i) Main analyses using an alternate phylogeny
We performed all our main analyses on an additional, separate
Heliconiini phylogeny (Cicconardi et al., 2022). Overall, we recorded 19
gregarious species, out of 57 included in Cicconardi et al. (2022). Our
model estimated eight independent transitions to gregariousness, and the
phylogenetic signal of social behaviour is estimated to be very strong
(λ = 1.0). Transitions between solitary and gregarious states are most
likely to occur at equal rates (X2(1) = 2.146,p = 0.143, transition rate = 0.033), with four reversals from
gregarious larvae back to solitary larvae across the phylogeny. Using
categorical social behaviour data, the ‘all rates different’ model is
better fitting (model comparison: X2(1) = 29.014,p < 0.001), with the highest transition rate estimated
to be from G2 to G3 (0.683 vs next highest G3 to G2 = 0.539).
As reported in our main analysis, solitary larvae feed on a greater
variety of host species than gregarious larvae (P-mean = -0.855, 95% CI
-1.673 – -0.083, PMCMC = 0.039). After omittingPassiflora hosts used by fewer than four larval species from the
data, we found no evidence of an interaction between larval social
behaviour and any host species. Additionally, we found that more
frequently used hosts by all larvae tend to grow in woods edge habitats
(P-mean = 2.989, 95% CI 1.322 – 4.681, PMCMC =
0.001, Table A6). Similar to our main results, we did not identify any
interactions between specific host plant traits, including leaf size,
and larval social behaviour (Table A6). We also found no interaction
between adult wingspan and host leaf size across gregarious larvae
(P-mean = -0.031, 95% CI -0.586 – 0.552, PMCMC= 0.914).