For many squirrel species, their intense – arguably coevolutionary – interactions with seed and nut producing trees have significantly shaped their biology and diversity. Here we provide an overview of this relationship in a range of forest types worldwide. We first review the evidence for how forest composition (conifer, hardwood, mixed hardwood and overall diversity of tree species) influences interactions between squirrels and seed trees and, ultimately, the role of squirrels as either seed predators or seed dispersers. We review, for example, the intense selective pressure squirrels exert on conifer trees as seed predators and the diversity of morphological traits and behavioral strategies that allow them to efficiently exploit this critical resource. In contrast, we show how the squirrel’s role shifts to one of seed disperser in hardwood forests and how the specifics of this interaction varies further with forest structure, forest composition and climatic conditions. We then review the growing evidence for the tight ecological and evolutionary dance between the squirrels and the oaks that has shaped the biology of both across the globe. We show how a suite of seed (acorn) characteristics (e.g., chemical gradients, germination schedules, seedling morphology and tolerance-resistance strategies) are all intimately tied to the scatter-hoarding decisions of several squirrel species. And, based on studies in oak forests in Central America, Mexico, North America, and Eurasia, we also highlight the behavioral strategy of embryo excision now reported for six species across at least four genera of squirrels. This behavior, glaringly absent in other scatter-hoarding rodents worldwide, is now known be an innate trait in at least two species, one in Asia and another in North America. We review extensive recent research on one species of squirrel, the Siberian chipmunk (Tamias sibiricus), which exhibits a suite of behavioral strategies unique to that of other squirrels that independently contributes to seed dispersal and establishment. Finally, we outline numerous remaining questions concerning plants and other taxa of squirrels still open to investigation.

中文翻译：

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松鼠种子相互作用：松鼠作为种子捕食者和种子传播者的进化策略和影响

对于许多松鼠物种而言，它们与产生种子和坚果的树木的强烈（可以说是共同进化）相互作用极大地塑造了它们的生物学和多样性。在这里，我们概述了全球范围内一系列森林类型中的这种关系。我们首先回顾了森林组成（针叶树、硬木、混合硬木和树种的整体多样性）如何影响松鼠和种子树之间的相互作用以及最终松鼠作为种子捕食者或种子传播者的作用的证据。例如，我们回顾了松鼠作为种子捕食者对针叶树施加的强烈选择压力，以及使它们能够有效利用这一关键资源的形态特征和行为策略的多样性。相比之下，我们展示了松鼠的角色如何转变为阔叶林中的种子传播者之一，以及这种相互作用的细节如何随着森林结构、森林组成和气候条件而进一步变化。然后，我们回顾了越来越多的证据表明松鼠和橡树之间紧密的生态和进化舞蹈已经塑造了全球两者的生物学。我们展示了一套种子（橡子）特性（例如，化学梯度、发芽时间表、幼苗形态和耐受性策略）如何与几种松鼠物种的分散囤积决策密切相关。而且，基于对中美洲、墨西哥、北美洲和欧亚大陆橡树林的研究，我们还强调了现在报道的至少四个松鼠属的六个物种的胚胎切除行为策略。这种行为在世界范围内的其他散布啮齿动物中明显不存在，现在已知是至少两个物种的先天特征，一个在亚洲，另一个在北美。我们回顾了最近对一种松鼠的广泛研究，西伯利亚花栗鼠 (Tamias sibiricus)，它展示了一套独特的行为策略，这些行为策略与其他松鼠的行为策略不同，这些策略独立地有助于种子传播和建立。最后，我们概述了许多尚待调查的松鼠植物和其他分类群的遗留问题。它展示了一套独特的行为策略，这些策略是其他松鼠独有的，这些策略独立地促进了种子的传播和建立。最后，我们概述了许多尚待调查的松鼠植物和其他分类群的遗留问题。它展示了一套独特的行为策略，这些策略是其他松鼠独有的，这些策略独立地促进了种子的传播和建立。最后，我们概述了许多尚待调查的松鼠植物和其他分类群的遗留问题。