Evolutionary relationships within the lamioid tribe Synandreae (Lamiaceae) based on multiple low-copy nuclear loci

Area of Science:

• Botany and Plant Systematics
• Molecular Phylogenetics
• Evolutionary Biology

Background:

• The Lamiaceae family's subfamily Lamioideae includes ten tribes, with Synandreae and Stachydeae being the only ones with New World members.
• Previous phylogenetic studies of Synandreae relied on plastid and nuclear ribosomal DNA, necessitating further investigation with additional markers.

Purpose of the Study:

• To re-evaluate the phylogenetic relationships within the plant tribe Synandreae.
• To investigate the evolutionary history and colonization patterns of Synandreae in the New World.
• To explore factors influencing the distribution and colonization success of Synandreae genera.

Main Methods:

• Incorporation of data from four low-copy nuclear loci: PHOT1, PHOT2, COR, and PPR.
• Phylogenetic analyses using combined chloroplast and nuclear DNA markers.
• Comparative analysis of colonization and migration patterns with related tribes.

Main Results:

• Confirmed the monophyly of tribe Synandreae and established sister relationships between Brazoria/Warnockia and Physostegia.
• Observed incongruence in the placement of Macbridea and Synandra, indicating unresolved relationships.
• Resolved a single colonization event for Synandreae in the New World during the Late Miocene/Tortonian, contrasting with Stachydeae's multiple colonization events.

Conclusions:

• The study reaffirms Synandreae's monophyly but highlights unresolved relationships within the tribe.
• Evidence points to a single, ancient colonization of the New World by Synandreae.
• Edaphic factors and polyploidy likely influenced the distribution and adaptive radiation of Synandreae, particularly the genus Physostegia.