Limits...
Spatially Heterogeneous Environmental Selection Strengthens Evolution of Reproductively Isolated Populations in a Dobzhansky – Muller System of Hybrid Incompatibility

View Article: PubMed Central - PubMed

ABSTRACT

Within-species hybrid incompatibility can arise when combinations of alleles at more than one locus have low fitness but where possession of one of those alleles has little or no fitness consequence for the carriers. Limited dispersal with small numbers of mate potentials alone can lead to the evolution of clusters of reproductively isolated genotypes despite the absence of any geographical barriers or heterogeneous selection. In this paper, we explore how adding heterogeneous natural selection on the genotypes (e.g., gene environment associations) that are involved in reproductive incompatibility affects the frequency, size and duration of evolution of reproductively isolated clusters. We conducted a simulation experiment that varied landscape heterogeneity, dispersal ability, and strength of selection in a continuously distributed population. In our simulations involving spatially heterogeneous selection, strong patterns of adjacency of mutually incompatible genotypes emerged such that these clusters were truly reproductively isolated from each other, with no reproductively compatible “bridge” individuals in the intervening landscape to allow gene flow between the clusters. This pattern was strong across levels of gene flow and strength of selection, suggesting that even relatively weak selection acting in the context of strong gene flow may produce reproductively isolated clusters that are large and persistent, enabling incipient speciation in a continuous population without geographic isolation.

No MeSH data available.


Related in: MedlinePlus

Generation 1250 for 5% maximum dispersal scenarios of (A) uniform selection (i.e., Landguth et al., 2015) and (B) heterogeneous selection of H = 0.9 and S = 64. Orange dots indicate genotype AABB, yellow dots indicate genotype aabb, and all other genotypes as green dots. (A) Shows the pattern of genotypes (red and blue mutually reproductively isolated and yellow compatible with both) in the pure isolation-by-distance framework of Landguth et al. (2015) without heterogeneous selection. (B) Shows the pattern of genotypes for a heterogeneous selection scenario with dispersal limited to 5% of the extent of the population and selection set at 64. In (A) there are few and small reproductively isolated clusters and these are not truly isolated as the yellow genotypes provide a genetic bridge for gene flow between red and blue. In contrast in (B) there is nearly complete elimination of the yellow “bridge” genotypes, and extensive, large and immediately adjacent patches of mutually isolated genotypes (red next to blue).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5121238&req=5

Figure 3: Generation 1250 for 5% maximum dispersal scenarios of (A) uniform selection (i.e., Landguth et al., 2015) and (B) heterogeneous selection of H = 0.9 and S = 64. Orange dots indicate genotype AABB, yellow dots indicate genotype aabb, and all other genotypes as green dots. (A) Shows the pattern of genotypes (red and blue mutually reproductively isolated and yellow compatible with both) in the pure isolation-by-distance framework of Landguth et al. (2015) without heterogeneous selection. (B) Shows the pattern of genotypes for a heterogeneous selection scenario with dispersal limited to 5% of the extent of the population and selection set at 64. In (A) there are few and small reproductively isolated clusters and these are not truly isolated as the yellow genotypes provide a genetic bridge for gene flow between red and blue. In contrast in (B) there is nearly complete elimination of the yellow “bridge” genotypes, and extensive, large and immediately adjacent patches of mutually isolated genotypes (red next to blue).

Mentions: In addition to the much larger total number, size, and duration of reproductively isolated patches when there is environmental selection, the pattern of cluster adjacency changes in critical ways that enable persistence of reproductively isolated clusters and therefore the potential for incipient speciation. Specifically in the Landguth et al. (2015) simulation, reproductively isolated clusters evolved only as a function of reproductive isolation and gene flow restriction by isolation-by-distance. This resulted in patterns of clusters in the landscape where putatively “reproductively isolated” clusters were rarely adjacent to clusters of individuals that were actually incompatible with them (Figure 3). They were most often adjacent to individuals that were not reproductively isolated from them, and clusters that were reproductively incompatible with them typically existed in other parts of the landscape with non-incompatible individuals in between. These non-incompatible individuals form a genetic “bridge” allowing gene flow between the putatively isolated clusters. While based on the criteria used by Landguth et al. (2015) this qualifies as evolution of reproductively isolated clusters, these clusters they were not isolated in the sense that individuals in these clusters could breed with the individuals that were adjacent to them, and could transfer genes between “isolated” clusters through the “bridge” of these compatible intervening individuals (Figure 3).


Spatially Heterogeneous Environmental Selection Strengthens Evolution of Reproductively Isolated Populations in a Dobzhansky – Muller System of Hybrid Incompatibility
Generation 1250 for 5% maximum dispersal scenarios of (A) uniform selection (i.e., Landguth et al., 2015) and (B) heterogeneous selection of H = 0.9 and S = 64. Orange dots indicate genotype AABB, yellow dots indicate genotype aabb, and all other genotypes as green dots. (A) Shows the pattern of genotypes (red and blue mutually reproductively isolated and yellow compatible with both) in the pure isolation-by-distance framework of Landguth et al. (2015) without heterogeneous selection. (B) Shows the pattern of genotypes for a heterogeneous selection scenario with dispersal limited to 5% of the extent of the population and selection set at 64. In (A) there are few and small reproductively isolated clusters and these are not truly isolated as the yellow genotypes provide a genetic bridge for gene flow between red and blue. In contrast in (B) there is nearly complete elimination of the yellow “bridge” genotypes, and extensive, large and immediately adjacent patches of mutually isolated genotypes (red next to blue).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121238&req=5

Figure 3: Generation 1250 for 5% maximum dispersal scenarios of (A) uniform selection (i.e., Landguth et al., 2015) and (B) heterogeneous selection of H = 0.9 and S = 64. Orange dots indicate genotype AABB, yellow dots indicate genotype aabb, and all other genotypes as green dots. (A) Shows the pattern of genotypes (red and blue mutually reproductively isolated and yellow compatible with both) in the pure isolation-by-distance framework of Landguth et al. (2015) without heterogeneous selection. (B) Shows the pattern of genotypes for a heterogeneous selection scenario with dispersal limited to 5% of the extent of the population and selection set at 64. In (A) there are few and small reproductively isolated clusters and these are not truly isolated as the yellow genotypes provide a genetic bridge for gene flow between red and blue. In contrast in (B) there is nearly complete elimination of the yellow “bridge” genotypes, and extensive, large and immediately adjacent patches of mutually isolated genotypes (red next to blue).
Mentions: In addition to the much larger total number, size, and duration of reproductively isolated patches when there is environmental selection, the pattern of cluster adjacency changes in critical ways that enable persistence of reproductively isolated clusters and therefore the potential for incipient speciation. Specifically in the Landguth et al. (2015) simulation, reproductively isolated clusters evolved only as a function of reproductive isolation and gene flow restriction by isolation-by-distance. This resulted in patterns of clusters in the landscape where putatively “reproductively isolated” clusters were rarely adjacent to clusters of individuals that were actually incompatible with them (Figure 3). They were most often adjacent to individuals that were not reproductively isolated from them, and clusters that were reproductively incompatible with them typically existed in other parts of the landscape with non-incompatible individuals in between. These non-incompatible individuals form a genetic “bridge” allowing gene flow between the putatively isolated clusters. While based on the criteria used by Landguth et al. (2015) this qualifies as evolution of reproductively isolated clusters, these clusters they were not isolated in the sense that individuals in these clusters could breed with the individuals that were adjacent to them, and could transfer genes between “isolated” clusters through the “bridge” of these compatible intervening individuals (Figure 3).

View Article: PubMed Central - PubMed

ABSTRACT

Within-species hybrid incompatibility can arise when combinations of alleles at more than one locus have low fitness but where possession of one of those alleles has little or no fitness consequence for the carriers. Limited dispersal with small numbers of mate potentials alone can lead to the evolution of clusters of reproductively isolated genotypes despite the absence of any geographical barriers or heterogeneous selection. In this paper, we explore how adding heterogeneous natural selection on the genotypes (e.g., gene environment associations) that are involved in reproductive incompatibility affects the frequency, size and duration of evolution of reproductively isolated clusters. We conducted a simulation experiment that varied landscape heterogeneity, dispersal ability, and strength of selection in a continuously distributed population. In our simulations involving spatially heterogeneous selection, strong patterns of adjacency of mutually incompatible genotypes emerged such that these clusters were truly reproductively isolated from each other, with no reproductively compatible “bridge” individuals in the intervening landscape to allow gene flow between the clusters. This pattern was strong across levels of gene flow and strength of selection, suggesting that even relatively weak selection acting in the context of strong gene flow may produce reproductively isolated clusters that are large and persistent, enabling incipient speciation in a continuous population without geographic isolation.

No MeSH data available.


Related in: MedlinePlus