Niche evolution versus niche conservatism and habitat loss determine persistence and extirpation in late Neogene European Fagaceae

Abstract

An increasing body of palaeobotanical data demonstrates a series of Pliocene and Pleistocene extirpations and extinctions of plant lineages in western Eurasia, which are believed to have been determined by the climatic properties of their related East Asian and North American sister lineages. We investigated the diversity of a widespread northern hemispheric plant family, Fagaceae, during the Late Pliocene of Portugal. We found a high diversity of Fagaceae comprising extant and extinct lineages. Dispersed pollen of Castanopsis and Quercus sect. Cyclobalanopsis represent the youngest records of these Himalayan-Southeast Asian groups in western Eurasia. Likewise, fossil-species of Quercus sect. Lobatae and the North American clade of sect. Quercus are the youngest records of these modern New World groups in western Eurasia. For the extinct Trigonobalanopsis, the pollen record of Portugal is the youngest known of this genus. Climate data of modern representatives demonstrate that a deterministic model can explain only a part of the Pliocene and Pleistocene extirpations. Modern cold month mean temperatures of Castanopsis and Quercus sect. Cyclobalanopsis and their last occurrences in western Eurasia in the Pliocene fit with a deterministic model (niche conservatism). In contrast, survival or extirpation of groups with high cold tolerance appear to have been more complex. Here, niche evolution, abundance and diversity of a lineage during pre-Pleistocene times, and habitat availability/loss determined the fate of Fagaceae lineages in western Eurasia.