Oral Paper

         Systematics

Molecular phylogeny of the Eryngium (Apiaceae) “Pacific” clade

Presenting Author
Ariana Padin
Description
The “Pacific” clade of Eryngium (Apiaceae, Saniculoideae) comprises 39 species from the Pacific Ocean coasts of Chile, Australia, and western USA, and two species from east-central South America. Previous studies on Eryngium suggested reticulated events and trans-Pacific dispersals involved in the diversification of the clade. However, these hypotheses need to be tested with more thorough sampling and further analyses. In this study, we use chloroplast and nuclear DNA sequences and an exhaustive sampling of the “Pacific” clade to identify factors that potentially drove its diversification. In particular, we want to find out if hybridizations occurred within this clade, and also if expansion to different areas correspond to single trans-Pacific dispersals. Morphological shifts within the clade are also analyzed as potential drivers for diversification/dispersification. To recognize these events, we inferred a dated phylogeny of the “Pacific” clade that was used to: identify morphological shifts, analyze whether lineages within the clade are geographically structured, and detect incongruence between plastid and nuclear-derived trees. The study corroborates that the clade is geographically structured across distant Pacific coasts, suggesting that unique trans-Pacific dispersals resulted in the diversification of each sublineage. Besides, a reticulation event was estimated at the base of a sublineage that colonized and diversified in an extreme arid environment as the Atacama region. This reticulation event is also associated with morphological shifts to tap-rooted, monocarpic plants at the beginning of the Pliocene (ca. 5 Ma) that are related to arid environments. Therefore, a combination of events such as the emergence of morphological novelties, the colonization of distant geographical areas, and hybridizations are estimated as likely factors involved in the diversification of the "Pacific" clade.