Asymmetric evolvability leads to specialization without trade-offs

Many organisms are specialized, and these narrow niches are often explained with trade-offs—inability for one organism to express maximal performance in two or more environments. However, evidence is lacking that trade-offs are sufficient to explain specialists. Several lines of theoretical inquiry suggest that populations can specialize without explicit trade-offs, as a result of relaxed selection in generalists for their performance in rare environments. Here I synthesize and extend these approaches, showing that emergent asymmetries in evolvability can push a population toward specialization in the absence of trade-offs and in the presence of substantial ecological costs of specialism. Simulations are used to demonstrate how adaptation to a more common environment interferes with adaptation to a less common but otherwise equal alternative environment, and that this interference is greatly exacerbated at low recombination rates. This adaptive process of specialization can
effectively trap populations in a suboptimal niche. These modeling results predict that transient differences in evolvability across traits during a single episode of adaptation could have long-term consequences for a population’s niche.
Methods
All data analyzed in the paper result from simulations. Both the code for producing these results and analyzing them are included.