Variation in ripe fruit hardness: a mechanical constraint?
Variation in ripe fruit hardness: a mechanical constraint?
复制标题
DOI：
10.1111/oik.08074
复制
发表时间：
2021-07
期刊：
影响因子：
3.4
通讯作者：
Kim Valenta;Henna D Bhramdat;G. Calhoun;D. J. Daegling;Omer Nevo
中科院分区：
文献类型：
--
作者：
Kim Valenta;Henna D Bhramdat;G. Calhoun;D. J. Daegling;Omer Nevo
肉质水果已经进化成对食果性种子传播者有吸引力。因此，许多水果特征，如大小、颜色、气味和营养含量，都被认为是食果动物施加选择压力的结果。与此同时，水果性状也受到一系列其他选择压力和限制的影响。其中一个特征就是水果硬度。一方面，触觉暗示被认为在食果行为中发挥作用，潜在地推动了对果皮特征的选择，包括硬度。另一方面，果皮特征也与种子捕食者和微生物等拮抗剂相互作用，这也可以施加选择压力，特别是在水果硬度方面。然而，皮肤硬度也可能不是由对生物压力的适应性反应驱动的，而是一种机械约束：水果中充满了富含水分的果肉和种子，这对皮肤施加了机械压力。果皮硬度可能仅仅是因为水果需要保持内部压力以保持水果的完整性。我们在一组95种马达加斯加本土植物上测试了水果机械约束假说。我们使用一个理论结构公式来模拟水果果皮所经历的内部压力，以测试果肉重量的变化是否可以预测水果的硬度。我们发现，虽然内部应力与果实硬度呈正相关，但对果实硬度差异的解释很小。这表明，机械约束对果实硬度的影响不大，因此生物因素可能对果实硬度的变化有很大影响。
Fleshy fruits have evolved to be attractive to frugivorous seed dispersers. As a result, many fruit traits like size, color, scent and nutritional content are assumed to be the result of selective pressures exerted by frugivores. At the same time, fruit traits are also subjected to a set of other selective pressures and constraints. One such trait is fruit hardness. On one hand, haptic cues have been suggested to play a role in frugivore behavior, potentially driving selection on fruit skin traits, including hardness. On the other hand, fruit skin traits also interact with antagonists, e.g. seed predators and microbes, which can also impose selective pressures, particularly with respect to fruit hardness. Yet skin hardness may also be driven not by adaptive response to biotic pressures, but rather a mechanical constraint: fruits are packed with water‐rich pulp and seeds which exert mechanical pressure on the skin. Skin hardness may simply result from the need for fruits to withhold internal pressure to maintain fruit integrity. We test the fruit mechanical constraint hypothesis on a set of 95 native Malagasy plant species. We used a theoretical structural formula to model internal pressure experienced by fruit skins to test whether variation in pulp weight predicts fruit hardness. We find that, while positively correlated, internal stress explains very little of the variance in fruit hardness. This suggests that mechanical constraints play a minor role in driving fruit hardness, and that biotic factors may therefore contribute substantially to variation in fruit hardness.