Geographic variation and core microbiota composition of <i>Anastrepha ludens</i> (Diptera: Tephritidae) infesting a single host across latitudinal and altitudinal gradients

<i>Anastrepha ludens</i> is a pestiferous tephritid fly species exhibiting extreme polyphagy. It develops optimally in hosts rich in sugar but low nitrogen content. We studied the geographical influence on the composition of <i>A. ludens</i>'s larval and newly emerged adult gut microbiota in altitudinal (0-2,000 masl) and latitudinal (ca. 800 km from 17° to 22°N latitude) transects along the coastline of the state of Veracruz, Mexico. In the 16 collection sites, we only collected <i>Citrus x aurantium</i> fruit (238 samples of <i>A. ludens</i> larvae and adults, plus 73 samples of pulp) to control for host effect, hypothesizing that there exists a conserved core microbiota that would be dominated by nitrogen-fixing bacteria. We found that latitude triggered more significant changes in the gut microbiota than altitude. Northern and southernmost samples differed the most in microbiota composition, with a trade-off between Acetobacteraceae and Rhizobiaceae driving these differences. As hypothesized, the core microbiota in each sampling site, contained the functional group of nitrogen-fixing bacteria. We conclude that <i>A. ludens</i> larvae can acquire multiple diazotrophic symbionts along its wide distribution range where it infests fruit with a high C:N ratio in the pulp.