Fluctuating Resources and the Evolution of Litter Size in the Arctic Fox
Fluctuating Resources and the Evolution of Litter Size in the Arctic Fox
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资源波动和北极狐产仔数的演变
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
A. Angerbjörn
中科院分区：
文献类型：
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作者：
M. Tannerfeldt;A. Angerbjörn
基本资源的波动对相应调整亲本投资的能力造成了强大的选择压力。在狗的家庭，犬科，方差在女性产前投资调整窝仔数。北极狐是一种生活在世界北方苔原上的小型犬科动物。牠们是食肉目中已知最大的一窝，可达18只幼仔，且一窝的大小变化很大。我们分析了整个物种北极圈范围内北极狐种群的数据。在某些地区，北极狐以数量波动很大的小型啮齿动物为食。相比之下，它们在鸟崖和沿着有更稳定的食物资源。食物的可获得性决定了北极狐的产仔数和种群规模。波动和稳定的北极狐种群之间的比较表明，波动与大的产仔数。窝仔数平均值、最大值和方差以及胎盘瘢痕计数平均值存在显著差异。我们已经讨论了五个假设的变化在产仔数的确定：一个充满活力，一个遗传（基于密度变化），一个饮食决定，一个基于生殖分配和一个基于反应规范的差异。我们的研究结果表明，在北极狐的产仔数是由直接资源水平和资源的可预测性程度的综合影响。我们描述的反应规范，表明如何从适应性可塑性的两个遗传策略，根据头奖假说，人口与不可预测的食物资源，一般有较大的产仔数。在每一种遗传策略或反应规范中，通过一些可塑性性状来调整窝仔数。这些性状受营养限制的影响，包括排卵率降低、产前损失和哺乳期窝仔数减少。
Fluctuations in essential resources cause a strong selection pressure on the ability to adjust parental investment accordingly. In the dog family, Canidae, variance in female prebirth investment is adjusted by litter size. The arctic fox, Alopex lagopus, is a small canid living on the northern tundras of the world. It has the largest known litter size in the order Carnivora, up to 18 young, and litter size is highly variable. We have analysed data from arctic fox populations throughout the species circumpolar range. In some areas, arctic foxes feed on strongly fluctuating populations of small rodents. In contrast, they have more stable food resources at bird cliffs and along coast lines. Food availability determines arctic fox litter and population sizes. A comparison between fluctuating and stable arctic fox populations showed that fluctuations are associated with large litter sizes. There were significant differences in litter size means, maxima and variances, as well as in placental scar count means. We have discussed five hypotheses on the determination of variation in litter size: one energetic, one genetic (based on density variation), one diet-determined, one based on reproductive allocation and one based on differences in reaction norms. Our findings suggest that litter size in the arctic fox is determined by the combined effect of immediate resource levels and the degree of resource predictability. We describe reaction norms that suggest how litter sizes result from adaptive plasticity within each of two genetic strategies where, according to the jackpot hypothesis, populations with unpredictable food resources generally have larger litter sizes. Within each genetic strategy, or reaction norm, litter sizes are adjusted through a number of plastic traits. These traits are influenced by nutritional limitations and include reduced ovulation rates, prenatal losses, and litter size reduction during the lactation period.