Behavioural Ecology Group, Department of Systematic Zoology and Ecology, ELTE Eötvös Loránd University, Budapest, Hungary.
Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary.
J Evol Biol. 2023 Jan;36(1):156-168. doi: 10.1111/jeb.14118. Epub 2022 Nov 14.
Brood sex ratios (BSRs) have often been found to be nonrandom in respect of parental and environmental quality, and many hypotheses suggest that nonrandom sex ratios can be adaptive. To specifically test the adaptive value of biased BSRs, it is crucial to disentangle the consequences of BSR and maternal effects. In multiparous species, this requires cross-fostering experiments where foster parents rear offspring originating from multiple broods, and where the interactive effect of original and manipulated BSR on fitness components is tested. To our knowledge, our study on collared flycatchers (Ficedula albicollis) is the first that meets these requirements. In this species, where BSRs had previously been shown to be related to parental characteristics, we altered the original BSR of the parents shortly after hatching by cross-fostering nestlings among trios of broods and examined the effects on growth, mortality and recruitment of the nestlings. We found that original and experimental BSR, as well as the interaction of the two, were unrelated to the fitness components considered. Nestling growth was related only to background variables, namely brood size and hatching rank. Nestling mortality was related only to hatching asynchrony. Our results therefore do not support that the observed BSRs are adaptive in our study population. However, we cannot exclude the possibility of direct effects of experimentally altered BSRs on parental fitness, which should be evaluated in the future. In addition, studies similar to ours are required on various species to get a clearer picture of the adaptive value of nonrandom BSRs.
亲代和环境质量通常会影响卵的性别比例（BSR），且许多假说表明非随机的性别比例可能具有适应性。为了专门检验偏向性 BSR 的适应性价值，必须厘清 BSR 和母体效应的后果。在多胎物种中，这需要进行交叉抚育实验，其中寄养父母要抚育来自多个窝巢的后代，并且要测试原始和操纵的 BSR 对适应度成分的交互作用。据我们所知，我们对领雀嘴鹎（Ficedula albicollis）的研究是首次满足这些要求的研究。在这个物种中，先前已经表明 BSR 与亲代特征有关，我们通过在三窝雏鸟之间进行交叉抚育来改变亲代的原始 BSR，并检查对雏鸟生长、死亡率和招募的影响。我们发现，原始和实验性 BSR 以及两者的相互作用与所考虑的适应度成分无关。雏鸟的生长仅与背景变量有关，即窝巢大小和孵化顺序。雏鸟的死亡率仅与孵化的不同步有关。因此，我们的结果并不支持在我们的研究群体中观察到的 BSR 是适应性的。然而，我们不能排除实验性改变的 BSR 对亲代适应性直接影响的可能性，这应该在未来进行评估。此外，需要在各种物种上进行类似的研究，以更清楚地了解非随机 BSR 的适应性价值。
