Abstract
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.
Highlights
There are approximately 111 species worldwide in the genus Pinus (Fisher, 2001)
Mean values followed by the different letter (a, b, c, and d) are significantly different as determined by multiple range test, and there is no significant difference between groups with the same letter
Our study shows that there are significant differences in the size of cones, seeds, and scales of the four species of animal-dispersed pines, but some similarities emerged in the cone structure of two species
Summary
Pines have two basic seed dispersal modes: wind dispersal, in which the seeds are small with relatively long wings and are carried by the wind away from the canopies of the parent trees (Mwase, Bjørnstad, Ntupanyama, Kwapata, & Bokosi, 2006); and animal dispersal, in which the seeds are relatively large and wingless (or functionally wingless) and unfit for wind dispersal. The four species of pines utilize different animals for seed dispersal (Table S2), including small forest rodents for Dabieshan white pine, birds and large rodents for Korean pine, birds and various rodents for Chinese white pine, and nutcrackers (N. caryocatactes) for Siberian dwarf pine. We predicted possible evolutionary patterns under which the four species of animal-dispersed pines emerged
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