Phylogenomics and biogeography of Cunoniaceae (Oxalidales) with complete generic sampling and taxonomic realignments

Abstract

Premise: Cunoniaceae are a family of shrubs and trees with 27 genera and ca. 335 species, mostly confined to tropical and wet temperate zones of the southern hemisphere. There are several known issues regarding generic limits, and the family also displays a number of intriguing long-range disjunctions.

Methods: We performed a phylogenomic study using the universal Angiosperms353 probe set for targeted sequence capture. We sampled 37 species covering all genera in the Cunoniaceae, and those in the three closely related families of the crown Oxalidales (Brunelliaceae, Cephalotaceae, and Elaeocarpaceae). We also performed analyses for molecular dating and ancestral area reconstruction.

Results: We recovered the topology (Cunoniaceae, (Cephalotaceae, (Brunelliaceae, Elaeocarpaceae))) and a well-resolved genus-level phylogeny of Cunoniaceae with strongly supported clades corresponding to all previously recognized tribes. As previously suspected, the genera Ackama and Weinmannia were recovered as paraphyletic. Australasia was inferred as the likely ancestral area for the family.

Conclusions: The current distribution of Cunoniaceae is best explained by long-distance dispersal with a few possible cases of Australasian-American vicariance events. Extinctions may have been important in determining the mostly Oceanian distribution of this family while some genera in the tribe Cunonieae and in New Caledonia have undergone recent bursts of diversification. New generic diagnoses, 80 new combinations, and one new name are provided for a recircumscribed Ackama (including Spiraeopsis), a much smaller Weinmannia (mostly New World), and a resurrected Pterophylla to accommodate Old World taxa previously in Weinmannia.

Keywords: Caldcluvia; Antarctica; Australia; Gondwana; Madagascar; relicts.

FIGURE 1

One representative of each of the four crown families of Oxalidales, clockwise from top left: Cunonia capensis L. (Cunoniaceae), drawn by Matilda Smith and reproduced from Curtis’ Bot. Mag. vol. 139, tab. 8504 (1913); Cephalotus follicularis Labill. (Cephalotaceae), drawn by Louis‐Constantin Stroobant and reproduced from L. B. van Hoote, Flore des serres et des jardins de l’Europe, vol. 3, tab. 8 (1847); Brunellia sibundoya Cuatrec. (Brunelliaceae), artist unknown. Reproduced from the Project to digitize the drawings of the Royal Botanical Expedition of the New Kingdom of Granada (1783–1816), directed by José Celestino Mutis: www.rjb.csic.es/icones/mutis. Royal Botanic Garden‐CSIC; Elaeocarpus grandiflorus Sm. (Elaeocarpaceae), drawn by Walter Hood Fitch and reproduced from Curtis’ Bot. Mag. vol. 78, tab. 4680 (1852).

FIGURE 2

Genus‐level phylogenetic tree of Cunoniaceae and its relationships with the closely related families Brunelliaceae, Cephalotaceae, and Elaeocarpaceae. Tree based on the universal Angiosperms353 probe set for targeted sequence capture. Numbers below branches represent local posterior probability values, and pie charts indicate quartet support.

FIGURE 3

Ancestral area reconstruction in Cunoniaceae and related families using the DEC+J model.

FIGURE 4

Distribution and diversity of Cunoniaceae according to the new taxonomic framework presented here. *Ceratopetalum is still extant in Australia, New Guinea, and New Britain. ^†Extinct genera (age of fossil deposit).