Complex reticulation in backbone subfamily relationships in Leguminosae.

Area of Science:

• Plant evolutionary biology
• Genomics
• Phylogenetics

Background:

• The legume phylogenetic history, especially during the diversification era, remains challenging due to conflicting evidence regarding backbone topology and whole genome duplications (WGDs).
• Resolving legume evolutionary pathways is crucial for understanding the diversification of this economically and ecologically important plant family.

Purpose of the Study:

• To clarify the phylogenetic relationships within the legume family, focusing on the backbone topology.
• To identify the number and timing of whole genome duplications (WGDs) across legume subfamilies.
• To investigate evidence of reticulate evolution, including ancient hybridization events.

Main Methods:

• Transcriptomic data from 473 gene families across 76 legume species representing all six subfamilies were analyzed.
• Phylogenetic analyses were conducted using superalignments and multi-tree coalescent-based methods.
• Concordance factor analysis and maximum pseudo-likelihood inference (PhyloNet) were employed to detect reticulation events.

Main Results:

• A robust legume backbone phylogeny was established, supported by multiple independent analyses.
• Evidence for independent whole genome duplications (WGDs) was found in each of the six legume subfamilies.
• Three subfamilies (Cercidoideae, Dialioideae, and Caesalpinioideae) showed patterns indicative of ancient allopolyploid hybridization.

Conclusions:

• The study resolves key aspects of legume phylogeny and confirms recurrent WGDs as a significant evolutionary force in the family.
• Reticulate evolution, including complex hybridization patterns, played a crucial role in the diversification of specific legume subfamilies.
• The findings provide a new framework for understanding legume evolutionary history and the impact of genome duplication and hybridization.