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Offspring Number (offspring + number)
Selected AbstractsAdjustment of Parental Investment in the Dung Beetle Onthophagus atripennis (Col., Scarabaeidae)ETHOLOGY, Issue 12 2006Shigeki Kishi If parents can invest resources optimally per offspring, they should adjust the amount of investment in an offspring according to environmental heterogeneity. Many studies have demonstrated changes in egg size or the amount of resource supplied in response to environmental heterogeneity. However, it remains unclear whether parents simply know the resource type a priori or can assess resource quality and adjust the quantity of investment accordingly. We examined the parental capability to adjust the amount of investment per offspring by providing Onthophagus atripennis dung beetle parents with one of three dung types of different quality: monkey dung (high quality), cow dung (low quality), or a mixture of monkey and cow dung (medium quality). The beetle parents cooperatively produce dung brood masses each with one egg under the ground. The size of a brood mass, on which a larva can only feed until adult, represents a large part of the amount of investment. Parents produced a greater number of smaller brood masses given high-quality resource, while they compensated for low quality of the resource by providing a larger amount of the resource, at the cost of offspring number. However, despite this compensation in the amount of food, offspring raised on low-quality food was still smaller than offspring raised on high-quality food. Thus, O. atripennis parents assessed resource quality partly and adjusted the amount of resource provided for their offspring. [source] POPULATION DIFFERENTIATION IN THE BEETLE TRIBOLIUM CASTANEUM.EVOLUTION, Issue 3 2007We used joint-scaling analyses in conjunction with rearing temperature variation to investigate the contributions of additive, non-additive, and environmental effects to genetic divergence and incipient speciation among 12 populations of the red flour beetle, Tribolium castaneum, with small levels of pairwise nuclear genetic divergence (0.033 < Nei's D < 0.125). For 15 population pairs we created a full spectrum of line crosses (two parental, two reciprocal F1's, four F2's, and eight backcrosses), reared them at multiple temperatures, and analyzed the numbers and developmental defects of offspring. We assayed a total of 219,388 offspring from 5147 families. Failed crosses occurred predominately in F2's, giving evidence of F2 breakdown within this species. In all cases where a significant model could be fit to the data on offspring number, we observed at least one type of digenic epistasis. We also found maternal and cytoplasmic effects to be common components of divergence among T. castaneum populations. In some cases, the most complex model tested (additive, dominance, epistatic, maternal, and cytoplasmic effects) did not provide a significant fit to the data, suggesting that linkage or higher order epistasis is involved in differentiation between some populations. For the limb deformity data, we observed significant genotype-by-environment interaction in most crosses and pure parent crosses tended to have fewer deformities than hybrid crosses. Complexity of genetic architecture was not correlated with either geographic distance or genetic distance. Our results support the view that genetic incompatibilities responsible for postzygotic isolation, an important component of speciation, may be a natural but serendipitous consequence of nonadditive genetic effects and structured populations. [source] Non-lethal effects of invertebrate predators on Daphnia: morphological and life-history consequences of water mite kairomoneFRESHWATER BIOLOGY, Issue 9 2008MAURICIO J. CARTER Summary 1. Here, we report morphological and life-historical changes in the cladoceran Daphnia ambigua in response to chemical cues released by the predatory water mite Piona chilensis. Both species are common inhabitants of southern temperate lakes. 2. We found significant differences in adult body size at first, second and third reproduction. Also, individuals exposed to kairomones had longer tail spines at first reproduction, and the resultant offspring had smaller bodies and shorter tail spines. 3. Exposure to mite cues did not exert effects on brood size at first reproduction, but decreased offspring number in subsequent broods. Similarly, only the second and third reproduction events were delayed by kairomone exposure. 4. The intrinsic population growth rate of predator-induced animals was lower than that in controls, but simulations based on a parameterized matrix model showed that the fitness costs could be overcome if the reported phenotypic responses reduced predation rate moderately. The gain in protection from predators needed to cancel out the reduction in fitness associated with predator cues was directly related to juvenile survival and fertility, and inversely related to adult survival. 5. This is the first work reporting phenotypic plasticity in Cladocera in response to kairomones released by water mites, which are conspicuous predators in many austral fresh waters. [source] Intraspecific seed trait variations and competition: passive or adaptive response?FUNCTIONAL ECOLOGY, Issue 3 2009Cyrille Violle Summary 1The phenotype of offspring depends on the abiotic and biotic environment in which the parents developed. However, the direct effects of competition experienced by parent plants on single-seed traits are poorly documented despite their impact on plant fitness. 2We hypothesize that single-seed traits can differentially respond to the resource deficiencies of parent plants due to competition: seed quality may decrease as seed number does, magnifying the negative effects of competition for offspring (,passive response' hypothesis), or increase and then enhance offspring fitness to offset the reduction in offspring number (,adaptive response' hypothesis). Here we tested these hypotheses for four single-seed traits. We assessed the sensibility of their responses to changes in competition intensity due to species with different competitive effects and to contrasting soil nitrogen conditions. 3In a common-garden experiment, four single-seed traits related to fitness , seed mass, seed nitrogen concentration (SNC), germinability and the timing of germination , were measured on a phytometer species transplanted in 14 different neighbours grown in monoculture with and without soil nitrogen limitation. 4Under nitrogen-limiting conditions, the responses of SNC and of the timing of germination were passive and mainly related to the effects of neighbours on soil nitrogen availability, as shown by the increase in SNC with N-fixing neighbours. Within-individual seed mass variability decreased with increasing competition intensity, as an adaptive response to counterbalance the reduction in seed production. With nitrogen supplementation, competitors had no detectable effect on single-seed traits despite an overall increase in SNC and germination rate, confirming their nitrogen-dependent passive responses to competition. Germinability did not change among treatments. 5The impact of competition on single-seed traits depends on both phytometer trait identity and resource modulation by neighbours. The passive response of seed chemical composition to competitors may magnify the competitive effects on offspring. By contrast, the adaptive response of seed size variability may offset these competitive effects. As a consequence, experiments looking at the fitness consequences of competition should not only consider the effects on fitness parameters of a target plant but also on the offspring. [source] Do placental species abort offspring?FUNCTIONAL ECOLOGY, Issue 2 2008DeAngelis model, Testing an assumption of the Trexler Summary 1We investigate how resource level affects reproduction in matrotrophic (Poeciliopsis prolifica) and lecithotrophic (P. monacha) fishes. 2One of our goals was to test an assumption of the Trexler,DeAngelis model for the evolution of matrotrophy, which was that matrotrophic species can adjust litter size by aborting offspring in low food conditions. Our more general goal was to elucidate other differences between the reproductive modes. 3Both species have superfetation and c. 30-day development time. Females of each species were assigned to high or low food availability for 30 days, or one gestation period. Any young born during that time interval would have initiated development before the initiation of the experiment. If embryos are aborted, then this would be seen as a reduction in brood size in the low food treatment relative to the high food treatment within this period. 4Our results suggest P. monacha responds to low food by sacrificing reproduction to maintain lipids, while P. prolifica maintains reproduction at the expense of lipids. Neither species showed a significant reduction in offspring number over the course of the experiment, suggesting that these species do not abort offspring in low food conditions. [source] Manipulation of offspring number and size: benefits of large body size at birth depend upon the rearing environmentJOURNAL OF ANIMAL ECOLOGY, Issue 2 2003Tuula A. Oksanen Summary 1Allocation of reproductive effort between the number and size of offspring determines the immediate rearing environment for the growing young. As the number of offspring increases, the amount of parental investment per individual offspring decreases, and the quality of the rearing environment is expected to decrease. This may result in a lower quality of offspring reared in such conditions. 2We studied the effects of the rearing environment on the quality of juvenile bank voles, Clethrionomys glareolus, with different initial body sizes at birth in a 2 × 2 factorial experiment. The rearing environment was manipulated by enlarging both the litter size by two extra pups, and mean offspring body size at birth by replacing the original litter with heavier pups from smaller litters. Offspring quality was estimated from body size measurements, parasitic infection with Eimeria spp. and the level of immune response to a novel antigen. 3The analyses revealed that large body size at birth was an advantage in ,normal' rearing environments, but a disadvantage in poor ones. The initially normal sized offspring grown in enlarged litters had a relatively good capacity for growth and high immune function confirming that a poor rearing environment alone does not reduce their quality. 4Our findings that the benefits of large body size depend on the rearing environment suggest that offspring body size is adjusted in relation to litter size, and thus the evolution of these two traits is combined. [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] Sex-specific transgenerational effects of early developmental conditions in a passerineBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2007CARLOS ALONSO-ALVAREZ Most studies dealing with the trade-off between offspring number and quality have overlooked the long-term consequences for the progeny. High investment in offspring number usually results in an increased competition among nest mates. The deterioration of the early developmental conditions, due to this increased competition, can impair individual quality over the long term, and subsequently affect survival and lifetime fecundity. Moreover, the consequences of the allocation rule to offspring number vs. quality can extend across generations and give raise to grandparental effects. These transgenerational trade-offs have been explored rarely. In the present study, we manipulated the breeding effort of captive zebra finches (Taeniopygia guttata) by offering them enlarged or reduced broods. Offspring reared under these conditions were allowed to breed freely in an outdoor aviary, during their entire lifespan. Second-generation fledglings whose mother was raised in enlarged broods were in lower body condition than offspring whose mother was raised in reduced broods. However, second-generation fledglings were not affected by the brood size experienced by the father. These results show that the solution of parental dilemma, whether producing a small number of high quality offspring or a large number of poor quality descendants, must take into account the long-term transgenerational effects acting on grandchildren. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 469,474. [source] Offspring production and development in the parasitoid wasp Melittobia clavicornis (Cameron) (Hymenoptera: Eulophidae) from JapanENTOMOLOGICAL SCIENCE, Issue 1 2004Jorge M. GONZÁLEZ Abstract The development time, sex ratio and offspring production of Melittobia clavicornis reared with wild, facultative and factitious hosts are presented. Known hosts and different biological aspects presented in previously published reports are summarized and clarified. Immature development time was equivalent or slightly longer than that of other Melittobia species, and the sex ratio was approximately 97% female. Total offspring numbers were considerably lower than that of other Melittobia species using the same hosts. We report female dimorphism in this species for the first time. The number and relative proportion of brachypterous morph females produced was higher than that in other species of the genus. [source] DOES EVOLUTION OF ITEROPAROUS AND SEMELPAROUS REPRODUCTION CALL FOR SPATIALLY STRUCTURED SYSTEMS?EVOLUTION, Issue 1 2000Esa Ranta Abstract., A persistent question in the evolution of life histories is the fitness trade-off between reproducing only once (semelparity) in a lifetime or reproducing repeated times in different seasons (iteroparity). The problem can be formulated into a research agenda by assuming that one reproductive strategy is resident (has already evolved) and by asking whether invasion (evolution) of an alternative reproductive strategy is possible. For a spatially nonstructured system, Bulmer (1994) derived the relationship v + PA < 1 (PA is adult survival; vbs and bs are offspring numbers for iteroparous and semelparous breeding strategies, respectively) at which semelparous population cannot be invaded by an iteroparous mutant. When the inequality is changed to v + PA > 1, invasion of a semelparous mutant is not possible. From the inequalities, it is easy to see that possibilities for evolutionary establishment of a novel reproductive strategy are rather narrow. We extended the evolutionary scenario into a spatially structured system with dispersal linkage among the subunits. In this domain, a rare reproductive strategy can easily invade a population dominated by a resident reproductive strategy. The parameter space enabling invasion is far more generous with spatially structured evolutionary scenarios than in a spatially nonstructured system. [source] Copepod life cycle adaptations and success in response to phytoplankton spring bloom phenologyGLOBAL CHANGE BIOLOGY, Issue 6 2009HANNO SEEBENS Abstract In a seasonal environment, the timing of reproduction is usually scheduled to maximize the survival of offspring. Within deep water bodies, the phytoplankton spring bloom provides a short time window of high food quantity and quality for herbivores. The onset of algal bloom development, however, varies strongly from year to year due to interannual variability in meteorological conditions. Furthermore, the onset is predicted to change with global warming. Here, we use a long-term dataset to study (a) how a cyclopoid copepod, Cyclops vicinus, is dealing with the large variability in phytoplankton bloom phenology, and (b) if bloom phenology has an influence on offspring numbers. C. vicinus performed a two-phase dormancy, that is, the actual diapause of fourth copepodid stages at the lake bottom is followed by a delay in maturation, that is, a quiescence, within the fifth copepodid stage until the start of the spring bloom. This strategy seems to guarantee a high temporal match of the food requirements for successful offspring development, especially through the highly vulnerable naupliar stages, with the phytoplankton spring bloom. However, despite this match with food availability in all study years, offspring numbers, that is, offspring survival rates were higher in years with an early start of the phytoplankton bloom. In addition, the phenology of copepod development suggested that also within study years, early offspring seems to have lower mortality rates than late produced offspring. We suggest that this is due to a longer predator-free time period and/or reduced time stress for development. Hence, within the present climate variability, the copepod benefited from warmer spring temperatures resulting in an earlier phytoplankton spring bloom. Time will show if the copepod's strategy is flexible enough to cope with future warming. [source] | ||||||||||