Phylogeny and biogeography of Eupatorium (Asteraceae: Eupatorieae) based on nuclear ITS sequence data

Area of Science:

• Botany
• Plant Taxonomy
• Molecular Phylogenetics

Background:

• The classification of the Eupatorieae tribe relies heavily on the precise definition of the Eupatorium genus.
• Previous classifications recognized a broad Eupatorium (sensu lato), encompassing numerous species across different continents.

Purpose of the Study:

• To test the validity of a recently proposed narrow circumscription of the Eupatorium genus.
• To investigate the phylogenetic relationships within the Eupatorieae tribe using molecular data.

Main Methods:

• Phylogenetic analysis was conducted using nucleotide sequence variation from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA.
• A total of 40 samples, representing 36 species of Eupatorieae, were analyzed, including species formerly within a broad Eupatorium classification.

Main Results:

• Parsimony analysis supported a narrow definition for Eupatorium, indicating Eupatoriadelphus is a distinct genus.
• The phylogenetic tree topology suggests Eupatorium and Eupatoriadelphus share a common North American ancestor with Liatris, separate from South American Eupatoriinae.
• Evidence indicates Eupatorium dispersed from North America to Europe during the late Pliocene, followed by radiation in Asia.

Conclusions:

• The narrow circumscription of Eupatorium is supported by phylogenetic evidence.
• The study clarifies the evolutionary history and biogeography of Eupatorium and related genera within the Eupatorieae tribe.
• Understanding these relationships is crucial for accurate plant classification and evolutionary studies.