Floral Assemblages and Patterns of Insect Herbivory during the Permian to Triassic of Northeastern Italy

Abstract

To discern the effect of the end-Permian (P-Tr) ecological crisis on land, interactions between plants and their insect herbivores were examined for four time intervals containing ten major floras from the Dolomites of northeastern Italy during a Permian–Triassic interval. These floras are: (i) the Kungurian Tregiovo Flora; (ii) the Wuchiapingian Bletterbach Flora; (iii) three Anisian floras; and (iv) five Ladinian floras. Derived plant–insect interactional data is based on 4242 plant specimens (1995 Permian, 2247 Triassic) allocated to 86 fossil taxa (32 Permian, 56 Triassic), representing lycophytes, sphenophytes, pteridophytes, pteridosperms, ginkgophytes, cycadophytes and coniferophytes from 37 million-year interval (23 m.yr. Permian, 14 m.yr. Triassic). Major Kungurian herbivorized plants were unaffiliated taxa and pteridosperms; later during the Wuchiapingian cycadophytes were predominantly consumed. For the Anisian, pteridosperms and cycadophytes were preferentially consumed, and subordinately pteridophytes, lycophytes and conifers. Ladinian herbivores overwhelming targeted pteridosperms and subordinately cycadophytes and conifers. Throughout the interval the percentage of insect-damaged leaves in bulk floras, as a proportion of total leaves examined, varied from 3.6% for the Kungurian (N = 464 leaves), 1.95% for the Wuchiapingian (N = 1531), 11.65% for the pooled Anisian (N = 1324), to 10.72% for the pooled Ladinian (N = 923), documenting an overall herbivory rise. The percentage of generalized consumption, equivalent to external foliage feeding, consistently exceeded the level of specialized consumption from internal feeding. Generalized damage ranged from 73.6% (Kungurian) of all feeding damage, to 79% (Wuchiapingian), 65.5% (pooled Anisian) and 73.2% (pooled Ladinian). Generalized-to-specialized ratios show minimal change through the interval, although herbivore component community structure (herbivore species feeding on a single plant-host species) increasingly was partitioned from Wuchiapingian to Ladinian. The Paleozoic plant with the richest herbivore component community, the coniferophyte Pseudovoltzia liebeana, harbored four damage types (DTs), whereas its Triassic parallel, the pteridosperm Scytophyllum bergeri housed 11 DTs, almost four times that of P. liebeana. Although generalized DTs of P. liebeana were similar to S. bergeri, there was expansion of Triassic specialized feeding types, including leaf mining. Permian–Triassic generalized herbivory remained relatively constant, but specialized herbivores more finely partitioned plant-host tissues via new feeding modes, especially in the Anisian. Insect-damaged leaf percentages for Dolomites Kungurian and Wuchiapingian floras were similar to those of lower Permian, north-central Texas, but only one-third that of southeastern Brazil. Global herbivore patterns for Early Triassic plant–insect interactions remain unknown.

Late Permian (Lopingian) Terrestrial Ecosystems: A Global Comparison With New Data From the Low Latitude Bletterbach Biota

“…Perhaps the most direct research on Permian plant-animal interactions comes from studies of the trophic relationships between herbivorous terrestrial arthropods and vascular plants. These studies span the early Permian of Texas (Schachat et al, 2014; the early and middle Permian of southeastern Brazil (Adami-Rodrigues et al, 2004a, 2004b; the late Permian to late Triassic of the Karoo Basin of South Africa (Prevec et al, 2009(Prevec et al, , 2010Labandeira et al, 2017) and the early Permian to Middle Triassic of the Dolomites, northeastern Italy (Wappler et al, 2015;Labandeira et al, 2016). The patterns emerging from this research provide an important baseline for understanding changes in plant-animal interactions across the Permo-Triassic transition.…”

Ecology and Evolution of Gall-Inducing Arthropods: The Pattern From the Terrestrial Fossil Record

“…The only other early Permian locality with DT data is the LeFaine flora of the Tregiovo Fm of northeastern Italy (Labandeira et al, 2016a;Bernardi et al, 2017), in which the broadleaved conifer Quadrocladus was minimally galled. This flora in eastern Euramerica displays few plant-insect interactions and lies in stark contrast the more heavily galled floras from Texas in western Euramerica.…”

The natural history of oviposition on a ginkgophyte fruit from the Middle Jurassic of northeastern China

“…Oviposition. We note that oviposition has been treated as a functional feeding group in the fossil plant–insect associational literature (e.g., Labandeira et al ., , ), a practice that is attributable to the feeding‐like damage that it causes and a persistent fossil record analogous to other functional feeding groups (Ding et al ., ).…”