Abstract
After maturation, Korean pine (Pinus koraiensis Siebold & Zucc.) seeds often cannot disperse to reach a suitable germination site. It is therefore difficult to naturally regenerate by itself and relies on animal dispersal. Squirrels hoard pine seeds as winter food and Korean pine seeds stored for overwintering might become the source of regeneration of the species. From field observations, the pine seeds are the food preference for squirrels during autumn in the Lesser Khingan Mountains in Northeast China. Such preference by squirrels has been attributed to high seed energy content and the ease of seed storage. However, it may also be expected from nutritional aspects that a coevolutionary relationship between squirrels and Korean pine species could be partially explained by the effect of active seed components and their physiological regulatory effects on squirrels. To test this hypothesis, control experiments were carried out to examine the modulatory effects of Korean pine nut oil (PNO) on intestinal microbiota, inflammatory profile and oxidative stress in mice. The results showed that, compared with mice fed a high-fat diet, PNO significantly improved the physical and the healthy state of mice. Histological analysis of the liver and epididymal fat tissue showed that PNO alleviated liver and adipocyte lesions, and inflammation caused by high-fat diets. PNO also significantly decreased atherosclerotic index and ameliorate serum lipid accumulation to prevent cardiovascular disease, which effect the positive control SG group. Moreover, PNO elevated superoxide dismutase and glutathione peroxidase enzyme activities and reduced malondialdehyde levels in the serum. 16S rRNA sequencing showed that PNO restored intestinal microbiota composition, significantly increasing the relative abundance of Lactobacillus and Akkermansia bacteria. These results suggest that Korean pine seeds not only provide adequate fat, protein and energy for squirrels, but also promote physical health and improve body immunity.
Highlights
Research on the coevolution or cooperative evolution of animals and plants has become an important topic in conservation biology and recovery ecology (Wall and Jenkins 2011; Gómez et al 2018; Silva et al 2021)
Many plant species are dispersed by animals that feed on the fruits or seeds while foraging, providing an unexpected dispersal service and forming a coevolutionary relationship
We found that squirrels fed on 12 and nine species of plants in the spring and summer, respectively (Tables 2 and 3)
Summary
Research on the coevolution or cooperative evolution of animals and plants has become an important topic in conservation biology and recovery ecology (Wall and Jenkins 2011; Gómez et al 2018; Silva et al 2021). Many plant species are dispersed by animals (e.g., birds, rodents and ants) that feed on the fruits or seeds while foraging, providing an unexpected dispersal service and forming a coevolutionary relationship. Korean pine is one of the most valuable evergreen species in northeast China (Kaviriri et al 2020) and its seed is a quality food source that provides high energy and is rich in phospholipids, unsaturated fatty acids, vitamins and minerals (Nergiz and Doenmez 2004; No et al 2015). Scatter-hoarding rodents, such as squirrels (Sciurus vulgaris L.), have the habit of feeding and storing pine seeds. Whether there is a coevolutionary relationship between squirrels and Korean pine, and if squirrels are attracted to forage and disperse seeds is a question worthy of study. Korean pine seeds are relatively large and wingless and not dispersed to suitable germination sites, which indicates that natural regeneration is almost totally dependent on animals
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