Kozak Passifloraceae Supplementary Materials

Antagonistic coevolution is often cited as a cornerstone of insect biodiversity theory, yet the historical stability of these interactions remains difficult to quantify across large radiations. This study integrates a new, comprehensive molecular phylogeny of the Passifloraceae with a high-density dataset of heliconian host-plant associations to re-evaluate classic models of their codivergence and coevolution. Reconstructing the diversification of Passiflora reveals a significant peak during the Miocene, and highlights contrasting dynamics among supersections. Analysis of the butterfly-plant interface reveals a remarkable lack of historical signal in host-plant usage. Contemporary associations are characterised by extreme macroevolutionary lability, where specialisation is not predicted by lineage age or geographic range, contradicting traditional gradualist models of niche expansion. However, a fundamental distinction emerges between the transient nature of specific host associations and the underlying evolutionary process. While individual host usage is fluid, the propensity for host-switching is a deeply conserved characteristic of specific heliconian lineages. This "Process vs. Pattern" distinction suggests that the evolutionary engine of the radiation is highly structured, even as the specific ecological realisations at the tips of the tree appear chaotic. Ultimately, coevolution in this iconic system acts as a facilitator for rapid niche exploration rather than a strict phylogenetic template, with host-switching lability representing the true conserved character of the radiation.