Combined Phylogenetic Analysis in Echinocereus (Cactaceae), the Use of Morphology, and Taxonomic Implications

Abstract

Phylogenies based on molecular characters has dominated publications rather than those based on morphological characters. Some authors have defended the use of morphology in phylogenetic reconstruction. In Cactaceae few studies have been made combining molecular and morphological characters. A good example about the use of morphology in phylogenetic analysis has been addressed in Echinocereus. Echinocereus is a morphologically diverse genus including 67 species that have been grouped into eight taxonomic sections based on morphological traits. Previous molecular phylogenetic analyses did not show entirely the relationships in Echinocereus species, and did not provide useful characters to recognize clades. Therefore, we performed a combined phylogenetic analysis with a set of 44 morphological characters and six chloroplast DNA sequences. Topologies from parsimony and Bayesian analyses resulted mostly congruent. However, relationships of E. poselgeri did not agree between analyses. A second bayesian analysis using long-branch extraction test resulted in a topology with a morphologically congruent position of E. poselgeri. Parsimony and Bayesian analyses corroborated the monophyly of Echinocereus, which included eight monophyletic groups. The clades did not recover the recent infrageneric classification. As a consequence, a new sectional classification for Echinocereus is proposed based on the eight recovered clades, which are supported by a combination of morphological and molecular characters. An identification key for sections in the genus is included.