Molecular phylogeny and dating of Asteliaceae (Asparagales): Astelia s.l. evolution provides insight into the Oligocene history of New Zealand

Abstract

Asteliaceae (4 genera, 36 species) are found on both continents and island archipelagos in the southern hemisphere and across the Pacific. The circumscription of Asteliaceae and intrageneric relationships are poorly understood. We generated a phylogeny including all genera and 99% of the species using DNA sequence data from chloroplast (trnL, psbA-trnH, rps16, and petL-psbE) and nuclear (NIA-i3) regions. Relaxed clock methods were applied to infer the age of the family and the timing of cladogenic events. Generic delimitations change as a result of this study. Collospermum is nested within Astelia and is recognized here only at the subgeneric level. Further, Astelia subgenera Astelia, Asteliopsis, and Tricella are paraphyletic and to achieve monophyly their recircumscriptions are proposed. Despite the presence of Asteliaceae taxa on multiple Gondwanan landmasses and proposed Cretaceous origins for the family, radiation of genera was during the Tertiary. The largest and oldest genus, Astelia s.l. (including Collospermum), radiated around the Eocene/Oligocene boundary (ca. 34.2 million years ago (Ma)). Astelia s.l. subgenera diverged from the Oligocene/Miocene boundary onwards (<24.0 Ma). These dates suggest that current distributions are most likely to be the result of long-distance dispersal. Alpine taxa in New Zealand and Australia radiated during the Late Miocene/Pliocene. These results are congruent with Astelia micro- and macro-fossil data and suggest that Astelia s.l. either persisted in New Zealand during the proposed Oligocene marine transgression or dispersed from Australia after the subsequent expansion of terrestrial habitat.