1 | Introduction
Plant distribution can be affected by climate changes, where climate warming can cause plant distribution areas to move more to the north (King et al., 2018), while anthropogenic influences, such as plant invasions via transportation (Ansong & Pickering, 2013; Banks et al., 2015), landscaping (Dodet & Collet, 2012), pollution control (An et al., 2007; Chu et al., 2006; Mao et al., 2019), and seed dispersal progression in the form of different modes of dispersal (Camargo et al., 2016), migration capacity (Pedrosa et al., 2019; Sunyer et al., 2013), feeding, and food storage behavior of animals can also change plant distributions (Barrere et al., 2020; Wang et al., 2019).
Seed dispersal promotes the regeneration of plants and the expansion of distribution areas (Levin et al., 2003). In this process, the seeds are first removed from the crowns of the parent tree by the dispersal agent (wind or animals) (Rodriguez-Perez & Traveset, 2010; Rother et al., 2016), and then the seed rain is formed after the seed interacts with the media, in which the pattern of seed rain would ultimately affect the spatial distribution of plants (Nathan & Mullerlandau, 2000; Wehncke & Reyes, 2019). Hence, the demographic process in a plant’s life cycle can be critical (Vivian & Panetta, 2005). The consequence of seed dispersal by animals would primarily be determined via the interactions between the disperser home ranges and the position of the seed-bearing plants.
Pinus plants are major components of the numerous montane ecosystems in Asia, North America, and Europe, and are widely distributed in the Northern Hemisphere (Keeley, 2012; Richardson, 1998). There are about 111 species of pines globally (Richardson, 1998), most of which have winged seeds that can spread effectively over long distances via the wind (Benkman, 1995; Cain et al., 2000). However, about 29 species of pines cannot complete effective wind dispersal because of their large and windless or functionally wingless seeds, hence, they are often dispersed by rodents or birds (Tomback & Linhart, 1990).
China is a globally important distribution area of Pinus plants with at least 23 species and 10 varieties of Pinus . The eight pines species include the Chinese white pine (P. armandii ), the Korean pine (P. koraiensis ), the Siberian dwarf pine (P. pumila ), the Dabieshan white pine (P. dabieshanensis ), the Hunan white pine (P. fenzeliana ), the Chilgoza pine (P. gerardiana ), the Lacebark pine (P. bungeana ), and the Siberian stone pine (P. sibirica ), which cannot be dispersed effectively by wind because of their windless or functionally wingless seeds that are over 90g (thousand-grain weight) (Benkman, 1995) (Table 1). Among these, there are two endangered pines, i.e. the Korean pine (VU) and the Dabieshan white pine (EN), which are endemic to China (Wang & Xie, 2004). We predicted that the pine seeds would be dispersed by animals. However, in addition to the Korean pine and Chinese white pine, the study of seed dispersal in other pines lacks sufficient field research, despite being important for understanding the ecological processes of montane ecosystems and protecting endangered pines.
Previous studies have focused on the seed dispersal process accompanied by the interaction between animals and plants, foraging behaviors, and the ecological consequences of seed dispersal. For example, Benkman et al. (1995) studied the American pines and found that the Red crossbills (Loxia curvirostra ) and the Lodgepole pine (Pinus contorta ) were in coevolutionary races, where the red squirrels (Tamiasciurus hudsonicus ) were absent, and the tree squirrels (Tamiasciurus ) were considered seed predators, they were all beneficial for seedling regeneration of the Limber pine (P. flexilis ) (Benkman et al., 1995). Vander (2010) mainly studied rodents and pines in America, and found that the Pinus plants, including other large-seeded plants such as the Cary spp and thePrunus spp., manipulate the scatter-hoarding behavior of seed-dispersing animals by producing large nutritious seeds, increasing the physical defense and masting, which improved the efficiency of seed dispersal (Vander , 2010). In addition, Lu (2002) studied the endangered pines in China as their focal species and they found that scatter-hoarding animals, such as chipmunk (Tamias sibiricus ), Eurasian red squirrel (Sciurus vulgaris ), and Eurasian nutcrackers (Nucifraga caryocatactes ), increased the regeneration of the Korean pine (P. koraiensis ) in the natural forest.
Furthermore, plants and their mutualist seed dispersers are products of diffuse coevolutionary processes. The current geographic distribution of plants and their dispersers is a result of coevolution. However, studies on the distribution match between the large-seeded pines and their seed dispersers is still scarce. We predicted that there would be strong positive correlations or a distribution match between animal-dispersed pines and animal dispersers. Our objectives were to investigate the large-seeded pines in China, summarize their distribution data, and examine the distribution relationship between these pines and their primary seed dispersers from the perspective of sympatry. This included a review of the large-scale distribution of the large-seeded pines, the animals that disperse pine seeds, and the existing literature regarding the seed dispersal of these pines.