Dense sampling of taxa and characters improves phylogenetic resolution among deltocephaline leafhoppers (Hemiptera: Cicadellidae: Deltocephalinae)

We analysed a phylogenomic dataset comprising 730 terminal taxa and >160,000 nucleotide positions obtained using anchored hybrid enrichment of genomic DNA for a sample of deltocephaline leafhoppers and outgroups. Maximum likelihood analyses of concatenated nucleotide and amino acid sequences as well as coalescent gene tree analysis, yielded well-resolved phylogenetic estimates that were highly congruent with most branches receiving maximum support. Some topological incongruence occurs among the trees resulting from different analyses, mainly distributed among very short branches at intermediate levels in the phylogeny, pertaining to relationships among some tribes and multi-tribe lineages restricted to particular continents. Coalescent gene tree analysis revealed extensive gene tree conflict at these nodes, suggesting that certain relationships may remain difficult to resolve consistently even with genome-scale datasets and dense taxon sampling. Ancestral character state reconstruction of feeding preference indicates that grass specialization has been acquired three or fewer times in some highly diverse but relatively derived lineages. Molecular divergence time estimation suggests that the earliest divergences in the subfamily occurred during the Cretaceous but that most modern tribes did not appear until after the Cretaceous-Palaeogene boundary and that grass specialist lineages generally diversified and spread at the same time as grasslands were becoming widespread globally. These analyses also show a high level of global biogeographic structure, with several large lineages of primarily arboreal deltocephalines restricted to particular regions or continents and long-distance dispersal among continents occurring primarily among grass-specialist lineages. The results represent a major improvement over previous analyses of this diverse subfamily, which were based on 152 or fewer taxa and data from morphology and partial sequences of two genes.