Figure 3.

Mycangium selectivity explains coarse phylogenetic congruence in Xylosandrus and Ambrosiella. (a) Ambrosia beetle lineages have maintained fidelity to either fungal clade but have been promiscuous within those clades. Permutations-based null model hypothesis test of phylogenetic congruence based on pairwise distances: coloured areas show null distributions of Procrustean sums of squares (higher values indicate less congruence) for 1000 permutations of the association matrix. Grey vertical lines show observed sums of squares. The observed sums of squares for all associations were lower than all permutations of the association matrix, indicating highly significant congruence. There was no significant congruence when the analysis was restricted to only association involving either the xylebori clade fungi or the beaveri clade. (b) In symbiont switching experiments, ambrosia fungi from the alternative beaveri clade were significantly less likely to be taken up by the mycangium of X. compactus than the typical symbiont (A. xylebori) and others in the xylebori clade. Model estimates for each clade (excluding typical symbiont) are shown as coloured symbols. (c) Experimental subjects had fungal spore loads similar to wild collected beetles for all Ambrosiella species except A. roeperi. Error bars represent 95% CI. Horizontal dotted lines show 95% CI for estimates from wild X. compactus caught while flying. (Online version in colour.)