61,848 research outputs found
Sexually size dimorphic brains and song complexity in passerine birds
No full textNeural correlates of bird song involve the volume of particular song nuclei in the brain that govern song development, production, and perception. Intra- and interspecific variation in the volume of these song nuclei are associated with overall brain size, suggesting that the integration of complex songs into the brain requires general neural augmentation. In a comparative study of passerine birds based on generalized least square models, we tested this hypothesis by exploring the interspecific relationship between overall brain size and repertoire size. We found no significant association between song complexity of males and brain size adjusted for body size. However, species in which males produced complex songs tended to have sex differences in overall brain size. This pattern became stronger when we controlled statistically for female song complexity by using sex differences in song complexity. In species with large differences in song complexity, females evolved smaller brains than did males. Our results suggest no role for the evolution of extended neural space, as reflected by total brain size, owing to song complexity. However, factors associated with sexual selection mirrored by sex differences in song complexity were related to sexual dimorphism in overall brain size
Understanding sedimentation in the Song Hong–Yinggehai Basin, South China Sea
No full textThe Cenozoic Song Hong–Yinggehai Basin in the South China Sea contains a large volume of sediment that has been used in previous studies, together with regional geomorphology, to argue for the existence of a large palaeodrainage system that connected eastern Tibet with the South China Sea. To test this and to understand the significance of sediment volumes deposited in the Song Hong–Yinggehai Basin, this study compared erosion histories of source regions with sediment volumes deposited during the two main stages in basin evolution spanning active rifting and subsidence (30–15.5 Ma) and postrift sedimentation (15.5 Ma to present). The study of basin provenance by detrital zircon U-Pb dating revealed Hainan was an important and continuous source of sediment, and a bedrock thermochronological study quantified its overall contribution to basin sedimentation. Comparison between the accumulated mass of basin sediment and volumes of eroded bedrock, calculated from apatite thermochronometry across the modern Red River drainage in northern Vietnam as well as Hainan Island, accounted for the bulk of sediment deposited since 30 Ma. Consequently, if an expanded paleodrainage ever existed it must have predated the Oligocene
Age-dependent health status and song characteristics in the barn swallow
No full textBird song has been hypothesized to evolve, partly, to signal health status of males, and song features should therefore correlate with parasite load. Immune function, parasitism, and secondary sexual characters can, however, differ between age classes, and any apparent relationship between song and parasite loads can be the result of systematic age effects. We tested for an age-dependent relationship between sexually selected characters and measures of parasitism in a Spanish population of the barn swallow Hirundo rustica. A comparison across age classes revealed that chewing lice load, song duration, mean peak amplitude frequency of songs, and tail length differed significantly between yearlings and adults. In a longitudinal analysis, we found significant evidence for mean peak amplitude frequency of songs, tail length and chewing louse parasitism, and a nonsignificant tendency for song duration to change with age of an individual. We found a significant association between song duration and chewing louse load and between hematocrit and peak amplitude frequency of the rattle, the typical harsh terminal syllable. In tests for associations between song traits and health status, while controlling for age, age and chewing louse load were independently related to song duration. We found a significant relationship between pairing success and song duration, implying that females may use this song trait in their choice of parasite-free males. Although the song of the barn swallow may provide information about both male age and parasite resistance, signaling of health status appears to be independent of age effects, in accordance with the theory of parasite-mediated sexual selection, suggesting that male signals can be used as reliable indicators of parasitism. Copyright 2005.age; barn swallow; bird song; chewing louse; hematocrit; sedimentation rate
Extrapair paternity and the evolution of bird song
No full textBird song is usually considered to have evolved in the context of sexual selection. Because extrapair paternity is a major component of sexual selection, mating advantages at the social level for males that produce songs of high quality may be transformed into higher success in extrapair paternity. Therefore, males with longer and more complex songs should suffer less from extrapair paternity intraspecifically, whereas species with high rates of extrapair paternity, reflecting intense sperm competition, should produce more elaborate songs. Although some intraspecific studies demonstrated a negative link between features of songs and extrapair paternity in own nest, others failed to detect such a relationship. Contrary to expectation, a meta-analysis of all studies revealed no significant intraspecific evidence for songs being associated with extrapair paternity. In addition, in comparative analyses based on generalized least squares (GLS) models, we found that no measures of song complexity and temporal output were significantly related to extrapair paternity interspecifically, even when potentially confounding factors such as social mating system, life history, migration, habitat, or sexual dichromatism were held constant. Only plumage dichromatism was significantly related to extrapair paternity. The absence of both intra- and interspecific relationships between measures of song variability and extrapair paternity suggests that factors other than postmating sexual selection have been the important evolutionary forces shaping differences in song. Copyright 2004.bird song; evolution; extrapair paternity; generalized least squares; meta-analysis; repertoire size; sexual selection
Song sharing and repertoire change as indicators of social structure in the Noisy Scrub-bird
Get PDFThe Endangered Noisy Scrub-bird is a small passerine that is seldom seen but often heard in its range on the south coast of Western Australia. The difficulties in observing this cryptic bird mean that little is known about its social system. The loud, conspicuous territorial song of the male provides a convenient, non-intrusive means by which to study this species.
The aim of this project was to investigate the patterns of song sharing and repertoire change in the Noisy Scrub-bird to provide indications of the social structure. It was found that groups of up to ten territorial males shared the same set of about five song types. Song groups were discrete, with members of a song group sharing most, if not all, of their song types. Males from different song groups had no song types in common.
Repertoire change was rapid and, with the exception of one individual, was found in every territorial male studied in the Mt Gardner population. It occurred simultaneously in all members of a song group, with males making the same changes to their shared songs. The source of repertoire change was mainly modification of existing song types with occasional divergence of a single song type into two distinct song types, as well as some innovation providing new song types. The average life of a song type was approximately 6 months. Although some song types persisted for the entire 16 month sampling period, they were continually modified and a year later could no longer be recognised as the same type.
Translocation of eight male scrub-birds to the Porongurup National Park provided an opportunity to combine individuals that initially did not share any songs. This allowed the process of song group formation to be studied. Within a one to two month period these males altered their songs so that they shared with their new neighbours. There was some evidence that the songs of dominant males were copied. Observation of the population established on Bald Island by translocation confirmed that there were no appreciable long-term effects on the songs of translocated Noisy Scrub-birds. Song group size, repertoire size and levels of song sharing were very similar to those found in the Mt Gardner population.
The striking feature of Noisy Scrub-bird song groupings was their discreteness and cohesiveness even in the presence of continual repertoire change. It is suggested that each song group consists of a dominant male whose songs are more attractive to females and/or effective in territory defence. This dominant male is surrounded by subordinate males that copy his effective songs. Repertoire change can be explained by the dominant male continually making changes to his songs, with the other males copying these changes to retain their mimicked effectiveness. Each song group may in fact represent a dispersed lek. The scenario suggested to explain Noisy Scrub-bird song groupings bears striking similarities to the hotshot hypothesis to explain lek formation whereby males cluster around a successful male.
This study demonstrates the potential of using song to investigate aspects of the social system of a species which is otherwise very difficult to observe. Management of an Endangered species such as the Noisy Scrub-bird will always benefit from increased knowledge about their social system. For example, this study showed that taking males from different song groups for translocation probably has little impact on their success at the new site because of their ability to rapidly alter their songs to form new song groups. An additional benefit of regularly monitoring the songs of translocated males was that it allowed ongoing identification of individuals, even though their songs were continually changing
Seasonal changes in patterns of gene expression in avian song control brain regions
Get PDFPhotoperiod and hormonal cues drive dramatic seasonal changes in structure and function of the avian song control system. Little is known, however, about the patterns of gene expression associated with seasonal changes. Here we address this issue by altering the hormonal and photoperiodic conditions in seasonally-breeding Gambel's white-crowned sparrows and extracting RNA from the telencephalic song control nuclei HVC and RA across multiple time points that capture different stages of growth and regression. We chose HVC and RA because while both nuclei change in volume across seasons, the cellular mechanisms underlying these changes differ. We thus hypothesized that different genes would be expressed between HVC and RA. We tested this by using the extracted RNA to perform a cDNA microarray hybridization developed by the SoNG initiative. We then validated these results using qRT-PCR. We found that 363 genes varied by more than 1.5 fold (>log(2) 0.585) in expression in HVC and/or RA. Supporting our hypothesis, only 59 of these 363 genes were found to vary in both nuclei, while 132 gene expression changes were HVC specific and 172 were RA specific. We then assigned many of these genes to functional categories relevant to the different mechanisms underlying seasonal change in HVC and RA, including neurogenesis, apoptosis, cell growth, dendrite arborization and axonal growth, angiogenesis, endocrinology, growth factors, and electrophysiology. This revealed categorical differences in the kinds of genes regulated in HVC and RA. These results show that different molecular programs underlie seasonal changes in HVC and RA, and that gene expression is time specific across different reproductive conditions. Our results provide insights into the complex molecular pathways that underlie adult neural plasticity
Humpback whale song on the southern ocean feeding grounds: implications for cultural transmission
No full textMale humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean
"New" seed in "old" China : impact of CIMMYT Collaborative Programme on maize breeding in South-Western China
No full textChina is the most populated country with the most limited amount of arable land per head of the population in the world. Development and distribution of modern varieties of the three staples, rice, wheat and maize, to insure national food security, have been the core tasks and first priority of its public research and extension systems since the early 1960s. This approach has been very successful resulting from the public effort and the initiatives and incentives of farmers. However, since the beginning of 1980s, China has begun to reform its economic and institutional systems and is experiencing a socio-economic transition period, from a planned economy towards a more market-oriented economy.New policies have been introduced and great changes have occurred in the social and economic context over the past 15 years. The changes that directly relate to agricultural innovation and food production are two important ones; rural reform started at the end of 1970s and commercialization of the public research and extension systems in the 1990s. As a result, more subsequent changes are emerging in the agricultural structure, the division of labour in the rural areas, and in the research orientation and incentives of public research and extension institutions. How to ensure food security, at both the national and farmers' household levels, through technology development and diffusion under the current circumstances in China becomes the main concern of this study.This book focuses on the impact of agricultural technology and relevant key factors in food security. It uses a social constructivist perspective, not only in assessing the impact of technology, but also in tracing the whole process of technology development and diffusion as a social construction. The Collaborative Programme between CIMMYT and Chinese NARS on Maize Breeding in South-western China which started at the end of 1970s and which paralleled the reforms and experienced the changes, serves as an unique case for conducting a comprehensive assessment and analysis. It is expected that the impact study of the Programme will generate valuable insights into the future options and prospects for China's agricultural research and extension systems and highlight the emerging issues of food security, poverty alleviation and sustainable agricultural development in China.The main objectives of the study are:to evaluate the impact of CIMMYT derived technologies in terms of their adoption by farmers (yield, surface, type of technology adopted). This includes farmers' assessment of the technologies, the way they apply them, their sources of information, their access to inputs, and the market of the produce at the local level.to study how the technologies were developed, the institutional contexts within which this happened, the objectives and perspectives of the scientists and officials involved. The focus of this part of the study is on the analysis of the principal institutional and organisational factors influencing the design, development and diffusion of the technologies.to identify the actors in the networks involved in the process of agricultural technology development and diffusion and examine ways for better linkage, integration and interaction between IARCs, NARS and the farmers' informal system, between formal science and indigenous science, and to find ways to tie into farmers' indigenous livelihood processes.Multiple perspectives and indicators have been adopted and used in a comprehensive and complementary way to study the impact of CIMMYT-related technology at both the macro and micro-levels, in terms of the general increase in yields and coverage at the provincial levels and the farmers' responses and strategies with respect to the technology at the household level. Subsequently, the institutional context for technology development and distribution, as well as the farmers' indigenous knowledge development practices are analysed and reflected upon from a perspective influenced by the literature on the social construction of technology in order to reveal the processes through which technology and innovation are shaped by social action.Empirically the study is designed into three major phases, i.e., exploratory, qualitative and quantitative. After the exploratory study at macro level, two distinct production environments, a relatively favourable area and a resource-poor and unfavourable area, are selected for an in-depth comparative case study using both qualitative and quantitative methods to address the emerging issues at the micro-level. The qualitative study is conducted through an in-depth investigation and participatory observation of farmers' responses and strategies towards the technology in the two contrasting farming systems. The quantitative study is carried out through a formal questionnaire survey of 200 farmers selected randomly from the two distinct case study areas. The research results of the three phases of field research were cross-checked with data and evidence obtained through different research methods.The main empirical and theoretical findings of the research are:The macro-level impact of the Programme in the three South-western provinces, made visible by mainly by government's statistics, As denoted above, generally speaking, is large with respect to the total release of MVs, their wide adoption, and the increment in maize production and productivity in the last 15 years.Further in-depth study revealed the large variation between regions and differentiation among farmers, in terms of gender, in adapting to the MVs, which mainly resulted from the changes which emerged after the recent reforms. With a single-minded purpose to increase productivity so as to ensure national food security, and driven by market incentives, most public efforts went into the development and diffusion of uniform high yielding MVs, especially single-cross F1 hybrids. As a result, regional variation and user differentiation, in terms of gender, are largely neglected in the technology design, development and distribution process by the formal knowledge system. This has generated differential impacts among rural people, by environment and by gender, at micro-level.Feminisationalization of agriculture has become a common phenomenon in the research area as a result of male-migration. In both favoured and difficult maize farming systems, women are playing a dominant role in food production and are fully responsible for post-harvest operations, seed selection and storage, and food processing activities. In most cases, women are seed selectors and plant breeders. However, women's significant role is not recognised and their specific needs, interests, and expertise are largely neglected in the technology design, development and diffusion process. As a result of productivity driven and gender-biased policies, the women farmers, who are overloaded by their multiple roles, are struggling to sustain the food security of their households and the state in the face of enormous constraints and difficulties. Under such circumstances new technologies have generated costs as well as benefits for rural women, especially these in poor marginal areas.There exists a large gap between farmers' heterogeneous needs and interests determined by their variable farming systems and livelihoods and the breeders' single minded pursuit of, and interest in, yield. This is especially true for poor farmers, mainly women, cultivating in harsh farming systems in remote marginal areas. However women farmers were making efforts to meet their own needs with their indigenous knowledge and through their own informal system.The real causes for the failure of the formal breeding programme to address the variation of farming systems and to respond to the heterogeneous needs of farmers in marginal areas are institutional rather than technical. Theoretically, from a constructivist point of view, the research revealed that three major constructions of the knowledge networks can be distinguished with respect to the technology development and distribution efforts of the Programme: Each is shaped by different social forces and contexts in different historical periods and each operates at different levels.Confronting the emerging challenges of the new social context, a more flexible institutional framework and comprehensive approach is needed to integrate more complex, varied perspectives in order to manoeuvre among the different policy goals, i.e., productivity, sustainability, equity and stability, based on a more adaptive, rather than a controlling, strategy. Recommendations have been made for the improvement of the Programme in particular and for the public agricultural knowledge system in general.A combination of the present modern technology-oriented approach and participatory approaches to involve farmers, mainly women, and their indigenous knowledge, and traditional farming practices, seems realistic and necessary to deal with the emerging issues. The combination of the approaches leads towards a more flexible, diverse, and sustainable approach, allowing agriculture to take account of the heterogeneous needs of farmers, especially the specific needs and interests of women farmers and the basic dynamics of the agro-ecosystem. Only so could it be possible to change from agricultural management targeted only at productivity to more responsive and adaptive management for sustainable agricultural development.Decentralisation of the formal systems and involvement of farmers in the technology design and development process is necessary and essential to stimulate collaboration between the two systems. The informal sector needs to know more about the complex ways of biotechnology, while the formal system need to know more about the complexity of poor farmers' farming system and their livelihoods. For instance, the importance of farmers' knowledge of landraces and their understanding of the micro-variations in the environment could become the basis for local level breeding or location-specific breeding. Through farmers' participation and cooperation, breeders can gain new insight in criteria, objectives, or evaluation techniques of farmers and the differentiation between regions and types of farmers (in terms of gender). As a result, appropriate varieties within a wide range of options can be produced to meet the heterogeneous needs resulting from regional variation and user differentiation.</OL
"New" seed in "old" China : impact of CIMMYT Collaborative Programme on maize breeding in South-Western China
No full textChina is the most populated country with the most limited amount of arable land per head of the population in the world. Development and distribution of modern varieties of the three staples, rice, wheat and maize, to insure national food security, have been the core tasks and first priority of its public research and extension systems since the early 1960s. This approach has been very successful resulting from the public effort and the initiatives and incentives of farmers. However, since the beginning of 1980s, China has begun to reform its economic and institutional systems and is experiencing a socio-economic transition period, from a planned economy towards a more market-oriented economy.New policies have been introduced and great changes have occurred in the social and economic context over the past 15 years. The changes that directly relate to agricultural innovation and food production are two important ones; rural reform started at the end of 1970s and commercialization of the public research and extension systems in the 1990s. As a result, more subsequent changes are emerging in the agricultural structure, the division of labour in the rural areas, and in the research orientation and incentives of public research and extension institutions. How to ensure food security, at both the national and farmers' household levels, through technology development and diffusion under the current circumstances in China becomes the main concern of this study.This book focuses on the impact of agricultural technology and relevant key factors in food security. It uses a social constructivist perspective, not only in assessing the impact of technology, but also in tracing the whole process of technology development and diffusion as a social construction. The Collaborative Programme between CIMMYT and Chinese NARS on Maize Breeding in South-western China which started at the end of 1970s and which paralleled the reforms and experienced the changes, serves as an unique case for conducting a comprehensive assessment and analysis. It is expected that the impact study of the Programme will generate valuable insights into the future options and prospects for China's agricultural research and extension systems and highlight the emerging issues of food security, poverty alleviation and sustainable agricultural development in China.The main objectives of the study are:to evaluate the impact of CIMMYT derived technologies in terms of their adoption by farmers (yield, surface, type of technology adopted). This includes farmers' assessment of the technologies, the way they apply them, their sources of information, their access to inputs, and the market of the produce at the local level.to study how the technologies were developed, the institutional contexts within which this happened, the objectives and perspectives of the scientists and officials involved. The focus of this part of the study is on the analysis of the principal institutional and organisational factors influencing the design, development and diffusion of the technologies.to identify the actors in the networks involved in the process of agricultural technology development and diffusion and examine ways for better linkage, integration and interaction between IARCs, NARS and the farmers' informal system, between formal science and indigenous science, and to find ways to tie into farmers' indigenous livelihood processes.Multiple perspectives and indicators have been adopted and used in a comprehensive and complementary way to study the impact of CIMMYT-related technology at both the macro and micro-levels, in terms of the general increase in yields and coverage at the provincial levels and the farmers' responses and strategies with respect to the technology at the household level. Subsequently, the institutional context for technology development and distribution, as well as the farmers' indigenous knowledge development practices are analysed and reflected upon from a perspective influenced by the literature on the social construction of technology in order to reveal the processes through which technology and innovation are shaped by social action.Empirically the study is designed into three major phases, i.e., exploratory, qualitative and quantitative. After the exploratory study at macro level, two distinct production environments, a relatively favourable area and a resource-poor and unfavourable area, are selected for an in-depth comparative case study using both qualitative and quantitative methods to address the emerging issues at the micro-level. The qualitative study is conducted through an in-depth investigation and participatory observation of farmers' responses and strategies towards the technology in the two contrasting farming systems. The quantitative study is carried out through a formal questionnaire survey of 200 farmers selected randomly from the two distinct case study areas. The research results of the three phases of field research were cross-checked with data and evidence obtained through different research methods.The main empirical and theoretical findings of the research are:The macro-level impact of the Programme in the three South-western provinces, made visible by mainly by government's statistics, As denoted above, generally speaking, is large with respect to the total release of MVs, their wide adoption, and the increment in maize production and productivity in the last 15 years.Further in-depth study revealed the large variation between regions and differentiation among farmers, in terms of gender, in adapting to the MVs, which mainly resulted from the changes which emerged after the recent reforms. With a single-minded purpose to increase productivity so as to ensure national food security, and driven by market incentives, most public efforts went into the development and diffusion of uniform high yielding MVs, especially single-cross F1 hybrids. As a result, regional variation and user differentiation, in terms of gender, are largely neglected in the technology design, development and distribution process by the formal knowledge system. This has generated differential impacts among rural people, by environment and by gender, at micro-level.Feminisationalization of agriculture has become a common phenomenon in the research area as a result of male-migration. In both favoured and difficult maize farming systems, women are playing a dominant role in food production and are fully responsible for post-harvest operations, seed selection and storage, and food processing activities. In most cases, women are seed selectors and plant breeders. However, women's significant role is not recognised and their specific needs, interests, and expertise are largely neglected in the technology design, development and diffusion process. As a result of productivity driven and gender-biased policies, the women farmers, who are overloaded by their multiple roles, are struggling to sustain the food security of their households and the state in the face of enormous constraints and difficulties. Under such circumstances new technologies have generated costs as well as benefits for rural women, especially these in poor marginal areas.There exists a large gap between farmers' heterogeneous needs and interests determined by their variable farming systems and livelihoods and the breeders' single minded pursuit of, and interest in, yield. This is especially true for poor farmers, mainly women, cultivating in harsh farming systems in remote marginal areas. However women farmers were making efforts to meet their own needs with their indigenous knowledge and through their own informal system.The real causes for the failure of the formal breeding programme to address the variation of farming systems and to respond to the heterogeneous needs of farmers in marginal areas are institutional rather than technical. Theoretically, from a constructivist point of view, the research revealed that three major constructions of the knowledge networks can be distinguished with respect to the technology development and distribution efforts of the Programme: Each is shaped by different social forces and contexts in different historical periods and each operates at different levels.Confronting the emerging challenges of the new social context, a more flexible institutional framework and comprehensive approach is needed to integrate more complex, varied perspectives in order to manoeuvre among the different policy goals, i.e., productivity, sustainability, equity and stability, based on a more adaptive, rather than a controlling, strategy. Recommendations have been made for the improvement of the Programme in particular and for the public agricultural knowledge system in general.A combination of the present modern technology-oriented approach and participatory approaches to involve farmers, mainly women, and their indigenous knowledge, and traditional farming practices, seems realistic and necessary to deal with the emerging issues. The combination of the approaches leads towards a more flexible, diverse, and sustainable approach, allowing agriculture to take account of the heterogeneous needs of farmers, especially the specific needs and interests of women farmers and the basic dynamics of the agro-ecosystem. Only so could it be possible to change from agricultural management targeted only at productivity to more responsive and adaptive management for sustainable agricultural development.Decentralisation of the formal systems and involvement of farmers in the technology design and development process is necessary and essential to stimulate collaboration between the two systems. The informal sector needs to know more about the complex ways of biotechnology, while the formal system need to know more about the complexity of poor farmers' farming system and their livelihoods. For instance, the importance of farmers' knowledge of landraces and their understanding of the micro-variations in the environment could become the basis for local level breeding or location-specific breeding. Through farmers' participation and cooperation, breeders can gain new insight in criteria, objectives, or evaluation techniques of farmers and the differentiation between regions and types of farmers (in terms of gender). As a result, appropriate varieties within a wide range of options can be produced to meet the heterogeneous needs resulting from regional variation and user differentiation
Reduced hole mobility due to the presence of excited states in poly-(3-hexylthiophene)
No full textCopyright 2007 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 93, 233306 (2008) and may be found at
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