Cones structure and seed traits of four species of large-seeded pines: adaptation to animal-mediated dispersal

Seed dispersal selection pressures may cause morphological differences in
cone structure and seed traits of large-seeded pine trees. We investigated
the cone, seed, and scale traits of four species of animal-dispersed pine
trees to explore the adaptations of morphological structures to different
dispersers. The four focal pines analyzed in this study were Chinese white
pine (Pinus armandi), Korean pine (P. koraiensis), Siberian dwarf pine (P.
pumila), and Dabieshan white pine (P. dabeshanensis). There are
significant differences in the traits of the cones and seeds of these four
animal-dispersed pines. The scales of Korean pine and Siberian dwarf pine
are somewhat opened after cone maturity, the seeds are closely combined
with scales, and the seed coat and scales are thick. The cones of Chinese
white pine and Dabieshan white pine are open after ripening, the seeds
fall easily from the cones, and the seed coat and seed scales are
relatively thin. The results showed that the cone structure of Chinese
white pine is similar to that of Dabieshan white pine, whereas Korean pine
and Siberian dwarf pine are significantly different from the other two
pines and vary significantly from each other. This suggests that species
with similar seed dispersal strategies exhibit similar morphological
adaptions. Accordingly, we predicted three possible seed dispersal
paradigms for animal-dispersed pines: the first, as represented by Chinese
white pine and Dabieshan white pine, relies upon small forest rodents for
seed dispersal; the second, represented by Korean pine, relies primarily
on birds and squirrels to disperse the seeds; and the third, represented
by Siberian dwarf pine, relies primarily on birds for seed dispersal. Our
study highlights the significance of animal seed dispersal in shaping cone
morphology, and our predictions provide a theoretical framework for
research investigating the coevolution of large-seeded pines and their
seed dispersers.

种子传播选择压力可能导致大种子松树的球果结构和种子性状出现形态差异。为探究形态结构对不同传播者的适应性，我们研究了四种动物传播型松树的球果、种子及种鳞性状。本研究分析的四种目标松树为华山松（Pinus armandi）、红松（P. koraiensis）、偃松（P. pumila）和大别山五针松（P. dabeshanensis）。这四种动物传播型松树的球果和种子性状存在显著差异。红松和偃松的种鳞在球果成熟后呈微张开状态，种子与种鳞结合紧密，且种皮和种鳞较厚。华山松和大别山五针松的球果成熟后完全张开，种子易从球果脱落，且种皮和种鳞相对较薄。结果表明，华山松的球果结构与大别山五针松相似，而红松和偃松则与另外两种松树存在显著差异，且二者之间也存在显著差异。这表明具有相似种子传播策略的物种表现出相似的形态适应性。据此，我们预测动物传播型松树存在三种可能的种子传播范式：第一种以华山松和大别山五针松为代表，依赖小型森林啮齿动物传播种子；第二种以红松为代表，主要依赖鸟类和松鼠传播种子；第三种以偃松为代表，主要依赖鸟类传播种子。本研究强调了动物种子传播在塑造球果形态中的重要性，我们的预测为探究大种子松树与其种子传播者协同进化的研究提供了理论框架。