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Comparative Approach (comparative + approach)
Selected AbstractsESTIMATING PHYLOGENETIC INERTIA IN TITHONIA (ASTERACEAE): A COMPARATIVE APPROACHEVOLUTION, Issue 2 2000Eduardo Morales Abstract., Phylogenetic inertia is a difficult issue in evolutionary biology because we have yet to reach a consensus about how to measure it. In this study a comparative approach is used to evaluate phylogenetic inertia in 14 demographic and morphological characters in 10 species and one subspecies of the genus Tithonia (Asteraceae). Three different methods, autocorrelational analysis, phylogenetic correlograms, and ancestor-state reconstruction, were used to evaluate phylogenetic inertia in these traits. Results were highly dependent on the method applied. Autoregression and phylogenetic eigenvector regression (PVR) methods found more inertia in morphological traits. In contrast, phylogenetic correlograms and ancestor-state reconstruction suggest that morphological characters exhibit less phylogenetic inertia than demographic ones. The differences between results are discussed and methods are compared in an effort to understand phylogenetic inertia more thoroughly. [source] International Corporate Governance , A Comparative Approach , By Thomas ClarkeCORPORATE GOVERNANCE, Issue 3 2008Bob Tricker No abstract is available for this article. [source] Mother,Infant Person- and Object-Directed Interactions in Latino Immigrant Families: A Comparative ApproachINFANCY, Issue 4 2008Linda R. Cote Cultural variation in durations, relations, and contingencies of mother,infant person-and object-directed behaviors were examined for 121 nonmigrant Latino mother,infant dyads in South America, Latina immigrants from South America and their infants living in the United States, and European American mother,infant dyads. Nonmigrant Latina mothers and infants engaged in person-directed behaviors longer than Latino immigrant or European American mothers and infants. Mother and infant person-directed behaviors were positively related; mother and infant object-related behaviors were related for some cultural groups but not others. Nearly all mother and infant behaviors were mutually contingent. Mothers were more responsive to infants' behaviors than infants were to mothers. Some cultural differences in responsiveness emerged. Immigrant status has a differentiated role in mother,infant interactions. [source] Penal Systems: A Comparative Approach , By M. Cavadino and J. DignanTHE BRITISH JOURNAL OF SOCIOLOGY, Issue 3 2007Barbara Mason No abstract is available for this article. [source] Low Pay in the UK: The Case for a Three Sector Comparative ApproachANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 1 2001Stephen Almond This paper represents a first attempt to examine empirically the comparative extensiveness of low pay in the third sector against the theoretical backdrop of both the generic labour market literature and the newly emerging specialist third sector literature. It shows that the third sector occupies an intermediate position between relatively high concentrations of low pay in the private sector and low concentrations in the public sector. These differences do not emerge simply because the categories of vulnerable workers identified in the generic labour market literature are less likely to be found in the third sector. Nor do they reflect differences in sectoral industry and occupation composition. Theoretical explanations for these differences are to be found in the third sector literature. [source] Occurrence and distribution of sesamoid bones in squamates: a comparative approachACTA ZOOLOGICA, Issue 3 2010Adriana Jerez Abstract Jerez, A., Mangione, S. and Abdala, V. 2010. Occurrence and distribution of sesamoid bones in squamates: a comparative approach.,Acta Zoologica (Stockholm) 91: 295,305 Sesamoids are defined as skeletal elements that develop within a continuous band of regular dense connective tissue (tendon or ligament) adjacent to an articulation or joint. In this work, we discuss developmental data on two squamate species, provide data on the onset of the squamate sesamoids and the muscles they are associated to. Our results show that Mabuya mabouya and Liolaemus albiceps exhibited rather similar ontogenetic patterns and that the first sesamoids appear in embryos. The ossifying sesamoid timing is different between M. mabouya and L. albiceps, being faster in the former. In adults, we found 41 sesamoids, considering both fore and hindlimbs. We did not find any intrataxonomic differences, or any differences between the right and left side of the specimens in relation to the sesamoid presence. We recognize four types of sesamoids: (1) embedded sesamoids; (2) interosseus sesamoids; (3) glide sesamoids; and (4) supporting sesamoids. A table is included with a preliminary survey of the sesamoid distribution pattern in 10 Squamate clades. [source] SCALES: a large-scale assessment model of soil erosion hazard in Basse-Normandie (northern-western France)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2010P. Le Gouée Abstract The cartography of erosion risk is mainly based on the development of models, which evaluate in a qualitative and quantitative manner the physical reproduction of the erosion processes (CORINE, EHU, INRA). These models are mainly semi-quantitative but can be physically based and spatially distributed (the Pan-European Soil Erosion Risk Assessment, PESERA). They are characterized by their simplicity and their applicability potential at large temporal and spatial scales. In developing our model SCALES (Spatialisation d'éChelle fine de l'ALéa Erosion des Sols/large-scale assessment and mapping model of soil erosion hazard), we had in mind several objectives: (1) to map soil erosion at a regional scale with the guarantee of a large accuracy on the local level, (2) to envisage an applicability of the model in European oceanic areas, (3) to focus the erosion hazard estimation on the level of source areas (on-site erosion), which are the agricultural parcels, (4) to take into account the weight of the temporality of agricultural practices (land-use concept). Because of these objectives, the nature of variables, which characterize the erosion factors and because of its structure, SCALES differs from other models. Tested in Basse-Normandie (Calvados 5500,km2) SCALES reveals a strong predisposition of the study area to the soil erosion which should require to be expressed in a wet year. Apart from an internal validation, we tried an intermediate one by comparing our results with those from INRA and PESERA. It appeared that these models under estimate medium erosion levels and differ in the spatial localization of areas with the highest erosion risks. SCALES underlines here the limitations in the use of pedo-transfer functions and the interpolation of input data with a low resolution. One must not forget however that these models are mainly focused on an interregional comparative approach. Therefore the comparison of SCALES data with those of the INRA and PESERA models cannot result on a convincing validation of our model. For the moment the validation is based on the opinion of local experts, who agree with the qualitative indications delivered by our cartography. An external validation of SCALES is foreseen, which will be based on a thorough inventory of erosion signals in areas with different hazard levels. Copyright © 2010 John Wiley & Sons, Ltd. [source] Competitive coexistence in spatially structured environments: a synthesisECOLOGY LETTERS, Issue 12 2003Priyanga Amarasekare Abstract Theoretical developments in spatial competitive coexistence are far in advance of empirical investigations. A framework that makes comparative predictions for alternative hypotheses is a crucial element in narrowing this gap. This review attempts to synthesize spatial competition theory into such a framework, with the goal of motivating empirical investigations that adopt the comparative approach. The synthesis presented is based on a major axis, coexistence in spatially homogeneous vs. heterogeneous competitive environments, along which the theory can be organized. The resulting framework integrates such key concepts as niche theory, spatial heterogeneity and spatial scale(s) of coexistence. It yields comparative predictions that can guide empirical investigations. [source] ESTIMATING PHYLOGENETIC INERTIA IN TITHONIA (ASTERACEAE): A COMPARATIVE APPROACHEVOLUTION, Issue 2 2000Eduardo Morales Abstract., Phylogenetic inertia is a difficult issue in evolutionary biology because we have yet to reach a consensus about how to measure it. In this study a comparative approach is used to evaluate phylogenetic inertia in 14 demographic and morphological characters in 10 species and one subspecies of the genus Tithonia (Asteraceae). Three different methods, autocorrelational analysis, phylogenetic correlograms, and ancestor-state reconstruction, were used to evaluate phylogenetic inertia in these traits. Results were highly dependent on the method applied. Autoregression and phylogenetic eigenvector regression (PVR) methods found more inertia in morphological traits. In contrast, phylogenetic correlograms and ancestor-state reconstruction suggest that morphological characters exhibit less phylogenetic inertia than demographic ones. The differences between results are discussed and methods are compared in an effort to understand phylogenetic inertia more thoroughly. [source] Enhancing catch-and-release science with biotelemetryFISH AND FISHERIES, Issue 1 2008Michael R. Donaldson Abstract Catch-and-release (C&R) angling is widely practised by anglers and is a common fisheries management strategy or is a by-product of harvest regulations. Accordingly, there is a growing body of research that examines not only the mortality associated with C&R, but also the sublethal physiological and behavioural consequences. Biotelemetry offers a powerful means of remotely monitoring the behaviour, physiology and mortality of fish caught and released in their natural environment, but we contend that its usefulness is still underappreciated by scholars and managers. In this study, we review the applications of biotelemetry in C&R science, identify novel research directions, opportunities and challenges. There are now about 250 C&R studies but only one quarter of these utilize biotelemetry. In fact, almost all of the C&R studies that have used biotelemetry have been conducted within the last decade. We found that the majority of C&R telemetry studies used either radio or acoustic telemetry, while comparatively few studies have used satellite technologies. Most C&R biotelemetry studies have been used to assess mortality rates, behavioural impairments or to evaluate the effects of displacement on fish. A small fraction of studies (<8%) have used physiological sensors despite the fact that these tools are highly applicable to understanding the multiple sublethal consequences of C&R and are useful for providing mechanistic insights into endpoints such as death. We conclude that C&R science has the potential to benefit greatly from biotelemetry technology, particularly with respect to providing more robust short-term and delayed mortality estimates and adopting a more integrative and comparative approach to understanding the lethal and sublethal impacts of C&R. However, there are still a number of challenges including (i) the need for appropriate controls and methodological approaches, (ii) the need for accounting for tagging and handling stress and mortality, and (iii) the need for certainty in assessing mortality. However, the benefits associated with C&R biotelemetry outweigh its disadvantages and limitations and thereby offer C&R researchers a suite of new tools to enhance fisheries management and conservation. [source] Relative influence of fisheries and climate on the demography of four albatross speciesGLOBAL CHANGE BIOLOGY, Issue 7 2010VIRGINIE ROLLAND Abstract Worldwide ecosystems are modified by human activities and climate change. To be able to predict future changes, it is necessary to understand their respective role on population dynamics. Among the most threatened species are top predators because of their position in the food web. Albatross populations are potentially affected by both human activities, especially longline fisheries, and climatic fluctuations. Based on long-term data (1985,2006), we conducted through a comparative approach a demographic analysis (adult survival and breeding success) on four albatross species breeding on the Indian Ocean sub-Antarctic Islands to assess the relative impact of climate and fisheries during and outside the breeding season. The study revealed that adult survival of almost all species was not affected by climate, and therefore probably canalized against climatic variations, but was negatively affected by tuna longlining effort in three species. Breeding success was affected by climate, with contrasted effects between species, with Southern Oscillation Index having an impact on all species but one. Differences in demographic responses depended on the foraging zone and season. In order to predict population trajectories of seabirds such as albatrosses, our results show the importance of assessing the relative influence of fishing and climate impacts on demography. [source] The difficulties of empire: present, past and future*HISTORICAL RESEARCH, Issue 205 2006Linda Colley Although empire is now an intensely fashionable subject of enquiry, much contemporary comment is relatively uninformed and lacks historical context. This is particularly significant in the light of the United States' purported new imperialism. This article considers the problems faced by those attempting to define empire, whether in the past or the present. It traces the origins of American imperialism to the beginnings of the republic and before, and compares it with the British experience, arguing in all cases for the importance of a wide-ranging and comparative approach to empire. Finally, it urges historians and political commentators to move beyond a concentration on dead European empires, to look as well at other and at present-day versions of the phenomenon, and to re-examine the overlap between nation and empire. [source] Comparative analysis of mt LSU rRNA secondary structures of Odonates: structural variability and phylogenetic signalINSECT MOLECULAR BIOLOGY, Issue 6 2003B. Misof Abstract Secondary structures of the most conserved part of the mt 16S rRNA gene, domains IV and V, have been recently analysed in a comparative study. However, full secondary structures of the mt LSU rRNA molecule are published for only a few insect species. The present study presents full secondary structures of domains I, II, IV and V of Odonates and one representative of mayflies, Ephemera sp. The reconstructions are based on a comparative approach and minimal consensus structures derived from sequence alignments. The inferred structures exhibit remarkable similarities to the published Drosophila melanogaster model, which increases confidence in these structures. Structural variance within Odonates is homoplastic, and neighbour-joining trees based on tree edit distances do not correspond to any of the phylogenetically expected patterns. However, despite homoplastic quantitative structural variation, many similarities between Odonates and Ephemera sp. suggest promising character sets for higher order insect systematics that merit further investigations. [source] Behavioural syndromes differ predictably between 12 populations of three-spined sticklebackJOURNAL OF ANIMAL ECOLOGY, Issue 6 2007NIELS J. DINGEMANSE Summary 1Animals often differ in suites of correlated behaviours, comparable with how humans differ in personality. Constraints on the architecture of behaviour have been invoked to explain why such ,behavioural syndromes' exist. From an adaptationist viewpoint, however, behavioural syndromes should evolve only in those populations where natural selection has favoured such trait covariance, and they should therefore exist only in particular types of population. 2A comparative approach was used to examine this prediction of the adaptive hypothesis. We measured behavioural correlations in 12 different populations of three-spined stickleback (Gasterosteus aculeatus) and assessed whether they indeed varied consistently according to the selective environment, where population was unit of analysis. 3For a sample of fry from each population, we measured five different behaviours within the categories of (i) aggression (towards conspecifics); (ii) general activity; and (iii) exploration,avoidance (of novel foods, novel environments and altered environments). 4We show that behavioural syndromes are not always the same in different types of stickleback population: the often-documented syndrome between aggressiveness, activity and exploratory behaviour existed only in large ponds where piscivorous predators were present. In small ponds where predators were absent, these behaviours were not (or only weakly) associated. 5Our findings imply that population variation in behavioural syndromes does not result from stochastic evolutionary processes, but may result instead from adaptive evolution of behaviour favouring what should prove to be optimal trait combinations. [source] Evolutionary transitions among dioecy, androdioecy and hermaphroditism in limnadiid clam shrimp (Branchiopoda: Spinicaudata)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 9 2009S. C. WEEKS Abstract Examinations of breeding system transitions have primarily concentrated on the transition from hermaphroditism to dioecy, likely because of the preponderance of this transition within flowering plants. Fewer studies have considered the reverse transition: dioecy to hermaphroditism. A fruitful approach to studying this latter transition can be sought by studying clades in which transitions between dioecy and hermaphroditism have occurred multiple times. Freshwater crustaceans in the family Limnadiidae comprise dioecious, hermaphroditic and androdioecious (males + hermaphrodites) species, and thus this family represents an excellent model system for the assessment of the evolutionary transitions between these related breeding systems. Herein we report a phylogenetic assessment of breeding system transitions within the family using a total evidence comparative approach. We find that dioecy is the ancestral breeding system for the Limnadiidae and that a minimum of two independent transitions from dioecy to hermaphroditism occurred within this family, leading to (1) a Holarctic, all-hermaphrodite species, Limnadia lenticularis and (2) mixtures of hermaphrodites and males in the genus Eulimnadia. Both hermaphroditic derivatives are essentially females with only a small amount of energy allocated to male function. Within Eulimnadia, we find several all-hermaphrodite populations/species that have been independently derived at least twice from androdioecious progenitors within this genus. We discuss two adaptive (based on the notion of ,reproductive assurance') and one nonadaptive explanations for the derivation of all-hermaphroditism from androdioecy. We propose that L. lenticularis likely represents an all-hermaphrodite species that was derived from an androdioecious ancestor, much like the all-hermaphrodite populations derived from androdioecy currently observed within the Eulimnadia. Finally, we note that the proposed hypotheses for the dioecy to hermaphroditism transition are unable to explain the derivation of a fully functional, outcrossing hermaphroditic species from a dioecious progenitor. [source] Comparative study in stingless bees (Meliponini) demonstrates that nest entrance size predicts traffic and defensivityJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2008M. J. COUVILLON Abstract Stingless bees (Meliponini) construct their own species-specific nest entrance. The size of this entrance is under conflicting selective pressures. Smaller entrances are easier to defend; however, a larger entrance accommodates heavier forager traffic. Using a comparative approach with 26 species of stingless bees, we show that species with greater foraging traffic have significantly larger entrances. Such a strong correlation between relative entrance area and traffic across the different species strongly suggests a trade-off between traffic and security. Additionally, we report on a significant trend for higher forager traffic to be associated with more guards and for those guards to be more aggressive. Finally, we discuss the nest entrance of Partamona, known in Brazil as boca de sapo, or toad mouth, which has a wide outer entrance but a narrow inner entrance. This extraordinary design allows these bees to finesse the defensivity/traffic trade-off. [source] Interspecific variation in plumage colour among birds: species recognition or light environment?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2002Melinda K. McNaught Abstract The traditional explanation for interspecific plumage colour variation in birds is that colour differences between species are adaptations to minimize the risk of hybridization. Under this explanation, colour differences between closely related species of birds represent reproductive character displacement. An alternative explanation is that interspecific variation in plumage colour is an adaptive response to variation in light environments across habitats. Under this explanation, differences in colour between closely related species are a product of selection on signal efficiency. We use a comparative approach to examine these two hypotheses, testing the effects of sympatry and habitat use, respectively, on divergence in male plumage colour. Contrary to the prediction of the Species Isolation Hypothesis, we find no evidence that sympatric pairs of species are consistently more divergent in coloration than are allopatric pairs of species. However, in agreement with the Light Environment Hypothesis, we find significant associations between plumage coloration and habitat use. All of these results remain qualitatively unchanged irrespective of the statistical methodology used to compare reflectance spectra, the body regions used in the analyses, or the exclusion of areas of plumage not used in sexual displays. Our results suggest that, in general, interspecific variation in plumage colour among birds is more strongly influenced by the signalling environment than by the risk of hybridization. [source] Antimicrobial peptide interactions with silica bead supported bilayers and E. coli: buforin II, magainin II, and arenicin,JOURNAL OF PEPTIDE SCIENCE, Issue 8 2009Ryan W. Davis Abstract Using the unique quantitative capabilities of hyperspectral confocal microscopy combined with multivariate curve resolution, a comparative approach was employed to gain a deeper understanding of the different types of interactions of antimicrobial peptides (AMPs) with biological membranes and cellular compartments. This approach allowed direct comparison of the dynamics and local effects of buforin II, magainin II, and arenicin with nanoporous silica bead supported bilayers and living E. coli. Correlating between experiments and comparing these responses have yielded several important discoveries for pursuing the underlying biophysics of bacteriocidal specificity and the connection between structure and function in various cellular environments. First, a novel fluorescence method for direct comparison of a model and living system is demonstrated by utilizing the membrane partitioning and environmental sensitivity of propidium iodide. Second, measurements are presented comparing the temporal dynamics and local equilibrium concentrations of the different antimicrobial agents in the membrane and internal matrix of the described systems. Finally, we discuss how the data lead to a deeper understanding of the roles of membrane penetration and permeabilization in the action of these AMPs. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd. [source] The young Lipset on the iron law of oligarchy: a taste of things to come1THE BRITISH JOURNAL OF SOCIOLOGY, Issue 2010Patrick McGovern Abstract Lipset's ,Democracy in Private Government' was a remarkable publication for three reasons. It was his first attempt to challenge Michels' ,iron law of oligarchy' and would lead to a programme of research that that would culminate with the publication of the widely admired classic study Union Democracy. Second, the inspiration for this work came from Lipset's student days when he was a socialist activist trying to understand why leftist governments often failed to carry out substantial programmes of social reform. Third, although it was one of his earliest publications it bears all the hallmarks of the work that would subsequently make Lipset a giant of political sociology: the enthusiasm for classic sociological problems; the appreciation of history; and the ingenious use of the small n comparative approach. Finally, I would argue that Lipset's study of democracy within private government represents a missed opportunity for sociology though there are signs that this is being rectified in recent years. [source] International medical graduates: Learning for practice in Alberta, CanadaTHE JOURNAL OF CONTINUING EDUCATION IN THE HEALTH PROFESSIONS, Issue 3 2007Jocelyn Lockyer PhD Abstract Introduction: There is little known about the learning that is undertaken by physicians who graduate from a World Health Organization,listed medical school outside Canada and who migrate to Canada to practice. What do physicians learn and what resources do they access in adapting to practice in Alberta, a province of Canada? Methods: Telephone interviews with a theoretical sample of 19 IMG physicians were analyzed using a grounded theory constant comparative approach to develop categories, central themes, and a descriptive model. Results: The physicians described two types of learning: learning associated with studying for Canadian examinations required to remain and practice in the province and learning that was required to succeed at clinical work in a new setting. This second type of learning included regulations and systems, patient expectations, new disease profiles, new medications, new diagnostic procedures, and managing the referral process. The physicians "settled" into their new setting with the help of colleagues; the Internet, personal digital assistants (PDAs), and computers; reading; and continuing medical education programs. Patients both stimulated learning and were a resource for learning. Discussion: Settling into Alberta, Canada, physicians accommodated and adjusted to their settings with learning activities related to the clinical problems and situations that presented themselves. Collegial support in host communities appeared to be a critical dimension in how well physicians adjusted. The results suggest that mentoring programs may be a way of facilitating settlement. [source] Doing interdisciplinarity: motivation and collaboration in research for sustainable agriculture in the UKAREA, Issue 4 2009Frances Harris This paper studies knowledge production in complex, collaborative research projects that brought together academics from different disciplines, research users and agricultural businesses. It takes a comparative approach, studying the interactions within interdisciplinary research teams from ten case studies, considering the process of collaboration from initial idea through to publication. The research developed a typology of participants in these projects, and identified the motivations and challenges of each. Our results analyse the process of research teams coming together and the relationships that are built up during the research. A particular challenge identified was the building of cooperation and trust. This issue is explored alongside issues of communication, methodology, data analysis and the process of drawing and publicising conclusions. [source] Belonging to a community-based football team: An ethnographic studyAUSTRALIAN OCCUPATIONAL THERAPY JOURNAL, Issue 4 2009Lorrae Mynard Purpose:,This study considered the benefits derived from participation in a community-based Australian Rules Football league in Melbourne, Australia. The RecLink league deliberately tackles the social and occupational disadvantages associated with mental illness, addictions, unemployment and homelessness. Methods:,An ethnographic methodology was used to study one team from the RecLink football league throughout an entire season. Fieldnotes were written following participant observation at training, games and events, and five in-depth interviews were conducted and transcribed. A constant comparative approach to data analysis was adopted. Results:,Three major themes were identified: a spirit of inclusion, team-building and meaning of team involvement. The first describes how members were accepted, welcomed and given the opportunity for team involvement, with the expectation that they ,had a go', and ,tried their best'. The second illustrates how the team collectively fostered a culture of friendship, cooperation and support. The third examines the significance of being part of the team, incorporating personal contributions and gains, and meanings attributed to team involvement. Conclusions:,These findings demonstrated how football can be used as non-clinical, community-based occupational therapy: enabling participation in a personally meaningful and culturally valued occupation. Occupational therapists are challenged to explore further how such community-based sports programs may complement existing clinical and welfare-based approaches to social disadvantage. [source] Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investmentBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010SUSANNE SHULTZ In birds, large brains are associated with a series of population-level phenomena, including invasion success, species richness, and resilience to population decline. Thus, they appear to open up adaptive opportunities through flexibility in foraging and anti-predator behaviour. The evolutionary pathway leading to large brain size has received less attention than behavioural and ecological correlates. Using a comparative approach, we show that, independent of previously recognized associations with developmental constraints, relative brain size in birds is strongly related to biparental care, pair-bonding, and stable social relationships. We also demonstrate correlated evolution between large relative brain size and altricial development, and that the evolution of both traits is contingent on biparental care. Thus, biparental care facilitates altricial development, which permits the evolution of large relative brain size. Finally, we show that large relative brain size is associated with pair-bond strength, itself a likely consequence of cooperation and negotiation between partners under high levels of parental investment. These analyses provide an evolutionary model for the evolution of and prevalence of biparental care, altricial development, and pair-bonding in birds. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 111,123. [source] Begging call matching between a specialist brood parasite and its host: a comparative approach to detect coevolutionBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009MICHAEL G. ANDERSON Studies of avian brood parasite systems have typically investigated the mimicry of host eggs by specialist parasites. Yet, several examples of similarity between host and parasite chick appearance or begging calls suggest that the escalation of host,parasite arms races may also lead to visual or vocal mimicry at the nestling stage. Despite this, there have been no large-scale comparative studies of begging calls to test whether the similarity of host and parasite is greater than predicted by chance or phylogenetic distance within a geographically distinct species assemblage. Using a survey of the begging calls of all native forest passerines in New Zealand, we show that the begging call of the host-specialist shining cuckoo (Chrysococcyx lucidus) is most similar to that of its grey warbler (Gerygone igata) host compared to any of the other species, and that this is unlikely to have occurred by chance. Randomization tests revealed that the incorporation of the shining cuckoo's begging calls into our species-set consistently reduced the phylogenetic signal within cluster trees based on begging call similarity. By contrast, the removal of the grey warbler calls did not reduce the phylogenetic signal in the begging call similarity trees. These two results support a scenario in which coevolution of begging calls has not taken place: the begging call of the host retains its phylogenetic signal, whereas that of the parasite has changed to match that of its host. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 208,216. [source] Plasticity, its cost, and phenotypic selection under water and nutrient stress in two annual grassesBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009SERGEI VOLIS A comparative approach can prove to be a useful tool for studying phenotypic plasticity, if applied to specific traits involved in adaptation to particular environment in more than one species across co-located populations. The present study tested whether two annual grasses, Hordeum spontaneum and Avena sterilis, belonging to the same guild, having similar stature, seed dispersal mechanism, breeding system, and genetic variation, and sampled in exactly the same environmentally specific locations, differed with respect to: (1) plasticity in traits involved in adaptation, namely the onset of reproduction and maternal investment involving the number of inflorescences, spikelets per inflorescence, the weight of individual spikelets, and abortion rate; (2) the cost of this plasticity, and (3) the pattern of phenotypic selection on the above traits. The two species exhibited highly differing amounts of phenotypic plasticity in the onset of flowering and several reproductive traits (number of inflorescences, spikelets per inflorescence, abortion rate), but no plasticity costs in any experimental environment. The two species demonstrated a decreasing similarity in the regulation of reproduction in four experimental environments: benign, water, nutrients and water × nutrient deficient. Correlational selection appears to contribute, although not solely, to the observed species differences with respect to the regulation of reproduction. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 581,593. [source] The geometry of coexistenceBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2000PRIYANGA AMARASEKARE Understanding the processes that maintain diversity has been the focus of extensive study, yet there is much that has not been integrated into a cohesive framework. First, there is a separation of perspective. Ecological and evolutionary approaches to diversity have progressed in largely parallel directions. Second, there is a separation of emphasis. In both ecology and population genetics, classical theories favour local explanations with emphasis on population dynamics and selection within populations, while contemporary theories favour spatial explanations, with emphasis on population structure and interactions among populations. What is lacking is a comparative approach that evaluates the relative importance of local and spatial processes in maintaining genetic and ecological diversity. I present a framework for diversity maintenance that emphasizes the comparative approach. I use a well-known but little-used mathematical approach, the perturbation theorem for dynamical systems, to identify key points of contact between ecological and population genetic theories of coexistence. These connections provide for a synthesis of several important concepts: population structure (source-sink versus extinction-colonization), spatial heterogeneity (intrinsic versus extrinsic) in fitness and competitive ability, and temporal scales over which local and spatial processes influence diversity. This framework ties together a large and diverse body of theory and data from ecology and population genetics. It yields comparative predictions that can serve as guidelines in biodiversity management. [source] Repeat Teenage Pregnancy in Two Cultures,The Meanings Ascribed by TeenagersCHILDREN & SOCIETY, Issue 3 2010Jean Clarke This qualitative study charts the views, feelings and experiences of two diverse, yet in many ways similar, groups of respondents from two cultures , one group of 26 respondents from the Caribbean islands of Jamaica and Barbados and the other group of 26 respondents from London, who have experienced repeat teenage pregnancies. The study uses a comparative approach to provide a psychosocial, emotional and economic understanding of the factors, which lead to repeat pregnancies. This study cautions against an over reliance on a mechanistic understanding and management of both single and repeat teenage pregnancies, and emphasises the fact that economic, social, psychological and emotional processes are also crucial to our understanding of repeat teenage pregnancies. [source] Task-dependent modulation of functional connectivity between hand motor cortices and neuronal networks underlying language and music: a transcranial magnetic stimulation study in humansEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2007R. Sparing Abstract Although language functions are, in general, attributed to the left hemisphere, it is still a matter of debate to what extent the cognitive functions underlying the processing of music are lateralized in the human brain. To investigate hemispheric specialization we evaluated the effect of different overt musical and linguistic tasks on the excitability of both left and right hand motor cortices using transcranial magnetic stimulation (TMS). Task-dependent changes of the size of the TMS-elicited motor evoked potentials were recorded in 12 right-handed, musically naive subjects during and after overt speech, singing and humming, i.e. the production of melody without word articulation. The articulation of meaningless syllables served as control condition. We found reciprocal lateralized effects of overt speech and musical tasks on motor cortex excitability. During overt speech, the corticospinal projection of the left (i.e. dominant) hemisphere to the right hand was facilitated. In contrast, excitability of the right motor cortex increased during both overt singing and humming, whereas no effect was observed on the left hemisphere. Although the traditional concept of hemispheric lateralization of music has been challenged by recent neuroimaging studies, our findings demonstrate that right-hemisphere preponderance of music is nevertheless present. We discuss our results in terms of the recent concepts on evolution of language and gesture, which hypothesize that cerebral networks mediating hand movement and those subserving language processing are functionally linked. TMS may constitute a useful tool to further investigate the relationship between cortical representations of motor functions, music and language using comparative approaches. [source] CORRELATED EVOLUTION OF MIGRATION AND SEXUAL DICHROMATISM IN THE NEW WORLD ORIOLES (ICTERUS)EVOLUTION, Issue 12 2009Nicholas R. Friedman The evolution of sexual dimorphism has long been attributed to sexual selection, specifically as it would drive repeated gains of elaborate male traits. In contrast to this pattern, New World oriole species all exhibit elaborate male plumage, and the repeated gains of sexual dichromatism observed in the genus are due to losses of female elaboration. Interestingly, most sexually dichromatic orioles belong to migratory or temperate-breeding clades. Using character scoring and ancestral state reconstructions from two recent studies in Icterus, we tested a hypothesis of correlated evolution between migration and sexual dichromatism. We employed two discrete phylogenetic comparative approaches: the concentrated changes test and Pagel's discrete likelihood test. Our results show that the evolution of these traits is significantly correlated (CCT: uncorrected P < 0.05; ML: LRT = 12.470, P < 0.005). Indeed, our best model of character evolution suggests that gains of sexual dichromatism are 23 times more likely to occur in migratory taxa. This study demonstrates that a life-history trait with no direct relationship with sexual selection has a strong influence on the evolution of sexual dichromatism. We recommend that researchers further investigate the role of selection on elaborate female traits in the evolution of sexual dimorphism. [source] ADAPTATION TO EXPERIMENTAL ALTERATIONS OF THE OPERATIONAL SEX RATIO IN POPULATIONS OF DROSOPHILA MELANOGASTEREVOLUTION, Issue 2 2008Max Reuter Theory predicts that males adapt to sperm competition by increasing their investment in testis mass to transfer larger ejaculates. Experimental and comparative data support this prediction. Nevertheless, the relative importance of sperm competition in testis size evolution remains elusive, because experiments vary only sperm competition whereas comparative approaches confound it with other variables, in particular male mating rate. We addressed the relative importance of sperm competition and male mating rate by taking an experimental evolution approach. We subjected populations of Drosophila melanogaster to sex ratios of 1:1, 4:1, and 10:1 (female:male). Female bias decreased sperm competition but increased male mating rate and sperm depletion. After 28 generations of evolution, males from the 10:1 treatment had larger testes than males from other treatments. Thus, testis size evolved in response to mating rate and sperm depletion, not sperm competition. Furthermore, our experiment demonstrated that drift associated with sex ratio distortion limits adaptation; testis size only evolved in populations in which the effect of sex ratio bias on the effective population size had been compensated by increasing the numerical size. We discuss these results with respect to reproductive evolution, genetic drift in natural and experimental populations, and consequences of natural sex ratio distortion. 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