College of Agriculture, Henan University of Science and Technology Luoyang, 471003, China.
College of Food & Bioengineering, Henan University of Science and Technology Luoyang, 471003, China.
Ecol Evol. 2014 Jan;4(1):59-66. doi: 10.1002/ece3.898. Epub 2013 Dec 11.
Several squirrel species excise the embryo of acorns of most white oak species to arrest germination for long-term storage. However, it is not clear how these acorns counter embryo excision and survive in the arms race of coevolution. In this study, we simulated the embryo excision behavior of squirrels by removing 4 mm of cotyledon from the apical end of white oak acorns differing in embryo depths to investigate the effects of embryo excision on acorn germination and seedling performance of white oak species. The embryo depth in the cotyledons was significantly different among white oak acorns, with Quercus mongolica containing the embryo most deeply in the acorns. We found that artificial embryo excision significantly decreased acorn germination rates of Quercus variabilis, Quercus acutissima, Quercus aliena, Quercus aliena var. acutiserrata, Quercus serrata. var. brevipetiolata but not Q. mongolica. Artificial embryo excision exerted significant negative impacts on seedling performance of all oak species except Quercus aliena. Our study demonstrates the role of embryo depth of acorns in countering embryo excision by squirrels and may explain the fact that squirrels do not perform embryo excision in acorns of Q. mongolica with deeper embryos. This apparent adaptation of acorns sheds light on the coevolutionary dynamics between oaks and their seed predators.
几种松鼠会切除大多数白橡树物种的橡子胚胎，以阻止其发芽，从而进行长期储存。然而，目前尚不清楚这些橡子如何对抗胚胎切除，并在协同进化的军备竞赛中存活下来。在这项研究中，我们通过从白橡树橡子的顶端切除 4 毫米的子叶来模拟松鼠的胚胎切除行为，以研究胚胎切除对不同深度白橡树种子萌发和幼苗生长的影响。子叶中胚的深度在白橡树橡子中存在显著差异，蒙古栎的胚最深。我们发现，人工胚胎切除显著降低了栓皮栎、麻栎、槲栎、锐齿槲栎、短柄槲栎的橡子萌发率，但蒙古栎不受影响。人工胚胎切除对除了栓皮栎以外的所有橡树物种的幼苗生长都有显著的负面影响。我们的研究表明，橡子胚的深度在对抗松鼠的胚胎切除方面发挥了作用，这可以解释为什么松鼠不会对胚更深的蒙古栎进行胚胎切除。这种橡子明显的适应性揭示了橡树与其种子捕食者之间协同进化的动态。
