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Adult Mass (adult + mass)
Selected AbstractsLEARNING ABILITY AND LONGEVITY: A SYMMETRICAL EVOLUTIONARY TRADE-OFF IN DROSOPHILAEVOLUTION, Issue 6 2008Joep M. S. Burger Learning ability can be substantially improved by artificial selection in animals ranging from Drosophila to rats. Thus these species have not used their evolutionary potential with respect to learning ability, despite intuitively expected and experimentally demonstrated adaptive advantages of learning. This suggests that learning is costly, but this notion has rarely been tested. Here we report correlated responses of life-history traits to selection for improved learning in Drosophila melanogaster. Replicate populations selected for improved learning lived on average 15% shorter than the corresponding unselected control populations. They also showed a minor reduction in fecundity late in life and possibly a minor increase in dry adult mass. Selection for improved learning had no effect on egg-to-adult viability, development rate, or desiccation resistance. Because shortened longevity was the strongest correlated response to selection for improved learning, we also measured learning ability in another set of replicate populations that had been selected for extended longevity. In a classical olfactory conditioning assay, these long-lived flies showed an almost 40% reduction in learning ability early in life. This effect disappeared with age. Our results suggest a symmetrical evolutionary trade-off between learning ability and longevity in Drosophila. [source] Embryo growth rates in birds and mammalsFUNCTIONAL ECOLOGY, Issue 3 2010Robert E. Ricklefs Summary 1.,Embryo mass growth curves of 36 species of bird and 18 species of mammal were fitted by sigmoidal Gompertz functions, in which k (days,1) describes the rate at which the embryo approaches an asymptotic mass A (g). 2.,The parameters of the Gompertz function were uncorrelated with parameters of power functions fitted to the same growth data, indicating that the two models describe different aspects of growth. 3.,Asymptotes of the Gompertz functions for embryonic growth averaged 2·5 times neonate size, but were well below adult mass. Thus, the pre- and postnatal phases of growth are distinct and have different target sizes. 4.,Embryo growth rate (k) decreases as the ,1/4 power of neonate size; values for mammals were 63% of those of birds, on average. 5.,Embryo growth rate can be predicted solely by the length of the incubation or gestation period, regardless of the size of the neonate, with the same relationship for birds and mammals. 6.,Postnatal growth rate (kG) scales linearly with embryonic growth rate (k), but is nearly five- times more rapid, on average, in birds than in mammals. kG and k have similar magnitude in birds, but kG is relatively much slower than k in mammals. 7.,Rate of actuarial senescence , (year,1), measured by the increase in mortality rate with age, is positively related to the rate of embryo growth in both birds and mammals, but is higher in the latter. Moreover, rate of ageing in birds is uniquely related to embryo growth while that in mammals is uniquely related to postnatal growth rate. Thus, development and ageing appear to be differently connected in birds and mammals, although the basis for these relationships is not known. [source] Effects of a toxicant on population growth rates: sublethal and delayed responses in blowfly populationsFUNCTIONAL ECOLOGY, Issue 6 2001S. J. MOE Summary 1,Previous studies have shown that cadmium exposure of blowfly populations (Lucilia sericata[Meigen 1826]) results in reduced population growth rate, but also in higher individual mass, because of reduced competition for food. In this study, the discrepancy between the positive effect on individual growth and the negative effect on population growth is investigated, by measuring direct and delayed effects of cadmium in the adult stage. 2,Blowfly populations were exposed to cadmium through the diet in four treatment combinations: larval stage, adult stage, both stages or neither stage. The effects on accumulation of cadmium, survival, development time, mass and reproductive rate were measured. 3,Cadmium was accumulated from both stages. 4,Individuals exposed to cadmium in the larval stage had higher mean pupal and adult mass (because of reduced densities), but also reduced adult longevity and fecundity. 5,Adult longevity and fecundity were also reduced by cadmium exposure in the adult stage. 6,In stage-structured populations, the link between individual-level and population-level responses to a toxicant may be complicated by stage-specific sensitivities to the toxicant, by delayed responses in the adult stage to sublethal effects in the juvenile stage, and by density-dependent compensatory responses to toxicant-induced mortality. [source] Individual variation in reproductive costs of reproduction: high-quality females always do betterJOURNAL OF ANIMAL ECOLOGY, Issue 1 2009Sandra Hamel Summary 1Although life-history theory predicts substantial costs of reproduction, individuals often show positive correlations among life-history traits, rather than trade-offs. The apparent absence of reproductive costs may result from heterogeneity in individual quality. 2Using detailed longitudinal data from three contrasted ungulate populations (mountain goats, Oreamnos americanus; bighorn sheep, Ovis canadensis; and roe deer, Capreolus capreolus), we assessed how individual quality affects the probability of detecting a cost of current reproduction on future reproduction for females. We used a composite measure of individual quality based on variations in longevity (all species), success in the last breeding opportunity before death (goats and sheep), adult mass (all species), and social rank (goats only). 3In all species, high-quality females consistently had a higher probability of reproduction, irrespective of previous reproductive status. In mountain goats, we detected a cost of reproduction only after accounting for differences in individual quality. Only low-quality female goats were less likely to reproduce following years of breeding than of nonbreeding. Offspring survival was lower in bighorn ewes following years of successful breeding than after years when no lamb was produced, but only for low-quality females, suggesting that a cost of reproduction only occurred for low-quality females. 4Because costs of reproduction differ among females, studies of life-history evolution must account for heterogeneity in individual quality. [source] The effect of egg size on post-hatching development in the Razorbill: an experimental studyJOURNAL OF AVIAN BIOLOGY, Issue 2 2000J. Mark Hipfner A recent experimental study reported that Thick-billed Murre Uria lomvia chicks that hatched from large eggs grew their wing feathers more quickly than did small-egg chicks. There is little evidence of this (or any other) egg-size effect on post-hatching development in other birds. Thick-billed Murres are marine birds of the family Alcidae that employ the unique "intermediate" developmental strategy: chicks go to sea after 15-30 days at the nest site, at <30% of adult mass, accompanied by their male parent. Rapid feather growth during the brief nestling period is critical to enable chicks to make the transition from life at the nest site to life at sea quickly and safely. At the Gannet Islands, Labrador, Canada, in 1996 and 1997, I tested whether egg size has the same effect on wing-feather growth in the Razorbill Alca torda, another of the intermediate auks. To control for underlying correlations between egg size and other parental attributes, eggs were switched randomly among pairs. As in other birds, egg size strongly predicted hatchling mass, and to less extent hatchling size (tarsus length), but had no effect on the rate at which nestlings gained mass. However, egg size had the same effect on wing growth in Razorbills as in Thick-billed Murres: the wings of large-egg chicks began rapid, linear growth sooner, indicating that early development of wing feathers was enhanced in large-egg chicks. Differences in wing length established in this manner persisted through the nestling period. Egg-size effects on feather growth have not been detected in experimental studies on other birds, suggesting that effects of the magnitude seen in Razorbills and Thick-billed Murres might reflect evolutionary priorities in the post-hatching development of intermediate auks. [source] The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterflyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2010K. GOTTHARD Abstract Switch-induced developmental plasticity, such as the diapause decision in insects, is a major form of adaptation to variable environments. As individuals that follow alternative developmental pathways will experience different selective environments the diapause decision may evolve to a cascade switch that induces additional adaptive developmental differences downstream of the diapause decision. Here, we show that individuals following alternative developmental pathways in a Swedish population of the butterfly, Pararge aegeria, display differential optimization of adult body mass as a likely response to predictable differences in thermal conditions during reproduction. In a more northern population where this type of selection is absent no similar difference in adult mass among pathways was found. We conclude that the diapause decision in the southern population appears to act as a cascade switch, coordinating development downstream of the diapause decision, to produce adult phenotypes adapted to the typical thermal conditions of their expected reproductive period. [source] Mass-dependent reproductive strategies in wild bighorn ewes: a quantitative genetic approachJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2000RÉale In the Ram Mountain bighorn sheep (Ovis canadensis) population, ewes differing by more than 30% in body mass weaned lambs with an average mass difference of only 3%. Variability in adult body mass was partly due to additive genetic effects, but inheritance of weaning mass was weak. Maternal effects could obscure genetic effects in the phenotypic expression of weaning mass, particularly if they reflected strategies of maternal expenditure that varied according to ewe mass. We performed a quantitative genetic analysis to assess genetic and environmental influences on ewe mass and on maternal expenditure. We used the mean daughters/mother regression method and Derivative Free Restricted Maximum Likelihood models to estimate heritability (h2) of ewe mass and indices of maternal expenditure. We found additive genetic effects on phenotypic variation in maternal mass, in lamb mass at weaning (absolute maternal expenditure) and in weaning mass relative to maternal mass at weaning (relative maternal expenditure). Heritability suggests that maternal expenditure has the potential to evolve. The genetic correlation of ewe mass and absolute maternal expenditure was weak, while ewe mass and relative maternal expenditure were strongly negatively correlated. These results suggest additive genetic effects on mass-dependent reproductive strategies in bighorn ewes. Mass-dependent reproductive strategies could affect lamb survival and phenotypic variation in adult mass. As population density increased and reproduction became costlier, small females reduced maternal expenditure more than large females. Constraints on reproductive strategy imposed by variations in resource availability are therefore likely to differ according to ewe mass. A general trend for a decrease in maternal expenditure relative to maternal size in mammals suggests that size-dependent negative maternal effects may be common. [source] Effects of genotype, elevated CO2 and elevated O3 on aspen phytochemistry and aspen leaf beetle Chrysomela crotchi performanceAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010Leanne M. Vigue 1Trembling aspen Populus tremuloides Michaux is an important forest species in the Great Lakes region and displays tremendous genetic variation in foliar chemistry. Elevated carbon dioxide (CO2) and ozone (O3) may also influence phytochemistry and thereby alter the performance of insect herbivores such as the aspen leaf beetle Chrysomela crotchi Brown. 2The present study aimed to relate genetic- and atmospheric-based variation in aspen phytochemistry to C. crotchi performance (larval development time, adult mass, survivorship). The experiment was conducted at the Aspen Free-Air CO2 Enrichment (FACE) site in northern Wisconsin. Beetles were reared on three aspen genotypes under elevated CO2 and/or O3. Leaves were collected to determine chemical characteristics. 3The foliage exhibited significant variation in nitrogen, condensed tannins and phenolic glycosides among genotypes. CO2 and O3, however, had little effect on phytochemistry. Nonetheless, elevated CO2 decreased beetle performance on one aspen genotype and had inconsistent effects on beetles reared on two other genotypes. Elevated O3 decreased beetle performance, especially for beetles reared on an O3 -sensitive genotype. Regression analyses indicated that phenolic glycosides and nitrogen explain a substantial amount (27,45%) of the variation in herbivore performance. 4By contrast to the negative effects that are typically observed with generalist herbivores, aspen leaf beetles appear to benefit from phenolic glycosides, chemical components that are largely genetically-determined in aspen. The results obtained in the present study indicate that host genetic variation and atmospheric concentrations of greenhouse gases will be important factors in the performance of specialist herbivores, such as C. crotchi, in future climates. [source] Density-dependent polyphenism and geographic variation in size among two populations of lubber grasshoppers (Romalea microptera)ECOLOGICAL ENTOMOLOGY, Issue 5 2009JASON E. JANNOT Abstract. 1. Density-dependent phase polyphenism occurs when changes in density during the juvenile stages result in a developmental shift from one phenotype to another. Density-dependent phase polyphenism is common among locusts (Orthoptera: Acrididae). 2. Previously, we demonstrated a longitudinal geographic cline in adult body size (western populations = small adults; eastern populations = large adults) in the eastern lubber grasshopper (Romalea microptera) in south Florida. As lubbers are confamilial with locusts, we hypothesised that the longitudinal size cline was partly due to density-dependent phase polyphenism. 3. We tested the effect of density, population, and density×population interaction on life-history traits (pronotum length, mass, cumulative development time, growth rate) of, and proportion surviving to, each of the five instars and the adult stage in a 2 × 3 factorial laboratory experiment with two lubber populations, each reared from hatchling to adult at three different densities. 4. The effect of density on life history and survival was independent of the effects of population on life history and survival. Higher densities led to larger adult sizes (pronotum, mass) and lower survivorship. The western population had smaller adult masses, fewer cumulative days to the adult stage, and higher survivorship than the eastern population. 5. Our data suggest that lubber grasshoppers exhibit density-dependent phase polyphenism initiated by the physical presence of conspecifics. However, the plastic response of adult size to density observed in the laboratory is not consistent with the relationship between phenotypes and adult density in the field. Genetic differences between populations observed in the laboratory could contribute to size and life-history differences among lubber populations in the field. [source] | ||||||||||