Taxonomy "under construction": advances in the systematics of Apocynaceae, with emphasis on the Brazilian Asclepiadoideae

Abstract

The Apocynaceae comprise approximately 5,000 species and are widely distributed. The family belongs to the Gentianales and can be easily recognized by the presence of latex and a style-head derived from the fusion of two carpels at the apex of the styles. The largest subfamily in Apocynaceae is Asclepiadoideae. Treated as the Asclepiadaceae for almost two centuries, it comprises about 3,000 species and is defined by stamens with bisporangiate anthers and pollen transferred in specialized units called pollinaria. Since the 19th century, floristic studies and taxonomic monographs have significantly contributed to the taxonomy of Brazilian Asclepiadoideae. Nevertheless, advances in understanding the internal relationships in the subfamily were not done until this millennium, with the popularization of phylogenetic studies based on molecular data and powerful computer analyses. Advances in the systematics of Apocynaceae have provided new interpretations on the morphological evolution and biogeography of the family and have led to important changes in its classification. Nevertheless, several taxonomic rearrangements are still needed and it can be said that the taxonomy of Apocynaceae is "under construction". In this article, the major taxonomic changes in the family are reviewed, with special attention given to the systematics of Neotropical groups. A cladogram of the Apocynaceae is presented, which highlights the phylogenetic position of the Brazilian genera and their diversity in number of native species. The main studies and the diversity of Asclepiadoideae in Brazil are summarized and perspectives for future research on the subfamily are presented.

Tropical Refuges with Exceptionally High Phylogenetic Diversity Reveal Contrasting Phylogenetic Structures

“…They are latescent plants with pentamerous, gamopetalous, isostemonous, bicarpelar flowers and comprise a broad range of habits (trees, shrubs, herbs, and lianas) and have pollen transferred as monads, tetrads, or in pollinia, berry-like or bifollicular fruits and seeds with or without coma. The family is widespread over the world, especially in tropical and subtropical regions, and occurs in almost any habitat, from lowland wet forests to deserts and grasslands in high altitudes [46,47]. In Brazil, such diversity is classified in three subfamilies: Apocynoideae, Asclepiadoideae, and Rauvolfioideae [47].…”

“…The family is widespread over the world, especially in tropical and subtropical regions, and occurs in almost any habitat, from lowland wet forests to deserts and grasslands in high altitudes [46,47]. In Brazil, such diversity is classified in three subfamilies: Apocynoideae, Asclepiadoideae, and Rauvolfioideae [47]. Asclepiadoideae comprises a clade that consists mainly of shrubs and lianas, and CD is an important centre of diversity of the subfamily.…”

Systematics ofPrestonia(Apocynaceae: Apocynoids: Echiteae) 80 Years After Woodson

“…Apocynaceae includes more than 366 genera and 5000 species (Rapini, 2012) and is distributed throughout the tropics, subtropics, and temperate regions. Endress and Bruyns (2000) recognized five subfamilies: Rauvolfioideae and Apocynoideae from the traditional Apocynaceae, and Periplocoideae, Secamonoideae, and Asclepiadoideae from the traditional Asclepiadaceae.…”

“…For example, Woodson said about his new species Aspidosperma pichonianum Woodson, "The species commemorates my friend M. Marcel Pichon, of the Muséum National d'Histoire Naturelle" (Woodson, 1951: 176). And, both died suddenly and tragically young in the midst of their careers: Woodson was 59 and Pichon only 33 years old, leaving a huge gap in the research of one of 10 largest families of flowering plants (Rapini, 2012).…”

Three new species of Marsdenia (Apocynaceae) from Brazil

“…It comprises a great morphological variation and is easily distinguished from the other genera of asclepiads in the New World by the erect pollinia, attached to the caudicles at the base. In Brazil, Marsdenia is represented by 34 species (Flora do Brasil 2020) and is the fourth asclepiad genus in number of species (Rapini 2012), occurring in diff erent types of vegetation, from the Amazonian and Atlantic rain forests to the Caatinga seasonally dry forests. During the preparation of the treatment of Marsdenia from Brazil, we recognized three new species of the genus, which are described below as M. paganuccii, M. paraibana and M. trisegmentata.…”