Seed removal by scatter-hoarding rodents is one of the most important dispersal mechanisms for many plant species. Rodents' caching preference among different species of seeds mainly depends on seed traits. Shrub vegetation is a major determinant of microhabitat heterogeneity in the forest understory and influences both rodent activity and foraging behavior, and seed germination and seedling establishment. However, very few studies have investigated how shrubs affect this important mutualistic plant–animal interaction and how this is influenced by seed traits.
Dr. WANG Bo and his colleague of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to explore differences among seeds with different traits in the effects of shrubs on seed caching by rodents. They used several series of artificial seeds with different traits (i.e., seed size, nutrient and tannin contents) to mimic different species of seeds.
The researchers monitored rodent choices of caching microhabitat for 3564 artificial seeds that varied in size, nutrient content, and tannin content.
They found thatthe probability of seeds being cached in shrubs vs. open habitat varied greatly among seeds with different sizes or nutrient contents. High-quality seeds (i.e., large size or high nutrient content) were cached more often in shrubs, while low-quality seeds were cached more often in open habitats. However, tannin content had no effects on the probability of seeds being cached in shrubs vs. open habitat.
They also found that shrub cover significantly increased the distances which seeds were transported by rodents. Shrub cover appeared to enhance dispersal quality for high-quality seeds, by increasing the seed dispersal distance and possibly also by providing an improved microclimate in the harsh environment.
The results showed that rodents selected different caching habitats for seeds with different sizes or nutrient contents, but not for different tannin contents. The rodents had no overall caching preference between shrubs and open habitats.