<b>Unraveling the Evolutionary History of Grass Flies (Diptera: Chloropidae): Phylogeny and Divergence Time Insights</b>

Chloropidae is one of the most species-rich families among acalyptrate flies, comprising approximately 3 000 described species across 204 genera worldwide. Using molecular data from six genes (four mitochondrial gene fragments: <i>COI</i>, <i>CytB</i>, <i>12S </i>rRNA, <i>16S</i> rRNA and two nuclear gene fragments: <i>28S</i> rRNA, <i>CAD</i>), we reconstructed the phylogeny of Chloropidae and provided the first time-calibrated phylogeny of the family. Our analyses strongly support the monophyly of Chloropidae and reveal the following inter-subfamily relationships: (Siphonellopsinae + (Chloropinae + (Oscinellinae + Rhodesiellinae))). Notably, Siphonellopsinae monophyly requires further testing as only one representative genus was included. We compared our results of Elachipterini (Oscinellinae) with recent morphological phylogeny. Our results validated <i>Discadrema</i> and<i> Togeciphus</i> as distinct genera. Marginal-likelihood estimations identified a Yule tree prior with 12 unlinked molecular clocks as the optimal BEAST model. Divergence time estimates place the Chloropidae crown age at 43.7 million years ago (Ma), with rapid subfamily diversification occurring around 42 Ma during the mid-Paleogene.