Aphid species specializing on milkweed harbor taxonomically similar bacterial communities that differ in richness and relative abundance of core symbionts

Abstract

Host plant range is arguably one of the most important factors shaping microbial communities associated with insect herbivores. However, it is unclear whether host plant specialization limits microbial community diversity or to what extent herbivores sharing a common host plant evolve similar microbiomes. To investigate whether variation in host plant range influences the assembly of core herbivore symbiont populations we compared bacterial diversity across three milkweed aphid species (Aphisnerii, Aphis asclepiadis, Myzocallis asclepiadis) feeding on a common host plant (Asclepias syriaca) using 16S rRNA metabarcoding. Overall, although there was significant overlap in taxa detected across all three aphid species (i.e. similar composition), some structural differences were identified within communities. Each aphid species harbored bacterial communities that varied in terms of richness and relative abundance of key symbionts. However, bacterial community diversity did not vary with degree of aphid host plant specialization. Interestingly, the narrow specialist A.asclepiadis harbored significantly higher relative abundances of the facultative symbiont Arsenophonus compared to the other two aphid species. Although many low abundance microbes were shared across all milkweed aphids, key differences in symbiotic partnerships were observed that could influence host physiology or additional ecological variation in traits that are microbially-mediated. Overall, this study suggests overlap in host plant range can select for taxonomically similar microbiomes across herbivore species, but variation in core aphid symbionts within these communities may still occur.

Modeling host–microbiome interactions to improve mechanistic understanding of aphid vectored plant pathogens

“…Precipitation is associated with increased early season activities of some aphid vectors (Crossley et al, 2022) and is predicted to indirectly benefit vector populations by generally supporting host plant health, including growth of both cereal crops and additional grass hosts that provide a "green bridge" for vector survival between growing seasons (Thackray et al, 2009;Rashidi et al, 2021). Relatedly, exposure to a greater diversity of host plants in a given landscape could in turn contribute to increases in symbiont diversity within vectors populations (Hansen and Moran, 2014;Blankenchip et al, 2018;Enders et al, 2022). Presence of additional grass hosts are also problematic because they can contribute to viral reservoirs in the landscape that then facilitate transfer to cereal crops (Rashidi et al, 2021).…”