Bartlow Andrew W, Agosta Salvatore J, Curtis Rachel, Yi Xianfeng, Steele Michael A
Department of Biology and The WIESS Institute for Environmental Science and Sustainability, Wilkes University, Wilkes Barre, Pennsylvania, USA.
Present address: Department of Biology, University of Utah, Salt Lake City, Utah, USA.
Integr Zool. 2018 May;13(3):251-266. doi: 10.1111/1749-4877.12287.
Fitness of parents and offspring is affected by offspring size. In oaks (Quercus spp.), acorns vary considerably in size across, and within, species. Seed size influences dispersal and establishment of oaks, but it is not known whether size imparts tolerance to seed predators. Here, we examine the relative extent to which cotyledon size serves as both a means for sustaining partial consumption and energy reserves for developing seedlings during early stages of establishment. Acorns of 6 oak species were damaged to simulate acorn predation by vertebrate and invertebrate seed predators. Seedling germination/emergence and growth rates were used to assess seedling performance. We predicted that if cotyledons are important for dispersal, acorns should show tolerance to partial seed consumption. Alternatively, if the cotyledon functions primarily as an energy reserve, damage should significantly influence seedling performance. Acorns of each species germinated and produced seedlings even after removing >50% of the cotyledon. Seed mass explained only some of the variation in performance. Within species, larger acorns performed better than smaller acorns when damaged. Undamaged acorns performed as well or better than damaged acorns. There was no pattern among individual species with increasing amounts of damage. In some species, simulated invertebrate damage resulted in the poorest performance, suggesting alternative strategies of oaks to sustain damage. Large cotyledons in acorns may be important for attracting seed dispersers and sustaining partial damage, while also providing energy to young seedlings. Success of oak establishment may follow from the resilience of acorns to sustain damage at an early stage.
亲本和子代的适合度会受到子代大小的影响。在栎属（栎树种类）中，不同种以及同一种内的橡子大小差异很大。种子大小会影响栎树的传播和定植，但目前尚不清楚种子大小是否能赋予对种子捕食者的耐受性。在这里，我们研究了子叶大小在多大程度上既作为维持部分消耗的一种方式，又作为幼苗在定植早期发育的能量储备。对6种栎树的橡子进行损伤处理，以模拟脊椎动物和无脊椎动物种子捕食者对橡子的捕食。利用种子萌发/出土和生长速率来评估幼苗的表现。我们预测，如果子叶对传播很重要，橡子应该表现出对部分种子被消耗的耐受性。或者，如果子叶主要作为能量储备，那么损伤应该会显著影响幼苗的表现。即使去除超过50%的子叶，每个物种的橡子仍能发芽并长出幼苗。种子质量仅解释了部分表现差异。在种内，受损时较大的橡子比较小的橡子表现更好。未受损的橡子表现与受损橡子相同或更好。随着损伤程度增加，各个物种之间没有呈现出特定模式。在某些物种中，模拟无脊椎动物造成的损伤导致表现最差，这表明栎树有应对损伤的其他策略。橡子中的大子叶可能对于吸引种子传播者和承受部分损伤很重要，同时也为幼苗提供能量。栎树定植成功可能源于橡子在早期阶段承受损伤的恢复能力。
