"Evolutionary rescue of niche constructors from habitat-exploiting invaders"Longcamp, AlexNiche construction, the process by which an organism increases its fitness by modifying its environment, can promote population persistence by allowing niche constructors to restore the density of reproductively suitable habitats. However, niche-constructing populations can be vulnerable to exploitation by non-niche-constructing "cheaters" who benefit from the constructed habitats without paying the cost of production. We first analytically approximated the probability that a declining niche-constructing population undergoes evolutionary rescue by evolving to withstand competition with an invasive cheater. We then analyze this probability under two different fitness costs of construction: a mortality cost that increases the constructor death and a fecundity cost that reduces the rate at which constructors reproduce. We find that fecundity costs are less harmful than mortality costs because the former not only reduce the reproductive variance experienced by the mutations responsible for rescue, but also decrease the density of habitats available to cheaters, providing more time for a rescue mutation to appear. We show that the latter benefit can even increase the probability of rescue. Finally, we consider an additional fecundity cost of "niche destruction," whereby an organism reduces its fitness by destroying its own habitat (e.g., through spite). Such costs are found to promote rescue more effectively than fecundity costs of construction because, in addition to reducing the rate at which new habitats are constructed, niche destruction removes pre-existing habitats that would otherwise be available to invaders. Our analytical approximations are validated with stochastic simulations. |
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