Plastome based phylogenetics and younger crown node age in Pelargonium.

Area of Science:

• Botany
• Genomics
• Phylogenetics

Background:

• The genus Pelargonium (Geraniaceae) is a major South African plant lineage.
• It exhibits significant morphological diversity, varied chromosome numbers, and extensive organelle genome rearrangements.
• Pelargonium represents the 7th largest clade within the Cape Floristic Region.

Purpose of the Study:

• To reconstruct a comprehensive phylogenetic tree for the genus Pelargonium.
• To investigate the evolutionary timing and major radiation events within the genus.
• To analyze the genomic diversity and relationships among Pelargonium species.

Main Methods:

• Phylogenetic analysis using 74 plastome exons and nuclear ribosomal DNA (rDNA) ITS regions from 120 Pelargonium species.
• Construction of a phylogenetic tree incorporating nucleotide, amino acid, and ITS sequence alignments.
• Dating analysis employing calibration evidence from multiple sources to estimate divergence times.

Main Results:

• Phylogenetic analyses confirmed the established five main subgeneric clades of Pelargonium, though one clade (A1) showed low bootstrap support.
• The estimated crown age for Pelargonium was determined to be 9.7 million years.
• This age is younger than prior estimates but aligns with recent findings for other Cape Floristic lineages.

Conclusions:

• The study provides a robust phylogenetic framework for the genus Pelargonium.
• The estimated crown age suggests a relatively recent and rapid diversification of Pelargonium.
• Findings contribute to understanding the evolutionary history of plant lineages in the Cape Floristic Region and Succulent Karoo biome.