Apocynaceae is one of the ten largest families of flowering plants and a key component of biodiversity hotspots in Southeast Asia, tropical America, and southern Africa. However, a limited fossil record and insufficient sampling, especially of Asian species, have hindered a clear understanding of its evolutionary timeline and diversification patterns.
In a study published in Journal of Systematics & Evolution, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Kunming Institute of Botany (KIB) of the Chinese Academy of Sciences reconstructed the phylogenetic tree of the Apocynaceae family. They sought to resolve the long-standing uncertainties in the classification and evolutionary history of this ecologically and economically important plant family.
The researchers built a high-resolution phylogeny using plastid coding sequences and performed molecular dating analyses with four key Apocynaceae macrofossils as calibration points.
The plastome-based phylogeny confirmed three subfamilies as monophyletic, consistent with modern classification systems. However, three tribes and five genera were identified as non-monophyletic, indicating a need for future taxonomic revisions.
Molecular dating analysis, incorporating recent fossil discoveries, estimated that Apocynaceae originated approximately 87.57 million years ago in the paleotropics, a region encompassing modern-day tropical Asia, Africa, and South America.
Furthermore, the researchers investigated the association between species diversification and functional traits in Apocynaceae family. They found that species with pollinia (cohesive pollen packets) showed a higher speciation rate than those without. Dry-fruited species diversified faster than those with fleshy fruits. Among different growth forms, herbs exhibited the highest speciation rate, followed by climbers, and self-supporting trees and shrubs had the lowest.
"By constructing a more complete phylogenetic tree of Apocynaceae, we have not only clarified the family's complex relationships and ancient origin but also provided evidence that the evolution of pollinia and dry fruits were key key factors driving its species richness, especially in the Asian tropics and subtropics," said YU Wenbin of XTBG.
Phylogeny of Apocynaceae based on 66 shared protein-coding genes in the plastome. (Image by YAO Xin)
First published: 12 October 2025
