2017/02/21 by Rodrigo Pracana, Anurag Priyam, Ilya Levantis +2 · 1 citation
Biochemistry, Genetics and Molecular Biology · Agricultural and Biological Sciences · #Insect and Arachnid Ecology and Behavior #Plant and animal studies #Insect and Pesticide Research #Biology #Supergene (geology) #Divergence (linguistics) #ANT #Chromosome #Evolutionary biology #Ecology #Genetics #Gene
paper · pdf · doi:10.1111/mec.14054
openalex publication_date 2017/02/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/03
Variation in social behaviour is common, yet little is known about the genetic architectures underpinning its evolution. A rare exception is in the fire ant Solenopsis invicta: Alternative variants of a supergene region determine whether a colony will have exactly one or up to dozens of queens. The two variants of this region are carried by a pair of 'social chromosomes', SB and Sb, which resemble a pair of sex chromosomes. Recombination is suppressed between the two chromosomes in the supergene region. While the X-like SB can recombine with itself in SB/SB queens, recombination is effectively absent in the Y-like Sb because Sb/Sb queens die before reproducing. Here, we analyse whole-genome sequences of eight haploid SB males and eight haploid Sb males. We find extensive SB-Sb differentiation throughout the >19-Mb-long supergene region. We find no evidence of 'evolutionary strata' with different levels of divergence comparable to those reported in several sex chromosomes. A high proportion of substitutions between the SB and Sb haplotypes are nonsynonymous, suggesting inefficacy of purifying selection in Sb sequences, similar to that for Y-linked sequences in XY systems. Finally, we show that the Sb haplotype of the supergene region has 635-fold less nucleotide diversity than the rest of the genome. We discuss how this reduction could be due to a recent selective sweep affecting Sb specifically or associated with a population bottleneck during the invasion of North America by the sampled population.