Molecular systematics of the Cactaceae

Area of Science:

• Botany
• Evolutionary Biology
• Phylogenetics

Background:

• The Cactaceae family is diverse, with complex evolutionary relationships that require robust phylogenetic investigation.
• Previous studies have not fully resolved the evolutionary history and taxonomic status of many cactus groups.

Purpose of the Study:

• To investigate the phylogenetic relationships within the Cactaceae family using molecular data.
• To assess the monophyly of recognized subfamilies, tribes, and genera within the Cactaceae.

Main Methods:

• Phylogenetic analyses were conducted using Bayesian, maximum-likelihood, and maximum-parsimony methods.
• Nucleotide sequences from the plastid gene region trnK-matK were utilized.
• A comprehensive sampling strategy included 666 plants representing 532 species, covering all four subfamilies, nine tribes, and 69% of genera.

Main Results:

• Strong support was found for three of the four recognized subfamilies, though inter-subfamily relationships were less defined.
• Within the Opuntioideae and Cactoideae subfamilies, only three tribes (Cacteae, Rhipsalideae, Opuntieae) were found to be monophyletic.
• Out of 42 genera sampled with multiple exemplars, only 17 were monophyletic, with most of these from the Cactoideae subfamily.

Conclusions:

• The current classification of Cactaceae requires revision, particularly regarding tribal and generic circumscriptions.
• Phylogenetic analysis highlights areas where taxonomic re-evaluation is necessary.
• Further molecular data may be required to fully resolve the evolutionary history of certain clades, such as Cylindropuntieae.