Phylogenetics and reticulate evolution in Pistacia (Anacardiaceae)

Area of Science:

• Botany
• Molecular Systematics
• Evolutionary Biology

Background:

• The classification and evolutionary history of Pistacia species (Anacardiaceae), known for their economic importance, remain debated.
• Previous studies have not fully resolved intrageneric relationships due to conflicting data.

Purpose of the Study:

• To clarify the phylogenetic position and intrageneric relationships within the genus Pistacia.
• To assess the congruence of different molecular markers in resolving Pistacia phylogeny.

Main Methods:

• Phylogenetic analysis of five DNA data sets: nuclear ribosomal ITS, NIA-i3, and plastid markers (ndhF, trnL-F, trnC-trnD).
• Analysis using Bayesian and parsimony methods on individual and combined data sets.
• Comparison of phylogenetic trees derived from nuclear and plastid DNA.

Main Results:

• Significant discordance was observed between nuclear ribosomal ITS, NIA-i3, and combined plastid DNA data sets.
• The nuclear ribosomal ITS data provided the most robust resolution of Pistacia species relationships.
• Pistacia was confirmed as monophyletic, but previous classifications were largely inconsistent with molecular findings.
• Evidence for reticulate evolution and hybridization was found, with Pistacia saportae identified as a hybrid.

Conclusions:

• Nuclear ribosomal ITS sequences are recommended for resolving Pistacia phylogeny, with lineage sorting potentially explaining conflicts with NIA-i3 data.
• The study challenges existing classifications and highlights the complexity of Pistacia evolution, including hybridization events.