The tuatara (Sphenodon punctatus)-the only living member of the reptilian order Rhynchocephalia (Sphenodontia), once widespread across Gondwana 1,2-is an iconic species that is endemic to New Zealand 2,3. A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes 2,4. Here we analyse the genome of the tuatara, which-at approximately 5 Gb-is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago. This lineage also shows moderate rates of molecular evolution, with instances of punctuated evolution. Our genome sequence analysis identifies expansions of proteins, non-protein-coding RNA families and repeat elements, the latter of which show an amalgam of reptilian and mammalian features. The sequencing of the tuatara genome provides a valuable resource for deep comparative analyses of tetrapods, as well as for tuatara biology and conservation. Our study also provides important insights into both the technical challenges and the cultural obligations that are associated with genome sequencing.

The field of molecular phylogenetics is being revolutionized with next‐generation sequencing technologies making it possible to sequence large numbers of genomes for non‐model organisms ushering us into the era of phylogenomics. The current challenge is no longer how to get enough data, but rather how to analyse the data and how to assess the support for the inferred phylogeny. Here, we focus on one of the largest animal groups on the planet – butterflies and moths (order Lepidoptera), whose phylogeny remains unresolved despite several recent phylogenomic studies. In this study, we assess the potential causes and consequences of the conflicting phylogenetic hypotheses. With a dataset consisting of 331 protein‐coding genes and the alignment length over 290,000 base pairs, including 200 taxa representing 83% of lepidopteran superfamilies, we compare phylogenetic hypotheses inferred from amino acid and nucleotide alignments. The resulting two phylogenies are discordant, especially with respect to the placement of the superfamily Gelechioidea, which is likely due to compositional bias and possible other model violations. Furthermore, we employed a series of analyses to dissect our dataset and demonstrate that there is sufficient phylogenetic signal to resolve much – but not all – of the lepidopteran tree of life. The relationships among superfamilies within Ditrysia, the most species rich lepidopteran clade containing 98% of the extant species, remain poorly resolved. We conclude that taxon sampling remains an issue even in phylogenomic analyses and recommend that poorly sampled highly diverse groups, such as Gelechioidea in Lepidoptera, should receive extra attention in the future.

The field of molecular phylogenetics is being revolutionised with next-generation sequencing technologies making it possible to sequence large numbers of genomes for non-model organisms ushering us into the era of phylogenomics. The current challenge is no longer how to get enough data, but rather how to analyse the data and how to assess the support for the inferred phylogeny. We focus on one of the largest animal groups on the planet - butterflies and moths (order Lepidoptera). We clearly demonstrate that there are unresolved issues in the inferred phylogenetic relationships of the major lineages, despite several recent phylogenomic studies of the group. We assess the potential causes and consequences of the conflicting phylogenetic hypotheses. With a dataset consisting of 331 protein-coding genes and the alignment length over 290 000 base pairs, including 200 taxa representing 81% of lepidopteran superfamilies, we compare phylogenetic hypotheses inferred from amino acid and nucleotide alignments. The resulting two phylogenies are discordant, especially with respect to the placement of the superfamily Gelechioidea, which is likely due to compositional bias of both the nucleotide and amino acid sequences. With a series of analyses, we dissect our dataset and demonstrate that there is sufficient phylogenetic signal to resolve much of the lepidopteran tree of life. Overall, the results from the nucleotide alignment are more robust to the various perturbations of the data that we carried out. However, the lack of support for much of the backbone within Ditrysia makes the current butterfly and moth tree of life still unresolved. We conclude that taxon sampling remains an issue even in phylogenomic analyses, and recommend that poorly sampled highly diverse groups, such as Gelechioidea in Lepidoptera, should receive extra attention in the future.