Plant-Insect Interactions from Early Permian (Kungurian) Colwell Creek Pond, North-Central Texas: the Early Spread of Herbivory in Riparian Environments

Abstract

Premise of research. Two previous studies examined the extent of insect herbivory in Early Permian habitats of north-central Texas, with varying results indicating minimal to modest levels of interaction diversity. In a comparison to two previous floras, we tested whether herbivory patterns in a third, slightly younger, assemblage, the Colwell Creek Pond (CCP) flora, most closely reflect plant host taxonomic affiliation, plant conspicuousness, habitat, geologic time, or other variable. Methodology. We assessed the diversity and frequency of insect herbivory on 2140 specimens at CCP. We examined the percent of leaf area removed by herbivory as a third, independent, measure of the effect of insect herbivore removal of host plant photosynthetic tissue. Pivotal results. In a moderately diverse flora of 12 taxa, we found evidence for hole feeding, margin feeding, surface feeding, piercing and sucking, oviposition, galling, seed predation, and wood boring. Some damage was fungally modified. Three herbivory measures consistently indicate that the two overwhelmingly herbivorized taxa were Auritifolia waggoneri, a peltasperm, and Taeniopteris spp., a form genus of unknown affinity. An approximate order of magnitude less herbivory was present for Evolsonia texana, a gigantopterid; indeterminate broad-leaved seed plants, possibly including a mixoneuroid odontopteroid and Rhachiphyllum; and Walchia piniformis, a conifer. A notable association occurred between W. piniformis and an aldegid hemipteran scale insect or precursor lineage. The remaining eight taxa displayed little or no herbivory. About 5% of seeds showed evidence for predation. Conclusions. Herbivory dominance on A. waggoneri and Taeniopteris spp. at CCP supports a hypothesis that the early expansion of herbivory in clastic depositional settings tracked broad-leaved seed plants, a pattern likely modified by other factors, such as conspicuousness. Insects targeted particular host plants and were specialists on certain foliar tissue types, such as galling on A. waggoneri and oviposition on Taeniopteris spp.