Biogeography of the monocotyledon astelioid clade (Asparagales): A history of long-distance dispersal and diversification with emerging habitats

Abstract

The astelioid families (Asteliaceae, Blandfordiaceae, Boryaceae, Hypoxidaceae, and Lanariaceae) have centers of diversity in Australasia and temperate Africa, with secondary centers of diversity in Afromontane Africa, Asia, and Pacific Islands. The global distribution of these families makes this an excellent lineage to test if current distribution patterns are the result of vicariance or long-distance dispersal and to evaluate the roles of tertiary climatic and geological drivers in lineage diversification. Sequence data were generated from five chloroplast regions (petL-psbE, rbcL, rps16-trnK, trnL-trnLF, trnS-trnSG) for 104 ingroup species sampled across global diversity. The astelioid phylogeny was inferred using maximum parsimony, maximum likelihood, and Bayesian inference methods. Divergence dates were estimated with a relaxed clock applied in BEAST. Ancestral ranges were reconstructed in 'BioGeoBEARS' applying the corrected Akaike information criterion to test for the best-fit biogeographic model. Diversification rates were estimated in Bayesian Analysis of Macroevolutionary Mixtures [BAMM]. Astelioid relationships were inferred as Boryaceae(Blandfordiaceae(Asteliaceae(Hypoxidaceae plus Lanariaceae))). The crown astelioid node was dated to the Late Cretaceous (75.2 million years; 95% highest posterior densities interval 61.0-90.0 million years) with an inferred Eastern Gondwanan origin. However, astelioid speciation events have not been shaped by Gondwanan vicariance. Rather long-distance dispersal since the Eocene is inferred to account for current distributions. Crown Asteliaceae and Boryaceae have Australian ancestral ranges and diversified since the Eocene. In Hypoxidaceae, Empodium, Hypoxis, and Pauridia have African ancestral ranges; Curculigo and Molineria have an Asian ancestral range and have diversified since the mid-Miocene. Diversification of Pauridia and the Curculigo clade has occurred steadily, while diversification of Astelia and Hypoxis was punctuated over time. Diversification of those genera coincides temporally with the expansion of the habitat types occupied by extant taxa, e.g., grassland habitat in Africa during the late Miocene and alpine habitat in New Zealand during the Pliocene.