Utilization of a wide range of exotic plant species by an exotic, <i>Solidago</i>-specialist aphid, <i>Uroleucon nigrotuberculatum</i> (Hemiptera: Aphididae)

Abstract The Anthropocene epoch is characterized by unprecedented rates of global biological invasions, resulting in the formation of novel ecological assemblages composed of multiple species with different origins. In this study, we focused on the recent expansion of host usage by the red goldenrod aphid, Uroleucon nigrotuberculatum, introduced to Japan from North America. Uroleucon nigrotuberculatum is well known to exclusively feed on Solidago spp in their native range, North America. Based on our observation, we hypothesize that in their introduced region (ie Japan), the aphid U. nigrotuberculatum, recently exhibited a broad host range, capable of exploiting a wide range of exotic plant species beyond the Solidago genus. We collected red aphid colonies from multiple exotic plant species in Hokkaido Island and also collected U. nigrotuberuculatum from multiple populations of S. altissima in Hokkaido and the main island of Japan. Then, we performed a phylogenetic analysis to determine genetic relationships among collected samples. Morphological characteristics were also examined. The phylogenetic analysis revealed no genetic variation among aphids collected from different exotic plants. All specimens clustered with U. nigrotuberculatum were found on S. altissima. Morphological examination confirmed key diagnostic features of U. nigrotuberculatum. We also performed field inoculation experiments. The red aphids collected from S. altissima could survive and reproduce on various exotic plant species, S. gigantea, Taraxacum officinale, and Senecio vulgaris. These results indicate a lack of host-associated genetic differentiation and support the utilization of these novel exotic plants by U. nigrotuberuculatum, potentially facilitating its further spread and ecological impact.