PLANT–INSECT ASSOCIATONS FROM THE EARLIEST PERMIAN WILLIAMSON DRIVE FLORA IN NORTH-CENTRAL TEXAS

The deep-time ecological relationships between plants and their arthropod herbivores have been studied for decades and have used a variety of biological and paleobiological approaches. The fossil record of plants, insects, and their associations of herbivory, pollination and mimicry provide valuable data for understanding patterns involving ecological and evolutionary associational processes between two most diverse groups on land. In our study of the Williamson Drive Flora of north-central Texas, we use both qualitative and quantitative analyses for: 1), examining the spectrum (diversity) of herbivory; and 2), estimating the amount of insect-mediated damage based on the frequency of damage type (or DT) occurrences and the herbivorized leaf area as a fraction of total leaf area. The Williamson Drive Flora occurs within the Markley Formation, was deposited in a fluvially dominated coastal-plain on the eastern shelf of the Midland Basin, and is composed of uppermost Pennsylvanian and lowermost Permian strata. This moderately diverse flora is dated probably to the Asselian Stage. Approximately 3,200 specimens have been evaluated and can be grouped into 48 plant taxa. The dominant taxa (in descending order) are: Macroneuropteris scheuchzeri, Calamites sp., Sphenophyllum sp., Annularia carinata, Pseudomariopteris cordato-ovata, and Lilpopia raciborskii. More than 620 herbivorized specimens were found and their DT occurrences were divided into seven functional feeding groups: hole feeding, margin feeding, surface feeding, oviposition, piercing and sucking, galling and wood boring. Of the 47 recorded DTs, four were new. Recent case studies have examined insect herbivory from the early Permian of Texas. Compared to the three other localities of this regional stratigraphic sequence from north-central Texas – Taint, Coprolite Bone Bed and Colwell Creek Pond – the Williamson Drive flora is the earliest and possesses a coal-swamp cast. This environment includes elevated abundance and diversity of plant taxa, inclusion of taxa such as Macroneuropteris and Calamites, representation by a high specimen numbers that often are leaf mats, and a display of specialized patterns of herbivory. Further analyses will explore additional patterns of herbivory, including possible insect culprits.