Abstract
Intraspecific competition for limited niches has been recognized as a driving force for adaptive radiation, but results for the role of interspecific competition have been mixed. Here, we report the adaptive diversification of the model bacteria Pseudomonas fluorescens in the presence of different numbers and combinations of four competing bacterial species. Increasing the diversity of competitive community increased the morphological diversity of focal species, which is caused by impeding the domination of a single morphotype. Specifically, this pattern was driven by more diverse communities being more likely to contain key species that occupy the same niche as otherwise competitively superior morphotype, and thus preventing competitive exclusion within the focal species. Our results suggest that sympatric adaptive radiation is driven by the presence or absence of niche-specific competitors.
Highlights
Adaptive radiation is a key component of biodiversity generation (Dieckmann and Doebeli, 1999; Schluter, 2000; Losos, 2010; Kassen, 2014)
We argue that the inconsistent results could be reconciled based on the theoretical framework emerging from biodiversityecosystem functioning studies (Schulze and Mooney, 1993; Tilman, 1997; Loreau et al, 2001)
A negative relationship was found between P. fluorescens diversity and proportion of wrinkly spreader (WS) (F1,94 = 369.82, p < 0.001; Figure 2), indicating that P. fluorescens diversity is caused by reduced proportions of WS morphotypes
Summary
Adaptive radiation is a key component of biodiversity generation (Dieckmann and Doebeli, 1999; Schluter, 2000; Losos, 2010; Kassen, 2014). Direct experimental tests of the role of interspecific competitors on diversification have typically used the bacterium Pseudomonas fluorescens as the focal species because of its propensity to morphologically diversify over 10s of generations. Gómez and Buckling (2013) demonstrated lower evolved diversity in resource use of an initially isogenic population of P. fluorescens in the presence vs absence of the natural microbial community in soil; Jousset et al (2016) reported that increasing the number of competing P. fluorescens isolates resulted in an increased diversifying selection of the focal strain; while Zhang et al (2012) reported little effect of a competitor (Pseudomonas putida) on P. fluorescens diversification. The present study measured the morphological diversification of P. fluorescens in the presence of microbial communities, in which a diversity gradient was set-up using four species, to determine the diversity of competing microbial communities on adaptive diversification
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