Sampling biases and Paleozoic sporomorphs diversity dynamics in Western Gondwana strata

Abstract

A dataset consisting of presence-absence data of 137 pollen and spore genera was elaborated with published sources from Pennsylvanian and Permian Atlantic (Paraná, Parnaíba, Amazonas, and Claromecó) and Pacific (Paganzo, Tarija, and Madre de Dios) basins of South America. The richness and origination, extinction, and sampling rates of sporomorphs were analyzed in order to address the effect of sampling biases over diversity estimations. Richness and sampling were estimated using the recently developed True Richness estimated using a Poisson Sampling (TRiPS) model. Origination, extinction, and sampling rates were estimated with Inverse Survivorship Models. The TRiPS analysis showed changes in richness during the studied interval. The highest richness was observed for the Cisuralian, and the lowest richness was recovered for the Pennsylvanian and Guadalupian. The best supported Inverse Survivorship Model revealed that the highest origination values occurred between the Gzhelian and Asselian, whereas the highest observed extinction rate occurred between the Kungurian and the Roadian. In particular, pollen grains showed higher net diversification than spores, while spores showed higher turnover than pollen grains. Also, an alternation in richness dominance was observed at the beginning of the Permian, with pollen grains showing higher richness after the Artinskian. Changes in total sporomorphs diversity, as well as differences between spores and pollen grains, may be related to changing climatic conditions in Western Gondwana during the late Paleozoic (from icehouse to greenhouse conditions) that could impact differently over plant communities. Although the fossil palynomorph record has been widely used as a biostratigraphic tool, our results highlight its importance and usefulness for the study of plant communities and their evolution in the past.