Arthropod and fungal herbivory at the dawn of angiosperm diversification: The Rose Creek plant assemblage of Nebraska, U.S.A.

Abstract

Quantitative studies rarely address arthropod herbivory on early angiosperms. We assessed arthropod herbivory from highly sampled, abundant, diverse, and well preserved Early Cretaceous (late Albian) Rose Creek plant assemblage of southeastern Nebraska, USA. We examined 2084 specimens representing 49 species/morphotypes of which 21 are angiosperms of Austrobaileyales, Chloranthales, Laurales, Magnoliales, and Eurosidae. We used six metrics to assess arthropod herbivory. Richness metrics were damage type (DT) richness, component community structure, and DT host-plant specialization level; intensity metrics were DT frequency, herbivorized surface area, and feeding event occurrences. Eleven functional feeding groups (FFGs) and 114 DTs were present; 87.3% were angiosperm interactions; and 3.14% of surface area was herbivorized. NMDS ordinations show herbivore component communities are distinctive on particular plant lineages, based on herbivorized surface area. Four mostly quantitative measures indicate that piercing-and-sucking and pathogens were the most highly ranked FFGs; mining, hole feeding, galling, and margin feeding were middle ranked; oviposition, surface feeding, and skeletonization were low ranked; and seed predation and borings were inconsequential. Component community structure of the three most intensively herbivorized hosts, a chloranthalean and two lauralean species, parallel that of a modern fern and four angiosperm species. DT specificities on plant hosts across the assemblage are generalists (64.10%), intermediates (17.95%), and specialists (17.95%). Mining and pathogens lacked whereas gallers were enriched in specialists. Most plant hosts display substantial herbivory richness and intensity, buttressed by distinct herbivore component communities of highly herbivorized species. The Rose Creek herbivory index approximates 0.72% of modern warm-temperate and 0.44% of tropical forests.