmid transfer through replica plating.