Sexual reproduction reshapes the genetic architecture of digital organisms

Ecology, Evolutionary Biology and Behavior Program, Michigan State University, East Lansing, MI 48824, USA.
Proceedings of the Royal Society B: Biological Sciences (Impact Factor: 5.05). 03/2006; 273(1585):457-64. DOI: 10.1098/rspb.2005.3338
Source: PubMed


Modularity and epistasis, as well as other aspects of genetic architecture, have emerged as central themes in evolutionary biology. Theory suggests that modularity promotes evolvability, and that aggravating (synergistic) epistasis among deleterious mutations facilitates the evolution of sex. Here, by contrast, we investigate the evolution of different genetic architectures using digital organisms, which are computer programs that self-replicate, mutate, compete and evolve. Specifically, we investigate how genetic architecture is shaped by reproductive mode. We allowed 200 populations of digital organisms to evolve for over 10 000 generations while reproducing either asexually or sexually. For 10 randomly chosen organisms from each population, we constructed and analysed all possible single mutants as well as one million mutants at each mutational distance from 2 to 10. The genomes of sexual organisms were more modular than asexual ones; sites encoding different functional traits had less overlap and sites encoding a particular trait were more tightly clustered. Net directional epistasis was alleviating (antagonistic) in both groups, although the overall strength of this epistasis was weaker in sexual than in asexual organisms. Our results show that sexual reproduction profoundly influences the evolution of the genetic architecture.

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Available from: Charles Ofria, Jan 07, 2014
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    • "Thus, evolution in Avida is open-ended, sometimes leading to surprising conclusions (Wilke et al. 2001) that might be missed in models lacking key elements such as mutational bias. Although Avida has previously been used to study evolution in microbe-like systems (Lenski et al. 1999; Wilke et al. 2001; Lenski et al. 2003; Chow et al. 2004; Misevic et al. 2006; Clune et al. 2011), we added new features resembling those found in more complex organisms, specifically the ingredients necessary for mate choice to evolve: sexual recombination (Misevic et al. 2006) with distinct mating types (males and females), and configurable sex-specific reproductive costs reflecting the differential investments (anisogamy) made by each sex in most animals; CPU instructions allowing organisms to develop display traits; and CPU instructions allowing females to exhibit directional mating preferences, analogous to sensory biases thought to trigger the evolution of new mate preferences (Fuller et al. 2005; Fuller 2009; Egger et al. 2011), with configurable costs for these mating preferences. Mating occurs in an area similar to a lek, with a number of competing males displaying at any given time, and females choosing among them. "
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    • "As Dennett (2002, p. E83) has emphasized, " evolution will occur whenever and wherever three conditions are met: replication, variation (mutation), and differential fitness (competition). " The Avida system fulfills all of these conditions, and it is thus a tractable model for investigating the general properties of evolving systems (Lenski et al. 1999, 2003; Adami et al. 2000; Wilke et al. 2001; Chow et al. 2004; Goings et al. 2004; Misevic et al. 2006; Pennock 2007; Clune et al. 2008, 2010). "
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    • "Both selection for robustness and for evolvability are indirect, making these properties potentially difficult to investigate experimentally. Past research has found evidence that evolvability (Bedau and Packard, 2003; Earl and Deem, 2004; Wagner and Altenberg, 1996; Woods et al., 2003), as well as robustness can be selected for (Altenberg, 2005; Wilke et al., 2001; Misevic et al., 2006; Azevedo et al., 2006) under a range of circumstances. However, in most of these studies the traits that evolved different robustness and evolvability had direct fitness benefit and were thus under direct selection. "

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