What drives diversification in a circum-Pacific plant lineage? Long-distance dispersals, niche expansions, and major climate events

PADIN A. L.; CALVIÑO, C. I.

Encuentro; III Virtual Meeting of Systematics, Biogeography and Evolution; 2022

University of North Carolina

Dispersals to new geographic areas can potentially drive organisms’ diversification.This depends on the adaptability of the species, as well as the environmental conditionsof the newly colonized areas. Therefore, “dispersifications” may be linkedto movements to niches similar to the ancestral ones as a consequence of nicheconservationism, but they may also be linked to the colonization of new niches(niche shift). The “Pacific” clade of Eryngium is a plant lineage that has a particularcircum-Pacific distribution that comprises Chile (including the Juan Fern´andezArchipelago), California, and Australia. This distribution suggests that this cladehas an extraordinary capacity for dispersal and colonization. These characteristicsmake it an interesting group to study the impact of the colonization of new areas onthe diversification of species. In this study, we investigated diversification patternsin the “Pacific” clade of Eryngium and analyzed whether these patterns are associatedwith long-distance dispersal, niche shift, or both. For that, we constructeda time-calibrated phylogeny using nuclear and chloroplast DNA sequence data thatwas used to perform ancestral area reconstructions to infer the most likely dispersalroute and to identify niche shifts. In addition, we analyzed clade diversification patternsusing two Bayesian methods: BAMM (Bayesian analysis of macroevolutionarymixtures) and BayesRate. Finally, we inferred whether the identified diversificationshifts were linked to the colonization of new areas or niches using BayesRate andstate-dependent speciation and extinction (SSE) models. The results obtained suggestthat in the “Pacific” clade occurred two shifts in diversification rates. Theseshifts occurred in the lineage composed of Californian Eryngium species (here referredto as the “Californian” lineage): one in the crown “Californian” lineage andthe other one in a sublineage of Temperate and Mediterranean species. One of theseshifts was linked to a long-distance dispersal to California, and the other one to asubsequent niche expansion to Mediterranean environments. Both shifts may alsobe related to historical climate events.