Critiques and new hope on divergence time estimation of Lepidoptera

Lepidoptera are one of the most diverse phytophagous insect groups (Scoble, 1992). In spite of their importance in terrestrial ecosystems, the evolutionary history of the Lepidoptera remains poorly known. Divergence time estimation over a robust phylogeny is a prerequisite for understanding their evolutionary biology. Recent empirical studies have found that molecular dating analyses are critically affected by the number and temporal distribution of fossil calibration points (Yang & Yoder, 2003; Hug & Roger, 2007), the interpretation of relationships between fossil and extant taxa (Benton & Ayala, 2003; Donoghue & Benton, 2007), and how fossil constraints are treated (Magallón, 2004; Ho & Phillips, 2009). Confident dating thus requires multiple fossils that are securely identified and of sufficient age. These requirements often are difficult to meet for the depauperate lepidopteran fossil record. There have been a few attempts to date molecular phylogeny for the entire Lepidoptera (Wahlberg et al., 2013) or a few subgroups, notably butterflies (Zakharov et al., 2004; Braby et al., 2005; Wahlberg, 2006; Peña & Wahlberg, 2008; Simonsen et al., 2011). We review the fossils and the calibration methods used from previous molecular dating studies of Lepidoptera and evaluate their results under the constraint of reliable dating. We also provide a list of lepidopteran fossils potentially useful for calibration points, and end on the perspective for dating the currently working phylogeny of Lepidoptera (Regier et al., 2013), using these fossils.