Contemporary ecological heterogeneity shapes candidate adaptive genomic variation across the native range of an invasive herbivore
Ecological heterogeneity within a species native range can shape genomic variation available for subsequent range expansion and biological invasion. The cactus moth, Cactoblastis cactorum, is a South American oligophagous herbivore on Opuntia that has become an invasive pest outside its native range. In Argentina, populations span wide climatic and geographic gradients and exploit both native…
Ecological differences within a species' native range can influence genomic diversity that contributes to successful range expansion and biological invasion. The cactus moth, Cactoblastis cactorum, originally from South America, has become an invasive pest in various regions outside its native habitat. In Argentina, this moth species inhabits a range of climates and geographic locations, feeding on both native Opuntia plants and the non-native O. ficus-indica crop.
By analyzing 136 individuals from 28 populations using ddRADseq data, researchers sought to identify genomic variations linked to contemporary ecological conditions.
Through genome-wide differentiation scans (XtX), a contrast between host-use populations, and genotype-environment association (GEA) analyses, scientists pinpointed genomic regions potentially associated with environmental adaptation. XtX analyses revealed 12 candidate regions, while host-use contrast identified 17 regions that differentiated populations feeding on O. ficus-indica versus native Opuntia, with several persisting even after a geographically restricted analysis.
GEA analyses further identified 167 covariate-specific loci, including candidate genes involved in detoxification and metabolism (CYP6B2), oxygen-sensing pathways (Egln1), and circadian regulation (TIMELESS).
Despite limited convergence among the different analyses, the findings were stronger than would be expected by chance. Temperature-associated loci in fax and Bag6 emerged within an XtX candidate region, while Hspg2 was independently identified in both host-use and environmental analyses and remained significant after accounting for geographic location.
Most of the candidate variants were found in non-coding genomic regions, with protein-altering variants being relatively rare. The identified candidate genes spanned a wide range of functions, suggesting a potentially regulatory and polygenic architecture for adaptation in C. cactorum.
In summary, the study uncovers a diverse genomic landscape shaped by climatic variation and the use of an introduced host, with certain loci consistently linked to localized adaptive differentiation across the native range of C. cactorum.
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