Relative impacts of environmental variation and evolutionary history on the nestedness and modularity of tree–herbivore networks

Nestedness and modularity are measures of ecological networks whose causative effects are little understood. We analyzed antagonistic plant–herbivore bipartite networks using common gardens in two contrasting environments comprised of aspen trees with differing evolutionary histories of defence against herbivores. These networks were tightly connected owing to a high level of specialization of arthropod herbivores that spend a large proportion of the life cycle on aspen. The gardens were separated by ten degrees of latitude with resultant differences in abiotic conditions. We evaluated network metrics and reported similar connectance between gardens but greater numbers of links per species in the northern common garden. Interaction matrices revealed clear nestedness, indicating subsetting of the bipartite interactions into specialist divisions, in both the environmental and evolutionary aspen groups, although nestedness values were only significant in the northern garden. Variation in plant vulnerability, measured as the frequency of herbivore specialization in the aspen population, was significantly partitioned by environment (common garden) but not by evolutionary origin of the aspens. Significant values of modularity were observed in all network matrices. Trait-matching indicated that growth traits, leaf morphology, and phenolic metabolites affected modular structure in both the garden and evolutionary groups, whereas extra-floral nectaries had little influence. Further examination of module configuration revealed that plant vulnerability explained considerable variance in web structure. The contrasting conditions between the two gardens resulted in bottom-up effects of the environment, which most strongly influenced the overall network architecture, however, the aspen groups with dissimilar evolutionary history also showed contrasting degrees of nestedness and modularity. Our research therefore shows that, while evolution does affect the structure of aspen–herbivore bipartite networks, the role of environmental variations is a dominant constraint.     

Ritual production of environmental history among the Arawakan Wakuénai of Venezuela

This essay examines ritual and ceremonial activities among the Arawakspeaking Wakuénai of the Venezuelan Amazon as processes of constructing power relations in changing historical and ecological conditions. Ritual evocations of the vertical dimension of power relations between mythic ancestors and human descendants adapt local populations to conditions of relatively severe stress, such as epidemics and scarcity of fish in long wet seasons. Other rituals evoke the horizontal dimension of power relations between affinally-related groups as a way of expanding the local descent group in conditions of lowered stress. These two ways of exercising ritual power link human populations to specific natural habitats and provide flexibility needed to adjust to demographic and other historical changes. Through ritual performances, the Wakuénai transform the natural environment into a cultural landscape of socialized objects and, conversely, remember the history of political relations among peoples through spirit-naming of natural species, objects, places, and geographic landmarks.     

Biotopic distribution, population structure, and some features of small mammal reproduction in Chisinau City

Comparative analysis of species composition, biotopic distribution, population structure, and reproduction of rodents and insectivores in Chisinau City was performed in October?CNovember 2008 (3029 traps days, 715 animals). Sylvaemus sylvaticus appeared to be the most numerous and widely distributed species, the reproductive strategy of which consisted of intense reproduction in the summer. The second most abundant species was Microtus rossiaemeridionalis, which had a different reproductive strategy, with part of its population continuing to reproduce actively in the autumn. Urban woodlands are the most close to natural biotopes by the species composition. The highest number of animals was defined for meadows and gardens. No rodents and insectivores are found on lawns and waste grounds.     

Dialectics of the Bowerbird: An Interpretative Account of Ritual and Symbolism in the Udabe valley,Papua New Guinea

The association of men and women with birds, as expressed in dance, is a common theme in Melanesian ritual. Often, this is seen as a means by which humans attain some relation with a transcendental reality. But this is only part of the picture. Pigs, in contrast to birds, represent an opposite sort of reality. It is argued here — by an interpretation of the gab — that through such rituals, men and women symbolically situate themselves between the two. The rituals are performed to overcome the precarious nature of human sexuality, appearance and aging associated with the life-cycle process, which contrast with that of both birds and pigs.     

A model for the origin of group reproduction during the evolutionary transition to multicellularity

During the evolution of multicellular organisms, the unit of selection and adaptation, the individual, changes from the single cell to the multicellular group. To become individuals, groups must evolve a group life cycle in which groups reproduce other groups. Investigations into the origin of group reproduction have faced a chicken-and-egg problem: traits related to reproduction at the group level often appear both to be a result of and a prerequisite for natural selection at the group level. With a focus on volvocine algae, we model the basic elements of the cell cycle and show how group reproduction can emerge through the coevolution of a life-history trait with a trait underpinning cell cycle change. Our model explains how events in the cell cycle become reordered to create a group life cycle through continuous change in the cell cycle trait, but only if the cell cycle trait can coevolve with the life-history trait. Explaining the origin of group reproduction helps us understand one of life''s most familiar, yet fundamental, aspects—its hierarchical structure.     

Ritual responses to drought: An examination of ritual expressions in Classic Maya written sources

Planting and rain-beckoning rituals are an extremely common way in which past and present human communities have confronted the risk of drought across a range of environments worldwide. In tropical environments, such ceremonies are particularly salient despite widespread assumptions that water supplies are unproblematic in such regions. We demonstrate for the first time that two common but previously under-appreciated Maya rituals are likely planting and rain-beckoning rituals preferentially performed at certain times of the year in close step with the rainy season and the Maya agricultural cycle. We also argue for considerable historical continuity between these Classic Maya ceremonies and later Maya community rituals still performed in times of uncertain weather conditions up to the present day across Guatemala, Belize, and eastern Mexico. During the Terminal Classic period (AD 800-900), the changing role played by ancient Maya drought-related rituals fits into a wider rhetorical shift observed in Maya texts away from the more characteristic focus on royal births, enthronements, marriages, and wars towards greater emphasis on the correct perpetuation of key ceremonies, and we argue that such changes are consistent with palaeoclimatic evidence for a period of diminished precipitation and recurrent drought.     

Question 1: Origin of Life and the Living State

The aim of this article is to discuss four topics: First, the origin of molecular reproduction. Second, the origin of agency – the capacity of a system to act on its own behalf. Agency is a stunning feature of human and some wider range of life. Third, to discuss a still poorly articulated feature of life noticed by the philosopher Immanuel Kant over 200 years ago: A self propagating organization of process. We have no theory for this aspect of life, yet it is central to life. Fourth, I will discuss constraints, as in Schroedinger’s aperiodic crystal (Schroedinger E, What is life? The physical aspect of the living cell, 1944), as information, part of the total non-equilibrium union of matter, energy, work, work cycles, constraints, and information that appear to comprise the living state.     

A comparison of the diversity of Jivaroan Gardens with that of the tropical forest

The proposition that tropical polycultural gardens simulate the structure and dynamics of the surrounding forest is examined in the light of research on Jivaroan manioc cultivation. Garden transects were used to measure the diversity of intercropped species and of locally recognized varieties of manioc. Huambisa and Aguaruna Jivaro gardens have much lower species diversities than the surrounding forest, even though crop compositions reflect the age, topography, and soil type of the swiddens. Furthermore, the number of manioc varieties is far greater than that of all other crop species combined. It is argued that a pure stand of Jivaroan manioc can itself be considered a polycrop of distinct cultivars with differing branching patterns, leaf shapes, and growth periods.     

Intraspecies variation of reproductive strategies in perch (Perca fluviatilis)

The variation of reproductive strategies in different populations of perch and intrapopulation groups differing in the rate of growth have been analyzed. Using a bioenergetic approach, the origin and differences between these groups have been studied. It was shown that bioenergetic mechanisms of regulation of the sizes and weight of the eggs lead to formation of the strategy of forced reproduction in the slow-growing group of perch, unlike the reproductive strategy of the fast-growing group of perch characterized by a later reaching of sexual maturity at a greater relative weight of gonads and spawning of larger eggs, which provides for a longer lifespan of larvae. The great number of age groups in the spawning part of this group compensates for a decrease in reproduction in years with unfavorable conditions.     

Microbial Community Structure of Leaf-Cutter Ant Fungus Gardens and Refuse Dumps

Background

Leaf-cutter ants use fresh plant material to grow a mutualistic fungus that serves as the ants'' primary food source. Within fungus gardens, various plant compounds are metabolized and transformed into nutrients suitable for ant consumption. This symbiotic association produces a large amount of refuse consisting primarily of partly degraded plant material. A leaf-cutter ant colony is thus divided into two spatially and chemically distinct environments that together represent a plant biomass degradation gradient. Little is known about the microbial community structure in gardens and dumps or variation between lab and field colonies.

Methodology/Principal Findings

Using microbial membrane lipid analysis and a variety of community metrics, we assessed and compared the microbiota of fungus gardens and refuse dumps from both laboratory-maintained and field-collected colonies. We found that gardens contained a diverse and consistent community of microbes, dominated by Gram-negative bacteria, particularly γ-Proteobacteria and Bacteroidetes. These findings were consistent across lab and field gardens, as well as host ant taxa. In contrast, dumps were enriched for Gram-positive and anaerobic bacteria. Broad-scale clustering analyses revealed that community relatedness between samples reflected system component (gardens/dumps) rather than colony source (lab/field). At finer scales samples clustered according to colony source.

Conclusions/Significance

Here we report the first comparative analysis of the microbiota from leaf-cutter ant colonies. Our work reveals the presence of two distinct communities: one in the fungus garden and the other in the refuse dump. Though we find some effect of colony source on community structure, our data indicate the presence of consistently associated microbes within gardens and dumps. Substrate composition and system component appear to be the most important factor in structuring the microbial communities. These results thus suggest that resident communities are shaped by the plant degradation gradient created by ant behavior, specifically their fungiculture and waste management.     

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch,Mexico

Economic Stratification Differentiates Home Gardens in the Maya Village of Pomuch, Mexico. In this paper, we analyze if economic stratification of peasant families in a Maya village in the Yucatán Peninsula of Mexico influences species composition and structure of home gardens. Our general hypothesis was that composition and structure reflect a higher dependence on home garden produce of relatively poorer families as compared to more prosperous families. We registered the cultivated trees and herbs in samples of twelve home gardens of poorer and wealthier families that had similar assets in the 1980s, and classified them by principal use and geographic origin. Total species richness of cultivated herbs was highest in home gardens of the more prosperous families, whereas total species richness of trees was highest in home gardens of the poorer families. Average species richness of trees and herbs and species composition was similar in both economic strata. Poorer families cultivated relatively more trees for uses other than fruit than richer families. The average and total number of native tree species and density of trees with diameter at breast height of less than 10 cm was significantly higher in poorer families’ home gardens than in those of wealthier families. We conclude that economic stratification leads to different production strategies in home gardens. Richer families are comparatively more interested in obtaining fruit occasionally and emphasize diversity of herbaceous ornamentals. Poorer families emphasize different uses, favor the native flora, and increase tree density. Thereby they contribute more to biodiversity conservation than wealthier families.     

Nucleotide sequence of the DNA replication origin for human papovavirus BKV: sequence and structural homology with SV40.

DNA and RNA sequencing techniques were used to obtain the sequence surrounding the origin of DNA replication for human papovavirus BKV. The structure is characterized by a true palindrome of 17 residues followed by two sets of symmetrical sequences and a stretch of 20 AT residues. Within the two symmetrical sequences is a segment containing a strong purine bias, 23 of 26 nucleotides. These structures are similar, if not identical, to those found in the region of the SV40 replication, origin. Within the homologous DNA segments, 60-80% of the BKV and SV40 nucleotides are the same. The remarkable similarity of BKV and SV40 sequences containing the origins of DNA replication would appear to confirm our previous suggestion of an evolutionary relationship between the two genomes. In addition, topological similarities between these sequences suggest the possibility of certain structural requirements for bidirectional replication origins in these superhelical DNAs.     

Preliminary investigations into a potential ant invader in Kruger National Park,South Africa

The super‐abundance of Lepisiota incisa (Forel) in settlement areas of Kruger National Park, South Africa has raised concerns that it might be exotic and could negatively impact on natural ecosystems. We documented the current distribution of this ant species around the main settlement in Kruger, assessed how ant diversity varies across habitats, and investigated potential mechanisms facilitating dominance by L. incisa. Around the main camp of Skukuza, pitfall traps were set in five habitats differing in anthropogenic influence. Baiting trails were conducted to determine whether L. incisa and native ants differed in numerical and behavioural dominance. Aggression assays were performed on L. incisa to provide information on colony structure. Although L. incisa was found in all habitats, it had a significantly higher abundance in gardens and appears confined to human‐disturbed areas. It was numerically dominant recruiting more workers to food baits than all other ant species combined. Aggression levels were low between most nests of L. incisa indicating a potential supercolony structure. More information is urgently needed on the genetics, physiology and origins of L. incisa, and monitoring of its current distribution is recommended. This species warrants attention because there may be significant potential for overseas invasion.     

On the origin of the sweet-smelling Parma violet cultivars (Violaceae): wide intraspecific hybridization, sterility, and sexual reproduction

Parma violets are reputed for their double, fragrant flowers and have been cultivated for centuries in Europe. However, due to a rather atypical morphology their taxonomic affinity has not been clarified. Authors have proposed an origin from three possible species, Viola alba, V. odorata, or V. suavis, or a hybrid origin. Using both ITS sequence variation and allozyme variation in 14 putative loci, we showed that the Parma violet cultivars have their origin within Viola alba and that they are best included in the Mediterranean subsp. dehnhardtii. There is no trace of interspecific hybridization. However, the cultivars appear to have a single origin in a wide hybrid within V. alba, involving parental plants from the eastern and western Mediterranean region; historical literature sources seem to indicate Turkey and Italy, respectively. The Parma violet cultivars possess high levels of allozyme heterozygosity and to some extent also within-individual ITS sequence variation. Losses of heterozygosity and within-individual ITS sequence variation in some of the cultivars indicate subsequent rare events of sexual reproduction, presumably through cleistogamous seed set. We unambiguously identify the closest wild relative of this group of cultivars, allowing growers to develop new selection procedures, and show a peculiar molecular process associated with human selection.     

Photoperiodism in humans and other primates: evidence and implications

Most of the anatomical and molecular substrates of the system that encodes changes in photoperiod in the duration of melatonin secretion, and the receptor molecules that read this signal, have been shown to be conserved in monkeys and humans, and the functions of this system appear to be intact from the level of the retina to the level of the melatonin-duration signal of change of season. While photoperiodic seasonal breeding has been shown to occur in monkeys, it remains unclear whether photoperiod and mediation of photoperiod's effects by melatonin influence human reproduction. Epidemiological evidence suggests that inhibition of fertility by heat in men in summer contributes to seasonal variation in human reproduction at lower latitudes and that stimulation of fertility by lengthening of the photoperiod in spring contributes to the variation at higher latitudes. Parallels between the seasonality of human reproduction and seasonal affective disorder suggest that they may be governed by common biological processes. Historical and experimental evidence indicates that human responses to seasonal changes in the natural photoperiod may have been more robust prior to the Industrial Revolution and that subsequently they have been increasingly suppressed by alterations of the physical environment.     

Plasmid profiles of Mycobacterium avium complex isolated from swine

Twenty strains of Mycobacterium avium complex (MAC) isolated from swine and five strains from humans were examined for drug susceptibility and plasmid content. Four strains of swine origin and two strains of human origin harbored plasmid DNAs differing in molecular weights. No relationship between plasmid contents and drug resistance was observed. Southern DNA-DNA hybridization showed that small plasmids from swine MAC strains were homologous to those from human origin at the nucleotide level.     

Potlatch and the articulation of modes of production: revisiting French Marxist Anthropology and the history of central Africa

This essay seeks to understand the potlatch as indicative of a wider category of exchange. Looking at the similarity in wild exchange rituals between northwestern America and central Africa the article argues that potlatch ritual is not as an archaic remnant but a product of the interaction between capitalist and ‘human’ modes of production. In this dynamic ‘human modes of production’ (see anon) did not become capitalist, but rather there was a ritual escalation related to a series of non-capitalist imperatives based in rights in people and theatrical displays of authority. In constructing the theoretical structure used to make this case I draw on and seek to rehabilitate the work of French Marxist Anthropologists working in central Africa, above all Georges Dupré and Pierre-Philippe Rey.     

Concerted evolution of male and female display traits in the European corn borer, Ostrinia nubilalis

Background  

Sexual reproduction entails the encounter of the sexes and the multiplicity of rituals is parallel to the diversity of mating systems. Evolutionary mechanisms such as sexual selection and sexual conflict have led to the elaboration of traits to gain attention and favours from potential partners. A paradox exists about how coordinated systems can evolve and diverge when there would seem to be a stabilising selection acting. Moth display traits – pheromones – constitute an advantageous model with which to address questions about the evolution of mating systems in animals. Both males and females can possess pheromones that are involved either in close- or long-range communication. Female and male pheromones appear to have different origins and to be under different evolutionary constraints, thus they might be envisioned as independently evolving traits. We conducted laboratory experiments to explore the role of scents released during courtship by males of the European corn borer, Ostrinia nubilalis.     

A biochemical study of adult and cystic stages of Echinococcus granulosus of human and animal origin from Kenya

A comparative biochemical study was performed on adult and cystic stages of Echinococcus granulosus. Basic quantitative differences in metabolism were apparent between the cystic forms of sheep origin from the UK and Kenya which suggest that each may represent a different geographical strain or sub-strain. The biochemistry of the human and sheep forms from Kenya was very similar, which probably reflects a certain close affinity between the two. The fact that the cattle, goat and camel forms of E. granulosus, from that country, were distinct biochemically, both from each other and from the sheep and human types, suggests the existence of an unusually complex strain picture there, and that these organisms are either non-infective or only poorly infective to man. The differences in biochemical composition and metabolism observed between adults produced experimentally and those obtained from naturally infected dogs, may have been as a result of their original hydatid source and/or their differing stage of development.     

Maternal risk of breeding failure remained low throughout the demographic transitions in fertility and age at first reproduction in Finland

Radical declines in fertility and postponement of first reproduction during the recent human demographic transitions have posed a challenge to interpreting human behaviour in evolutionary terms. This challenge has stemmed from insufficient evolutionary insight into individual reproductive decision-making and the rarity of datasets recording individual long-term reproductive success throughout the transitions. We use such data from about 2,000 Finnish mothers (first births: 1880s to 1970s) to show that changes in the maternal risk of breeding failure (no offspring raised to adulthood) underlay shifts in both fertility and first reproduction. With steady improvements in offspring survival, the expected fertility required to satisfy a low risk of breeding failure became lower and observed maternal fertility subsequently declined through an earlier age at last reproduction. Postponement of the age at first reproduction began when this risk approximated zero-even for mothers starting reproduction late. Interestingly, despite vastly differing fertility rates at different stages of the transitions, the number of offspring successfully raised to breeding per mother remained relatively constant over the period. Our results stress the importance of assessing the long-term success of reproductive strategies by including measures of offspring quality and suggest that avoidance of breeding failure may explain several key features of recent life-history shifts in industrialized societies.