Department of Biological Sciences, North Dakota State University, Fargo, North Dakota.
Department of Biology, Adelphi University, Garden City, New York.
Mol Ecol. 2019 Jan;28(1):114-126. doi: 10.1111/mec.14952.
Annual reproductive success is often highest in individuals that initiate breeding early, yet relatively few individuals start breeding during this apparently optimal time. This suggests that individuals, particularly females who ultimately dictate when offspring are born, incur costs by initiating reproduction early in the season. We hypothesized that increases in the ageing rate of somatic cells may be one such cost. Telomeres, the repetitive DNA sequences on the ends of chromosomes, may be good proxies of biological wear and tear as they shorten with age and in response to stress. Using historical data from a long-term study population of dark-eyed juncos (Junco hyemalis), we found that telomere loss between years was greater in earlier breeding females, regardless of chronological age. There was no relationship between telomere loss and the annual number of eggs laid or chicks that reached independence. However, telomere loss was greater when temperatures were cooler, and cooler temperatures generally occur early in the season. This suggests that environmental conditions could be the primary cause of accelerated telomere loss in early breeders.
年繁殖成功率通常在早期开始繁殖的个体中最高，但相对较少的个体在这个明显的最佳时期开始繁殖。这表明个体，特别是最终决定后代出生时间的雌性，在季节早期开始繁殖会付出代价。我们假设体细胞衰老速度的增加可能就是这样的代价之一。端粒是染色体末端的重复 DNA 序列，随着年龄的增长以及对压力的反应，它们会缩短，因此可以作为生物磨损的良好指标。我们利用来自深色田鸡（Junco hyemalis）长期研究群体的历史数据发现，无论其实际年龄如何，早期繁殖的雌性在不同年份之间的端粒损失更大。端粒损失与当年产卵数或达到独立生活的雏鸟数之间没有关系。然而，当温度较低时，端粒损失会更大，而低温通常出现在季节早期。这表明环境条件可能是早期繁殖者端粒加速损失的主要原因。
