Insect herbivory from early Permian Mitchell Creek Flats of north-central Texas: Opportunism in a balanced component community

Abstract

The Mitchell Creek Flats locality (MCF) contains a flora from the early Permian (Cisuralian) of north-central Texas that has been qualitatively and quantitatively evaluated for insect herbivory. The level of herbivory is average for a middle Cisuralian flora from this region, although there is a relatively modest number of specimens. Three ecological features of this deposit are noteworthy in the context of the larger plant insect interaction trends that have been studied across the region. First is a well-balanced distribution across the MCF flora of the five functional feeding groups (FFGs) of external foliage feeding, piercing and sucking, oviposition, galling, and seed predation. These five FFGs encompass 22 discrete insect-mediated damage types (DTs) that indicate a variety of generalized and specialized herbivory. Second is the elevated incidence and diversity of seven gall DTs, indicating an arid environment. Third is the pattern of opportunistic herbivory on the cycadophyte Taeniopteris spp., the single, overwhelmingly dominant host that represents 47.5% of all foliage, 56.9% of all interactions, and 16 of the 22 DTs. This distribution of insect-mediated damage suggests a diverse community of opportunistic, generalized and specialized insect herbivores, including a guild of xeric-adapted gallers engaged in a variety of feeding styles that overwhelmingly targeted Taeniopteris spp. as a host plant. This characterization is consistent with an opportunistic herbivory strategy and supports Feeny s apparency hypothesis, in which the most conspicuous, accessible plant at a site is disproportionately and most extensively herbivorized.