Mitochondrial population genomics supports a single pre-Clovis origin with a coastal route for the peopling of the Americas

It is well accepted that the Americas were the last continents reached by modern humans, most likely through Beringia. However, the precise time and mode of the colonization of the New World remain hotly disputed issues. Native American populations exhibit almost exclusively five mitochondrial DNA (mtDNA) haplogroups (A-D and X). Haplogroups A-D are also frequent in Asia, suggesting a northeastern Asian origin of these lineages. However, the differential pattern of distribution and frequency of haplogroup X led some to suggest that it may represent an independent migration to the Americas. Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple-migration models. A detailed demographic history of the mtDNA sequences estimated with a Bayesian coalescent method indicates a complex model for the peopling of the Americas, in which the initial differentiation from Asian populations ended with a moderate bottleneck in Beringia during the last glacial maximum (LGM), around similar to 23,000 to similar to 19,000 years ago. Toward the end of the LGM, a strong population expansion started similar to 18,000 and finished similar to 15,000 years ago. These results support a pre-Clovis occupation of the New World, suggesting a rapid settlement of the continent along a Pacific coastal route.

Rethinking the development, dissemination and adoption of agricultural technologies

This paper focuses on the higher order factors affecting successful adoption of technologies. Drawing on the "actor-oriented perspective" in rural sociology, it is argued that successful examples of adoption at this higher level result from a complex conjunction of people and events, with outcomes that may have been quite unanticipated at the outset. From this perspective, research and extension projects and programs are viewed as arenas in which social actors–village leaders, farmers, researchers (local and international), aid officials, municipal agents, extension workers, and traders–pursue their own short- and long-term objectives and strategies. To this end, they maneuver, negotiate, organize, cooperate, participate, coerce, obstruct, form coalitions, adopt, adapt, and reject, all within a specific geographical and historical context.

Migration of Husbands, Remittances and Agricultural Production: Impacts when Wives Head Households in Rural Kenya

This paper uses data collected from migrants' wives in the Nyeri district of Kenya. The main objective is to determine whether migration and remittances contribute to the development of agriculture. Our results suggest that most migrants are pushed out of rural areas, belong to the group of low-paid workers in urban areas, send little and irregular remittances to their wives back in rural areas and that these remittances are mainly used for consumption purposes and do not contribute to any significant development in agriculture. Our results also indicate that altruism or social obligation might be the main reason for migrants sending remittances back to their rural wives.

Testing for Market Power in Multiple-Input, Multiple-Output Industries: The Australian Grains and Oilseeds Industries

Recent empirical studies have found significant evidence of departures from competition in the input side of the Australian bread, breakfast cereal and margarine end-product markets. For example, Griffith (2000) found that firms in some parts of the processing and marketing sector exerted market power when purchasing grains and oilseeds from farmers. As noted at the time, this result accorded well with the views of previous regulatory authorities (p.358). In the mid-1990s, the Prices Surveillence Authority (PSA 1994) determined that the markets for products contained in the Breakfast Cereals and Cooking Oils and Fats indexes were "not effectively competitive" (p.14). The PSA consequently maintained price surveillence on the major firms in this product group. The Griffith result is also consistent with the large number of legal judgements against firms in this sector over the past decade for price fixing or other types of non-competitive behaviour. For example, bread manufacturer George Weston was fined twice during 2000 for non-competitive conduct and the ACCC has also recently pursued and won cases against retailer Safeway in grains and oilseeds product lines.

Robust parameter settings of evolutionary algorithms for the optimisation of agricultural systems models

Numerical optimisation methods are being more commonly applied to agricultural systems models, to identify the most profitable management strategies. The available optimisation algorithms are reviewed and compared, with literature and our studies identifying evolutionary algorithms (including genetic algorithms) as superior in this regard to simulated annealing, tabu search, hill-climbing, and direct-search methods. Results of a complex beef property optimisation, using a real-value genetic algorithm, are presented. The relative contributions of the range of operational options and parameters of this method are discussed, and general recommendations listed to assist practitioners applying evolutionary algorithms to the solution of agricultural systems. (C) 2001 Elsevier Science Ltd. All rights reserved.

Gag-Pol supplied in trans is efficiently packaged and supports viral function in human immunodeficiency virus type 1

The intracellular trafficking and subsequent incorporation of Gag-Pol into human immunodeficiency virus type 1 (HIV-1) remains poorly defined. Gag-Pol is encoded by the same mRNA as Gag and is generated by ribosomal frameshifting. The multimerization of Gag and Gag-Pol is an essential step in the formation of infectious viral particles. In this study, we examined whether the interaction between Gag and Gag-Pol is initiated during protein translation in order to facilitate the trafficking and subsequent packaging of Gag-Pol into the virion. A conditional cotransfection system was developed in which virion formation required the coexpression of two HIV-1-based plasmids, one that produces both Gag and Gag-Pol and one that only produces Gag-Pol. The Gag-Pol proteins were either immunotagged with a His epitope or functionally tagged with a mutation (K65R) in reverse transcriptase that is associated with drug resistance. Gag-Pol packaging was assessed to determine whether the Gag-Pol incorporated into the virion was preferentially packaged from the plasmid that expressed both Gag and Gag-Pol or whether it could be packaged from either plasmid. Our data show that translation of Gag and Gag-Pol from the same mRNA is not critical for virion packaging of the Gag-Pol polyprotein or for viral function.

Foraging by the endangered black-breasted button-quail (Turnix melanogaster) within fragmented rainforest of an agricultural landscape

We studied the foraging habitat of the endangered black-breasted button-quail (Turnix melanogaster) in 13 rainforest patches of an agricultural landscape (23.4 km(2)) in eastern Australia to assess its use of fragmented habitats outside conservation reserves. The species foraged only in the three largest patches (17.4, 40.0, 63.8 ha in size), all of which were connected to open eucalypt forest, and in intact rainforest. Occurrence of birds was greatest in the largest patch. The maximum number of individuals within the study area was estimated to be 22. Radio-tracking of nine birds revealed that three were resident in the largest patch for periods of over 100 days; no movements between patches were detected. Three radio-tagged birds were taken by avian and mammalian predators. Our results indicated that the long-term future of the species in agricultural landscapes is bleak and that management action is urgently needed to arrest its decline in these ecosystems, (C) 2001 Elsevier Science Ltd. All rights reserved.

Advances in application of climate prediction in agriculture

Agricultural ecosystems and their associated business and government systems are diverse and varied. They range from farms, to input supply businesses, to marketing and government policy systems, among others. These systems are dynamic and responsive to fluctuations in climate. Skill in climate prediction offers considerable opportunities to managers via its potential to realise system improvements (i.e. increased food production and profit and/or reduced risks). Realising these opportunities, however, is not straightforward as the forecasting skill is imperfect and approaches to applying the existing skill to management issues have not been developed and tested extensively. While there has been much written about impacts of climate variability, there has been relatively little done in relation to applying knowledge of climate predictions to modify actions ahead of likely impacts. However, a considerable body of effort in various parts of the world is now being focused on this issue of applying climate predictions to improve agricultural systems. In this paper, we outline the basis for climate prediction, with emphasis on the El Nino-Southern Oscillation phenomenon, and catalogue experiences at field, national and global scales in applying climate predictions to agriculture. These diverse experiences are synthesised to derive general lessons about approaches to applying climate prediction in agriculture. The case studies have been selected to represent a diversity of agricultural systems and scales of operation. They also represent the on-going activities of some of the key research and development groups in this field around the world. The case studies include applications at field/farm scale to dryland cropping systems in Australia, Zimbabwe, and Argentina. This spectrum covers resource-rich and resource-poor farming with motivations ranging from profit to food security. At national and global scale we consider possible applications of climate prediction in commodity forecasting (wheat in Australia) and examine implications on global wheat trade and price associated with global consequences of climate prediction. In cataloguing these experiences we note some general lessons. Foremost is the value of an interdisciplinary systems approach in connecting disciplinary Knowledge in a manner most suited to decision-makers. This approach often includes scenario analysis based oil simulation with credible models as a key aspect of the learning process. Interaction among researchers, analysts and decision-makers is vital in the development of effective applications all of the players learn. Issues associated with balance between information demand and supply as well as appreciation of awareness limitations of decision-makers, analysts, and scientists are highlighted. It is argued that understanding and communicating decision risks is one of the keys to successful applications of climate prediction. We consider that advances of the future will be made by better connecting agricultural scientists and practitioners with the science of climate prediction. Professions involved in decision making must take a proactive role in the development of climate forecasts if the design and use of climate predictions are to reach their full potential. (C) 2001 Elsevier Science Ltd. All rights reserved.