Sawaya Gina M, Goldberg Adam S, Steele Michael A, Dalgleish Harmony J
Department of Biology, College of William and Mary, Williamsburg, Virginia, USA.
Department of Biology, Wilkes University, Wilkes-Barre, Pennsylvania, USA.
Integr Zool. 2018 May;13(3):319-330. doi: 10.1111/1749-4877.12311.
The conditional mutualism between scatterhoarders and trees varies on a continuum from mutualism to antagonism and can change across time and space, and among species. We examined 4 tree species (red oak [Quercus rubra], white oak [Quercus alba], American chestnut [Castanea dentata] and hybrid chestnut [C. dentata × Castanea mollissima) across 5 sites and 3 years to quantify the variability in this conditional mutualism. We used a published model to compare the rates of seed emergence with and without burial to the probability that seeds will be cached and left uneaten by scatterhoarders to quantify variation in the conditional mutualism that can be explained by environmental variation among sites, years, species, and seed provenance within species. All species tested had increased emergence when buried. However, comparing benefits of burial to the probability of caching by scatterhoarders indicated a mutualism in red oak, while white oak was nearly always antagonistic. Chestnut was variable around the boundary between mutualism and antagonism, indicating a high degree of context dependence in the relationship with scatterhoarders. We found that different seed provenances did not vary in their potential for mutualism. Temperature did not explain microsite differences in seed emergence in any of the species tested. In hybrid chestnut only, emergence on the surface declined with soil moisture in the fall. By quantifying the variation in the conditional mutualism that was not caused by changes in scatterhoarder behavior, we show that environmental conditions and seed traits are an important and underappreciated component of the variation in the relationship between trees and scatterhoarders.
贮藏种子的动物与树木之间的条件性互利共生关系在从互利共生到对抗的连续统一体上变化，并且会随时间和空间以及物种的不同而改变。我们在5个地点对4种树木（红栎[Quercus rubra]、白栎[Quercus alba]、美国栗[Castanea dentata]和杂交栗[C. dentata×Castanea mollissima]）进行了为期3年的研究，以量化这种条件性互利共生关系的变异性。我们使用一个已发表的模型，将有埋藏和无埋藏情况下的种子出苗率与种子被贮藏种子的动物贮藏且未被吃掉的概率进行比较，以量化可由地点、年份、物种以及物种内种子种源之间的环境变异所解释的条件性互利共生关系的变异。所有测试物种在被埋藏时出苗率都有所提高。然而，将埋藏的益处与贮藏种子的动物贮藏的概率进行比较表明，红栎存在互利共生关系，而白栎几乎总是处于对抗关系。栗树在互利共生和对抗的边界附近表现出变异性，这表明其与贮藏种子的动物之间的关系高度依赖环境。我们发现不同的种子种源在互利共生潜力方面没有差异。温度并不能解释所测试的任何物种种子出苗的微生境差异。仅在杂交栗中，秋季地表出苗率随土壤湿度下降。通过量化并非由贮藏种子的动物行为变化引起 的条件性互利共生关系的变异，我们表明环境条件和种子特性是树木与贮藏种子的动物之间关系变异的一个重要但未得到充分认识的组成部分。
