Abstract Infraspecific taxa in plants are often established solely based on morphological variation. To enhance the methodological rigour of botanical classifications, various techniques can be combined in what is known as integrative taxonomy. Among species of Oxalis from the Brazilian Cerrado, O. pyrenea var. macrochaeta, from O. section Thamnoxys, markedly differs from the typical variety O. pyrenea var. pyrenea, while it resembles O. caesariata from O. section Foliosae. In this study, we investigated the phylogenetic position and taxonomic circumscription of O. pyrenea var. macrochaeta using morphological, anatomical, molecular (sequences of the nuclear ITS and plastidial trnL-trnF and petA-psbJ), ecological, and geographical data. Our molecular phylogeny placed O. pyrenea var. macrochaeta as sister to O. caesariata within a clade with other three species of the O. section Foliosae, while the typical variety remained in O. section Thamnoxys. Indeed, we found 91 out of the 2293 DNA sites analysed were unambiguously different between the two varieties of O. pyrenea. Morphological features, such as erect, depressed-ovoid capsules, suggested that O. pyrenea var. macrochaeta is misplaced within O. section Thamnoxys. Oxalis pyrenea var. macrochaeta and O. caesariata share a range of leaf and flower bud characters, as revealed by light and scanning electron microscopy. Each taxon can be distinguished by leaflet shape, petiole length, and bract length. Based on these data, O. pyrenea var. macrochaeta is here transferred from O. section Thamnoxys to O. section Foliosae and elevated to species rank as O. macrochaeta (Lourteig) J.Vasques & Rhoden.
Vasques et al. (Tue,) studied this question.
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