The Lopingian (late Permian) flora from the Bletterbach Gorge in the Dolomites, Northern Italy: a review

Abstract

This paper reviews the plant macro- and microfossil (palynoflora) record from the upper Permian Bletterbach succession in the Dolomites, northeastern Italy, and provides a survey of evidence of plant-insect interactions from the same strata. Plant megafossils (including in situ pollen and charcoal) come from several stratigraphic horizons within the section, and include sphenophytes, seed ferns (Sphenopteris, Germaropteris, alethopterid pinnules), putative cycadophytes (Taeniopteris), ginkgophytes (Baiera, Sphenobaiera, other probable ginkgophyte remains) and conifers (Ortiseia, Pseudovoltzia, Dolomitia, Majonica, Quadrocladus). Fossils of uncertain botanical affinities include Leptostrobus-like ovuliferous capsules, permineralised wood and charcoal. Specimens initially interpreted as lycophytes are regarded as inconclusive. Bletterbach plants displaying evidence of insect herbivory indicate an herbivory level of 1.95%, which is low in comparison to other Permian floras worldwide, but perhaps attributable to taphonomic bias. Plant-insect interactions preserved in the Bletterbach flora are dominated by external foliage feeding, followed by oviposition and galling, and exhibit rare presence of seed predation and wood boring. The maximum number of insect associations for a single Bletterbach plant was found on the conifer Pseudovoltzia liebeana, which displays four, mostly generalized associations. Based on approximately contemporary insect faunas in Europe, it is likely that the Bletterbach flora was consumed by a diverse assemblage of insect herbivores. Large monosaccate, taeniate bisaccate, monolete bisaccate and alete bisaccate pollen grains are the dominant forms in palynological samples, whereas spores are rare (pollen grains and spores indicate that the late Permian flora must have included many taxa, such as several lycophytes, which presently have not been documented from allochtonous macrofossils. In summary, the different lines of fossil evidence indicate that the Bletterbach flora ranges among the most diverse and complex of Lopingian floras from Euramerica.