Paper No. 163-11
Presentation Time: 4:20 PM
INSECT HERBIVORY FROM THE LOWER PERMIAN SANZENBACHER FLORA FROM NORTH-CENTRAL TEXAS
In establishing insect and plant diversity through geological time it is necessary to understand the evolution of ancient terrestrial ecosystems, phylogeny reconstruction, and the development of evolutionary lineages to test ecological hypotheses involving inter-organismic antagonisms and mutualisms. We examined plant–insect interactions to understand how insect herbivores occupied particular feeding niches during the late Paleozoic. We documented patterns of insect herbivory at the early Permian Sanzenbacher Locality in north-central Texas, probably dating to the Wolfcampian Stage. The Sanzenbacher deposit consists of ca. 300 specimens of vascular plants embedded in a mudstone matrix associated with a fluvial depositional environment. This flora is dominated, in decreasing order of abundance, by the genera Pecopteris, Autunia, Neurodontopteris, Cordaites, Mariopteris and Rhachiphyllum. By (i) recording the frequency of insect-mediated damage, (ii) establishing the particular spectrum of damage types (DTs) present, and (iii) documenting the percent of herbivorized foliage by area for each taxon, indices were calculated to express the DT frequency and richness for each host species and for the entire bulk flora. These three modes of estimating fossil herbivory also allow determination of the proportion of specialized vs. generalized herbivory and which plant host taxon was the most consumed. The sphenopsid genus, Sphenophyllum, and the medullosan genus, Neurodontopteris, were the most highly damaged of the major morphotypes based on sufficiently adequate sample sizes. However, Annularia had the greatest herbivory but sample sizes were too low for acceptance. The most common insect damage, in decreasing abundance, was hole feeding, margin feeding, piercing and sucking (mostly scale insect marks), and surface feeding. The elevated presence of circular to ovoidal scale marks, likely attributable to coccoid Hemiptera, was notable. Herbivory for the bulk flora was 2.65 %, somewhat less than a third of most modern values. These data, when analyzed multivariately with several other floras from the early Permian of north-central Texas, will provide an assessment of herbivory in a mosaic of environments during an approximate 20 million time interval.