Research Training Program

A flora comprising three Lower Permian sites from north-central Texas were examined for insect folivory: mouth of Brushy Creek, Brushy Creek, and Upper Brushy Creek. This flora was examined qualitatively for presence and category of damage, and quantitatively to calculate extent and amount of damage. Primary constituents of the flora include the conifer Walchia, the cordaite Cordaites, and the gigantopterid Zeilleropteris. Analysis of 365 specimens yielded a foliage removal rate of 0.083%. Frequency of attack by folivores was 1.9%. Only 7 of the 365 specimens exhibited folivory, four of which can be categorized as margin feeding. Skeletonization and hole feeding also were evident, but in markedly smaller numbers. The seed fern Callipteris spp. demonstrated the highest frequency of attack, indicating a host-specificity for this taxon in particular and perhaps for seed-ferns in general.

Modern levels of herbivory in tropical and subtropical forests range between 7.5% and 12.0%. The greater Brushy Creek flora in comparison, exhibits a far lower rate. A flora of approximately the same age (Artinskian) exhibits a foliage removal rate of 2.55%, 30 times that of greater Brushy Creek. Previous studies have shown that pteridosperms and gigantopterids are the primary targets of insect folivory and this study confirms those observations. Overall folivory rates may be low because this flora is dominated by Walchia spp. and Cordaites spp., genera that rarely get herbivorized or in which herbivory is difficult to detect.