Microbial community assembly at Evolution Canyon: Does dormancy dilute the effects of dispersal and filtering?
Dispersal, drift, and environmental filtering are primary processes that influence the assembly and structure of ecological communities. However, species traits and life history strategies may affect these processes to varying degrees. Dormancy, a reversible state of low metabolic activity, likely influences these processes by allowing individuals to overcome dispersal limitation and environmental filtering. Here, we examine the relative influence of dormancy on community assembly using a combination of spatially explicit individual-based modeling and a 16S rRNA-based molecular survey of active (transcript) and total (gene) soil bacterial communities at Evolution Canyon, Israel. Given the proximity (ca. 150 m) of its two environmentally distinct slopes – a xeric, south facing slope and a mesic, north facing slope – and the high level of dispersal by microorganisms, Evolution Canyon provides an excellent opportunity to test the importance of dormancy on community structure and assembly.
Individual-based modeling suggests that dormancy effects community assembly in two ways. First, dormancy reduces the strength of environmental filtering on local taxa. Second, dormancy dampens dispersal limitation and increases the probability of successful colonization. Together, these effects should act to minimize compositional differences between communities. In contrast, we found that environmental filtering at Evolution Canyon (PERMANOVA, R2 = 0.43) had a strong effect on both the active and total portions of the bacterial community. Our results suggest that environmental filtering and dormancy are the primary factors influencing microbial assembly despite high rates of dispersal between the proximate slopes at Evolution Canyon. In summary, the main effect of dormancy on community assembly appears to be mediated by the maintenance of local diversity through temporal storage.