Fig. 2. Individual long-term memory retention correlates with the abundance of bee gut microbes, and L. apis supplementation enhances long-term memory.

a The correlations between learning speed/memory retention and the abundance of bacterial phylotypes. Colours indicate the coefficient r values from two-sided Spearman correlation analyses (*p = 0.034). Bonferroni corrected p values for all spearman correlations are shown in Supplementary Data 3. LL learning speed in the Learning group (n = 15 bees), LM learning speed in the Memory group (n = 14 bees), MM memory performance in the Memory group. b The percentage of correct choices in the memory retention test correlated positively with the abundance of Lactobacillus Firm-5. c Learning speed did not correlate with Firm-5 abundance. The t value is the indicator for learning speed (Methods). High t values indicate slow learning whereas low t values indicate fast learning. Coefficient r and significance p values in (b) and (c) are from Spearman correlation analyses, n = 14 bees. d L. apis supplemented diet increased its abundance in the bee hindgut (two-sided Mann-Whitney U test with Bonferroni correction: Firm-5, U = 0, n = 5 bees for both groups, p = 0.048) compared with Control (sugar without L. apis). e Bees with L. apis increase in gut by supplementation (n = 34) had better long-term memory, compared with Control (n = 32) (GLMM, df = 64, ***p = 3.656 × 10⁻⁵; Supplementary Table 1). Filled circle colours indicate different colonies (n = 2). Data are presented as mean ± SEM in (d) and (e). Source data are provided as a Source Data file.