Divergence time estimation of genus Tribolium by extensive sampling of highly conserved orthologs

<p><i>Tribolium castaneum</i>, the red flour beetle, is among the most well-studied eukaryotic genetic model organisms. <i>Tribolium</i> often serves as a comparative bridge from highly derived <i>Drosophila</i> traits to other organisms. Simultaneously, as a member of the most diverse order of metazoans, Coleoptera,  <i>Tribolium</i> informs us about innovations that accompany hyper diversity. However, understanding the tempo and mode of evolutionary innovation requires well-resolved, time-calibrated phylogenies, which are not available for <i>Tribolium</i>. The most recent effort to understand <i>Tribolium</i>phylogenetics used two mitochondrial and three nuclear markers. The study concluded that the genus may be paraphyletic and reported a broad range for divergence time estimates. Here we employ recent advances in Bayesian methods to estimate the relationships and divergence times among <i>Tribolium castaneum</i>, <i>T. brevicornis</i>, <i>T. confusum</i>, <i>T. freemani</i>, and <i>Gnatocerus cornutus </i>using 1368 orthologs conserved across all five species and an independent substitution rate estimate. We find that the most basal split within <i>Tribolium</i> occurred ~86 Mya [95% HPD 85.90–87.04 Mya] and that the most recent split was between <i>T. freemani</i> and <i>T. castaneum</i> at ~14 Mya [95% HPD 13.55-14.00]. Our results are consistent with broader phylogenetic analyses of insects and suggest that Cenozoic climate changes played a role in the <i>Tribolium </i>diversification.</p>