Africa has undergone a progressive aridification during the last 20 My that presumably impacted organisms and fostered the evolution of life history adaptations. We test the hypothesis that shift to living in ant nests and feeding on ant brood by larvae of phyto-predaceous Lepidochrysops butterflies was an adaptive response to the aridification of Africa that facilitated the subsequent radiation of butterflies in this genus. Using anchored hybrid enrichment we constructed a time-calibrated phylogeny for Lepidochrysops and its closest, non-parasitic relatives in the Euchrysops section (Poloyommatini). We estimated ancestral areas across the phylogeny with process-based biogeographical models and diversification rates relying on time-variable and clade-heterogeneous birth-death models. The Euchrysops section originated with the emerging Miombo woodlands about 22 million years ago (Mya), and spread to drier biomes as they became available in the late Miocene. The diversification of the non-parasitic lineages decreased as aridification intensified around 10 Mya, culminating in diversity decline. In contrast, the diversification of the phyto-predaceous Lepidochrysops lineage proceeded rapidly from about 6.5 Mya when this unusual life history likely first evolved. The Miombo woodlands were the cradle for diversification of the Euchrysops section, and our findings are consistent with the hypothesis that aridification during the Miocene selected for a phyto-predaceous life history in species of Lepidochrysops, with ant nests likely providing caterpillars a safe refuge from fire and a source of food when vegetation was scarce.

Description of the files: 2_PHASED_ALIGNMENTS: Individual phased alignments used as input to produce gene trees in IQ-TREE. In fasta format.-- 3_UNPHASED_ALIGNMENTS: Individual alignments used to produce the full ML tree. In fasta format.-- 4_CONCATENATED_ALIGNMENT: The full concatenated alignment in phylip format and a .nex file with the models and partition scheme.-- 5_DATING: Concatenated reduced alignment in phylip format and the fixed input tree in Newick format used for dating. Taxon names were renamed since MCMCtree cannot handle taxon names longer than 49 characters. The file Rename.txt can be used to rename files back to the original names using sed: sed -f Rename.txt file > renamed_file. Convergence_plots.pdf contains plots of the mean age and upper and lower 95% highest posterior density (HPD) credibility intervals of two and two MCMCtree runs against each other to assure convergence of MCMC chains.-- 6_GENETREES: Genetrees used for input in ASTRAL. In Newick format.-- 7_FINAL_TREES: The ASTRAL species tree (Fig. S2), full ML tree (Fig. S1) and reduced, dated ML tree (Fig. 1, Fig. S4), with only on specimen included per species. The dated tree is in nexus format, and the others in Newick format.

Peer reviewed