Humoral immunocompetence correlates with date of egg-laying and reflects work load in female tree swallows

Because quality differences between individuals affect fitness,much research has attempted, with limited success, to relatephysiological condition (e.g., body reserves), to differencesin life history between individuals. Recently, it has beensuggested that immunocompetence may reflect condition, andit thus may mediate variation in individual quality and reproductiveperformance and, ultimately, fitness. We measured humoral immunocompetence(HIC) by immunizing female tree swallows with a harmless antigenand measured the specific antibody responses in a novel enzyme-linkedimmunosorbent assay developed for passerine birds. HIC was stronglycorrelated with egg-laying date, an important determinant ofreproductive success in female tree swallows. We also investigatedthe effect of increased workload on HIC by manipulating femaleflight costs by clipping flight feathers. Clipped females hadlower HIC than nonclipped females. These data suggest that HICis a measure that may reflect phenotypic quality and also appearsto be sensitive to increased workload in female tree swallows.     

植物种群的繁殖对策

植物种群的繁殖对策钟章成（西南师范大学,重庆６３０７１５）ＲｅｐｒｏｄｕｃｔｉｖｅＳｔｒａｔｅｇｉｅｓｏｆＰｌａｎｔＰｏｐｕｌａｔｉｏｎｓ．￥ＺｈｏｎｇＺｈａｎｇｃｈｅｎｇ（ＳｏｕｔｈｗｅｓｔＣｈｉｎａＴｅａｃｈｅｒｓＵ－ｎｉｖｅｒｓｉｔｙ,Ｃｈｏｎ...     

Age-related shapes of the cost of reproduction in vertebrates

The shape of the association between age and the cost of reproduction varies across species. However, it is unclear whether there are any general patterns in the way the cost of reproduction varies with life history, taxon or ecological function. Using a simple theoretical method, we identified three characteristic patterns to describe the age-related survival cost of reproduction. The most frequent pattern is an approximately exponential decay (ED) with increasing age. Two additional u-shaped patterns were identified, where the cost of reproduction was higher for young and old individuals compared with intermediate-aged individuals. The majority of these u-shaped curves suggested higher costs of reproduction at older ages (RQ), with the rest suggesting a higher cost at young ages (LQ). While predators were most likely to exhibit ED-shaped cost curves, herbivores were equally likely to exhibit ED and RQ curves; birds were likely to exhibit ED-shaped curves and mammals were split equally between ED and RQ curves. These findings suggest that there may be predictable differences in the age-related shape of the cost of reproduction between species, but further research is required to identify the mechanisms generating such differences.     

Age-specific life history tactics in organisms with determinate growth: Optimal models for non-optimal behavior?

Among organisms with determinate growth, optimization models predict that reproductive effort should increase as individuals approach old age, but the assumptions of these models may be inappropriate because the senescence that generates the necessary selective pressure may be not itself be optimal. Population genetics models were constructed to examine whether genes for age-specific changes in reproductive effort could invade a population in which senescence was maintained at equilibrium levels by a balance between mutation and selection. In asexually reproducing organisms, it was found that strategies of increasing reproductive effort could not normally invade the population. In sexually reproducing organisms, however, recombination was found to be important and genes for age-specific changes in effort could spread in the population under most circumstances.     

The energetics of asexual reproduction: Pedal laceration in the symbiotic sea anemone Aiptasia pulchella (Carlgren, 1943)

Asexual reproduction of the symbiotic sea anemone Aiptasia pulchella (Carlgren, 1943) was studied in the context of energy budgets determined under a variety of light and feeding conditions. Continuous darkness significantly increased rates of pedal laceration (the method of asexual reproduction), while different feeding rates had no significant effect. Digestive assimilation efficiency averaged 63% for whole brine shrimp, and conversion efficiencies (assimilated energy into biomass) averaged 31%. There were no significant differences between the conversion efficiencies of energy obtained from light or food. The index of reproductive effort (RE) for pedal laceration was very low, ranging from 0.004 to 0.044. This low RE associated with a substantial rate of asexual reproduction may, in part, explain the widespread success of certain sea anemones.