Department of Biosciences, University of Sheffield, Sheffield S10 2TN, United Kingdom.
Institute of Zoology, Zoological Society of London, London NW8 7LS, United Kingdom.
Proc Natl Acad Sci U S A. 2024 Sep 3;121(36):e2319104121. doi: 10.1073/pnas.2319104121. Epub 2024 Aug 26.
Hatching failure affects up to 77% of eggs laid by threatened bird species, yet the true prevalence and drivers of egg fertilization failure versus embryo mortality as underlying mechanisms of hatching failure are unknown. Here, using ten years of data comprising 4,371 eggs laid by a population of a threatened bird, the hihi (, we investigate the relative importance of infertility and embryo death as drivers of hatching failure and explore population-level factors associated with them. We show that of the 1,438 eggs that failed to hatch (33% of laid eggs) between 2010 and 2020, 83% failed due to embryo mortality, with the majority failing in the early stages of embryonic development. In the most comprehensive estimates of infertility rates in a wild bird population to date, we find that fertilization failure accounts for around 17% of hatching failure overall and is more prevalent in years where the population is smaller and more male biased. Male embryos are more likely to die during early development than females, but we find no overall effect of sex on the successful development of embryos. Offspring fathered by within-pair males have significantly higher inbreeding levels than extra-pair offspring; however, we find no effect of inbreeding nor extra-pair paternity on embryo mortality. Accurately distinguishing between infertility and embryo mortality in this study provides unique insight into the underlying causes of reproductive failure over a long-term scale and reveals the complex risks of small population sizes to the reproduction of threatened species.
孵化失败影响到多达 77%的受威胁鸟类所产的卵，但导致孵化失败的受精失败和胚胎死亡的确切发生率以及作为孵化失败潜在机制的真正驱动因素尚不清楚。在这里，我们使用了十年的数据，这些数据包括一个受威胁鸟类种群中 4371 枚卵的产卵情况，研究了不孕和胚胎死亡作为孵化失败的驱动因素的相对重要性，并探讨了与之相关的种群水平因素。我们表明，在 2010 年至 2020 年间未能孵化的 1438 枚卵（占产卵量的 33%）中，83%是由于胚胎死亡导致的，其中大多数死亡发生在胚胎发育的早期阶段。在迄今为止对野生鸟类种群中不孕率的最全面估计中，我们发现受精失败总体上占孵化失败的 17%左右，在种群规模较小且雄性偏多的年份更为普遍。雄性胚胎在早期发育过程中比雌性胚胎更容易死亡，但我们没有发现性别对胚胎成功发育的总体影响。在配对内雄性所产的后代比配对外雄性所产的后代具有更高的近亲繁殖水平；然而，我们没有发现近亲繁殖或配对外交配对胚胎死亡率有影响。在这项研究中准确区分不孕和胚胎死亡提供了对长期范围内生殖失败潜在原因的独特见解，并揭示了小种群规模对受威胁物种繁殖的复杂风险。
