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Fitness Traits (fitness + trait)
Selected AbstractsEffects of temperature on disease progression and swimming stamina in Ichthyophonus -infected rainbow trout, Oncorhynchus mykiss (Walbaum)JOURNAL OF FISH DISEASES, Issue 10 2009R Kocan Abstract Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 °C, 15 °C and 20 °C for 28 days to monitor mortality and disease progression. Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced mean-day-to-death at higher temperature. In a second experiment, Ichthyophonus -infected fish were reared at 15 °C for 16 weeks then subjected to forced swimming at 10 °C, 15 °C and 20 °C. Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish. The difference in performance between infected and uninfected fish became significant at 15 °C (P = 0.02) and highly significant at 20 °C (P = 0.005). These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids. This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas. [source] Passage through alternative hosts changes the fitness of Fusarium graminearum and Fusarium pseudograminearumENVIRONMENTAL MICROBIOLOGY, Issue 2 2007Olufemi A. Akinsanmi Summary Species of the necrotrophic fungal pathogen Fusarium that cause head blight and crown rot of cereals including wheat also infect a number of alternative host plants. This raises the prospect of more damaging pathogen strains originating and persisting as highly successful saprophytes on hosts other than wheat. The immediate impact on pathogenic (aggressiveness) and saprophytic (growth rate and fecundity) behaviour of six isolates with low, moderate or high initial aggressiveness was examined in two species of Fusarium after their passage through 10 alternative plant hosts. One passage through alternative hosts significantly reduced the pathogenic fitness of most isolates, but this change was not associated with a concomitant change in their overall saprophytic behaviour. The overall weak association between aggressiveness, fecundity and growth rate both before and after passage through the alternative hosts indicate that pathogenic and saprophytic fitness traits may be independently controlled in both Fusarium species. Thus, there was no trade-off between pathogenic and saprophytic fitness in these necrotrophic plant pathogens. [source] SYNTHESIS: Evolutionary consequences of fishing and their implications for salmonEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Jeffrey J. Hard Abstract We review the evidence for fisheries-induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries-induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long-term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long-term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done. [source] Correlated changes in fertility and fitness traits in lines of oMt1a-oGH transgenic mice selected for increased 8-week body weight,JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 2 2000F. Siewerdt Correlated responses in fitness and fertility traits were compared in transgenic and nontransgenic lines of mice selected for increased 8-week body weight. Two replicates of lines which either carried or did not carry the sheep metallothionein-1a sheep growth hormone transgene (oMt1a-oGH) were established. Host lines had been previously selected for rapid growth or selected randomly. Within-litter selection was carried out for 13 generations, and a randomly selected control line was kept for each set of replicate lines. Mice were genotyped every generation for the presence of the transgene, but this information was not used in selection decisions. The oMt1a-oGH construct was activated by adding 25 mm ZnSO4 to the drinking water from 3 weeks (weaning) until 8 weeks of age. Zinc stimulation of the transgene was not carried out during mating, gestation and lactation. Correlated responses in fitness traits were measured by regression of least-squares means (as deviations from the control lines) on generation number. Two fitness indexes were defined to combine the information on individual fitness traits. The proportion of infertile matings was higher in generations 7 to 13 than in generations 0 to 6. Correlated responses to selection showed an increase in the cohabitation to littering interval in nontransgenic lines and an increase in litter sizes in lines from the selected background. Preweaning pup survival did not change over generations. Overall fitness increased in the transgenic line from the selection background whereas no changes were observed in the transgenic line from the control background. The initial frequency of 0.5 of the transgene was reduced to less than 0.10 in the selected background, but increased to an average of 0.62 in the control lines. The comparison of specific mating groups involving transgenic and nontransgenic mates revealed that the only consistent disadvantage in having a transgenic parent was the increase in the length of the cohabitation to littering interval. Major fitness problems were not associated with the oMt1a-oGH transgene, which makes this construct a potential choice for use in livestock breeding programmes. Zusammenfassung Korrelierte Reaktionen der Merkmale Fertilität und Fitness wurden bei transgenen und nicht trans-genen Mäuselinien verglichen. Es wurden zwei Nachzüchtungen von Linien erstellt, die entweder das ovine Metallothionein-1a Wachstumshormon transgen tragen bzw. es nicht tragen. Zuvor waren Wirts-linien entweder auf schnelles Wachstum selektiert oder zufällig ausgesucht worden. Die Selektion erfolgte innerhalb der Würfe auf erhöhtes 8-Wochengewicht für 13 Generationen, und eine zufällig selektierte Kontroll-Linie wurde für jede der replizierten Linien gehalten. In jeder Generation wurden die Mäuse auf die Anwesenheit des Transgens genotypisiert, aber diese Information wurde nicht für Selektionsentscheidungen herangezogen. Das oMt1a-oGH Konstrukt wurde durch Zugabe von 25 mm ZnSO4 zum Trinkwasser ab der dritten Woche (Absetzen) bis zum Alter von acht Wochen aktiviert. Während der Paarung, der Trächtigkeit und der Laktation wurde keine Zink-Stimulation der transgenen Tiere durchgeführt. Korrelationen zwischen Fitnessmerkmalen und der Generationsnummer wurden durch Regression der kleinsten Quadrate (als Abweichung von den Kontroll-Linien) erhalten. Es wurden zwei Fitness-Indizes definiert, um die Information individueller Fitness-Merkmale zu kombinieren. Der Anteil an unfruchtbaren Paarungen war von der 7. bis zur 13. Generation höher als bei der 0. bis zur 6. Generation. Korrelationen bezüglich Selektion zeigten ein Anstieg der Kohabitation mit dem Wurfintervall bei nicht transgenen Tieren und einen Anstieg der Wurfgrößen bei den Linien der selektierten Gruppe. Das Überleben von Jungen vor dem Absetzten veränderte sich nicht über die Generationen. Allgemeine Fitness stieg bei der transgenen Linie der selektierten Gruppe an, während bei der transgenen Linie der Kontrollgruppe keine Veränderungen beobachtet wurden. Ein Vergleich von spezifischen Paarungsgruppen, die transgene und nicht transgene Paarungen einbezog, ergab, daß der einzige Nachteil eines transgenen Elternteils darin besteht, daß die Länge der Kohabitation mit dem Wurfintervall ansteigt. Mit dem oMt1a-oGH Transgen waren keine schweren Fitness-Probleme verbunden, so daß dieses Konstrukt eine potentielle Wahl für die Verwendung bei Nutztier-Zuchtprogrammen sein könnte. [source] Interactive effects of environmental stress and inbreeding on reproductive traits in a wild bird populationJOURNAL OF ANIMAL ECOLOGY, Issue 6 2006A. B. MARR Summary 1Conservation biologists are concerned about the interactive effects of environmental stress and inbreeding because such interactions could affect the dynamics and extinction risk of small and isolated populations, but few studies have tested for these interactions in nature. 2We used data from the long-term population study of song sparrows Melospiza melodia on Mandarte Island to examine the joint effects of inbreeding and environmental stress on four fitness traits that are known to be affected by the inbreeding level of adult birds: hatching success, laying date, male mating success and fledgling survival. 3We found that inbreeding depression interacted with environmental stress to reduce hatching success in the nests of inbred females during periods of rain. 4For laying date, we found equivocal support for an interaction between parental inbreeding and environmental stress. In this case, however, inbred females experienced less inbreeding depression in more stressful, cooler years. 5For two other traits, we found no evidence that the strength of inbreeding depression varied with environmental stress. First, mated males fathered fewer nests per season if inbred or if the ratio of males to females in the population was high, but inbreeding depression did not depend on sex ratio. Second, fledglings survived poorly during rainy periods and if their father was inbred, but the effects of paternal inbreeding and rain did not interact. 6Thus, even for a single species, interactions between the inbreeding level and environmental stress may not occur in all traits affected by inbreeding depression, and interactions that do occur will not always act synergistically to further decrease fitness. [source] Lack of fitness costs associated with pyriproxyfen resistance in the B biotype of Bemisia tabaciPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2009David W Crowder Abstract BACKGROUND: The insect growth regulator pyriproxyfen has provided effective control of the whitefly Bemisia tabaci Gennadius in many countries. Here, whether or not fitness costs were associated with pyriproxyfen resistance in a laboratory-selected resistant strain (QC02-R) of the B biotype was determined. RESULTS: Mortality caused by pyriproxyfen and fitness traits over time were measured in unselected and selected hybrid strains, which were created by crossing individuals of the resistant strain with individuals of a susceptible strain. Fitness costs were not associated with resistance in QC02-R, as mortality caused by pyriproxyfen did not increase over time in unselected hybrid strains and fitness traits were similar in unselected and selected hybrid strains. Using a new method to examine the inheritance of resistance, based on data from fitness cost experiments, it was estimated that pyriproxyfen resistance is controlled by two loci in the QC02-R strain. CONCLUSION: The lack of fitness costs associated with pyriproxyfen resistance could promote the evolution of resistance in field populations with similar traits to QC02-R. Copyright © 2008 Society of Chemical Industry [source] Endangered, apparently: the role of apparent competition in endangered species conservationANIMAL CONSERVATION, Issue 4 2010N. J. DeCesare Abstract Conservation biologists have reported growing evidence of food-web interactions as causes of species endangerment. Apparent competition is an indirect interaction among prey species mediated by a shared predator, and has been increasingly linked to declines of prey species across taxa. We review theoretical and empirical studies of apparent competition, with specific attention to the mechanisms of asymmetry among apparently competing prey species. Asymmetry is theoretically driven by niche overlap, species fitness traits, spatial heterogeneity and generalist predator behavior. In real-world systems, human-induced changes to ecosystems such as habitat alteration and introduced species may be ultimate sources of species endangerment. However, apparent competition is shown to be a proximate mechanism when resultant changes introduce or subsidize abundant primary prey for predator populations. Demonstration of apparent competition is difficult due to the indirect relationships between prey and predator species and the potential for concurrent exploitative competition or other community effects. However, general conclusions are drawn concerning the characteristics of prey and predator species likely to exhibit asymmetric apparent competition, and the options for recovering endangered species. While short-term management may be required to avoid imminent extinction in systems demonstrating apparent competition, we propose adaptive conservation efforts directed at long-term recovery. [source] Association between SNP Heterozygosity and Quantitative Traits in the Framingham Heart StudyANNALS OF HUMAN GENETICS, Issue 4 2009Didahally R. Govindaraju Summary Associations between multilocus heterozygosity and fitness traits, also termed heterozygosity and fitness correlations (HFCs), have been reported in numerous organisms. These studies, in general, indicate a positive relationship between heterozygosity and fitness traits. We studied the association between genome-wide heterozygosity at 706 non-synonymous and synonymous SNPs and 19 quantitative traits, including morphological, biochemical and fitness traits in the Framingham Heart Study. Statistically significant association was found between heterozygosity and systolic and diastolic blood pressures as well as left ventricular diameter and wall thickness. These results suggest that heterozygosity may be associated with traits, such as blood pressure that closely track environmental variations. Balancing selection may be operating in the maintenance of heterozygosity and the major components of blood pressure and hypertension. Genome wide SNP heterozygosity may be used to understand the phenomenon of dominance as well as the evolutionary basis of many quantitative traits in humans. [source] Differential and reversible responses of common fen meadow species to abandonmentAPPLIED VEGETATION SCIENCE, Issue 1 2003Regula Billeter Binz & Heitz (1990) Abstract. We studied the effects of abandonment on two common fen plant species. In mown and a chronosequence of abandoned fen meadows spanning 35 yr, we measured fitness traits of the sedge Carex davalliana and the forb Succisa pratensis. Cessation of mowing had little effect on fitness traits and seed production of C. davalliana, but seedling density decreased more than threefold. Population density of S. pratensis decreased with increasing community biomass, but was not affected by the cessation of mowing. However, flowering frequency increased threefold and seed production was 20% higher in fallow meadows. Consequently, seedling density of S. pratensis increased nearly threefold after abandonment. However, these changes were not dependent on the age of the fallow. In a common garden and germination experiment, we found no differences in either species between plants from fallows and mown fen meadows, except for the height of the flowering stalk of S. pratensis. The combined results from the common garden experiment and the field studies indicate that changes in fitness traits observed in fallows were mostly phenotypic and likely to be reversible. If other species react in similar ways, there is a high potential for re-establishing traditional fen meadow communities from fallows by mowing. [source] | |||||||||||||