Addison BriAnne, Benowitz-Fredericks Z Morgan, Hipfner J Mark, Kitaysky Alexander S
Centre for Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6.
Gen Comp Endocrinol. 2008 Aug;158(1):5-9. doi: 10.1016/j.ygcen.2008.05.020. Epub 2008 Jun 8.
It is widely believed that female birds strategically allocate androgens to yolk in the manner that best equips offspring for feeding conditions during their development. Because most avian studies have focused on multi-egg clutch species, and interpreted results within the framework of sibling competition, we still know little about how yolk androgens might be allocated in direct response to environmental conditions. Most oceanic birds are long-lived and lay single-egg clutches, and their breeding success is tightly linked to highly variable marine production. That combination: a variable breeding environment, long lives, and single-egg clutches, makes oceanic birds good subjects to test hypotheses about yolk androgen allocation strategies. We measured concentrations of two yolk androgens, androstenedione (A4) and testosterone (T), in the single-egg clutches laid by early-laying Cassin's (Ptychoramphus aleuticus) and rhinoceros (Cerorhinca monocerata) auklets at Triangle Island, British Columbia, Canada, in 2002-2004. Environmental conditions including sea-surface temperatures and the timing and intensity of marine primary production varied over the 3 years, and in response, both the timing and success of seabird breeding varied. As in other avian species, concentrations of A4 and T varied markedly among individual eggs in both species (by factors of 3-8), yet contrary to expectation, little of the variation could be attributed to year effects. The high interindividual variation and the lack of interannual variation suggest a non-adaptive explanation for yolk androgen deposition relative to environmental conditions in these species.
人们普遍认为，雌性鸟类会以最有利于后代在发育过程中适应觅食条件的方式，将雄激素有策略地分配到卵黄中。由于大多数鸟类研究都集中在多枚卵的窝卵数物种上，并在同胞竞争的框架内解释结果，因此我们对卵黄雄激素如何直接响应环境条件进行分配仍然知之甚少。大多数海鸟寿命长且产单枚卵的窝卵数，它们的繁殖成功率与高度变化的海洋生产力紧密相关。这种组合：可变的繁殖环境、长寿和单枚卵的窝卵数，使海鸟成为检验卵黄雄激素分配策略假说的良好研究对象。我们测量了2002年至2004年在加拿大不列颠哥伦比亚省三角岛，早期产卵的卡辛氏海雀（Ptychoramphus aleuticus）和犀角海雀（Cerorhinca monocerata）所产单枚卵窝卵数中的两种卵黄雄激素——雄烯二酮（A4）和睾酮（T）的浓度。在这3年中，包括海面温度以及海洋初级生产力的时间和强度在内的环境条件有所变化，相应地，海鸟繁殖的时间和成功率也有所不同。与其他鸟类物种一样，两种海雀的单个卵中A4和T的浓度在个体间差异显著（相差3至8倍），然而与预期相反，几乎没有差异可归因于年份效应。个体间的高差异和年际间的缺乏差异表明，对于这些物种中卵黄雄激素相对于环境条件的沉积，存在一种非适应性的解释。
