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Resource Acquisition (resource + acquisition)
Selected AbstractsThe Impact of the Roles, Structure and Process of Boards on Firm Performance: evidence from TurkeyCORPORATE GOVERNANCE, Issue 2 2005Veysel Kula This study aims at investigating the impact of the roles, structure and process of boards on performance of Turkish companies. Drawing on the data obtained from a sample of 386 mostly small and non-listed stock ownership companies, it was found that the separation of chairman and general manager positions has significant positive impact on firm performance. From the board roles of control, service and resource acquisition, firm performance was found to be positively related only to the level of adoption of resource acquisition role. It was also found that the effectiveness, information access and performance evaluation attributes of boards are positively and significantly associated with firm performance. [source] Forage collection, substrate preparation, and diet composition in fungus-growing antsECOLOGICAL ENTOMOLOGY, Issue 3 2010HENRIK H. DE FINE LICHT 1. Variation and control of nutritional input is an important selective force in the evolution of mutualistic interactions and may significantly affect coevolutionary modifications in partner species. 2. The attine fungus-growing ants are a tribe of more than 230 described species (12 genera) that use a variety of different substrates to manure the symbiotic fungus they cultivate inside the nest. Common ,wisdom' is that the conspicuous leaf-cutting ants primarily use freshly cut plant material, whereas most of the other attine species use dry and partly degraded plant material such as leaf litter and caterpillar frass, but systematic comparative studies of actual resource acquisition across the attine ants have not been done. 3. Here we review 179 literature records of diet composition across the extant genera of fungus-growing ants. The records confirm the dependence of leaf-cutting ants on fresh vegetation but find that flowers, dry plant debris, seeds (husks), and insect frass are used by all genera, whereas other substrates such as nectar and insect carcasses are only used by some. 4. Diet composition was significantly correlated with ant substrate preparation behaviours before adding forage to the fungus garden, indicating that diet composition and farming practices have co-evolved. Neither diet nor preparation behaviours changed when a clade within the paleoattine genus Apterostigma shifted from rearing leucocoprinous fungi to cultivating pterulaceous fungi, but the evolutionary derived transition to yeast growing in the Cyphomyrmex rimosus group, which relies almost exclusively on nectar and insect frass, was associated with specific changes in diet composition. 5. The co-evolutionary transitions in diet composition across the genera of attine ants indicate that fungus-farming insect societies have the possibility to obtain more optimal fungal crops via artificial selection, analogous to documented practice in human subsistence farming. [source] Appraising the roles of nutrient availability, global change, and functional traits during the angiosperm rise to dominanceECOLOGY LETTERS, Issue 5 2010Kevin E. Mueller Ecology Letters (2010) 13: E1,E6 Abstract To explain the rise of angiosperms during the Cretaceous, Berendse & Scheffer (Ecol. Lett., 12, 2009, 865) invoke feedbacks between leaf litter, soil nutrients, and growth, overlooking other factors affecting resource acquisition by Cretaceous plants. We evaluate their hypothesis, highlight alternative explanations, and emphasize use of a broader framework for understanding the angiosperm radiation. [source] How do plants know when other plants are flowering?ECOLOGY LETTERS, Issue 11 2009Resource depletion, mast-seeding in a perennial wildflower, pollen limitation Abstract Mast-seeding is the synchronous and periodic reproduction by plant populations. This phenomenon has been widely studied from a community-level perspective, but we know extremely little about how plants are able to synchronize reproduction. Here, we present the first experimental test of proximate mechanisms of mast-seeding, by preventing reproduction in an iteroparous, mast-seeding wildflower. Through a series of experiments, we show that mobile carbohydrate stores (NSC) control alternate-year flowering by individual plants; seed set depletes NSC which prevents flowering the following year. Plants are synchronized by density-dependent pollen limitation; when plants flower asynchronously, they set fewer seeds, which prevents NSC depletion. Therefore, these individual plants flower in subsequent years and become synchronized. Because mast-seeding is a consequence of physiological controls of reproduction, differences in plant resource acquisition and allocation could dramatically change patterns of seed production, and changes in plant consumers and pollinators could change selection on physiological and developmental pathways. [source] Community-Led Social Venture CreationENTREPRENEURSHIP THEORY AND PRACTICE, Issue 2 2007Helen Haugh The addition of new enterprises to the economy has long been considered essential to economic growth. The process of venture creation in the private sector has been heavily researched and frequently modeled, although few models explain the process of nonprofit enterprise creation. Nonprofit social ventures pursue economic, social, or environmental aims, generating at least part of their income from trading. They fill market gaps between private enterprise and public sector provision, and, increasingly, policy makers consider them to be valuable agents in social, economic, and environmental regeneration and renewal. This article presents findings from a qualitative study of the inception of five community-led nonprofit social ventures, producing a model of the stages of venture creation: (1) opportunity identification, (2) idea articulation, (3) idea ownership, (4) stakeholder mobilization, (5) opportunity exploitation, and (6) stakeholder reflection. A formal support network and a tailor-made support network are also part of the model, contributing resources to the new venture and assisting progression through the stages. The model highlights the resource acquisition and network creation that precede formal venture creation. In the nonprofit sector, these activities are undertaken by volunteers who do not have a controlling interest in the new venture. For practitioners, the model identifies critical stages in the process of community-led social venture creation and two areas where assistance is most needed: pre-venture business support and postcreating effective networks. [source] ADAPTIVE CHANGE IN THE RESOURCE-EXPLOITATION TRAITS OF A GENERALIST CONSUMER: THE CEOLUTION AND COEXISTENCE OF GENERALISTS AND SPECIALISTSEVOLUTION, Issue 3 2006Peter A. Abrams Abstract Mathematical models of consumer-resource systems are used to explore the evolution of traits related to resource acquisition in a generalist consumer species that is capable of exploiting two resources. The analysis focuses on whether evolution of traits determining the capture rates of two resources by a consumer species produce one generalist, two specialists, or all three types, when all types are characterized by a common fitness function. In systems with a stable equilibrium, evolution produces one generalist or two specialists, depending on the second derivative of the trade-off relationship. When there are sustained population fluctuations, the nature of the trade-off between the consumer's capture rates of the two resources still plays a key role in determining the evolutionary outcome. If the trade-off is described by a choice variable between zero and one that is raised to a power n, polymorphic states are possible when n > 1, which implies a positive second derivative of the curve. These states are either dimorphism, with two relatively specialized consumer types, or trimorphism, with a single generalist type and two specialists. Both endogenously driven consumer-resource cycles, and fluctuations driven by an environmental variable affecting resource growth are considered. Trimorphic evolutionary outcomes are relatively common in the case of endogenous cycles. In contrast to a previous study, these trimorphisms can often evolve even when new lineages are constrained to have phenotypes very similar to existing lineages. Exogenous cycles driven by environmental variation in resource growth rates appear to be much less likely to produce a mixture of generalists and specialists than are endogenous consumer-resource cycles. [source] CONSTANCY OF THE G MATRIX IN ECOLOGICAL TIMEEVOLUTION, Issue 6 2004Mats BjÖrklund Abstract The constancy of the genetic variance-covariance matrix (G matrix) across environments and populations has been discussed and tested empirically over the years but no consensus has so far been reached. In this paper, I present a model in which morphological traits develop hierarchically, and individuals differ in their resource allocation and acquisition patterns. If the variance in resource acquisition is many times larger than the variance in resource allocation then strong genetic correlations are expected, and with almost isometric relations among traits. As the variation in resource acquisition decreases below a certain threshold, the correlations decrease overall and the relations among traits become a function of the allocation patterns, and in particular reflecting the basal division of allocation. A strong bottleneck can break a pattern of strong genetic correlation, but this effect diminishes rapidly with increasing bottleneck size. This model helps to understand why some populations change their genetic correlations in different environments, whereas others do not, since the key factor is the relation between the variances in resource acquisition and allocation. If a change in environment does not lead to a change in this ratio, no change can be expected, whereas if the ratio is changed substantially then major changes can be expected. This model can also help to understand the constancy of morphological patterns within larger taxa as a function of constancy in resource acquisition patterns over time and environments. When this pattern breaks, for example on islands, larger changes can be expected. [source] The capture and gratuitous disposal of resources by plantsFUNCTIONAL ECOLOGY, Issue 1 2001Thomas H. Summary 1,Every plant will die if light, water or nutrients are withheld for long enough. It is natural to think of plants in general as having evolved a strong drive for resource acquisition as a survival mechanism. All else being equal, an individual that sequesters more material from the environment than its neighbour must be at a competitive advantage. 2,But the resource capture imperative seems at odds with the profligacy of some characteristic developmental and metabolic processes in many plants. Here, using leaf senescence as a vantage point, we consider whether a kind of wilful inefficiency of resource use may not be essential for success as a terrestrial autotroph. [source] Nursing Diagnosis Extension and Classification: Ongoing PhaseINTERNATIONAL JOURNAL OF NURSING TERMINOLOGIES AND CLASSIFICATION, Issue 2003Martha Craft-Rosenberg BACKGROUND The Nursing Diagnosis Extension and Classification Project (NDEC) has been active for almost a decade. The team began with the formation of a team of investigators at The University of Iowa College of Nursing. From 1994 until 2000 the research team consisted of 16 investigators who were experts in nursing care across the lifespan. They also represented expertise in both qualitative and quantitative research. The aims of the NDEC research are to evaluate and revise NANDA diagnoses, to validate the diagnoses using a clinical information system, and to develop candidate diagnoses. MAIN CONTENT POINTS Phase 1 of the NDEC research has yielded 116 refined and developed nursing diagnoses that have been submitted to NANDA. Of these, 65 have been approved and 54 appeared in Nursing Diagnoses: Definitions and Classification, 1999,2000 along with 39 NDEC products. In the 2000,2001 edition, 7 diagnoses refined by NDEC and 7 new diagnoses submitted by NDEC are included. As only about half the NDEC products have appeared in NANDA publications, the three-level review process (Diagnosis Review Committee, membership, and Board) has been discussed with the NANDA board. This request is currently being honored by the Diagnosis Review Committee; however, review by the membership and review by the NANDA board is just beginning to move in this direction. Phase 2, clinical validation of the NDEC work, is being conducted at a long-term care facility. It will also be conducted at a large teaching hospital. All the NDEC refinement and development work has been submitted for clinical validation. Currently validation is planned at the label level only. Phase 3 involves identification of candidate diagnoses. Many of the candidate diagnoses were developed during the concept analysis phase, when NDEC team members identified the need for additional diagnoses. Nurses in practice have submitted other candidate diagnoses. In total 195 candidate diagnoses have been identified and placed into a database. In order for the NDEC team to make decisions regarding priorities for diagnosis development, the diagnoses in the candidate database are compared to diagnoses in other classifications that have already been developed. Several classifications are used for comparison including the Omaha System and the Home Health Care Classification. A large table is used to compare candidate label to other labels. Candidate diagnosis included in other classifications will be given lower priority for development by NDEC. CONCLUSIONS The NDEC work plan includes work on diagnoses to be resubmitted to the NANDA Diagnosis Review Committee. It is hoped that the Web site for NLINKS will facilitate the work of diagnosis refinement and development. NDEC will continue to work with any investigator who is seeking assistance. The last part of the work plan is resource acquisition and recruitment of investigators to continue the refinement and development of diagnoses. [source] Deterministic assembly of land snail communities according to species size and dietJOURNAL OF ANIMAL ECOLOGY, Issue 4 2010Brandon Schamp Summary 1.,We investigated whether coexisting snail species in 145 treeless fen communities in the Western Carpathian Mountains differed more in size and diet than would be expected by chance, as predicted for traits commonly associated with competition and differential resource acquisition under limiting similarity theory. 2.,Contrary to expectations, coexisting snail species were no more different in body size than expected by chance under a null model. However, variation in body size played a significant role in structuring snail communities: coexisting snail species were significantly more similar with respect to body size. 3.,We developed two new test statistics to expand our investigation of limiting similarity to include diet, a nominal trait. We tested whether communities of snails were characterized by a greater richness of diet, and whether different diets were represented more or less evenly within communities. Communities of snails were significantly less evenly distributed than expected by chance, with detritivores being over-represented relative to predatory strategies. 4.,We also examined the effect of water pH and conductivity, herbaceous cover, and bryophyte and vascular plant richness, on these trends by examining how the effect size of our tests varied across these gradients. Convergence in species size increased with increasing habitat pH. Specifically, smaller snail species were over-represented in fen communities in general, and this effect was accentuated in increasingly calcareous fens. 5.,Theory predicts that traits related strongly to environmental conditions are more likely to be convergent. Our findings support this suggestion, as small snail species have an advantage in tolerating freezing conditions over winter when refuges are limited. 6.,These results add to the growing body of literature demonstrating that variation in body size and diet play a strong role in structuring communities, although frequently in ways not predicted by limiting similarity theory. Finally, our results increase our understanding of how species are assembled non-randomly into communities with respect to important traits. [source] Lizard community structure along environmental gradientsJOURNAL OF ANIMAL ECOLOGY, Issue 2 2010Lauren B. Buckley Summary 1. ,How the total number of individuals in a community is divided among its species is governed by both the distribution of species along landscape-scale environmental gradients and by local resource partitioning. In vertebrate ectotherms, abiotic environmental conditions may constrain geographic distributions more strongly than local population densities due to thermal constraints on resource acquisition and due to behavioural thermoregulation. 2. ,We investigate whether local density and species richness are decoupled for lizard communities within the Southwest US by comparing 18 species-abundance distributions. 3. ,While species richness decreases strongly with decreasing temperature, there is no significant relationship between temperature or resource availability (net primary productivity) and the total number of individuals within a community. Consequently, in more species-rich communities species have lower mean abundances. 4. ,This suggestion that lizard species richness is not a function of an area's capacity to support more individuals questions for this group species diversity theories based on this assumption. [source] Consequence of herbivory for the fitness cost of herbicide resistance: photosynthetic variation in the context of plant,herbivore interactionsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2005A. J. Gassmann Abstract The cost of adaptations may depend on environmental conditions. We consider how the fitness cost of resistance to the herbicide triazine in Amaranthus hybridus interacts with folivory from the beetle Disonycha glabrata. Triazine-resistant (TR) genotypes suffer a fitness cost because of a pleiotropic reduction in the light reaction of photosynthesis, which in turn often leads to a reduction in photosynthetic rate. We found that the fitness cost of triazine resistance was 360% greater in the presence than absence of D. glabrata. This resulted from multiple phenotypic trade-offs, with TR plants suffering greater herbivory and displaying a diminished tolerance of damage. Our work highlights the importance of incorporating appropriate ecological variation into the assessment of fitness trade-offs. The results of this study also illustrate the potential for herbivores to impose selection on photosynthetic variation, and for variation in resource acquisition to obscure fitness costs. [source] WATER MOTION, MARINE MACROALGAL PHYSIOLOGY, AND PRODUCTIONJOURNAL OF PHYCOLOGY, Issue 3 2000Catriona L. Hurd Water motion is a key determinant of marine macroalgal production, influencing directly or indirectly physiological rates and community structure. Our understanding of how marine macroalgae interact with their hydrodynamic environment has increased substantially over the past 20 years, due to the application of tools such as flow visualization to aquatic vegetation, and in situ measurements of seawater velocity and turbulence. This review considers how the hydrodynamic environment in which macroalgae grow influences their ability to acquire essential resources and how macroalgae might respond physiologically to fluctuations in their hydrodynamic regime with a focus on: (1) the biochemical processes occurring within the diffusion boundary layer (DBL) that might reduce rates of macroalgal production; (2) time scales over which measurements of velocity and DBL processes should be made, discussing the likelihood of in situ mass transfer limitation; (3) if and how macroalgal morphology influences resource acquisition in slow flows; and (4) ecobiomechanics and how hydrodynamic drag might influence resource acquisition and allocation. Finally, the concept that macroalgal production is enhanced in wave-exposed versus sheltered habitats is discussed. [source] Predictors of plant phenology in a diverse high-latitude alpine landscape: growth forms and topographyJOURNAL OF VEGETATION SCIENCE, Issue 5 2009Marianne Iversen Abstract Question: Different plant growth forms may have distinctly different functioning in ecosystems. Association of phenological patterns with growth form will therefore help elucidate the role of phenology in an ecosystem. We ask whether growth forms of common vascular plants differ in terms of vegetative and flowering phenology, and if such phenological differences are consistent across environmental gradients caused by landscape-scale topography. Location: A high-latitude alpine landscape in Finnmark County, Norway (70°N). Methods: We assessed vegetative and flowering phenology repeatedly in five growth forms represented by 11 common vascular plant species across an altitudinal gradient and among differing slope aspects. Results: Species phenology clustered well according to growth form, and growth form strongly explained variation in both flowering and vegetative phenology. Altitude and aspect were poor predictors of phenological variation. Vegetative phenology of the growth forms, ranked from slowest to fastest, was in the order evergreen shrubs Toward a stoichiometric framework for evolutionary biologyOIKOS, Issue 1 2005Adam D. Kay Ecological stoichiometry, the study of the balance of energy and materials in living systems, may serve as a useful synthetic framework for evolutionary biology. Here, we review recent work that illustrates the power of a stoichiometric approach to evolution across multiple scales, and then point to important open questions that may chart the way forward in this new field. At the molecular level, stoichiometry links hereditary changes in the molecular composition of organisms to key phenotypic functions. At the level of evolutionary ecology, a simultaneous focus on the energetic and material underpinnings of evolutionary tradeoffs and transactions highlights the relationship between the cost of resource acquisition and the functional consequences of biochemical composition. At the macroevolutionary level, a stoichiometric perspective can better operationalize models of adaptive radiation and escalation, and elucidate links between evolutionary innovation and the development of global biogeochemical cycles. Because ecological stoichiometry focuses on the interaction of energetic and multiple material currencies, it should provide new opportunities for coupling evolutionary dynamics across scales from genomes to the biosphere. [source] Socioeconomic status, education, and reproduction in modern women: An evolutionary perspectiveAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010Susanne Huber Although associations between status or resources and reproduction are positive in premodern societies and also in men in modern societies, in modern women the associations are typically negative. We investigated how the association between socioeconomic status and reproductive output varies with the source of status and resources, the woman's education, and her age at reproductive onset (proxied by age at marriage). By using a large sample of US women, we examined the association between a woman's reproductive output and her own and her husband's income and education. Education, income, and age at marriage are negatively associated with a woman's number of children and increase her chances of childlessness. Among the most highly educated two-thirds of the sample of women, husband's income predicts the number of children. The association between a woman's number of children and her husband's income turns from positive to negative when her education and age at marriage is low (even though her mean offspring number rises at the same time). The association between a woman's own income and her number of children is negative, regardless of education. Rather than maximizing the offspring number, these modern women seem to adjust investment in children based on their family size and resource availability. Striving for resources seems to be part of a modern female reproductive strategy,but, owing to costs of resource acquisition, especially higher education, it may lead to lower birthrates: a possible evolutionary explanation of the demographic transition, and a complement to the human capital theory of net reproductive output. Am. J. Hum. Biol. 22:578,587, 2010. © 2010 Wiley-Liss, Inc. [source] Progress in Parasitic Plant Biology: Host Selection and Nutrient TransferPLANT BIOLOGY, Issue 2 2006H. Shen Abstract: Host range varies widely among species of parasitic plants. Parasitic plants realize host selection through induction by chemical molecular signals, including germination stimulants and haustoria-inducing factors (HIFs). Research on parasitic plant biology has provided information on germination, haustorium induction, invasion, and haustorial structures and functions. To date, some molecular mechanisms have been suggested to explain how germination stimulants work, involving a chemical change caused by addition of a nucleophilic protein receptor, and direct or indirect stimulation of ethylene generation. Haustorium initiation is induced by HIFs that are generated by HIF-releasing enzymes from the parasite or triggered by redox cycling between electrochemical states of the inducers. Haustorium attachment is non-specific, however, the attachment to a host is facilitated by mucilaginous substances produced by haustorial hairs. Following the attachment, the intrusive cells of parasites penetrate host cells or push their way through the host epidermis and cortex between host cells, and some types of cell wall-degrading enzymes may assist in the penetration process. After the establishment of host-parasite associations, parasitic plants develop special morphological structures (haustoria) and physiological characteristics, such as high transpiration rates, high leaf conductance, and low water potentials in hemiparasites, for nutrient transfer and resource acquisition from their hosts. Therefore, they negatively affect the growth and development and even cause death of their hosts. [source] Transformational Leadership and Organizational Innovation: The Roles of Internal and External Support for Innovation,THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 3 2009Lale Gumusluo Leadership has been suggested to be an important factor affecting innovation. A number of studies have shown that transformational leadership positively influences organizational innovation. However, there is a lack of studies examining the contextual conditions under which this effect occurs or is augmented. Therefore, this study aimed to investigate the impact of transformational leadership on organizational innovation and to determine whether internal and external support for innovation as contextual conditions influence this effect. Organizational innovation was conceptualized as the tendency of the organization to develop new or improved products or services and its success in bringing those products or services to the market. Transformational leadership was hypothesized to have a positive influence on organizational innovation. Furthermore, this effect was proposed to be moderated by internal support for innovation, which refers to an innovation supporting climate and adequate resources allocated to innovation. Support received from external organizations for the purposes of knowledge and resource acquisition was also proposed to moderate the relationship between transformational leadership and organizational innovation. To test these hypotheses, data were collected from 163 research and development (R&D) employees and managers of 43 micro- and small-sized Turkish entrepreneurial software development companies. Two separate questionnaires were used to collect the data. Employees' questionnaires included measures of transformational leadership and internal support for innovation, whereas managers' questionnaires included questions about product innovations of their companies and the degree of support they received from external institutions. Organizational innovation was measured with a market-oriented criterion developed specifically for developing countries and newly developing industries. Hierarchical regression analysis was used to test the hypothesized effects. The results of the analysis provided support for the positive influence of transformational leadership on organizational innovation. This finding is significant because this positive effect was identified in micro- and small-sized companies, whereas previous research focused mainly on large companies. In addition, external support for innovation was found to significantly moderate this effect. Specifically, the relationship between transformational leadership and organizational innovation was stronger when external support was at high levels than when there was no external support. This study is the first to investigate and empirically show the importance of this contextual condition for organizational innovation. The moderating effect of internal support for innovation, however, was not significant. This study shows that transformational leadership is an important determinant of organizational innovation and encourages managers to engage in transformational leadership behaviors to promote organizational innovation. In line with this, transformational leadership, which is heavily suggested to be a subject of management training and development in developed countries, should also be incorporated into such programs in developing countries. Moreover, this study highlights the importance of external support in the organizational innovation process. The results suggest that technical and financial support received from outside the organization can be a more important contextual influence in boosting up innovation than an innovation-supporting internal climate. Therefore, managers, particularly of micro- and small-sized companies, should play external roles such as boundary spanning and should build relationships with external institutions that provide technical and financial support. The findings of this study are especially important for managers of companies that plan to or currently operate in countries with developing economies. [source] Variation in ecophysiology and carbon economy of invasive and native woody vines of riparian zones in south-eastern QueenslandAUSTRAL ECOLOGY, Issue 6 2010OLUSEGUN O. OSUNKOYA Abstract Exotic and invasive woody vines are major environmental weeds of riparian areas, rainforest communities and remnant natural vegetation in coastal eastern Australia, where they smother standing vegetation, including large trees, and cause canopy collapse. We investigated, through glasshouse resource manipulative experiments, the ecophysiological traits that might facilitate faster growth, better resource acquisition and/or utilization and thus dominance of four exotic and invasive vines of South East Queensland, Australia, compared with their native counterparts. Relative growth rate was not significantly different between the two groups but water use efficiency (WUE) was higher in the native species while the converse was observed for light use efficiency (quantum efficiency, AQE) and maximum photosynthesis on a mass basis (). The invasive species, as a group, also exhibited higher respiration load, higher light compensation point and higher specific leaf area. There were stronger correlations of leaf traits and greater structural (but not physiological) plasticity in invasive species than in their native counterparts. The scaling coefficients of resource use efficiencies (WUE, AQE and respiration efficiency) as well as those of fitness (biomass accumulated) versus many of the performance traits examined did not differ between the two species-origin groups, but there were indications of significant shifts in elevation (intercept values) and shifts along common slopes in many of these relationships , signalling differences in carbon economy (revenue returned per unit energy invested) and/or resource usage. Using ordination and based on 14 ecophysiological attributes, a fair level of separation between the two groups was achieved (51.5% explanatory power), with AQE, light compensation point, respiration load, WUE, specific leaf area and leaf area ratio, in decreasing order, being the main drivers. This study suggests similarity in trait plasticity, especially for physiological traits, but there appear to be fundamental differences in carbon economy and resource conservation between native and invasive vine species. [source] Body size variation in insects: a macroecological perspectiveBIOLOGICAL REVIEWS, Issue 1 2010Steven L. Chown Body size is a key feature of organisms and varies continuously because of the effects of natural selection on the size-dependency of resource acquisition and mortality rates. This review provides a critical and synthetic overview of body size variation in insects from a predominantly macroecological (large-scale temporal and spatial) perspective. Because of the importance of understanding the proximate determinants of adult size, it commences with a brief summary of the physiological mechanisms underlying adult body size and its variation, based mostly on findings for the model species Drosophila melanogaster and Manduca sexta. Variation in nutrition and temperature have variable effects on critical weight, the interval to cessation of growth (or terminal growth period) and growth rates, so influencing final adult size. Ontogenetic and phylogenetic variation in size, compensatory growth, scaling at the intra- and interspecific levels, sexual size dimorphism, and body size optimisation are then reviewed in light of their influences on individual and species body size frequency distributions. Explicit attention is given to evolutionary trends, including gigantism, Cope's rule and the rates at which size change has taken place, and to temporal ecological trends such as variation in size with succession and size-selectivity during the invasion process. Large-scale spatial variation in size at the intraspecific, interspecific and assemblage levels is considered, with special attention being given to the mechanisms proposed to underlie clinal variation in adult body size. Finally, areas particularly in need of additional research are identified. [source]
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