Home About us Contact
|
Home About us Contact | ||
|
|
||
Current Ideas (current + idea)
Selected AbstractsEditors' Introduction: Birds and AgricultureJOURNAL OF APPLIED ECOLOGY, Issue 5 2000S.J. Ormerod 1.,Around 10% of recent papers in the Journal of Applied Ecology have examined interactions between birds and agriculture. This statistic reveals the important role now played by ecologists in assessing the effects of agricultural development worldwide. It also reflects the position of birds as both indicators and targets of agricultural change: their patterns of behaviour, distribution, seasonal phenology and demography track closely onto the spatial and temporal scales of agricultural intensification. 2.,Papers in this Special Profile illustrate how research in this sphere has shifted towards assessing the processes by which birds are affected ecologically by agricultural change. The works examine spatial patterns in extinction; assess long-term trends in bird abundance and agricultural practice; reveal how foraging and breeding performance in farmland birds varies between habitats; and evaluate the role of large-scale modelling in examining hypotheses about the influences of land management on birds. The final paper shows that birds can have intrinsically positive value in agricultural systems. 3.,All the papers propose management prescriptions for agricultural areas that blend the microscopic , for example, how to modify local land structure to benefit birds , and the macroscopic , for example, by suggested inputs into land-use policy. Perhaps most pertinent is the key conclusion that agricultural change is multivariate, so that straightforward univariate effects on birds are unlikely. Restoration of impacted populations might therefore require holistic strategies that encourage appropriately scaled agricultural extensification. Success would be most likely if farmers, conservationists and other key players were engaged collaboratively in the process. 4.,Current ideas about restoring farmland bird populations share a common assumption: if agricultural practice has reduced populations hitherto, then agricultural practice can restore the losses. We suggest that this assumption carries a range of predictions that now require testing through sustainable farm management , a situation ideally suited to ,BACI' style experiments. 5.,We reiterate the need to expand work on other groups of organisms affected negatively or positively by agricultural management to allow a broader perspective of impacts or benefits. [source] Process in the evolution of bird migration and pattern in avian ecogeographyJOURNAL OF AVIAN BIOLOGY, Issue 2 2000Christopher P. Bell Current ideas about the evolution of bird migration equate its origin with the first appearance of fully migratory populations, and attribute its evolution to a selective advantage generated by increased breeding success, gained through temporary emigration from resident populations to breed in under-exploited seasonal areas. I propose an alternative hypothesis in which migration first appears as a temporary directional shift away from the breeding site outside the reproductive period, in response to seasonal variation in the direction and/or severity of environmental gradients. Fully migratory populations then appear through either extinction of sedentary phenotypes, or colonisation of vacant seasonal areas by migrants. Where colonisation occurs, resident ancestral populations can be driven to extinction by competition from migrants which invade their range outside the breeding season, resulting in fully migratory species. An analogous process drives the evolution of migration between high latitudes and the tropics, since extension of breeding range into higher latitudes may drive low latitude populations to extinction, resulting in an overall shift of breeding range. This process can explain reverse latitudinal gradients in avian diversity in the temperate zone, since the breeding ranges of migratory species concentrate in latitudes where they enjoy the highest breeding success. Near absence of forest-dwelling species among Palaearctic-African migrants is attributable to the lack of forest in northern Africa for much of the Tertiary, which has precluded selection both for southward extension of migration by west Palaearctic forest species, and northward breeding colonisation by African forest species. [source] Hidden patterns of colony size variation in seabirds: a logarithmic point of viewOIKOS, Issue 12 2008Roger Jovani Explaining the huge variability present in bird colony sizes within and between species is intimately related to the understanding of the proximate and ultimate reasons for bird coloniality. However, natural patterns of colony size frequency distributions (CSFDs) remain poorly known. It is widely believed that colonial birds have similar long-tailed (highly right-skewed) CSFDs and that species mainly differ in their maximum colony sizes (in the length of the ,tail' of their CSFDs). We used data from the Seabird 2000 project (20 species; 19 978 colonies; 3 779 919 nests), the largest and most detailed dataset currently available, to analyse the CSFDs of seabird breeding in Britain and Ireland. Log-transformations of colony sizes revealed that the often reported long-tailed CSFDs in common histograms were hiding contrasting patterns, mainly log-normal but also power law CSFDs. The different statistical characteristics of CSFDs did not co-occur at random within species and were in fact highly correlated (e.g. a large geometric mean correlated with a large coefficient of variation). A PCA with these characteristics revealed a smoothed transition between species' CSFD. Therefore, (a) a logarithmic analysis will allow different aspects of what is currently only referred to as ,colony size variation' to be quantified; (b) we challenge the current idea that all species show similar long-tailed CSFDs; (c) we offer a new (unified) view of colony size variation and discuss how these new patterns confirm, challenge and may advance theoretical and applied research into bird coloniality. [source] PARASITES, THEIR RELATIONSHIPS AND THE DISINTEGRATION OF SCROPHULARIACEAE SENSU LATOCURTIS'S BOTANICAL MAGAZINE, Issue 4 2010Michael F. Fay Summary. Plants that parasitise other plants have been among the most difficult plant groups to fit into classification systems due to their modified biology and their often highly reduced morphology. They are now considered to be found in about 16 families of flowering plants. Here we summarise current ideas about their relationships and provide information about their characteristics and utilisation. A major consequence of the revised classification of Orobanchaceae and related families has been the break-up of the traditional Scrophulariaceae, and here we summarise the new classification, focusing on genera of horticultural interest. [source] Ecological fitting by phenotypically flexible genotypes: implications for species associations, community assembly and evolutionECOLOGY LETTERS, Issue 11 2008Salvatore J. Agosta Abstract Ecological fitting is the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition. This paper has four major aims. First, we review the original concept of ecological fitting and relate it to the concept of exaptation and current ideas on the positive role of phenotypic plasticity in evolution. Second, we propose phenotypic plasticity, correlated trait evolution and phylogenetic conservatism as specific mechanisms behind ecological fitting. Third, we attempt to operationalize the concept of ecological fitting by providing explicit definitions for terms. From these definitions, we propose a simple conceptual model of ecological fitting. Using this model, we demonstrate the differences and similarities between ecological fitting and ecological resource tracking and illustrate the process in the context of species colonizing new areas and forming novel associations with other species. Finally, we discuss how ecological fitting can be both a precursor to evolutionary diversity or maintainer of evolutionary stasis, depending on conditions. We conclude that ecological fitting is an important concept for understanding topics ranging from the assembly of ecological communities and species associations, to biological invasions, to the evolution of biodiversity. [source] Wnt signaling in hematopoiesis: Crucial factors for self-renewal, proliferation, and cell fate decisionsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010Frank J.T. Staal Abstract A large number of studies from many different laboratories have implicated the Wnt signaling pathway in regulation of hematopoiesis. However, different inducible gain- and loss-of-function approaches yielded controversial and some times contradictory results. In this prospect we will review the current ideas on Wnt signaling in hematopoiesis and early lymphopoiesis. Reviewing this large body of knowledge let us to hypothesize that different levels of activation of the pathway, dosages of Wnt signaling required and the interference by other signals in the context of Wnt activation collectively explain these controversies. Besides differences in dosage, differences in biological function of Wnt proteins in various blood cell types also is a major factor to take into account. Our own work has shown that while in the thymus Wnt signaling provides cytokine-like, proliferative stimuli to developing thymocytes, canonical Wnt signaling in HSC regulates cell fate decisions, in particular self-renewal versus differentiation. J. Cell. Biochem. 109: 844,849, 2010. © 2010 Wiley-Liss, Inc. [source] Late-Quaternary palaeoclimatic research in Fennoscandia , A historical reviewBOREAS, Issue 4 2010H. JOHN B. BIRKS Birks, H. J. B. & Seppä, H. 2010: Late-Quaternary palaeoclimatic research in Fennoscandia , A historical review. Boreas, Vol. 39, pp. 655,673. 10.1111/j.1502-3885.2010.00160.x. ISSN 0300-9483. Ideas and understanding of Late-Quaternary climatic history, especially in the Lateglacial and the postglacial, were initiated in Fennoscandia in the 19th century with pioneering studies on peat stratigraphy, megafossils and macrofossils. This review traces the history of palaeoclimatic research and the development of current ideas about climatic changes, with particular reference to the Lateglacial and its rapid climatic fluctuations, such as the Younger Dryas period, and to the Holocene, with its thermal maximum and shifts in precipitation. [source] Towards integrated paediatric services in the Netherlands: a survey of views and policies on collaboration in the care for children with cerebral palsyCHILD: CARE, HEALTH AND DEVELOPMENT, Issue 5 2007B. J. G. Nijhuis Abstract Aim, Worldwide, family-centred and co-ordinated care are seen as the two most desirable and effective methods of paediatric care delivery. This study outlines current views on how team collaboration comprising professionals in paediatric rehabilitation and special education and the parents of children with disabilities should be organized, and analyses the policies of five paediatric rehabilitation settings associated with the care of 44 children with cerebral palsy (CP) in the Netherlands. Methods, For an overview of current ideas on collaboration, written statements of professional associations in Dutch paediatric rehabilitation were examined. The policy statements of the five participating settings were derived from their institutional files. Documents detailing the collaborative arrangements involving the various professionals and parents were evaluated at the institutional level and at the child level. Involvement of the stakeholders was analysed based on team conferences. Results, Also in the Netherlands collaboration between rehabilitation and education professionals and parents is endorsed as the key principle in paediatric rehabilitation, with at its core the team conference in which the various priorities and goals are formulated and integrated into a personalized treatment plan. As to their collaborative approaches between rehabilitation centre and school, the five paediatric settings rarely differed, but at the child level approaches varied. Teams were large (averaging 10.5 members), and all three stakeholder groups were represented, but involvement differed per setting, as did the roles and contributions of the individual team members. Conclusion, Collaboration between rehabilitation and education professionals and parents is supported and encouraged nationwide. Views on collaboration have been formulated, and general guidelines on family-centred and co-ordinated care are available. Yet, collaborative practices in Dutch paediatric care are still developing. Protocols that carefully delineate the commitments to collaborate and that translate the policies into practical, detailed guidelines are needed, as they are a prerequisite for successful teamwork. [source] Proceedings of the Australian Physiological and Pharmacological Society Symposium: New Frontiers in Muscle Research Hybrid skeletal muscle fibres: a rare or common phenomenon?CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2001Gabriela MM Stephenson SUMMARY 1. The main aim of the present review is to raise awareness of the molecular complexity of single skeletal muscle fibres from ,normal' and ,transforming' muscles, in recognition of the many types of hybrids that have been observed in vertebrate skeletal muscle. The data used to illustrate various points made in the review were taken from studies on mammalian (mostly rat) and amphibian muscles. 2. The review provides a brief overview of the pattern and extent of molecular heterogeneity in hybrid muscle fibres and of the methodological problems encountered when attempting to identify and characterize such fibres. Particular attention is given to four types of skeletal muscle hybrids: (i) myosin heavy chain (MHC) hybrids; (ii) mismatched MHC,myosin light chains (MLC) hybrids; (iii) mismatched MHC,regulatory protein hybrids; and (iv) hybrids containing mismatched MHC,sarcoplasmic reticulum protein isoforms. 3. Some of the current ideas regarding the functional significance, origin and cognitive value of hybrid fibres are examined critically. [source] | ||||||||||