Late Permian flora and vegetation changes near the Permian-Triassic boundary in the Landete section of the Alcotas Formation (SE Iberian Ranges, Spain)

On the basis of rich and diverse Thuringian palynomorph samples gathered from successive levels of the Landete section (Alcotas Formation, SE Iberian Ranges), the succession of palynofloras and the vegetation dynamics have been studied in detail with the aid of quantitative analysis. The aim of this study is to elucidate the timing and scenario of the biotic crisis during the latest Permian before the actual Permian-Triassic boundary and to determine the shape of the extinction at the local level. Four successive associations have been recognized through time; the oldest, a Klausipollenites-Lueckisporites association. This was followed by a Klausipollenites-Falcisporites, an Alisporites-Lueckisporites and, finally, a re-establishment of a Klausipollenites-Lueckisporites association. It is worth noting the scarcity or lack of fungal remains which indicates that in this area the “fungal-spike” event cannot be demonstrated. The palynomorph associations are dominated by non-striate bisaccate pollen and verrucate spores in contrast with other palynofloras from Western Europe, North America and continental series in Eurasia. The study indicated the absence of transitional floras and a dieback of diversity that ranges from 35% to 67% depending on the group. Population density of the 27 taxa identified underwent a significant decline (ca. 75% average), indicating that, at least at a local level, the biotic crisis occurred prior to the P/T boundary. Futhermore, the quantitative analysis of the successive palynomorph assemblages allowed us to locally recognize the evolution of vegetation in which competitive exclusion and competitive release events took place.