Vedder Oscar, Kürten Nathalie, Bouwhuis Sandra
1 Groningen Institute for Evolutionary Life Sciences, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands.
2 Institute of Avian Research "Vogelwarte Helgoland," An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany.
Physiol Biochem Zool. 2017 Jul/Aug;90(4):453-460. doi: 10.1086/691690.
Embryonic development time is thought to impact life histories through trade-offs against life-history traits later in life, yet the inference is based on interspecific comparative analyses only. It is largely unclear whether intraspecific variation in embryonic development time that is not caused by environmental differences occurs, which would be required to detect life-history trade-offs. Here we performed a classical common-garden experiment by incubating fresh eggs of free-living common terns (Sterna hirundo) in a controlled incubation environment at two different temperatures. Hatching success was high but was slightly lower at the lower temperature. While correcting for effects of year, incubation temperature, and laying order, we found significant variation in the incubation time embryos required until hatching and in their heart rate. Embryonic heart rate was significantly positively correlated within clutches, and a similar tendency was found for incubation time, suggesting that intrinsic differences in embryonic development rate between offspring of different parents exist. Incubation time and embryonic heart rate were strongly correlated: embryos with faster heart rates required shorter incubation time. However, after correction for heart rate, embryos still required more time for development at the lower incubation temperature. This suggests that processes other than development require a greater share of resources in a suboptimal environment and that relative resource allocation to development is, therefore, environment dependent. We conclude that there is opportunity to detect intraspecific life-history trade-offs with embryonic development time and that the resolution of trade-offs may differ between embryonic environments.
胚胎发育时间被认为会通过与生命后期的生活史特征进行权衡来影响生活史，但这种推断仅基于种间比较分析。很大程度上尚不清楚是否存在不由环境差异引起的胚胎发育时间的种内变异，而这是检测生活史权衡所必需的。在这里，我们进行了一项经典的共同花园实验，在可控的孵化环境中，将自由生活的普通燕鸥（Sterna hirundo）的新鲜卵在两种不同温度下进行孵化。孵化成功率很高，但在较低温度下略低。在校正年份、孵化温度和产卵顺序的影响后，我们发现胚胎孵化所需的孵化时间及其心率存在显著差异。在一窝卵中，胚胎心率显著正相关，孵化时间也有类似趋势，这表明不同亲本的后代在胚胎发育速率上存在内在差异。孵化时间和胚胎心率密切相关：心率较快的胚胎所需孵化时间较短。然而，在校正心率后，在较低孵化温度下胚胎仍需要更多时间来发育。这表明在次优环境中，除发育外的其他过程需要更多资源份额，因此相对分配给发育的资源取决于环境。我们得出结论，有机会通过胚胎发育时间检测种内生活史权衡，并且不同胚胎环境中权衡的分辨率可能不同。
