Sphenomorphini unravelled: a phylogenomic framework and generic reassessments for Australia’s most species-rich vertebrate radiation

Australia has the world's most species-rich scincid lizard fauna (family Scincidae) with over 500 recognised species across three highly diverse radiations. One of these radiations is Tribe Sphenomorphini which comprises Australia's most species-rich endemic vertebrate radiation, with ∼280 recognised species plus considerable undescribed diversity. The varied ecomorphology and high species richness of Australian Sphenomorphini has been a focus of biogeographic and macroevolutionary analyses, however some relationships remain unresolved. Here, we combine a new phylogenomic dataset with weighted summary-coalescent tree inference and data filtering methods to produce a robust phylogeny spanning all Australian sphenomorphine genera and most recognised species-level taxa. Our results align with prior studies showing an early-burst signature of rapid speciation in the Miocene. Our phylogeny exhibits a deep split between lineages concentrated in arid (∼220 species, 3 genera) versus more mesic and temperate lineages (∼76 species, 18 genera) some 27.8-25.4 Ma, implying early divergence and widespread niche conservatism within these relatively arid- versus mesic-biome associated lineages. Analyses also support most established genera and supra-generic clades but find some conflicting relationships that challenge monophyly and current systematics within the genera Concinnia and Saiphos and allied taxa. We provide generic reassignments to address these issues. Species delimitation analyses support previous work indicating Australian species diversity remains moderately underestimated by current taxonomy.