Timing between successive introduction events determines establishment success in bacteria with an Allee effect

Abstract

Propagule pressure is a leading determinant of population establishment. Yet, an experimental understanding of how propagule size and number (two principal parts of propagule pressure) determine establishment success remains incomplete. Theoretical studies suggest that the timing between introduction events, a component of propagule number, can influence establishment success. However, this dynamic has rarely been explored experimentally. Using Escherichia coli engineered with an Allee effect, we investigated how the timing of two introduction events influences establishment. For populations introduced below the Allee threshold, establishment occurred if the time between two introduction events was sufficiently short, with the length of time between events further reduced by reducing growth rate. Interestingly, we observed that as the density of bacteria introduced in one introduction event increased, the time between introduction events that allowed for establishment increased. Using a mathematical model, we provide support that the mechanism behind these trends is the ability of the first population to modify the environment, which can pave the way for establishment of the second population. Our results provide experimental evidence that the temporal distribution of introduction events regulates establishment, furthering our understanding of propagule pressure and may have implications in invasion biology and infectious disease.

Evolutionary Pathways and Trajectories in Antibiotic Resistance

“…Not only might a possible confluence of clonal waves in different hosts promote dissemination, but the rise of a wave in the single host (possibly following the introduction of an external clone) can influence the success of establishing successive kin clones. The first rising population modifies the environment, which can pave the way for establishing the second population (1045). The HGT of adaptive genes (including antibiotic resistance) from the first successes might "convert" other coexisting clones in co-successful resistant clones.…”

The role of preadaptation, propagule pressure and competition in the colonization of new habitats

“…A high propagule pressure increases the chance that some of the immigrants can establish in the new habitat, for instance by having the right genetic make‐up. Also, it reduces the probability of extinction, which is more likely to occur in small population sizes due to Allee effects, founder effects, genetic (inbreeding, drift) and demographic stochasticity (Ellstrand and Elam , Newman and Pilson , Dressler et al ). Third, in order to establish populations and further expand, individuals need to cope with the ecological context of the new habitat, i.e.…”

Microbial invasion of a toxic medium is facilitated by a resident community but inhibited as the community co-evolves

“…What determines the ability of an invasive species to colonize an existing ecosystem depends on the characteristics of both the invading species and the resident community (7, 8). Many theoretical and empirical studies have established factors that influence invasion outcome, such as propagule pressure (9–14), resident community productivity (15), genotypic richness of invaders (13, 16) or the resident community (3, 13, 17–20), community niche coverage (3, 21, 22) and abiotic conditions (e.g. the presence of antibiotics (23)).…”