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Generalist
Kinds of Generalist Terms modified by Generalist Selected AbstractsADAPTIVE 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] Compatibility and Bundling with Generalist and Specialist FirmsTHE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 2 2000Vincenzo Denicolo I analyze compatibility and bundling choices when one generalist firm offering both components of a system competes against two specialist firms each supplying one component only (but not the same one). I show that the generalist firm may have an incentive to choose incompatibility or engage in pure bundling when one component is less differentiated than the other. In this case, the system is more differentiated than the relatively undifferentiated component, and so under incompatibility the specialist firm that produces the undifferentiated component will relax price competition. This may result in higher profits for some of the competing firms. [source] WORK OF FEMALE RURAL DOCTORSAUSTRALIAN JOURNAL OF RURAL HEALTH, Issue 2 2004Jo Wainer Objectives: To identify the impact of family life on the ways women practice rural medicine and the changes needed to attract women to rural practice. Design: Census of women rural doctors in Victoria in 2000, using a self-completed postal survey. Setting: General and specialist practice. Subjects: Two hundred and seventy-one female general practitioners and 31 female specialists practising in Rural, Remote and Metropolitan Area Classifications 3,7. General practitioners are those doctors with a primary medical degree and without additional specialist qualifications. Main outcome measure: Interaction of hours and type of work with family responsibilities. Results: Generalist and specialist women rural doctors carry the main responsibility for family care. This is reflected in the number of hours they work in clinical and non-clinical professional practice, availability for oncall and hospital work, and preference for the responsibilities of practice partnership or the flexibility of salaried positions. Most of the doctors had established a satisfactory balance between work and family responsibilities, although a substantial number were overworked in order to provide an income for their families or meet the needs of their communities. Thirty-six percent of female rural general practitioners and 56% of female rural specialists preferred to work fewer hours. Female general practitioners with responsibility for children were more than twice as likely as female general practitioners without children to be in a salaried position and less likely to be a practice partner. The changes needed to attract and retain women in rural practice include a place for everyone in the doctor's family, flexible practice structures, mentoring by women doctors and financial and personal recognition. [source] Variation among individual butterflies along a generalist,specialist axis: no support for the ,neural constraint' hypothesisECOLOGICAL ENTOMOLOGY, Issue 3 2007BRIAN WEE Abstract 1.,Degree of host specialisation was a continuous variable in a population of Edith's checkerspot butterfly (Euphydryas editha). A novel host, Collinsia torreyi, had been added to the diet in response to anthropogenic disturbance, and then abandoned prior to the current study. Butterflies either showed no preference or preferred their traditional host, Pedicularis semibarbata. 2.,Strength of preference for Pedicularis over Collinsia was measured in the field and used to estimate host specialisation of individual butterflies. Efficiency was estimated from the times taken by each insect to perform two tasks: (i) identification of a Pedicularis plant as a host, and (ii) successful initiation of oviposition after the decision to do so had been made. 3.,There was no clear trend for association between host specialisation and either measure of efficiency. Generalists were not slower than specialists at identifying Pedicularis as a host or at handling it after deciding to oviposit. 4.,Prior work indicated that generalists paid no detectable cost in terms of reduced discrimination among individuals of their preferred host species. 5.,In contrast to other species, generalist E. editha paid in neither time nor accuracy. Why then does the diet not expand? Behavioural adaptations to the traditional host caused maladaptations to the novel host and generated short-term constraints to evolutionary expansion of diet breadth. To date, however, no long-term constraints have been found in this system. In those traits investigated to date, increased adaptation to the novel host has not caused reduced adaptation to the traditional host. [source] Foraging in nature: foraging efficiency and attentiveness in caterpillars with different diet breadthsECOLOGICAL ENTOMOLOGY, Issue 4 2004E. A. Bernays Abstract., 1. Seventy-seven individual last-instar caterpillars foraging in the field were examined for 6 h each. They represented four species of Arctiidae of similar size and habitat use. Two, Hypocrisias minima and Pygarctia roseicapitis, are specialists restricted to particular plant genera. The other two, Grammia geneura and Estigmene acrea, are extreme generalists that use many host plant species from multiple plant families. 2. Parameters of behavioural efficiency were monitored. Generalists spent more time walking, rejected more potential host plants, took longer to decide to feed after inspecting a plant, and took relatively more small feeding bouts compared with specialists. 3. This is the first test of differential foraging efficiency in the field in relation to diet breadth of insects and the data indicate that generalists are less efficient in their foraging activities and may suffer from divided attention. The need for attentiveness to enhance efficiency and thereby reduce ecological risk is discussed. [source] Implications of predatory specialization for cranial form and function in canidsJOURNAL OF ZOOLOGY, Issue 3 2009G. J. Slater Abstract The shape of the cranium varies widely among members of the order Carnivora, but the factors that drive the evolution of differences in shape remain unclear. Selection for increased bite force, bite speed or skull strength may all affect cranial morphology. We investigated the relationship between cranial form and function in the trophically diverse dog family, Canidae, using linear morphometrics and finite element (FE) analyses that simulated the internal and external forces that act on the skull during the act of prey capture and killing. In contrast to previous FE-based studies, we compared models using a newly developed method that removes the effects of size and highlights the relationship between shape and performance. Cranial shape varies among canids based on diet, and different selective forces presumably drove evolution of these phenotypes. The long, narrow jaws of small prey specialists appear to reflect selection for fast jaw closure at the expense of bite force. Generalists have intermediate jaw dimensions and produce moderate bite forces, but their crania are comparable in strength to those of small prey specialists. Canids that take large prey have short, broad jaws, produce the largest bite forces and possess very strong crania. Our FE simulations suggest that the remarkable strength of skulls of large prey specialists reflect the additional ability to resist extrinsic loads that may be encountered while struggling with large prey items. [source] Reliability of the V-scope system in the measurement of arm movement in children with obstetric brachial plexus palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 11 2006Andrea E Bialocerkowski PhD BApp Sc (Physio) MApp Sc (Physio) This study reports on a novel methodology using the V-scope to quantify elbow and shoulder movement in young children with obstetric brachial plexus palsy (OBPP), and the intra-and interreliability of this method. The V-scope, a portable, inexpensive movement analysis system, was configured in an L-shape, with two transmitting towers placed on the floor and one 1.35m off the ground. These towers received ultrasonic pulses from buttons that were placed over standardized landmarks of the child's trunk, chest, and upper limb. Two physiotherapists (a paediatric and a generalist) facilitated the maximum range of active elbow flexion/extension and shoulder abduction/flexion in 30 children with OBPP (18 females, 12 males; age range 6mo-4y 7mo; mean age 2y 6mo [SD 1y 2mo]). Assessments were conducted on two occasions, one week apart. The V-scope was found to be feasible to use by a specialist and a generalist physiotherapist, demonstrating moderate to high reliability coefficients, small measurement errors, and lack of missing data. The pediatric physiotherapist was more reliable in measuring elbow and shoulder movement compared with the generalist physiotherapist, which suggests that the same experienced, pediatric physiotherapist should assess elbow and shoulder movement across all occasions of testing. [source] The molecular receptive range of an olfactory receptor in vivo (Drosophila melanogaster Or22a)DEVELOPMENTAL NEUROBIOLOGY, Issue 14 2006Daniela Pelz Abstract Understanding how odors are coded within an olfactory system requires knowledge about its input. This is constituted by the molecular receptive ranges (MRR) of olfactory sensory neurons that converge in the glomeruli of the olfactory bulb (vertebrates) or the antennal lobe (AL, insects). Aiming at a comprehensive characterization of MRRs in Drosophila melanogaster we measured odor-evoked calcium responses in olfactory sensory neurons that express the olfactory receptor Or22a. We used an automated stimulus application system to screen [Ca2+] responses to 104 odors both in the antenna (sensory transduction) and in the AL (neuronal transmission). At 10,2 (vol/vol) dilution, 39 odors elicited at least a half-maximal response. For these odorants we established dose-response relationships over their entire dynamic range. We tested 15 additional chemicals that are structurally related to the most efficient odors. Ethyl hexanoate and methyl hexanoate were the best stimuli, eliciting consistent responses at dilutions as low as 10,9. Two substances led to calcium decrease, suggesting that Or22a might be constitutively active, and that these substances might act as inverse agonists, reminiscent of G-protein coupled receptors. There was no difference between the antennal and the AL MRR. Furthermore we show that Or22a has a broad yet selective MRR, and must be functionally described both as a specialist and a generalist. Both these descriptions are ecologically relevant. Given that adult Drosophila use approximately 43 ORs, a complete description of all MRRs appears now in reach. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Foregut ossicles morphology and feeding of the freshwater anomuran crab Aegla uruguayana (Decapoda, Aeglidae)ACTA ZOOLOGICA, Issue 4 2010Veronica Williner Abstract Williner, V. 2009. Foregut ossicles morphology and feeding of the freshwater anomuran crab Aegla uruguayana (Decapoda, Aeglidae). ,Acta Zoologica (Stockholm) 91: 408,415. The acquisition and processing of food is critical to animal survival and reproductive success. This work describes the foregut ossicles of Aegla uruguayana, which have been proposed to impart trophic characteristics. In addition, stomach contents were analysed using Index of Relative Importance and Weighted Result Index to characterize the diet. The Pearre index was applied to analyse trophic selectivity. We found A. uruguayana has a morphological foregut typical of macrophage organisms. Stomach contents included items typical of omnivorous, generalist and opportunistic feeding modes. Vegetal remains included algae (filamentous, unicellular and colonial morphotypes), insect larvae, oligochaetes, microcrustaceans (copepods and cladocerans), mites, tardigrades, juveniles of A. uruguayana and rotifers. Morphological descriptions of the foregut can reveal feeding habits and provide data on the possible trophic profile of a species, while guiding the selection of appropriate methodology for subsequent analysis. Our stomach content data corroborated the foregut description, but the presence of small prey suggested A. uruguayana utilizes both predation and detritivory trophic strategies. [source] First record of the brachiopod Lingulella waptaensis with pedicle from the Middle Cambrian Burgess ShaleACTA ZOOLOGICA, Issue 2 2010Sandra Pettersson Stolk Abstract Pettersson Stolk, S., Holmer, L. E. and Caron, J -B. 2010. First record of the brachiopod Lingulella waptaensis with pedicle from the Middle Cambrian Burgess Shale. ,Acta Zoologica (Stockholm) 91: 150,162 The organophosphatic shells of linguloid brachiopods are a common component of normal Cambrian,Ordovician shelly assemblages. Preservation of linguloid soft-part anatomy, however, is extremely rare, and restricted to a few species in Lower Cambrian Konservat Lagerstätten. Such remarkable occurrences provide unique insights into the biology and ecology of early linguloids that are not available from the study of shells alone. Based on its shells, Lingulella waptaensis Walcott, was originally described in 1924 from the Middle Cambrian Burgess Shale but despite the widespread occurrence of soft-part preservation associated with fossils from the same levels, no preserved soft parts have been reported. Lingulella waptaensis is restudied herein based on 396 specimens collected by Royal Ontario Museum field parties from the Greater Phyllopod Bed (Walcott Quarry Shale Member, British Columbia). The new specimens, including three with exceptional preservation of the pedicle, were collected in situ in discrete obrution beds. Census counts show that L. waptaensis is rare but recurrent in the Greater Phyllopod Bed, suggesting that this species might have been generalist. The wrinkled pedicle protruded posteriorly between the valves, was composed of a central coelomic space, and was slender and flexible enough to be tightly folded, suggesting a thin chitinous cuticle and underlying muscular layers. The nearly circular shell and the long, slender and highly flexible pedicle suggest that L. waptaensis lived epifaunally, probably attached to the substrate. Vertical cross-sections of the shells show that L. waptaensis possessed a virgose secondary layer, which has previously only been known from Devonian to Recent members of the Family Lingulidae. [source] Are forest birds categorised as "edge species" strictly associated with edges?ECOGRAPHY, Issue 4 2003Louis Imbeau In recent years, studies of bird-habitat relationships undertaken in the context of habitat fragmentation have led to the widespread use of species categorisation according to their response to edge alongside mature forest patches (edge species, interior species, interior-edge generalist species). In other research contexts, especially in less fragmented landscapes dominated by a forested land base in various age classes, bird-habitat relationships are often described in relation to their use of various successional stages (early-successional species, mature forest species, generalist species). A simple comparison of these two commonly-used classifications schemes in a close geographical range for 60 species in eastern North America as well as for 36 species in north-western Europe clearly reveals that in these two particular biomes the two classifications are not independent. We believe that this association is not only a semantic issue and has important ecological consequences. For example, almost all edge species are associated with early-successional habitats when a wide range of forest age-classes are found in a given area. Accordingly, we suggest that most species considered to prefer edge habitats in agricultural landscapes are in fact only early-successional species that could not find shrubland conditions apart from the exposed edges of mature forest fragments. To be considered a true edge species, a given species should require the simultaneous availability of more than one habitat type and consequently should be classified as a habitat generalist in its use of successional stages. However, 28 out of 30 recognised edge species were considered habitat specialists in terms of successional status. Based on these results, we conclude that "real edge species" are probably quite rare and that we should make a difference between true edge species and species which in some landscapes, happen to find their habitat requirements on edges. [source] Variation among individual butterflies along a generalist,specialist axis: no support for the ,neural constraint' hypothesisECOLOGICAL ENTOMOLOGY, Issue 3 2007BRIAN WEE Abstract 1.,Degree of host specialisation was a continuous variable in a population of Edith's checkerspot butterfly (Euphydryas editha). A novel host, Collinsia torreyi, had been added to the diet in response to anthropogenic disturbance, and then abandoned prior to the current study. Butterflies either showed no preference or preferred their traditional host, Pedicularis semibarbata. 2.,Strength of preference for Pedicularis over Collinsia was measured in the field and used to estimate host specialisation of individual butterflies. Efficiency was estimated from the times taken by each insect to perform two tasks: (i) identification of a Pedicularis plant as a host, and (ii) successful initiation of oviposition after the decision to do so had been made. 3.,There was no clear trend for association between host specialisation and either measure of efficiency. Generalists were not slower than specialists at identifying Pedicularis as a host or at handling it after deciding to oviposit. 4.,Prior work indicated that generalists paid no detectable cost in terms of reduced discrimination among individuals of their preferred host species. 5.,In contrast to other species, generalist E. editha paid in neither time nor accuracy. Why then does the diet not expand? Behavioural adaptations to the traditional host caused maladaptations to the novel host and generated short-term constraints to evolutionary expansion of diet breadth. To date, however, no long-term constraints have been found in this system. In those traits investigated to date, increased adaptation to the novel host has not caused reduced adaptation to the traditional host. [source] A comparison of the host-searching efficiency of two larval parasitoids of Plutella xylostellaECOLOGICAL ENTOMOLOGY, Issue 1 2002Xin-Geng Wang Summary 1. A host specialist parasitoid is thought to have greater efficiency in locating hosts or greater ability to overcome host defence than a generalist species. This leads to the prediction that a specialist should locate and parasitise more hosts than a generalist in a given arena. The work reported here tested these predictions by comparing the host-searching behaviour of Diadegma semiclausum (a specialist) and Cotesia plutellae (an oligophagous species), two parasitoids of larval Plutella xylostella. 2. Both parasitoids employed antennal search and ovipositor search when seeking hosts but D. semiclausum also seemed to use visual perception in the immediate vicinity of hosts. 3. Larvae of P. xylostella avoided detection by parasitoids by moving away from damaged plant parts after short feeding bouts. When they encountered parasitoids, the larvae wriggled vigorously as they retreated and often hung from silk threads after dropping from a plant. 4. These two parasitoids differed in their responses to host defences. Diadegma semiclausum displayed a wide-area search around feeding damage and waited near the silk thread for a suspended host to climb up to the leaf, then attacked it again. Cotesia plutellae displayed an area-restricted search and usually pursued the host down the silk thread onto the ground. 5. Diadegma semiclausum showed a relatively fixed behavioural pattern leading to oviposition but C. plutellae exhibited a more plastic behavioural pattern. 6. The time spent by the two parasitoids on different plants increased with increasing host density, but the time spent either on all plants or a single plant by D. semiclausum was longer than that of C. plutellae. Diadegma semiclausum visited individual plants more frequently than C. plutellae before it left the patch, and stung hosts at more than twice the rate of C. plutellae. 7. The results indicated that the host-location strategies employed by D. semiclausum were adapted better to the host's defensive behaviour, and thus it was more effective at detecting and parasitising the host than was C. plutellae. [source] Competitive interactions and persistence of two nematode species that parasitize Drosophila recensECOLOGY LETTERS, Issue 6 2001S.J. Perlman Drosophila recens is parasitized in the wild by two nematodes, Howardula aoronymphium, a host generalist, and Parasitylenchus nearcticus, a host specialist known only from D. recens. In order to understand how these two parasite species coexist, we compared their ability to infect and grow in D. recens, their effects on host fecundity and survival, and whether one parasite species was competitively superior in double infections. The specialist nematode P. nearcticus had greater rates of infection and reproduction than the generalist H. aoronymphium, and completely sterilized females in single and mixed infections. The specialist was competitively superior in mixed infections, as generalist motherworms were significantly smaller than in single infections. These results suggest that P. nearcticus might competitively exclude H. aoronymphium if D. recens were the only host available. It is likely that H. aoronymphium persists in D. recens by transmission from other, more suitable host species. [source] Rural hospital generalist and emergency medicine training in Papua New GuineaEMERGENCY MEDICINE AUSTRALASIA, Issue 2 2007David Symmons Abstract The present paper describes the role of the hospital generalist in rural Papua New Guinea (PNG) and the contribution of emergency medicine training to that practice. Generalist practice in Tinsley District Hospital in Western Highlands Province is described, with emphasis on emergency surgery and anaesthesia. The potential of the PNG emergency medicine training programme for preparing generalists is discussed. Tinsley Hospital served a population of 40 000 people, with 4000 admissions and 300,400 operations performed annually. Two doctors and 50 nurses and community health workers provided care with minimal resources. The doctors provided supervision and teaching for nurses, community health workers, hospital administrators and primary health carers, including on long range medical patrols. Over 16 months, doctors performed 243 emergency surgical procedures including orthopaedics, general surgery, obstetrics and gynaecology. The generalist in rural hospitals is required to perform a wide variety of medical tasks in isolated settings yet there is no active postgraduate training programme. The Master of Medicine, Emergency Medicine programme includes rotations through the major disciplines of surgery, anaesthesia, internal medicine, paediatrics, obstetrics and gynaecology. It has the potential to train doctors in PNG for a generalist role as graduates will learn the foundations of the required skills. [source] Sociodemographic disparities in epilepsy care: Results from the Houston/New York City health care use and outcomes studyEPILEPSIA, Issue 5 2009Charles E. Begley Summary Purpose:, The purpose of this study was to identify sociodemographic disparities in health care use among epilepsy patients receiving care at different sites and the extent to which the disparities persisted after adjusting for patient characteristics and site of care. Methods:, Three months of health care use data were obtained from baseline interviews of approximately 560 patients at four sites. One-half of the patients were from a Houston site and two NYC sites that serve predominantly low-income, minority, publicly insured, or uninsured patients. The other half were at the remaining site in Houston that serves a more balanced racial/ethnic and higher sociodemographic population. Differences in general and specialist visits, hospital emergency room (ER) care, and hospitalizations were associated with race/ethnicity, income, and coverage. Logistic regression was used to assess the extent to which the differences persisted when adjusting for individual patient characteristics and site of care. Results:, Compared to whites, blacks and Hispanics had higher rates of generalist visits [odds ratio (OR) = 5.3 and 4.9, p < 0.05), ER care (OR = 3.1 and 2.9, p < 0.05) and hospitalizations (OR = 5.4 and 6.2, p < 0.05), and lower rates of specialist visits (OR = 0.3 and 0.4, p < 0.05). A similar pattern was found related to patient income and coverage. The magnitude and significance of the disparities persisted when adjusting for individual characteristics but decreased substantially or were eliminated when site of care was added to the model. Discussion:, There are sociodemographic disparities in health care for people with epilepsy that are largely explained by differences in where patients receive care. [source] THE EVOLUTION OF SPECIFICITY IN EVOLVING AND COEVOLVING ANTAGONISTIC INTERACTIONS BETWEEN A BACTERIA AND ITS PHAGEEVOLUTION, Issue 1 2008Virginie Poullain The evolution of exploitative specificity can be influenced by environmental variability in space and time and the intensity of trade-offs. Coevolution, the process of reciprocal adaptation in two or more species, can produce variability in host exploitation and as such potentially drive patterns in host and parasite specificity. We employed the bacterium Pseudomonas fluorescens SBW25 and its DNA phage ,2 to investigate the role of coevolution in the evolution of phage infectivity range and its relation with phage growth rate. At the phage population level, coevolution led to the evolution of broader infectivity range, but without an associated decrease in phage growth rate relative to the ancestor, whereas phage evolution in the absence of bacterial evolution led to an increased growth rate but no increase in infectivity range. In contrast, both selection regimes led to phage adaptation (in terms of growth rates) to their respective bacterial hosts. At the level of individual phage genotypes, coevolution resulted in within-population diversification in generalist and specialist infectivity range types. This pattern was consistent with a multilocus gene-for-gene interaction, further confirmed by an observed cost of broad infectivity range for individual phage. Moreover, coevolution led to the emergence of bacterial genotype by phage genotype interactions in the reduction of bacterial growth rate by phage. Our study demonstrates that the strong reciprocal selective pressures underlying the process of coevolution lead to the emergence and coexistence of different strategies within populations and to specialization between selective environments. [source] THE EVOLUTIONARY HISTORY OF MYCORRHIZAL SPECIFICITY AMONG LADY'S SLIPPER ORCHIDSEVOLUTION, Issue 6 2007Richard P. Shefferson Although coevolution is acknowledged to occur in nature, coevolutionary patterns in symbioses not involving species-to-species relationships are poorly understood. Mycorrhizal plants are thought to be too generalist to coevolve with their symbiotic fungi; yet some plants, including some orchids, exhibit strikingly narrow mycorrhizal specificity. Here, we assess the evolutionary history of mycorrhizal specificity in the lady's slipper orchid genus, Cypripedium. We sampled 90 populations of 15 taxa across three continents, using DNA methods to identify fungal symbionts and quantify mycorrhizal specificity. We assessed phylogenetic relationships among sampled Cypripedium taxa, onto which we mapped mycorrhizal specificity. Cypripedium taxa associated almost exclusively with fungi within family Tulasnellaceae. Ancestral specificity appears to have been narrow, followed by a broadening after the divergence of C. debile. Specificity then narrowed, resulting in strikingly narrow specificity in most of the taxa in this study, with no taxon rewidening to the same extant as basal members of the genus. Sympatric taxa generally associated with different sets of fungi, and most clades of Cypripedium -mycorrhizal fungi were found throughout much of the northern hemisphere, suggesting that these evolutionary patterns in specificity are not the result of biogeographic lack of opportunity to associate with potential partners. Mycorrhizal specificity in genus Cypripedium appears to be an evolvable trait, and associations with particular fungi are phylogenetically conserved. [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] VACCINATION, WITHIN-HOST DYNAMICS, AND VIRULENCE EVOLUTIONEVOLUTION, Issue 1 2006Jean-Baptiste André Abstract We explore the potential consequences of vaccination on parasite epidemiology and evolution. Our model combines a microscopic (within-host dynamics) and a macroscopic (epidemiological dynamics) description of the interaction between the parasite and its host. This approach allows relevant epidemiological traits such as parasite transmission, parasite virulence, and host recovery to emerge from a mechanistic model of acute infection describing the interaction between the parasite and the host immune system. We model the effect of a vaccine as an activator of immunity enhancing the replication rate of lymphocytes, their initial density at infection's initiation, their efficacy to kill the parasite, or their activation delay after infection. We analyze the evolution of the replication rate of parasites and show that vaccination may promote the evolution of faster replicating and, consequently, more virulent strains. We also show that intermediate vaccination coverage may lead to the coexistence of two different parasite strategies (a low-virulence strain adapted to naive hosts, and a high-virulence strain, more generalist, adapted to both naive and vaccinated hosts). We discuss the consequences of various vaccination strategies under different epidemiological situations using several distinct measures to evaluate the cost induced by the parasite on individuals and entire host populations. [source] BEHAVIORAL ADAPTATIONS INCREASE THE VALUE OF ENEMY-FREE SPACE FOR HELIOTHIS SUBFLEXA, A SPECIALIST HERBIVOREEVOLUTION, Issue 4 2002Sara J. Oppenheim Abstract We investigated the importance of specialized behaviors in the use of enemy-free space by comparing the host-use behavior of two closely related moths, Heliothis subflexa Guenee and H. virescens Fabricius. Heliothis subflexa is a specialist on plants in the genus Physalis, whereas H. virescens is an extreme generalist, feeding on plants in at least 14 families. Heliothis subflexa uses the inflated calyx surrounding Physalis fruits as enemy-free space, and field rates of parasitism for H. subflexa on Physalis are much lower than for H. virescens on tobacco and cotton, common hosts found in the same habitat as Physalis. If Physalis' architecture were solely responsible for H. subflexa's low rates of parasitism on Physalis, we predicted thatH. virescens larvae experimentally induced to feed on Physalis would experience parasitism rates similar to those ofH. subflexa. We found, however, that specialized host-use and host-acceptance behaviors are integral to the use of enemy-free space on Physalis and strongly augment the effects of the structural refuge. In laboratory assays, we found considerable differences between the larval behavior of the specialist, H. subflexa, and the generalist, H. virescens, and these contributed to H. subflexa's superior use of enemy-free space on Physalis. We tested the importance of these behavioral differences in the field by comparing parasitism of H. virescens on Physalis, H. virescens on tobacco, and H. subflexa on Physalis by Cardiochiles nigriceps Vierick, a specialist braconid parasitoid. For H. virescens, a threefold decrease in parasitism occurred when feeding on Physalis (mean parasitism ± SEM = 13 ± 4%) rather than tobacco (43 ± 4%), a difference we attribute to the structural refuge provided by Physalis. However, parasitism ofH. virescens on Physalis was more than ten times as great as that of H. subflexa on Physalis (1 ± 4%), supporting the hypothesis that specialized behaviors have a substantial impact on use of Physalis as enemy-free space. Behavioral adaptations may be central to the use of enemy-free space by phytophagous insects and may act as an important selective force in the evolution of dietary specialization. [source] Pond canopy cover: a resource gradient for anuran larvaeFRESHWATER BIOLOGY, Issue 3 2006LUIS SCHIESARI Summary 1.,The gradient in pond canopy cover strongly influences freshwater species distributions. This study tested the effects of canopy cover on the performance of two species of larval anurans, a canopy cover generalist (Rana sylvatica, the wood frog) and an open-canopy specialist (R. pipiens, the leopard frog), and tested which factors co-varying with canopy cover mediate these effects. 2.,A field transplant experiment demonstrated that canopy cover had negative performance effects on both species. However, leopard frogs, which grow faster than wood frogs in open-canopy ponds, were more strongly affected by closed-canopy pond conditions. 3.,Closed-canopy ponds had lower temperature, dissolved oxygen (DO), and food nutritional quality as indicated by carbon-to-nitrogen ratio (C : N) analysis of field-sampled food types, and of gut contents of transplanted larvae. 4.,Laboratory experiments demonstrated that higher temperature and food quality but not DO substantially increased larval growth. However, only food quality increased growth rates of leopard frogs more than wood frogs. 5.,The strong correlation of growth rates to gut content C : N in the field, and the similarity of growth curves as a function of resource quality in the field and laboratory, strongly suggest that resources are of primary importance in mediating intraspecific, and especially interspecific differences in performance across the canopy cover gradient. [source] Food webs in tropical Australian streams: shredders are not scarceFRESHWATER BIOLOGY, Issue 5 2005KIM CHESHIRE Summary 1. Macroinvertebrates were collected in dry and wet seasons from riffles and pools in two streams in tropical north Queensland. Total biomass, abundance and species richness were higher in riffles than in pools but did not differ between streams or seasons. 2. Gut contents of all species were identified. Cluster analysis based on gut contents identified five dietary groups: I, generalist collectors; II, generalist shredders and generalist predators; III, generalist scrapers; IV, specialist shredders; and V, specialist predators. Species were allocated to functional feeding groups (FFGs) based on these dietary groups. 3. Many species were generalist in their diets, but specialist predators and shredders were particularly prominent components of the invertebrate assemblages in terms of biomass and species richness. 4. Community composition (proportions of biomass, abundance and species richness of the different FFGs) varied between habitat types, but not between streams or seasons, although differences between riffles and pools varied with season. 5. Comparison of the fauna of 20 streams showed that our study sites were similar to, or not atypical of, low-order streams in the Queensland wet tropics. [source] How is geriatrics different from general internal medicine?GERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 4 2004Thomas E Finucane Geriatrics and general internal medicine overlap greatly: most sick patients seen by a generalist are elderly and geriatricians care for nearly the full spectrum of diseases seen in internal medicine. Differences between the two disciplines can be seen in the areas of patient care, research and administration. As a group, geriatric patients are different from young adults because they are more likely to have multiple chronic illnesses, to depend on others, to be frail and to die in the near future. Each of these characteristics requires special knowledge on the part of the physician. The research agenda in geriatrics extends from attempts to find the molecular basis of sarcopenia and frailty to clinical research on the support of caregivers, who are themselves critically important to patients. In the US, nursing homes are required to have medical directors; this position is largely administrative and requires a distinct set of knowledge and attitudes. Clinical care, research and administrative efforts must all respond to the enormous number of patients who will develop cognitive impairment over the next three decades. Because the number of elderly patients so far exceeds the ability of geriatricians to provide care, education and ,geriatricizing' other specialties will also be an important mission for geriatricians. Proper reimbursement presents a serious challenge to physicians who care for the frail elderly. If geriatricians take care of the frailest, sickest and most vulnerable patients, but reimbursement mechanisms cannot recognize this fact, then all geriatricians will soon go bankrupt. [source] Changes in the composition of British butterfly assemblages over two decadesGLOBAL CHANGE BIOLOGY, Issue 7 2008ADELA GONZÁLEZ-MEGÍAS Abstract Changes in the abundance and distribution of individual species have been widely documented in Britain and other countries in recent decades, but little has been done to determine changes in community composition over broad geographic areas. Here, we studied species turnover in 51 butterfly assemblages in Britain since 1976, examining extinction and colonisation events together with variation in the abundances of the species. We showed that the species turnover that occurred over 20 years in Britain was associated with colonisation and extinction events and also with variability in the abundance of the species. These changes in community composition differed according to the habitat requirements of the species and their previous distributions, being more evident for habitat specialists and for southerly distributed species. Colonising species often became abundant components of the communities they joined, although this was more evident for generalist than for specialist species. The abundance of species following their arrival, increased with time since colonisation. Species turnover associated with southerly species expanding northwards is consistent with being a response to climate change. The results suggest that climate- and habitat-driven changes in the identity and abundance of species within communities are widespread, and probably ubiquitous. Similar changes are likely to be occurring in other groups of organisms that are similarly undertaking major range shifts associated with climate change. [source] The education and training needs of health librarians,the generalist versus specialist dilemmaHEALTH INFORMATION & LIBRARIES JOURNAL, Issue 3 2007Tatjana Petrinic Aims and objectives:, The aims of the study were to examine whether and how librarians with a generalist background can transfer to roles demanding more expert knowledge in the health sector. The objectives were (i) to compare the education and training needs of health librarians with science degrees with the education and training needs of health librarians with arts and humanities degrees; (ii) to compare the education and training needs of librarians working in the National Health Service (NHS) sector with the education and training needs of librarians working for the health sector but within higher education. Methods:, Face-to-face interviews with 16 librarians, a convenience sample of librarians working in the Thames Valley NHS region. Results:, The main findings confirmed that structured continuing professional development (CPD) is required to meet the rapidly changing needs in the health sector. The emphasis ought to be on teaching skills, outreach work, marketing and promotion, research skills and methods, subject knowledge and terminology, and management skills. Library school curricula do not appear to meet the demands of medical library posts. A first degree in scientific subjects is advantageous in the early stages of a career but diminishes with continuing training and experience. There is no evidence of a significant difference in training needs and provision between the librarians in NHS posts as opposed to those in higher education (HE) posts. Conclusions:, The conclusions suggest that library schools need to update their programmes to include teaching skills, advanced search skills, project management skills, research methods, with more practical exercises. Particular attention should be given to librarians with a first degree in non-scientific subjects in terms of time allocated for CPD, quality of training and access to reliable mentorship. [source] Looks are important: parasitic assemblages of agromyzid leafminers (Diptera) in relation to mine shape and contrastJOURNAL OF ANIMAL ECOLOGY, Issue 3 2004Adriana Salvo Summary 1We test the hypothesis that leaf mine appearance can affect the risk of leafminers being discovered by parasitoids, and therefore influence parasitic assemblages, using a comparative study of parasitic complexes associated with 28 agromyzid species in Central Argentina. Analyses were based on size, structure (defined as the number of species in host-range categories) and impact (percentage parasitism) of parasitic complexes on leafminers. Mine appearance was defined in terms of shape (linear, linear-blotch, blotch) and colour (high or low contrast with the leaf lamina). 2Irrespective of the agromyzid species involved, significant differences were found in the structure of the parasitoid complexes: specialists were more abundant and generalists rarer than expected in blotch and cryptically coloured mines. 3There were no differences in average parasitoid species richness and parasitism rates among differently coloured or shaped galleries. However, mine appearance significantly affected parasitic assemblage structure, with shape driving generalist species richness and contrast influencing that of specialists. Mine shape also affected parasitism rates, which were highest for generalists in linear mines, and for specialists in blotch mines. The existence of a gradient of discovery from the cryptically coloured blotch mines to the most apparent highly contrasting linear ones was supported by significant correlations of this gradient with richness and parasitism rates of generalist and specialist parasitoids. 4Taxonomic composition of parasitic complexes (analysed through parasitoid species abundance) was separated significantly according to host mine shape. An even more significant classification of assemblages was achieved when the combination of mine shape and colour was considered in the discoverability gradient. 5Our results suggest that despite leaf mines being an ecologically homogeneous resource, their morphology might offer varying degrees of refuge against different parasitoids. [source] Ecological factors drive differentiation in wolves from British ColumbiaJOURNAL OF BIOGEOGRAPHY, Issue 8 2009Violeta Muñoz-Fuentes Abstract Aim, Limited population structure is predicted for vagile, generalist species, such as the grey wolf (Canis lupus L.). Our aims were to study how genetic variability of grey wolves was distributed in an area comprising different habitats that lay within the potential dispersal range of an individual and to make inferences about the impact of ecology on population structure. Location, British Columbia, Canada , which is characterized by a continuum of biogeoclimatic zones across which grey wolves are distributed , and adjacent areas in both Canada and Alaska, United States. Methods, We obtained mitochondrial DNA control region sequences from grey wolves from across the province and integrated our genetic results with data on phenotype, behaviour and ecology (distance, habitat and prey composition). We also compared the genetic diversity and differentiation of British Columbia grey wolves with those of other North American wolf populations. Results, We found strong genetic differentiation between adjacent populations of grey wolves from coastal and inland British Columbia. We show that the most likely factor explaining this differentiation is habitat discontinuity between the coastal and interior regions of British Columbia, as opposed to geographic distance or physical barriers to dispersal. We hypothesize that dispersing grey wolves select habitats similar to the one in which they were reared, and that this differentiation is maintained largely through behavioural mechanisms. Main conclusions, The identification of strong genetic structure on a scale within the dispersing capabilities of an individual suggests that ecological factors are driving wolf differentiation in British Columbia. Coastal wolves are highly distinct and representative of a unique ecosystem, whereas inland British Columbia grey wolves are more similar to adjacent populations of wolves located in Alaska, Alberta and Northwest Territories. Given their unique ecological, morphological, behavioural and genetic characteristics, grey wolves of coastal British Columbia should be considered an Evolutionary Significant Unit (ESU) and, consequently, warrant special conservation status. If ecology can drive differentiation in a highly mobile generalist such as the grey wolf, ecology probably drives differentiation in many other species as well. [source] Diet composition of Xenopus borealis in Taita Hills: effects of habitat and predator sizeAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Beryl A. Bwong Abstract Frogs in the genus Xenopus are ubiquitous in sub-Saharan Africa, yet very little is recorded on their ecology. They are commonly found in anthropogenically disturbed habitats, but how do these compare to conspecifics from natural habitats? The diet of Xenopus borealis from three different sites in Taita Hills, Kenya was established based on a sample of 77 (54 females and 23 males) specimens from two disturbed and one pristine sites. Xenopus borealis from all the sites was found to be a dietary generalist, feeding predominantly on invertebrates. A total of twelve invertebrate orders both terrestrial and aquatic were recorded in addition to amphibian eggs, tadpoles and fish. Frogs from the pristine forest were smaller and had ingested more terrestrial prey items than frogs in the disturbed open habitat ponds. The stomach content (both by mass and quantity) was independent of body size. The results suggest that X. borealis is an opportunistic generalist predator which may be constrained by food availability in its natural habitat. However, disturbed habitats provide abundant food items which are enough to significantly increase the mean size of the population. Résumé Les grenouilles du genre Xenopus sont présentes partout en Afrique subtropicale, mais il existe peu de travaux sur leur écologie. On les trouve fréquemment dans des habitats perturbés par les hommes, mais comment ces grenouilles-ci se comparent-elles à leurs congénères des habitats naturels ? On a pu établir le régime alimentaire de Xenopus borealis sur trois sites différents des Taita Hills, au Kenya, d'après un échantillon de 77 individus (54 femelles et 23 mâles) de deux sites perturbés et d'un site intact. Xenopus borealis s'est avéréêtre un consommateur généraliste sur tous les sites, se nourrissant principalement d'invertébrés. On a noté la présence d'un total de 12 ordres d'invertébrés, terrestres et aquatiques, auxquels s'ajoutent des ,ufs d'amphibiens, des têtards et des poissons. Les grenouilles des forêts intactes étaient plus petites et mangeaient des proies plus terrestres que celles des points d'eau d'habitats ouverts perturbés. Le contenu stomacal (aussi bien par la masse que par la quantité) était indépendant de la taille corporelle. Les résultats suggèrent que X. borealis est un prédateur généraliste opportuniste qui peut être limité par la disponibilité de la nourriture dans son habitat naturel. Par contre, des habitats perturbés fournissent une nourriture abondante, suffisante pour augmenter significativement la taille moyenne de la population. [source] A study of a training scheme for Macmillan nurses in Northern IrelandJOURNAL OF CLINICAL NURSING, Issue 2 2008BSocSc, Cert Ed., DipDN, Johnston Gail PhD Aim., To evaluate a one year training scheme for Macmillan Nurses. Background., The role of the clinical nurse specialist has evolved and expanded greatly over the past few years so that it now encompasses components far beyond the traditional nursing remit of direct clinical practice. While several studies have looked at the barriers and facilitators to this process for clinical nurse specialists in particular, none has looked at the benefits of a structured training scheme which involves both a theoretical and clinical component. Methods., Tape recorded, semi-structured interviews were undertaken with a purposive sample of trainees who undertook the scheme, their practice-based facilitators and another person(s) involved in the trainee's support Analysis., Tapes were transcribed verbatim and each transcript anonymized to prevent identification of participants. Data were analysed thematically using the main headings of expectations, experience and impact and the structured prompts from the aide-memoir within these headings. Results., Results showed that the majority of respondents felt the scheme had been successful with one of the main achievements being that trainees were perceived to be adequately prepared to take on the role of a CNS on completion of the scheme. While the Role Development Programme was thought to provide a good academic structure for the scheme some participants thought that more theory on symptom control and communication skills and a placement in a specialist palliative care centre should also be included. Conclusion., The Macmillan Trainee Scheme has succeeded in its objectives to facilitate the transition from generalist to specialist nursing. It should be extended to include an induction and consolidation period and more theoretical input on communication skills and symptom control. Relevance to clinical practice., With these improvements, the scheme could be used as a standard model for training specialist practitioners and a means to address the current issues of workforce planning. [source] | ||||||||||||||||||||||||||||||||||||||||||||||