Introduction: Have hunter-gatherers ever lived in tropical rain forest independently of agriculture?

It has often been assumed that peoples living today as foragers in tropical rain forests are remnants of paleolithic populations that have been subsisting in their forest habitats for millennia and have only recently come into contact with sources of domesticated plants and animals. Independently, the two of us have published articles that challenge this view and propose the hypothesis that hunter- gatherers could never have lived in tropical rain forest without direct or indirect access to cultivated foods. This article serves as an introduction to six articles in this issue of Human Ecology, all devoted to this hypothesis. To provide background for this journal's readers, we summarize here our original articles.     

The tropical rain forest: Is it a productive environment for human foragers?

A recent debate in ecological anthropology concerns the availability of wild foods for human foragers in tropical forests. This article is a response to the five essays in this same issue of Human Ecology that examine the hypothesis that hunter-gatherers could never have lived in tropical rain forest without direct or indirect access to cultivated foods. We clarify the hypothesis and assess the evidence offered to date. Archeological evidence suggests foraging without cultivation in Malaysia. We propose a program of ecological studies and archeological research which, if undertaken, should provide the evidence necessary to falsify the hypothesis.     

The wild yam question: How well could independent hunter-gatherers live in a tropical rain forest ecosystem?

It has been generally assumed until recently that tropical rain forests are food-rich biomes for human foragers, and that prehistoric hunter-gatherers once lived completely independent of cultivated foods in such environments. An alternative hypothesis that such forests are actually food-poor for humans is proposed here. Specifically, that wild starch foods such as yams were so scarce and so hard to extract that human foragers could not have lived in such biomes without recourse to cultivated foods. The symbiotic relationship found today between tropical forest hunter-gatherers and farmers is not a recent phenomenon, but evolved long ago as an adaptive strategy for successfully exploiting the tropical forest.     

Nuage constituents arising from mitochondria: Is it possible?

An ultrastructural study of nuage-mitochondria complexes in spermatogonia of the sea urchin, Anthocidaris crassispina, was carried out. Release of mitochondrial contents into the cytoplasm was observed. The mitochondrial derivatives persisted as cristae-containing globules of friable material that subsequently contacted and integrated with nuage. The present ultrastructural findings agree with the results of other researchers who proposed that germ plasm substance probably produced by the nucleus is supplemented by the mitochondrial genome.     

A rain forest dusk chorus: cacophony or sounds of silence?

A rain forest dusk chorus consists of a large number of individuals of acoustically communicating species signaling at the same time. How different species achieve effective intra-specific communication in this complex and noisy acoustic environment is not well understood. In this study we examined acoustic masking interference in an assemblage of rain forest crickets and katydids. We used signal structures and spacing of signalers to estimate temporal, spectral and active space overlap between species. We then examined these overlaps for evidence of strategies of masking avoidance in the assemblage: we asked whether species whose signals have high temporal or spectral overlap avoid calling together. Whereas we found evidence that species with high temporal overlap may avoid calling together, there was no relation between spectral overlap and calling activity. There was also no correlation between the spectral and temporal overlaps of the signals of different species. In addition, we found little evidence that species calling in the understorey actively use spacing to minimize acoustic overlap. Increasing call intensity and tuning receivers however emerged as powerful strategies to minimize acoustic overlap. Effective acoustic overlaps were on average close to zero for most individuals in natural, multispecies choruses, even in the absence of behavioral avoidance mechanisms such as inhibition of calling or active spacing. Thus, call temporal structure, intensity and frequency together provide sufficient parameter space for several species to call together yet communicate effectively with little interference in the apparent cacophony of a rain forest dusk chorus.     

Elimination of onchocerciasis from Africa: possible?

Human onchocerciasis, a parasitic disease found in 28 African countries, six Latin American countries and Yemen, causes blindness and severe dermatological problems. In 1987, efforts to control this infection shifted from vector approaches to include the mass distribution of ivermectin - a drug donated by Merck & Co. for disease control in Africa and for disease elimination in the Americas. Currently, almost 25 years later, with the Americas being highly successful and now approaching elimination, new evidence points towards the possibility of successful elimination in Africa. We suggest several major changes in the programmatic approach that through focused goal-directed effort could achieve global elimination of onchocerciasis by 2025.     

Is it possible to predict amyloidogenic regions from sequence alone?

Identification of potentially amyloidogenic regions in polypeptide chains is very important because the amyloid fibril formation can be induced in most normal proteins. In our work we suggest a new method to detect amyloidogenic regions in protein sequence. It is based on the assumption that packing is tight inside an amyloid and therefore regions which could potentially pack well would have a tendency to form amyloids. This means that the regions with strong expected packing of residues would be responsible for the amyloid formation. We use this property to identify potentially amyloidogenic regions in proteins basing on their amino acid sequences only. Our predictions are consistent with known disease-related amyloidogenic regions for 8 of 11 amyloid-forming proteins and peptides in which the positions of amyloidogenic regions have been revealed experimentally. Predictions of the regions which are responsible for the formation of amyloid fibrils in proteins unrelated to disease have been also done.     

Is there a role for arbuscular mycorrhizal fungi in production agriculture?

This review presents the point of view that arbuscular mycorrhizal fungi (AMF) do not play a vital role in the nutrition and growth of plants in many production-orientated agricultural systems. Highly available soil P often limits AM colonisation and causes the C-costs to the host to outweigh any benefits from colonisation. Even when P availability is low and AM colonisation levels are high, as may occur in organic and biodynamic agricultural systems, AMF may not always contribute to plant growth for reasons not yet understood. AM fungal activity may also be greatly limited by soil fumigation, non-responsive plant varieties, or rotations based primarily on non-mycorrhizal crops or crops of low AM dependency. Thus, profitability may sometimes be enhanced by management practices, such as tillage and P-fertilisation, which limit AM colonisation. Manipulation of agricultural systems to favour AMF must occur only if there is clear evidence that AMF make a positive contribution to yield or are vital for maintenance of ecosystem health and sustainability. A crucial role for AMF in soil structural stability or in enhancing micronutrient concentrations in produce may be sufficient evidence and may eventually compel consideration of AMF responsiveness when breeding new crop varieties.     

Histological alterations in fish from Sydney reefs: possible biomarkers for environmental effects?

This study examines the utility of histopathology in the damselfish, Parma microlepis, as a biomarker for the effects of organochlorine pesticides and hexachlorobenzene (HCB). Linkages between organochlorine residue concentrations and contaminant-associated histological effects in fish were examined using field collections and a manipulative field experiment. The distribution of 11 frequently identified organochlorines were measured in wild fish at different spatial scales, spanning 270 km of coastline centred around the Sydney region. Histopathology was used to investigate possible effects on liver, gills and gonad tissues in these fish. Pearson correlations and correlative multivariate statistical techniques were used to explore possible associations between concentrations of organochlorines in fish collected from the field and histological alterations in tissues. Only 6% of correlations between organochlorine residues and histological alterations in fish from field collections, were significant. A weak correlation was found between the occurrence of lamellar fusion in gills and the concentration of aldrin and dieldrin in a manipulative field experiment. A hypothetical model is suggested to explain these results.     

Indicator taxa revisited: useful for conservation planning?

Aim Indicators for biodiversity are needed to facilitate the identification of complementary reserve networks for biodiversity conservation. One widely adopted approach is to use indicator taxa, i.e. a single taxon such as birds or butterflies, despite the ongoing debate regarding their usefulness as indicators of broader biodiversity. Here we assess several aspects, such as influence of species number, of indicator taxa for three extensive data sets to improve our insight into the effectiveness of indicator taxa. Location Denmark, sub‐Saharan Africa and Uganda. Methods First, we investigate to what extent variation in species number between indicator taxa (e.g. 488 mammal spp. vs. 210 snake spp.) is causing the differences in effectiveness between indicator taxa. Second, we investigate whether indicator taxa are capable of outperforming indicator groups composed of random sets of species chosen among all taxa. Finally, we assess the correlation of specific properties such as mean range size of the indicator taxa to their effectiveness. We investigate these aspects of the effectiveness of indicator taxa through the separate analysis of three distinct distributional species data sets: sub‐Saharan Africa (4,039 spp.), Denmark (847 spp.) and Uganda (2,822 spp.). Results We overall found that indicator taxa comprising a greater number of species tend to perform better than indicator taxa with fewer species (e.g. 488 mammal spp. outperform 210 snake spp.), although there are some exceptions. Second, we found most indicator taxa to perform worse than indicator groups consisting of a comparable number of species selected among all taxa. Finally, the effectiveness of indicator taxa was seen to correlate poorly with selected distributional properties such as mean range size of the indicator taxa, suggesting that it is difficult to predict which taxa are efficient biodiversity indicators. Main conclusions Overall, these findings might suggest that focus should simply be on increasing the number of species among all taxa as basis for priority setting, rather than striving to obtain the ‘perfect’ indicator taxa.     

Is a cultural ethology possible?

The possibility, desirability, and potential outcomes of applying ethological methods to the study of culture-specific human behaviors are investigated. Ethology and culture are explored. A new term, instruction, and its use in cultural ethology are proposed. Genetics and survival value are related to cultural ethology. A cultural ethology is given a possible theoretical foundation, and current attempts at a cultural ethology are appraised. A research program in cultural ethology and related fields is proposed.This article is a completely rewritten version of a paper of the same title delivered at the annual meeting of the Southern Anthropological Society at Gainesville, Florida, in February 1968 and published inResearch Previews 15(1): 37–47, April 1968.     

Stereotactic radiation therapy for skull base recurrences: Is a salvage approach still possible?

AimA literature review was performed to analyse the role of stereotactic radiotherapy given in a single shot or in a fractionated fashion for recurrent skull base tumours in order to ascertain if it can be a real salvage approach.BackgroundThe management of recurrent skull base tumours can have a curative or palliative intent and mainly includes surgery and RT.Materials and methodsOne-thousand-ninety-one articles were found in the search databases and the most relevant of them were analysed and briefly described.ResultsData on recurrences of meningioma, pituitary adenoma, craniopharyngioma, chordoma and chondrosarcoma, vestibular schwannoma, glomus jugulare tumours, olfactory neuroblastoma and recurrences from head and neck tumours invading the base of skull are reported highlighting the most relevant results in terms of local control, survival, side effects and complications.ConclusionsIn conclusion, it emerges that SRS and FSRT are effective and safe radiation modalities of realize real salvage treatment for recurrent skull base tumours.     

Does proximity to a mature forest contribute to the seed rain and recovery of an abandoned agriculture area in a semiarid climate?

Proximity to forests contributes to the recolonisation of anthropogenic‐disturbed areas through seed input. We evaluated the role of proximity to a mature forest in the recolonisation of an agricultural area that has been abandoned for 18 years and is currently a young forest. Seed rain was monitored at fixed distances from the mature forest. The type of surface recolonisation (germination versus resprouting) and the reproductive season were measured in both forests. The majority of plants recolonising the young forest originated from seed germination. Proximity to the mature forest contributed to the seed rain in the young forest; however, 18 years has not provided sufficient time for the recolonisation of 80 species present in the mature forest. Some species shared between forests differed in their fruiting season and seed dispersal. The seed rain had a total species richness of 56, a total density of 2270 seeds·m^?2·year^?1 and predominance of self‐ and wind dispersal. A significant reduction in seed rain with increasing distance from the mature forest was observed. The young forest contained 35 species not observed in the mature forest, and the floristic similarity between the two forests was 0.5, indicating that the two forests are floristically distinct.     

Are compound leaves an adaptation to seasonal drought or to rapid growth? Evidence from the Amazon rain forest

Aim To assess the hypotheses that compound leaves of trees in the Amazon forest are an adaptation to drought and/or rapid growth. Location Amazon rain forest, South America. Methods Genera from 137 permanent forest plots spread across Amazonia were classified into those with compound leaves and those with simple leaves. Metrics of compound leaf prevalence were then calculated for each plot and regression models that accounted for spatial autocorrelation were used to identify associations between climate variables and compound leaf structure. We also tested for associations between compound leaf structure and a variety of ecological variables related to life history and growth strategies, including wood density, annual increase in diameter and maximum height. Results One plant family, Fabaceae, accounts for 53% of compound‐leaved individuals in the dataset, and has a geographical distribution strongly centred on north‐east Amazonia. On exclusion of Fabaceae from the analysis we found no significant support for the seasonal drought hypothesis. However, we found evidence supporting the rapid growth hypothesis, with possession of compound leaves being associated with faster diameter growth rates and lower wood densities. Main conclusion This study provides evidence that possession of compound leaves constitutes one of a suite of traits and life‐history strategies that promote rapid growth in rain forest trees. Our findings highlight the importance of carefully considering the geographical distribution of dominant taxa and spatial clustering of data points when inferring ecological causation from environment–trait associations.     

Biodiversity and Land uses at a regional scale: Is agriculture the biggest threat for reptile assemblages?

The human exploitation of land resources (land use) has been considered the major factor responsible for changes in biodiversity within terrestrial ecosystems given that it affects directly the distribution of the fauna. Reptiles are known to be particularly sensitive to habitat change due to their ecological constraints. Here, the impact of land use on reptile diversity was analysed, choosing Catalonia (NE Iberia) as a case study. This region provides a suitable scenario for such a biogeographical study since it harbours: 1) a rich reptile fauna; 2) a highly diverse environment showing strong variation in those variables usually shaping reptile distributions; and 3) good species distribution data. Potential species richness was calculated, using ecological modelling techniques (Ecological Niche Factor Analysis – ENFA). The subtraction of the observed from the potential species richness was the dependent variable in a backwards multiple linear regression, using land use variables. Agriculture was the land use with the strongest relation with the non-fulfilment of the potential species richness, indicating a trend towards a deficit of biodiversity. Deciduous forest was the only land use negatively related with the subtracted species richness. Results indicate a clear relationship between land use and biodiversity at a mesoscale. This finding represents an important baseline for conservation guidelines within the habitat change framework because it has been achieved at the same spatial scale of chorological studies and management policies.     

Acoustic and magnetic communication in plants: Is it possible?

Over the last two decades, important insights into our understanding of plant ecology and the communicative nature of plants have not only confirmed the existence of a wide range of communication means used by plants, but most excitingly have indicated that more modalities remain to be discovered. In fact, we have recently found that seeds and seedlings of the chili plant, Capsicum annuum, are able to sense neighbors and identify relatives using alternative mechanisms beyond previously studied channels of plant communication. In this addendum, we offer a hypothetical mechanistic explanation as to how plants may do this by quantum-assisted magnetic and/or acoustic sensing and signaling. If proven correct, this hypothesis prompts for a re-interpretation of our current understanding of plasticity in germination and growth of plants and more generally, calls for developing a new perspective of these biological phenomena.     

Microtubule-bundling studies revisited: is there a role for MAPs?

The molecular mechanism of microtubule bundling has been enveloped in controversy for the past few years. At the centre of the debate are MAPs: are they necessary for the formation of microtubule bundles? In this article, Gloria Lee and Roland Brandt weigh the evidence and propose that microtubule stability might be the crucial factor in microtubule bundling. Perhaps then MAPs might act as spacer molecules between microtubules.     

Motive for Killing: What Drives Prey Choice in Wild Predators?

Carnivorous animals are assumed to consume prey to optimise energy intake. Recently, however, studies using Nutritional Geometry (NG) have demonstrated that specific blends of macronutrients (e.g. protein, fat and in some cases carbohydrates), rather than energy per se, drive the food selection and intake of some vertebrate and invertebrate predators in the laboratory. A vital next step is to examine the role of nutrients in the foraging decisions of predators in the wild, but extending NG studies of carnivores from the laboratory to the field presents several challenges. Biologging technology offers a solution for collecting relevant data which when combined with NG will yield new insights into wild predator nutritional ecology.     

Abundance of climbing plants in a southern temperate rain forest: host tree characteristics or light availability?

Question: In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location: Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40°39′S, 72°09′W; 350 m a.s.l.) and Pastahue (42°22′S, 73°49′W; 285 m a.s.l.). Methods: We sampled vines in 60 25‐m² plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree ≥1.50‐m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results: Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion: We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor.