Can endopolyploidy explain body size variation within and between castes in ants?

Endoreduplication is the process by which the nuclear genome is repeatedly replicated without mitotic cell division, resulting in nuclei that contain numerous additional genome copies. Endoreduplication occurs widely throughout Eucarya and is particularly common in angiosperms and insects. Although endoreduplication is an important process in the terminal differentiation of some specialized cell types, and often increases cell size and metabolism, the direct effects of increasing nuclear ploidy on cell function are not well resolved. Here, we examine if endoreduplication may play a role in body size and/or caste differentiation in ants. Nuclear ploidy was measured by flow cytometry of whole individuals (providing the basis for overall body size patterns) and individual body segments for multiple polymorphic ant species. We used cell cycle values, interpreted as the mean number of endocycles performed by each cell in the sample, as our measure of overall endoreduplication. Among females of four polymorphic ant species, endoreduplication was positively related with size within the worker caste, but was not related to caste generally in two species where we also examined queens. Additionally, abdomens had the greatest endoreduplication of all body parts regardless of caste or size. We also found that males, having derived from haploid unfertilized eggs, had the highest rates of endoreduplication and may compensate for their haploid origin by performing an additional endocycle relative to females. These results suggest that endoreduplication may play a role in body size variation in eusocial insects and the development of some segment‐specific tissues.     

Intracolony variation of bacterial gut microbiota among castes and ages in the fungus-growing termite Macrotermes gilvus

The fungus-growing termites Macrotermes cultivate the obligate ectosymbiontic fungi, Termitomyces. While their relationship has been extesively studied, little is known about the gut bacterial symbionts, which also presumably play a crucial role for the nutrition of the termite host. In this study, we investigated the bacterial gut microbiota in two colonies of Macrotermes gilvus, and compared the diversity and community structure of bacteria among nine termite morphotypes, differing in caste and/or age, using terminal restriction fragment length polymorphism (T-RFLP) and clonal analysis of 16S rRNA. The obtained molecular community profiles clustered by termite morphotype rather than by colony, and the clustering pattern was clearly more related to a difference in age than to caste. Thus, we suggest that the bacterial gut microbiota change in relation to the food of the termite, which comprises fallen leaves and the fungus nodules of Termitomyces in young workers, and leaves degraded by the fungi, in old workers. Despite these intracolony variations in bacterial gut microbiota, their T-RFLP profiles formed a distinct cluster against those of the fungus garden, adjacent soil and guts of sympatric wood-feeding termites, implying a consistency and uniqueness of gut microbiota in M. gilvus. Since many bacterial phylotypes from M. gilvus formed monophyletic clusters with those from distantly related termite species, we suggest that gut bacteria have co-evolved with the termite host and form a microbiota specific to a termite taxonomic and/or feeding group, and furthermore, to caste and age within a termite species.     

Genetic variation in South Indian castes: evidence from Y-chromosome, mitochondrial, and autosomal polymorphisms

Background

Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations.

Results

We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (R_ST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu R_ST = 0.96%, Andhra Pradesh R_ST = 0.77%) exceeds the estimate of variation between these geographically separated groups (R_ST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data.

Conclusion

Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions.     

On estates and castes

Conclusion Estate systems can be found in societies ranging from pre-State socioeconomic formations such as that of the Northwest Coast Indians, to politically organized pre-capitalist societies such as ancient Rome and Medieval Europe. The features of each estate system vary accordingly; they fit the social structure, but they all share one trait in common: in estate societies, there is a direct homology between stratification and relations of production. The estates are closely aligned with the classes; they differ from classes primarily because they crystallize into a structure what is actually a political and economic process, and they provide an ideology which justifies inequality as a natural, inherited reality. (Timocracies are an exception, but they historically derive from estate systems based on descent.) Relations of inequality are evident, but they are presented in such a way that inequality seems inescapable. There is a clear consciousness of inequality, but little understanding of the possibilities of equality. In contrast, the caste system does not display this homology between stratification and relations of production. By using estate as an analytical concept, we are freed from the category mistake of simply defining castes, along with estates, not to speak of classes, as somehow equivalent systems of stratification, or status.I shall not bring up here the further question of the definition of rank, a term that has been radically misapplied by conventional anthropologists.Jerôme Rousseau is Associate Professor of Anthropology at McGill University, Montreal.     

Evaluating Dominance Styles in Assamese and Rhesus Macaques

Researchers have suggested that several types of agonistic and affiliative behavior covary as a set of species-specific traits, and have used the term dominance style to describe the covariation. We compared measures of dominance style between a group of Assamese macaques (Macaca assamensis) and a group of rhesus macaques (M. mulatta), though kinship information was unknown. Assamese and rhesus female-female dyads each showed a low proportion of counter aggression and a low conciliatory tendency, suggesting that they have despotic social relationships. They also showed a despotic pattern on several other types of agonistic and affiliative behavior, such as approach outcomes and grooming distributions, which is consistent with the covariation of dominance style traits. Assamese male-male dyads showed relatively high levels of reconciliation and counter aggression versus other macaque males portrayed in the literature, suggesting that Assamese males have a tolerant dominance style. Insofar as macaque dominance style depends on the behavior of females, we suggest that Assamese macaques, like rhesus macaques, have despotic social relationships, which contrasts with evidence of a strong correlation between phylogeny and dominance style in macaques. Further, our results indicate that strong male bonding and tolerant dominance relationships among males are independent of female dominance style. Lastly, some measures of agonistic behavior, such as rate of aggression or proportion of bites, are likely altered in competitive environments and thus are not useful indicators of dominance style.     

Study of blood groups, ABH secretors and hemoglobin variants in three upper castes of West Bengal, India

In a serological survey it is found that the Brahmins, Kayasthas and Vaidyas, the three upper castes of Bengalis in West Bengal, cannot be differentiated satisfactorily with respect to ABO blood groups. The Brahmins and Kayasthas differ only slightly in the chromosome frequencies of RH blood groups. The difference in allele frequency for the secretor gene between the Brahmins and Kayasthas is negligible, but there is a marked decrease in frequency in the Vaidyas. In general, incidence of abnormal HbE among Bengalis is very low.     

Physical variation and history in Melanesia and Australia

Local biological variation is marked in Melanesia. Some of it may result from gene flow from Micronesia, but the essential variation appears to result from isolation due to social fragmentation, and to genetic drift in place. In different regions, the variation may correspond well with language relationships, and probably constitutes differentiation which has been preserved over a considerable period, especially since the arrival of horticulture and development of village farming. However, none of this patterning suggests distinct waves of migration into Melanesia. Variation among Australian aboriginal groups is smaller, though far from absent. It may reflect a hunting culture together with social customs allowing more intertribal marriage than is typical of Melanesia. While phenotypically Australians and Melanesians differ, cranially they are closely allied, as against other major human groups. It is suggested that the genetic and phenotypic variety is old, that it existed in the previous home of the Australo-Melanesians (Old Melanesia, comprising present Indonesia and the Phillipines) at least back to 40,000 years ago, and that much of the variation in Melanesia and Australia, including their differences, results from the sampling process involved when different groups out of the original populations made early crossings of the water barriers from Old Melanesia.     

The distribution pattern of rhesus and Assamese monkeys in Nepal

Surveys of the distribution and some ecological characteristics of rhesus monkeys (Macaca mulatta) and Assamese monkeys (M. assamensis) in Nepal were conducted during 234 days in 1976, 1978, and 1984. Rhesus monkeys dominated in the tropical, subtropical, and temperate forests below 3,000 m a.s.l. all over Nepal. Assamese monkeys were patchily distributed along rivers in the tropical and subtropical areas. Both species principally utilized forests parapatrically. The mean troop size of rhesus monkeys (29.5) was significantly larger than that of Assamese monkeys (19.1). Discontinuous distribution of Assamese monkeys probably appeared as a result of the expansion of rhesus monkey distribution in the mid- and late-Pleistocene. Because of small distribution areas and small numbers of monkeys, urgent conservation policy must be pursued.     

Distribution and population variation of total number of palmar triradii among 20 Dhangar castes of Maharashtra,India

The paper deals with the bilateral palmar prints of 3000 males belonging to 20 Dhangar castes of Maharashtra which were analysed (1) to compare the pattern of variation of palmar triradii with respect to other traits, (2) to examine the degree of similarity between clusters based on dermatoglyphics anthropometry and genetic markers and (3) relating these similarities with their ethnographic and geographic proximities. The results of this study confirm the general presumptions, (a) that dermal traits, in general, and palmar characters, in particular, do help in understanding the biologic/ethnic affinities among different groups both at macro and micro levels and (b) the different types of traits, which are likely to be influenced by different genetic and/or environmental factors give rise to different clustering patterns.     

Diurnal variation of metabolites in three individual participants

The circadian system influences virtually all biological functions. Understanding the impact of circadian variation on metabolism may provide insight into mechanisms of circadian-associated disorders and guide the implementation of chrono-therapy. Previous research has reported circadian variation in 7–20% of metabolites in human blood. In this study, untargeted metabolomics profiles were measured using blood of two healthy men and one healthy woman, collected every 2 h for up to 48 h under carefully controlled conditions. The pattern of variation of each metabolite over time was examined on each participant separately, using both one- and two-order harmonic models. A total of 100 of 663 metabolites, representing all metabolite categories, showed diurnal rhythmic concentrations that exceeded the Bonferroni threshold (P < 2.5 × 10^?5). Overall, peak times of many metabolites were clustered during the afternoon-midnight, including the majority of amino acids, all peptides, all lysolipids and all phospholipids, whereas the majority of steroids peaked in the morning. We observed substantial inter-individual variation for both peak times and amplitudes in these three subjects. In conclusion, at least 15% of blood metabolites, representing a broad group of biological pathways, exhibit diurnal variation in three participants. The average peak times of most of these metabolites are clustered in morning or afternoon-midnight. Further work is needed to validate and extend this work in more individuals.     

Physical worker castes in colonies of an acacia-ant (Crematogaster nigriceps) correlated with an intra-colonial division of defensive behaviour

Summary: Crematogaster nigriceps (Emery) is one of the acacia-ants inhabiting the swollen thorns of Acacia drepanolobium trees in East Africa. The ants show two distinctive behaviours in response to being disturbed. Some ants ("Defenders") readily leave the swollen thorns to defend the tree, whilst others ("Domestics") remain inside the swollen thorns and will not move unless provoked into doing so. Analysis of head length and head width measurements of the ants shows conclusively that the two behavioural castes are also physical castes. Defenders have significantly larger heads (Head length 0.97 mm - 0.006, Head width 0.98 mm - 0.006) than the Domestics (Head length 0.78 mm - 0.008, Head width 0.81 mm - 0.007). It is concluded that there is an intra-colonial division of defensive behaviour within the worker ants of C. nigriceps, mirrored by a physical sub-division of the worker caste.     

Seasonal variation in primary productivity in three tropical ponds

Summary Primary productivity values ranged from 1.5 to 15.8 gc/M²/day in Othakadai pond; 2.0 to 8.0 gc/M²/day in Teppakulam tank and 1.05 to 5.4 gc/M²/day in Yanamalai pond. Among the three ponds, highest annual yield was recorded in Othakadai pond (2000.2 gc/M²/yr) next in order comes Teppakulam tank (1211.8 gc/M²/yr) and lastly Yanamalai pond (810.7 gc/M²/yr). In all three ponds temperature and chlorophyll-a showed a more or less direct correlation to productivity values. Alkalinity values and productivity values showed a positive correlation in Othakadai and Yanamalai ponds, while no relationship between alkalinity and productivity could be established in Teppakulam tank.Formed part of a Ph. D. Thesis submitted to Madurai University.     

Site variation in reproductive synchrony in three neotropical figs

Abstract. To investigate the persistence of figs and their short-lived pollinators in highly seasonal environments and in small populations, three native figs were studied near the edge of their range in Sonora, Mexico. The reproductive phenologies of Ficus insipida (Willd.) and F. petiolaris (H.B.K.) were contrasted between a drier site with small populations and a wetter site with large populations. In addition, F. pertusa (L.) phenology was censused in the wetter site and compared with findings from Central America. Trees from smaller populations in the drier site produced less synchronous crops. Individuals within populations became reproductively synchronized at the population level but rapidly attained asynchrony in the drier site because of a breakdown in within-tree crop synchrony. Sexual-phase overlap occurred in all species and sites. Intraspecific variation in reproductive phenology may explain the persistence of figs and fig wasps in highly seasonal environments and small populations.     

Reconciliation and relationship quality in Assamese macaques (Macaca assamensis)

A consistent conclusion in reconciliation research is that animals that reconcile are likely to have strong social bonds. This has led to the hypothesis that reconciliation occurs most often between valuable social partners. We tested this hypothesis in a group of Assamese macaques (Macaca assamensis) living near a temple in Assam, India. Using focal sample and ad libitum data collection, we recorded the occurrence of reconciliation, grooming, and agonistic aiding, and the outcomes of approach. We used matrix association methods (TauKr correlation) to correlate reconciliation with grooming, aiding, and approach outcome. Females reconciled more often with females with which they had stronger grooming and aiding relationships. The correlation between reconciliation and aiding was significant for support to the aggressor and the victim. In contrast, no such correlations with reconciliation were found for males. This study provides evidence that females reconcile most often with valuable and compatible social partners. The results do not support the relationship-quality hypothesis for males, and we suggest that future studies give more consideration to the possibility that males reconcile for reasons other than to repair relationships with valuable partners.     

Antennal olfactory sensitivity in response to task-related odours of three castes of the ant Atta mexicana (hymenoptera: formicidae)

Abstract.  The relationship between scent composition and antennal sensitivity in different castes of Atta mexicana is investigated under laboratory conditions. Extracts of dead ants are analysed by gas chromatography-mass spectrometry to identify the compounds presumably responsible for the specific undertaking behaviour. Oleic acid is identified as one compound that triggers undertaking behaviour. To determine differences in odour reception between workers of different castes (i.e. foragers, undertakers and soldiers), further antennal sensitivity to task-related odours is tested using electroantennographic techniques. Soldiers are the most specialized caste because of their low response to all odours, except odourants related to alarm pheromones. The behavioural specialization of soldiers and their reduced behavioural repertoire are discussed.