Plastid phylogenomics illuminates backbone relationships, divergence times and character evolution in Caryophyllaceae.

backgroundThe family Caryophyllaceae has traditionally been divided into three subfamilies (i.e. Alsinoideae, Caryophylloideae, Paronychioideae). However, the monophyly of each subfamily has been challenged, while boundaries, phylogenetic relationships, and divergence times of particular tribes and genera still remain to be inferred.

resultsOur plastome-derived phylogenies strongly support the monophyly of Caryophyllaceae with a dated crown age of ca. 56.4 Mya (Late Paleocene). While the three traditional subfamilies proved non-monophyletic, relationships among 11 previously recognized tribes were fully resolved. However, in contrast to earlier studies, we identified tribe Eremogoneae (represented by Eremogone griffithii) as sister to tribe Sileneae, and the monotypic genus Thylacospermum (T. caespitosum) as a member of Caryophylleae. BBM inferred that the ancestral states of Caryophyllaceae include: presence of stipules; free sepals; absence of petals; five stamens; and utricle or achene fruit.

conclusionsThis is the first comprehensive phylogenomic analysis of Caryophyllaceae that strongly supports the subdivision of the family into 11 tribes. While the initial divergence of this family (ca. 56.4 Mya) may be associated with the Paleocene-Eocene Thermal Maximum (PETM; ca. 55.5 Mya), tribes only started to diversify either during the Late Eocene (ca. 35.1-31.6 Mya) or, in particular, during the Late Oligocene to Mid-Miocene (25.5-15.5 Mya). This temporal coincidence suggests that the origin and diversification of many, if not the majority of Caryophyllaceae genera may have been shaped by global cooling and/or aridification events since the Mid-to-Late Miocene as well as the Pliocene-Pleistocene.