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Population genomics of a symbiont in the early stages of a pest invasion
Author(s) -
Brown Amanda M. V.,
Huynh Lynn Y.,
Bolender Caitlin M.,
Nelson Kelly G.,
McCutcheon John P.
Publication year - 2014
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.12366
Subject(s) - biology , pest analysis , population genomics , population , symbiosis , ecology , mutualism (biology) , genomics , botany , genome , genetics , gene , bacteria , demography , sociology
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 M egacopta cribraria and its bacterial nutritional symbiont C andidatus 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 I shikawaella confers the pest status—that is, the ability to thrive on soybeans—in some M egacopta species, we performed a genomic study on I shikawaella from US . M egacopta cribraria populations to understand the role of the symbiont in driving host plant preferences. We included I shikawaella 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 I shikawaella in J apan, 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 I shikawella 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.