Aim: The geographic distribution of plants influenced by seed dispersal, but this influence on plants that use animals as seed dispersers is often overlooked. Here, we took large-seeded pines and primary seed dispersers as examples to explore the effects of existing or potential seed dispersal on the distribution of plants based on the geographical distribution of the two trophic species, it required understanding of (a) the distribution range and distribution characteristics of each species, and (b) the overlapping of distribution areas of animals and plants to explore whether they match.

Location: China

Methods: To find the target species, we identified eight large-seeded pine species in China in terms of seed size and wing traits as well as four primary seed disperser species in terms of body size, seed-diet, food hoarding behavior and frequencies in existing studies. Then, we obtained species distribution information from books and literature and used ArcGIS for mapping. Finally, we analyzed the distribution relationship by overlapping the distribution areas and patterns comprehensively.

Results: We identified eight species of large-seeded pines (Pinus fenzeliana, P. gerardiana, P. dabeshanensis, P. koraiensis, P. pumila, P. bungeana, P. armandii, and P. sibirica) and four species of primary seed dispersers (Nucifraga caryocatactes, Sciurus vulgaris, Tamias sibiricus, and Sciurotamias davidianus). These eight species of large-seeded pines interlaced from the Northeast to the Southwest of China along the mountains with an average altitude of 1000-2000 m, while each species of primary seed disperser had a wide distribution range that overlapped completely or partially with that of four or more species of the large-seeded pines. Not only that, our findings provided potential seed dispersers for pines that lack sufficient research on seed dispersal.

Main conclusions: The distribution pattern of large-seeded pines and the primary seed dispersers was matched, we believed that reciprocal relationship promotes this distribution pattern. Our study highlights the importance of incorporating the ecological consequences of geographical distribution into reciprocal interactions between species and biodiversity conservation.

In the study of 27 species of Pinus plants in North America, it was found that seed mass greater than 90mg would not be able to effectively be dispersed through the wind, but it was more suitable for animal dispersal (Benkman, 1995b; Greene & Johnson, 1993). Based on the results, we defined Pinus plants with wingless or functionally wingless and heavy seeds (a single seed over 90mg) as large-seeded pines (Zhang, M. Y. et al., 2020).

Several search engines were used to identify publications with abstracts that contain the Latin or Chinese names of the pines as well as the words “seed” and “seed dispersers”. These search engines included Web of Science, Biological Abstracts, China National Knowledge Internet, and Wildlife & Ecology Studies Worldwide. We retained only articles, reviews, and theses published in English and Chinese. After searching, 24 Chinese articles and 18 English articles were selected in terms of their contained information regarding seed dispersal of the 8 specified species of pines (S1), the seed dispersers of the large-seeded pines were recorded in each study (S2), and then we collected seed traits data of Pinus plants’ seeds in China, including seed mass, seed size (length and width) and wing length, by consulting books and some of the above literatures(S3).

Not only that, we looked for ecological traits of seed dispersers, according to the animal directory collected (S2), including body mass, seed-diet (the proportion of seeds in the diet) and hoarding behaviors of animals (S4). We used animals’ body mass (g), seed-diet and hoarding behavior as determinants of seed dispersal outcomes of large-seeded pines (Park, 2002; Riceoxley, 1993; Tomback & Linhart, 1990; Wang, Z. et al., 2018) that may influence the efficiency of seed dispersal. By examining the significance of frequency of occurrence and different ecological traits, we would identify the primary seed dispersers of Pinus plants.

Geographic distribution range data collection

To the best of our knowledge, the detailed pines and animal ranges available were Flora of China (Flora of China, http://www.iplant.cn/) and Fauna Sinica (Luo, 2000; Zhang, Z. X., 2007) , which were published by Science Press and hosted by the Chinese Academy of Science, and we used the data we needed from these books. Although these data are considered a landmark for studies conducted on the ecology and conservation of pines, rodents, and birds, updating the databases is demanding, because neglecting added information can be detrimental to conservation efforts (Hughes, 2017).

Besides, we also referred to books that contain geographic distribution information of target plants and animals. Pinus dabeshanensis and its Origin (Peng & Jiang, 1999), Tibet Vegetation (Chinese academy of sciences, 1988) and Floristics of Seed Plants from China (Wu, Z. Y., 2011) were as literary references for the distribution of pines, while A Checklist on the Classification and Distribution of the Birds of China (Third Edition) (Zheng, 2017), China’s Mammal Diversity and Geographic Distribution (Jiang et al., 2015), and Study on Rodents in Typical Semi-desert and Desert Areas of China (Wu, X. D. et al., 2008) were the literary references for the distribution of seed dispersers.

Distribution maps and analyses

Based on the data collected on the distribution range of species we mapped the distribution of large-seeded pine and their primary seed dispersers. During the drawing process, we excluded the habitats of lakes, rivers, and deserts, which are not suitable for these plants and animals to live based on the known distribution areas. In addition, apart from the animals specially designated as having a discrete distribution in the literature, it was assumed that animals were present in a certain area. Compared to the habitats of animals, if there was no significant difference in the geographical environment of adjacent areas, we assumed the animal’s distribution in those areas.

Then, we fitted the distribution map of different seed dispersers and Pinus plants respectively, and calculated the area occupied by animals in different pine distribution areas and calculated the proportion by using the intersection function.

ArcGIS 10.2 (Esri, USA) was used to analyze and visualize the results based on the 1:3,000,000 scale of the Chinese administrative geography vector map.