Abstract
Natural environments, like soils or the mammalian gut, frequently contain microbial consortia competing within a niche, wherein many species contain genetically encoded mechanisms of interspecies competition. Recent computational work suggests that physical structures in the environment can stabilize local competition between species that would otherwise be subject to competitive exclusion under isotropic conditions. Here we employ Lotka-Volterra models to show that interfacial competition localizes to physical structures, stabilizing competitive ecological networks of many species, even with significant differences in the strength of competitive interactions between species. Within a limited range of parameter space, we show that for stable communities the length-scale of physical structure inversely correlates with the width of the distribution of competitive fitness, such that physical environments with finer structure can sustain a broader spectrum of interspecific competition. These results highlight the potentially stabilizing effects of physical structure on microbial communities and lay groundwork for engineering structures that stabilize and/or select for diverse communities of ecological, medical, or industrial utility.
Highlights
Natural environments from scales of microbes [1,2,3,4] to large ecosystems [5,6,7,8] are replete with communities whose constituent species stably coexist at similar trophic levels, despite apparent competition for space and resources
Recent computational work suggests that physical structures in the environment can stabilize local competition between species that would otherwise be subject to competitive exclusion under isotropic conditions
Within a limited range of parameter space, we show that for stable communities the length-scale of physical structure inversely correlates with the width of the distribution of competitive fitness, such that physical environments with finer structure can sustain a broader spectrum of interspecific competition
Summary
Natural environments from scales of microbes [1,2,3,4] to large ecosystems [5,6,7,8] are replete with communities whose constituent species stably coexist at similar trophic levels, despite apparent competition for space and resources. At the other extreme are so-called ‘neutral theories’ which offer the null-hypothesis that organisms coexisting at similar trophic levels are–per capita–reproducing, consuming, and migrating at similar rates, and maintenance of biodiversity is tantamount to a high-dimensional random-walk through abundance space [23,24,25]. Such models often require connections to an external meta-community to maintain long-term stability [26], lest random fluctuations will eventually drive finite systems toward lower diversity [27,28]. Many other mechanisms (which we cannot do justice to here) have been proposed for maintenance of diversity in competitive ecosystems, including but not limited to: stochasticity and priority effects [29,30]; environmental variability [31]; models that encode specific relationships between species to maintain diversity [32] (including the classic rock-paper-scissors spatial game [11], cross-feeding [33,34,35,36,37], metabolic trade-offs [38,39,40], or cross-protection [41]); varied interaction models [42]; higher-order interactions– beyond pairwise–that stabilize diversity [43,44,45,46]; and systems where evolution and ecological competition happen simultaneously [47,48]
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