RT Journal Article
SR Electronic
T1 Natural selection can favor ratchet robustness over mutational robustness
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 121087
DO 10.1101/121087
A1 Yinghong Lan
A1 Aaron Trout
A1 Daniel Michael Weinreich
A1 Christopher Scott Wylie
YR 2018
UL http://biorxiv.org/content/early/2018/06/12/121087.abstract
AB The vast majority of fitness-affecting mutations are deleterious. How natural populations evolve to cope is a question of fundamental interest. Previous studies have reported the evolution of mutational robustness, that is, natural selection favoring populations with less deleterious mutations. By definition, mutational robustness provides a short-term fitness advantage. However, this overlooks the fact that mutational robustness decreases finite asexual populations’ ability to purge recurrent deleterious mutations. Thus, mutational robustness also results in higher risk of long-term extinction by Muller’s ratchet. Here, we explore the tension between short- and long- term response to deleterious mutations. We first show that populations can resist the ratchet if either the selection coefficient or the ratio of beneficial to deleterious mutations increases as fitness declines. We designate these properties as ratchet robustness, which fundamentally reflects a negative feedback between mutation rate and the tendency to accumulate more mutations. We also find in simulations that populations can evolve ratchet robustness when challenged by deleterious mutations. We conclude that mutational robustness cannot be selected for in the long term, but it can be favored in the short-term, purely because of temporary fitness advantage. We also discuss other potential causes of mutational robustness in nature.