“Tipping points in resource abundance drives irreversible changes in community structure”

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Seth D. Haney and Adam M. Siepielski (May 2018)

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Extreme changes in resources can cause irreversible shifts in community structure – a tipping point

Extreme environmental change may be the key driver of ecological and evolutionary dynamics shaping biological communities

Global climate change has made what were seemingly extraordinary environmental conditions, such as prolonged droughts, heat waves, and extreme precipitation events commonplace. Such extremes in environmental fluctuation can cause critical changes in the resources available to vulnerable species. How might such extreme changes impact the stability of ecological communities?

In this new study, Seth D. Haney and Adam M. Siepielski use mathematical modeling to show that extreme changes in resources can cause irreversible evolutionary changes and critical shifts in communities. They find that while small to moderate changes in resource abundance have little effect on ecological and evolutionary dynamics, when resource scarcities are sufficiently extreme, a critical transition—a tipping point—occurs. This causes consumer traits to diverge and restructures the community in a way that outlasts the resource scarcity. Therefore, even though traits can readily evolve in response to minor resource fluctuations, large environmental shifts may be the dominant driver of long-lasting impacts on community structure. Past changes in environmental conditions can thus lock community structure up, unless a large-magnitude perturbation occurs. These results shed new light on the potential long-term impacts caused by climate change on ecological communities.


Abstract

Global climate change has made what were seemingly extraordinary environmental conditions, such as prolonged droughts, commonplace. One consequence of extreme environmental change is concomitant changes in resource abundance. How will such extreme resource changes impact biodiversity? We developed a trait-based consumer-resource model to examine how resource abundance affects the potential for adaptive evolution and coexistence among competitors. We found that moderate changes in resource abundance have little effect on trait evolution. However, when resource scarcities were sufficiently extreme, a critical transition–a tipping point–occurred, which caused consumer traits to diverge and re-structured the community in a way that outlasted the scarcity. Therefore, even though traits can evolve in response to minor resource fluctuations, large environmental shifts may be necessary for producing long-lasting impacts on community structure. These results may also help to illuminate patterns of stasis frequently observed in nature, despite the considerable evidence demonstrating rapid evolutionary change.