A new exceptionally preserved sawfly fossil (Hymenoptera: Pergidae) and an evaluation of its utility for divergence time estimation and biogeography

Abstract

We report the discovery of the first fossil of an Australian species of Pergidae, Baladi warru gen. et sp. n., found at McGraths Flat, a newly discovered Miocene Konservat-Lagerstätte in central New South Wales. Using morphological data from the well-preserved fossil, along with a previously published molecular dataset of 59 taxa and a newly generated molecular dataset for 8 taxa, we constructed a data matrix and generated the first chronogram for Pergidae that incorporates internal calibration points. Our data reveal that Baladi warru belongs to the subfamily Perginae and is closely related to the Australian genera Cerealces and Xyloperga (tribe Cerealcini). According to our analysis, the origin of Pergidae appears slightly younger than previously hypothesised; however, additional calibration points are needed for a more detailed age constraint. Furthermore, ancestral character reconstruction indicates four independent adaptations to toxic Myrtaceae as host plants, while biogeographic analyses suggest that sympatry followed by founder events were the primary processes shaping the current disjunct distribution of pergids. Two significant founder events correspond with transitions to utilising Myrtaceae as host plants. With the approval of the Mudgee Local Aboriginal Land Council, Wiradjuri words were used to name the newly described species. ‘Baladi’ means ‘saw’ and ‘warru’ means ‘wasp’. This name honours the Traditional Owners of the lands on which the fossil was collected.