Stabilizing role of seed banks and the maintenance of bacterial diversity

ABSTRACTCoexisting species often exhibit negative frequency dependence due to mechanisms that promote population growth and persistence when rare. These stabilizing mechanisms maintain diversity through interspecific niche differences, but also through life-history strategies like dormancy that buffer dynamics in fluctuating environments. However, there are few tests demonstrating how seed banks contribute to long-term community dynamics and the maintenance of diversity. Using multi-year, high-frequency bacterial community data from a north temperate lake, we documented patterns consistent with stabilizing coexistence, including differential responses of bacterial taxa to environmental conditions and the presence of a seed bank. By maintaining rare taxa over winter periods, the seed bank contributed to recurrent seasonal dynamics. Last, strong negative frequency dependence in rare, but metabolically active, taxa suggested biotic interactions promoted coexistence. Together, our results provide field-based evidence that niche differences and seed banks stabilize bacterial community dynamics and contribute to the maintenance of microbial diversity in nature.