Scatter-hoarding rodents are effective dispersal agents for many plant species. Several studies have shown that rodents repeatedly re-cache seeds. Some studies have indicated that several seed traits (e.g. seed size and tannin content) might be related to the seed re-caching process. However, few studies have directly examined how varied seed traits affect this important process.
Dr. WANG Bo and his teachers of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study during September to November in 2007, in a natural forest at the Shangri-La Alpine Botanical Garden (27°54′ N, 99°38′ E, altitude 3456 m), Yunnan province, SW China. They developed a series of experiments using artificial seeds to test the effect of each single seed trait (i.e. seed size, nutrient or tannin content) on repeated seed movement by varying single traits experimentally, while keeping other traits constant. By detecting the fates of 3564 artificial seeds with univariate seed traits, they aimed to address the following predictions: 1) Seeds with larger size and higher nutrient or tannin content were more likely to be re-cached; 2) Seeds cached closer to their original releasing plots were more likely to be re-cached.
Their study found that the likelihood of seeds being re-cached increased with seed size, but not with nutrient content or tannin content. Furthermore, seed size also demonstrated a much more consistent and overwhelming effect than nutrient and tannin content on the primary foraging decision at the rodents' initial encounter with a seed .Most plant species that depended on scatter-hoarding rodents for seed dispersal bore relatively large seeds. Larger seeds usually had a much greater chance of being scatter-cached while small ones had a greater chance of being eaten. Meanwhile, large seeds were often more likely to produce seedlings.
The researchers therefore believed that the foraging preference for large seeds by scatter-hoarding rodents may have played an important role in the evolution of large seeds.
The study was funded by the National Natural Science Foundation of China (31100315), Key Project of Chinese Academy of Sciences (KSCX2-EW-Q-17), and the Youth Innovation Promotion Association of Chinese Academy of Sciences.
The study entitled “Factors influencing repeated seed movements by scatter-hoarding rodents in an alpine forest” has been published in Scientific Reports.
