Fruit development of Lithocarpus (Fagaceae) and the role of heterochrony in their evolution
Fruit development of Lithocarpus (Fagaceae) and the role of heterochrony in their evolution
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DOI：
10.1007/s10265-020-01168-1
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发表时间：
2020-03-01
影响因子：
2.8
通讯作者：
Cannon, Charles H.
中科院分区：
文献类型：
--
作者：
Chen, Xi;Kohyama, Takashi S.;Cannon, Charles H.
石栎属壳斗科石栎属（Stone Oaks）植物是东亚热带、亚热带森林中重要的冠层树种，其果实是昆虫和脊椎动物的重要食物来源。本属的果实形态变异较大，表现为两种果型：橡子型和内藏花托型。然而，分化成这两种果实类型的进化机制与对比形态仍然是一个谜。为了揭示两种果实类型的形态发生特征，我们观察了20种柯属植物从坐果到成熟的组织分化和发育。与栎属果实不同，柯属果实内果皮分化晚于外果皮和中果皮。壳斗为发育中的种子提供了进一步的保护，特别是橡子型果实。柯属和栎属的果实有着相似的天敌。在坐果时，橡子和封闭花托类型在很大程度上是相同的，具有相似的组织形态和分化序列。两种果实类型成熟时的显著差异来自果皮和花托组织发育的速率和程度不同。我们发现，两种组织之间的异时性可以产生实质上不同的生态策略来保护和传播它们的种子，这对于两种果实类型的进化至关重要。
Stone oaks, or Lithocarpus species of Fagaceae are ecologically important canopy trees in the tropical and subtropical forests over East Asia, and the fruits of which are important food sources for insects and vertebrates there. The great fruit morphological variation of this genus represents two fruit types, acorn and enclosed receptacle fruit types. However, the evolutionary mechanisms of differentiation into these two fruit types with contrasting morphology remain a puzzle. To reveal the morphogenetic properties of two fruit types, we observed tissue differentiation and development among 20 Lithocarpus species from fruit set to maturity. Unlike in fruits of Quercus, the endocarp differentiation in Lithocarpus fruits occurred later than exocarp and mesocarp. Cupules provided further protection of developing seeds, particularly of acorn-type fruits. Fruits of Lithocarpus and Quercus acorns share similar insect predators. At fruit set, both acorn and enclosed receptacle types were largely identical, with similar tissue morphology and the sequence of differentiation. The distinct difference between two fruit types at maturity came from varied rates and degrees of development between the pericarp and receptacle tissues. We found that heterochrony between two tissues could create substantially divergent ecological strategies for protection and dispersal of their seeds, which is essential for the evolution of two fruit types.