Cornales (Dogwood)

Abstract

Cornales, a relatively small, but morphologically diverse, order of flowering plants, consist of trees, shrubs, lianas, rhizomatous herbs and rarely aquatic herbs. The order represents an early divergent lineage in the Asterid clade and has a cosmopolitan distribution, occurring from cold temperate regions to the tropics, rarely in subarctic zones. Four to ten families, depending on how Cornaceae are circumscribed, comprise the order. Recent molecular phylogenetic studies supported a classification of 10 families that diverged during the late Cretaceous and early Tertiary. Many of the 10 families are small and with restricted, modern distributions, but have fossils occurring in areas outside their present distribution. Common representatives include the dogwoods (e.g., Cornus florida (flowering dogwood), Cornus kousa (kousa dogwood), Cornus canadensis (bunchberry), Cornus mas (European cornelian cherry), Cornus sericea (red‐osier dogwood), Nyssa sylvatica (black gum), Davidia involucrata (dove tree), Hydrangea macrophylla (Hydrangea), Deutzia spp. (deutzias) and Philadelphus spp. (mock oranges)), which are widely cultivated as ornamentals. Several species are medicinally important, including Cornus officinalis (cornelian cherry), Camptotheca acuminata (Happy tree), Curtisia dentata (assegai tree) and Alangium salvifolium (sage‐leaved alangium). Key Concepts: Phylogenetic studies are essential to understanding and conserving biodiversity. Phylogeny depicts evolutionary relationships of species and speciation events, providing the basis for classification and understanding macro‐ and microevolution. Including more species and molecular data in phylogenetic studies can help to clarify relationships that were obscured by morphology and difficult to resolve due to rapid radiation. The age of a lineage on a phylogeny can be estimated using molecular data with a relaxed molecular clock calibrated from fossils (referred to as divergence time estimation). Time estimation for a given lineage is substantially affected by molecular data, taxon sampling and the phylogenetic nodes calibrated by the fossils. Dated phylogeny provides the temporal framework to understand diversification patterns and speciation events in absolute historical time that can be linked to specific events in the Earth's history. Fossils are important records of past distributions of a lineage, providing data on extinction, speciation, and morphological evolution through time.