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Smaller Body Size (smaller + body_size)
Selected AbstractsPrenatal growth, postnatal growth and trait anxiety in late adulthood , the Helsinki Birth Cohort StudyACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2010J. Lahti Lahti J, Räikkönen K, Pesonen A-K, Heinonen K, Kajantie E, Forsén T, Osmond C, Barker DJP, Eriksson JG. Prenatal growth, postnatal growth and trait anxiety in late adulthood , the Helsinki Birth Cohort Study. Objective:, Trait anxiety may predispose to anxiety disorders and cardiovascular events. We tested whether prenatal growth or postnatal growth from birth to 11 years of age and in adulthood predict trait anxiety in late adulthood. Method:, Women (n = 951) and men (n = 753) reported trait anxiety using the Spielberger Trait Anxiety Scale at an average age of 63.4 years and growth was estimated from records. Results:, Higher trait anxiety was predicted by smaller body size at birth, in infancy and in adulthood. Moreover, faster growth particularly from seven to 11 years of age and slower growth between 11 and 63 years predicted higher trait anxiety. Conclusion:, We found a pattern of pre- and postnatal growth that predisposed to higher trait anxiety in late adulthood. This pattern resembles that found to increase the risk of cardiovascular events and, thus, points to a shared common origin in a suboptimal prenatal and childhood developmental milieu. [source] Gamete production and sexual size dimorphism in an insect (Orchesella cincta) with indeterminate growthECOLOGICAL ENTOMOLOGY, Issue 2 2002G. Ernsting Abstract 1. The relationship of growth and body size with reproductive effort in animal species has been studied much less for males than for females. This imbalance applies to Orchesella cincta (L.) (Collembola), an insect with indeterminate growth, in which egg production is related positively to body size and negatively to growth. 2. To allow a comparison of the reproductive effort of male and female O. cincta, development and growth in immature stages of both sexes, and growth and spermatophore production for adult males were studied. 3. Embryonic development time and hatchling size did not differ between prospective males and females, but from hatching on the trajectories diverged, with males growing more slowly and maturing earlier and at a much smaller body size than females. 4. Neither the number of spermatophores deposited in the first adult instar (= inter-moult period) nor the total number of spermatophores deposited during seven instars was related to body size or growth. 5. Differences in growth rate between instars with and without spermatophore deposition indicated that the physiology of spermatophore production inhibits growth, which, however, was compensated for during the next instar. 6. The difference in the relationship of gamete production with body size and growth between males and females explains the divergence of their size at maturity. [source] EVOLUTION UNDER RELAXED SEXUAL CONFLICT IN THE BULB MITE RHIZOGLYPHUS ROBINIEVOLUTION, Issue 9 2006Magdalena Tilszer Abstract The experimental evolution under different levels of sexual conflict have been used to demonstrate antagonistic coevolution in muscids, but among other taxa a similar approach has not been employed. Here, we describe the results of 37 generations of evolution under either experimentally enforced monogamy or polygamy in the bulb mite Rhizoglyphus robini. Three replicates were maintained for each treatment. Monogamy makes male and female interests congruent; thus selection is expected to decrease harmfulness of males to their partners. Our results were consistent with this prediction in that females from monogamous lines achieved lower fecundity when housed with males from polygamous lines. Fecundity of polygamous females was not affected by mating system under which their partners evolved, which suggests that they were more resistant to male-induced harm. As predicted by the antagonistic coevolution hypothesis, the decrease in harmfulness of monogamous males was accompanied by a decline in reproductive competitiveness. In contrast, female fecundity and embryonic viability, which were not expected to be correlated with male harmfulness, did not differ between monogamous and polygamous lines. None of the fitness components assayed differed between individuals obtained from crosses between parents from the same line and those obtained from crosses between parents from different lines within the same mating system. This indicates that inbreeding depression did not confound our results. However, interpretation of our results is complicated by the fact that both males and females from monogamous lines evolved smaller body size compared to individuals from polygamous lines. Although a decrease in reproductive performance of males from monogamous lines was still significant when body size was taken into account, we were not able to separate the effects of male body size and mating system in their influence on fecundity of their female partners. [source] CHARACTER DISPLACEMENT AS THE "BEST OF A BAD SITUATION": FITNESS TRADE-OFFS RESULTING FROM SELECTION TO MINIMIZE RESOURCE AND MATE COMPETITIONEVOLUTION, Issue 10 2005Karin S. Pfennig Abstract Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected. [source] Microgeographic life history variation in an alpine caddisfly: plasticity in response to seasonal time constraintsFRESHWATER BIOLOGY, Issue 1 2009LISA N. S. SHAMA Summary 1.,Temporally constrained environments, such as habitats with short growth seasons or short hydroperiods, cause potentially strong selection on life histories. Depending on the predictability of these events and the extent of spatial and temporal heterogeneity, local populations could become adapted either via a fixed phenotype or via life history plasticity in response to these environmental cues. 2.,We used a common garden experiment to investigate microgeographic variation in life history responses to combined changes in photoperiod (ambient/late) and hydroperiod (constant/drying) time constraint cues in an alpine caddisfly (Trichoptera). We compared six populations (three permanent/three temporary streams) originating from a small, alpine floodplain and which spanned an expected gradient in growth period duration (GPD) with distance from glaciers. 3.,We made two main predictions in relation to locally varying selection pressures: (i) populations nearest glaciers (shorter GPD and strongest time constraints) should have the fastest development rates and (ii) populations from permanent streams should be less able to respond to drying hydroperiods than populations from temporary streams. 4.,All populations and both sexes accelerated development in response to late season photoperiod cues. However, only permanent stream populations showed an increase in development time with increasing GPD, suggesting that other factors were influencing populations in temporary streams. 5.,Permanent stream populations showed countergradient variation (genetic and environmental influences were in opposition) in development time, and under-compensation of growth rates resulted in a converse Bergmann cline in body size (smaller body size along gradients of declining season length). The extent of plasticity in response to hydroperiod, and the combined effects of both time constraints, differed between populations and sexes, but were not consistent among populations. 6.,Taken together, our results suggest adaptive plasticity in response to season length. The lack of a predictable pattern in response to hydroperiod may be due to gene flow or weak selection. We conclude that spatially structured populations can strongly differ in phenotypic plasticity even at microgeographic scales. [source] Energy density patterns of nectar resources permit coexistence within a guild of Neotropical flower-visiting batsJOURNAL OF ZOOLOGY, Issue 1 2004Marco Tschapka Abstract Neotropical rainforests support guilds of nectar feeding bats (Phyllostomidae: Glossophaginae) with up to six coexisting species. To analyse guild structure and mechanisms of coexistence in a Costa Rican tropical lowland rainforest, the resource use and morphology of bats were compared to the energetic characteristics of preferred nectar resources and their spatio-temporal distribution. The relative abundance of nectar-feeding bats was determined from mistnet captures over 26 months. Food items were identified by analysis of pollen loads and faecal samples. Phenology, flower density and nectar sugar content of resource plants permitted quantitative estimations of resource availability expressed as energy density (kJ ha,1 day,1) throughout the annual cycle. Four glossophagine bat species co-occurred at La Selva: two permanent residents (Glossophaga commissarisi, Hylonycteris underwoodi) and two seasonal species (Lichonycteris obscura, Lonchophylla robusta) that were found in small numbers during a period of high nectar availability. The two resident species differed in their abundance and in their temporal feeding strategies. After the main flowering peak, the common G. commissarisi shifted to a more frugivorous diet, while the rarer H. underwoodi fed on the few remaining bat-flowers. Resource plant species differed in their energy density by up to two orders of magnitude. Hylonycteris underwoodi visited more often plant species with a low energy yield than G. commissarisi. Because of its smaller body size and a wing morphology that promotes fast flight, H. underwoodi appears to be better adapted to low and scattered nectar resource levels. The two seasonal species differed greatly in body mass, which suggests different strategies for high-quality resource tracking. Large body mass in Lonchophylla robusta provides an energy buffer that permits daily commuting flights between a permanent roost and profitable foraging areas, while the small Lichonycteris obscura seems to track resources nomadically. It is proposed that energy density may be a major niche dimension that restricts access of species to certain habitats and that may profoundly influence the structure of nectar-feeding bat guilds. [source] The influence of density on post-weaning growth in roe deer Capreolus capreolus fawnsJOURNAL OF ZOOLOGY, Issue 3 2002A. J. M. Hewison Abstract In temperate ungulates, the body weight of juveniles at the onset of winter is a crucial determinant of survival and can also influence subsequent reproductive success. However, growth may be retarded post-weaning, during winter, as a result of resource restriction and/or the demands of thermoregulation in harsh climatic conditions. Post-weaning growth rates of juveniles were compared in relation to varying density in two populations of roe deer Capreolus capreolus (Chizé, Dourdan) monitored for 10 and 15 years, respectively. Body growth of fawns continued over the post-weaning stage of the juvenile period (October,March) at the rate of 0.017 kg/day at Chizé and 0.014 kg/day at Dourdan. Deer density had no influence on this post-weaning growth rate of juveniles in their first winter. However, deer born in years of high density weighed less at a given date than those born in years of low density because of their smaller body size at the onset of winter, indicating density-dependent rates of growth before weaning. At Chizé, the sexes grew at the same rate, but sexual dimorphism was apparent as males weighed about 1 kg (8%) more than females at a given date. At Dourdan, no significant sexual dimorphism was detected, although females tended to be heavier than males at a given date. We conclude that density influences juvenile body weight (through its effect on birth weight and/or post-natal growth rate) before weaning in this species and, despite continued growth after weaning, during winter, roe deer whose early growth is limited through interspecific competition cannot compensate for this early restriction. [source] The relative importance of birds and bees in the pollination of Metrosideros excelsa (Myrtaceae)AUSTRAL ECOLOGY, Issue 5 2009GABRIELE SCHMIDT-ADAM Abstract Exclusion experiments were used to assess the effect of different pollinator groups on outcrossing and seed production in Metrosideros excelsa. The main study site was Little Barrier Island, New Zealand where indigenous bird and native solitary bees are the main flower visitors. Our results showed that native birds were more important pollinators of M. excelsa than native bees. Seed production was much higher in open pollination than in two exclusion experiments where either birds were excluded and native bees only had access to flowers, or where all pollinators had been excluded. The number of fertile seeds per capsule was 45% higher after open pollination than in treatments with bee visitation only and 28% higher than in treatments where all flower visitors were excluded. Estimated outcrossing rates were significantly higher (tm = 0.71) for open pollination in the upper canopy (>4 m above-ground level) where bird visitation is presumed to be more frequent than for a treatment with native bee access only (tm = 0.40). Our results also suggest that a large proportion of seeds (66%) arise from autonomous self-pollination when all pollinators are excluded. In four trees of a modified mainland population with predominantly introduced birds and a mixture of introduced and native bees there was no decrease in seed production for the treatment allowing bee access only, indicating that , in contrast to native bees , honeybees may be more efficient pollinators of M. excelsa. Observation of the foraging behaviour of both groups of bees showed that native bees contact the stigma of flowers less frequently than honeybees. This is likely to be a consequence of their smaller body size relative to honeybees. [source] Adaptive Offspring Sex Ratio Depends on Male Tail Length in the GuppyETHOLOGY, Issue 11 2006Kenji Karino A biased sex ratio in a brood is considered to be an adaptive strategy under certain circumstances. For example, if the expected reproductive success of one sex is greater than that of the other, parents should produce more offspring of the former sex than the latter. A previous study has documented that in the guppy, Poecilia reticulata, the female offspring of males possessing proportionally longer tails exhibit smaller body sizes and show decreased reproductive outputs than those of males having shorter tails. On the other hand, the total lengths of the male offspring of the long-tailed males are larger because of their longer tails; consequently, they exhibit greater sexual attractiveness to females. Therefore, it has been hypothesized that this asymmetry in the expected reproductive success between the male and female offspring of long-tailed males may result in a biased sex ratio that is dependent on the tail lengths of their fathers. This hypothesis was tested in the present study. The results showed that the females that mated with long-tailed males produced more male offspring than those that mated with short-tailed males. Logistic regression analysis showed that the ratio of tail length to the standard length of the fathers is a determinant factor of the sex of their offspring. These results suggest that the manipulation of the offspring sex ratios by parents enhances the overall fitness of the offspring. [source] | ||||||||||