Invasive species often depend on microbial symbionts, but few studies have examined the evolutionary dynamics of symbionts during the early stages of an invasion. The insect Megacopta cribraria and its bacterial nutritional symbiont Candidatus Ishikawaella capsulata invaded the southeastern US in 2009. While M. cribraria was initially discovered on wild kudzu plants, it was found as a pest on soybeans within 1 year of infestation. Because prior research suggests Ishikawaella confers the pest status—that is, the ability to thrive on soybeans—in some Megacopta species, we performed a genomic study on Ishikawaella from US. Megacopta cribraria populations to understand the role of the symbiont in driving host plant preferences. We included Ishikawaella samples collected in the first days of the invasion in 2009 and from 23 locations across the insect's 2011 US range. The 0.75 Mb symbiont genome revealed only 47 fixed differences from the pest-conferring Ishikawaella in Japan, with only one amino acid change in a nutrition-provisioning gene. This similarity, along with a lack of fixed substitutions in the US symbiont population, indicates that Ishikawella likely arrived in the US capable of being a soybean pest. Analyses of allele frequency changes between 2009 and 2011 uncover signatures of both positive and negative selection and suggest that symbionts on soybeans and kudzu experience differential selection for genes related to nutrient provisioning. Our data reveal the evolutionary trajectory of an important insect-bacteria symbiosis in the early stages of an invasion, highlighting the role microbial symbionts may play in the spread of invasive species.
rawvar_rmdup.ind1
Raw SNP data from Index 1 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind2
Raw SNP data from Index 2 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind3
Raw SNP data from Index 3 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind4
Raw SNP data from Index 4 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind5
Raw SNP data from Index 5 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind6
Raw SNP data from Index 6 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind7
Raw SNP data from Index 7 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind8
Raw SNP data from Index 8 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind9
Raw SNP data from Index 9 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind10
Raw SNP data from Index 10 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind11
Raw SNP data from Index 11 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind12
Raw SNP data from Index 12 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind13
Raw SNP data from Index 13 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind14
Raw SNP data from Index 14 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind15
Raw SNP data from Index 15 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind16
Raw SNP data from Index 16 for Ishikawaella U.S. 2009 (ground zero) from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind17
Raw SNP data from Index 17 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind18
Raw SNP data from Index 18 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind19
Raw SNP data from Index 19 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind20
Raw SNP data from Index 20 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind21
Raw SNP data from Index 20 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind22
Raw SNP data from Index 22 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind23
Raw SNP data from Index 23 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.
rawvar_rmdup.ind24
Raw SNP data from Index 24 for Ishikawaella U.S. 2011 from Illumina HiSeq generated using GATK.