Abstract
Selfish genetic elements have been found in the genomes of many species, yet our understanding of their evolutionary dynamics is only partially understood. A number of distinct selfish Medea elements are naturally present in many populations of the red flour beetle (Tribolium castaneum). Although these Medea elements are predicted by models to increase in frequency within populations because any offspring of a Medea‐bearing mother that do not inherit at least one Medea allele will die, experiments demonstrating an increase in a naturally occurring Medea element are lacking. Our survey of the specific Medea element, M1, in the United States showed that it had a patchy geographic distribution. From the survey, it could not be determined if this distribution was caused by a slow process of M1 colonization of discrete populations or if some populations lacked M1 because they had genetic factors conferring resistance to the Medea mechanism. We show that populations with naturally low to intermediate M1 frequencies likely represent transient states during the process of Medea spread. Furthermore, we find no evidence that genetic factors are excluding M1 from US populations where the element is not presently found. We also show how a known suppressor of Medea can impair the increase of M1 in populations and discuss the implications of our findings for pest‐management applications of Medea elements.
Highlights
Since the first selfish genetic elements (SGEs) were discovered nearly a century ago (Gershenson, 1928), they have been described in a wide variety of organisms, yet their evolutionary implications are only partially understood and practical uses are just being explored (Burt & Trivers, 2006; Macias, Ohm, & Rasgon, 2017; Piaggio et al, 2017)
Models of Medea and experiments with synthetic Medea constructs in Drosophila species predict that as long as there are no fitness costs, the element will increase in frequency rapidly once introduced into a non-Medea population (Akbari et al, 2014; Buchman et al, 2018; Chen et al, 2007; Huang, Lloyd, Legros, & Gould, 2009; Smith, 1998; Wade & Beeman, 1994; Ward et al, 2010)
These models are useful in predicting the effectiveness of a particular approach before costly constructs and strains are built and field trials are performed
Summary
Since the first selfish genetic elements (SGEs) were discovered nearly a century ago (Gershenson, 1928), they have been described in a wide variety of organisms, yet their evolutionary implications are only partially understood and practical uses are just being explored (Burt & Trivers, 2006; Macias, Ohm, & Rasgon, 2017; Piaggio et al, 2017). SGEs are inherited more frequently than expected by Mendelian inheritance as a result of mechanisms that either kill the alternative allele, increase the element's own replication, or preferentially segregate the element into gametes during meiosis (Burt & Trivers, 2006) They are able to increase in frequency by eschewing the laws of inheritance, and they can affect the evolutionary trajectory of a population by impacting the fitness of individuals carrying the elements (typically negatively, though some examples of the positive fitness effects of SGEs exist) and by spreading linked, hitchhiking alleles (Fishman & Kelly, 2015; Werren, Nur, & Wu, 1988). Hypothesis 3 The known hybrid incompatibility factor, H, will inhibit increase in frequency of M1, and high frequency of M1 will cause a decline in H frequency
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