Poster

         Pteridology

A Western viewpoint on the extreme Palearctic separation of Woodwardioideae ferns.

Presenting Author
Sonia Molino
Description
The Paleotropical floristic element of the Western Palearctic has been greatly diminished due to geological and climatic fluctuations during the Cenozoic. Among the representatives of this element stand out ferns, particularly the subfamily Woodwardioideae. This subfamily shows a great disjunction on both sides of the Palearctic, with Woodwardia unigemmata Makino (Nakai) in East Asia and Woodwardia radicans (L.) Sm. (Blechnaceae) surviving in climate refugees in Western Europe and the Macaronesian archipelagos. This distribution makes Woodwardioideae an ideal candidate for testing the evolution of the Paleotropical Geoflora in the Palearctic. To investigate the origin of this disjunction, we reconstructed the phylogenetic relationships and divergence times of the subfamily Woodwardioideae using four plastid DNA regions. Additionally, we sampled W. radicans throughout its distribution range and performed phylogenomic analyses based on genotyping by sequencing (GBS). Our results show a divergence between W. radicans and W. unigemmata in the Pliocene, 3.7 (1.35-7.18) Mya. Subsequently, in the western part of the distribution, W. radicans took refuge in Macaronesian archipelagos, from where it appears to have recolonized the continental enclaves in the last 0.8 Mya. The study provides new insights into the evolutionary history of Woodwardioid ferns, challenging the traditional view that certain Paleotropical elements are relicts from the Miocene. Furthermore, our findings highlight the pivotal role played by archipelagos as biodiversity refuges at the extremes of disjunct ranges, and as sources of diversity for recolonization of continents. This holds significant implications for conservation endeavors, particularly for populations of island species threatened by climate change and habitat loss.