Environment-dependent reversal of a life history trade-off in the seed beetle Callosobruchus maculatus
Environment-dependent reversal of a life history trade-off in the seed beetle Callosobruchus maculatus
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DOI：
10.1046/j.1420-9101.2003.00535.x
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发表时间：
2003-05-01
影响因子：
2.1
通讯作者：
Fry, JD
中科院分区：
文献类型：
--
作者：
Messina, FJ;Fry, JD
环境操纵一直表明，资本繁殖种子甲虫 Callosobruchus maculatus 的繁殖成本很高，因为失去种子或配偶的雌性产卵较少，从而延长了它们的寿命。然而，生育力和寿命在种群内往往呈正相关，这可能是资源获取方面个体差异的结果。我们进行了一项分巢实验，该实验将种子可用性（种子存在或不存在）的操纵与每个环境中的繁殖力和寿命的定量遗传分析结合起来。每个性状在每个环境中都具有显着的遗传性。种子的可用性不仅改变了环境之间的平均繁殖力和寿命，而且还改变了性状在环境内的关联方式。表型和遗传相关性的迹象从有种子时的正值转变为无种子时的负值。即使在体重（资源获取的潜在指标）的影响得到统计控制后，这种逆转仍然持续存在。跨环境遗传相关性呈正相关，但每个性状均显着小于 1。我们认为，繁殖力与寿命关系的逆转取决于环境之间资源获取和资源分配基因座相对重要性的转变。特别是，只有当种子稀缺或缺乏时，繁殖成本在个体层面上才可能变得明显，因为繁殖努力的差异变得足够大，足以压倒资源获取的差异。尽管它们普遍依赖于幼虫阶段获得的资源，但 C. maculatus 的繁殖力和寿命在生理或遗传意义上似乎并不紧密耦合。
Environmental manipulations have consistently demonstrated a cost of reproduction in the capital-breeding seed beetle, Callosobruchus maculatus, as females deprived of seeds or mates lay fewer eggs and thereby increase their longevity. Yet fecundity and longevity tend to be positively correlated within populations, perhaps as a consequence of individual differences in resource acquisition. We conducted a split-brood experiment that combined a manipulation of seed availability (seeds present or absent) with a quantitative-genetic analysis of fecundity and lifespan in each environment. Each trait was significantly heritable in each environment. Seed availability not only altered mean fecundity and longevity between environments, but also modified how the traits were correlated within environments. The signs of both the phenotypic and genetic correlations switched from positive when seeds were present to negative when seeds were absent. This reversal persisted even after the effect of body mass (a potential indicator of resource acquisition) was statistically controlled. Cross-environment genetic correlations were positive but significantly less than one for each trait. We suggest that the reversal of the fecundity-longevity relationship depends on a shift in the relative importance of resource-acquisition and resource-allocation loci between environments. In particular, a cost of reproduction may be apparent at the individual level only when seeds are scarce or absent because differences in reproductive effort become large enough to overwhelm differences in resource acquisition. Despite their common dependence on resources acquired during larval stages, fecundity and lifespan in C. maculatus do not appear to be tightly coupled in a physiological or genetic sense.