Genomic Vulnerability to Climate Change of a Seasonal Dispersal Insect Within a Small Spatial Scale

Seasonal migration represents one of the most fascinating behaviours observed throughout the animal kingdom. Understanding the spatial ecological and evolutionary dynamics of seasonally migratory animals is important to predict their responses to anthropogenic climate change. Unlike the directional and closed-circuit round-trip migratory pattern in most seasonally migratory animal species, many migratory insects exhibit a tangled reticular movement instead of a simple transition between sites. Consequently, the interplay between gene flow and natural selection in seasonal dispersal of insects may display a unique pattern and affect the potential of migratory insects to climate change. To characterise such pattern and evaluate the adaptive potential of seasonally migratory insects to future climate, we used genomic data from 32 populations of the seasonal dispersal and invasive oriental fruit fly (Bactrocera dorsalis) sampled across year-round and seasonal areas in the mountains of southwest China (MSWC). Despite significant ecological niche differences between populations of year-round and seasonal areas, we found no significant population structure both within and across areas. In addition, genomic landscape and vulnerability analyses suggested that the northwestern and northeastern populations possessed distinct genetic compositions and reduced adaptive potential compared to the southern populations. Finally, we predicted the migration distance and direction that may allow the current populations to persist under future climates. Our findings demonstrate that gene flow plays a predominant role in homogenising genetic variation at genome-wide scale while natural selection shapes genetic variation patterns at specific loci possibly involved in adaptation in seasonally migratory insects.