Unravelling the Mexican Magnolia dealbata (Magnoliaceae) species complex

Abstract

In the last two decades, approximately 80 new Magnolia species have been described from the Neotropics; thus this region now hosts almost half of the world’s known Magnolia diversity. Many of these likely are not segregate taxa but rather separate populations or groups of populations of the previously broadly circumscribed, widespread species. Such is possibly the case of the Magnolia dealbata species complex (belonging to Magnolia sect. Macrophylla), distributed throughout the Sierra Madre Oriental mountain range in Eastern Mexico. This species complex has been divided into six morphospecies based on morphological criteria only. However, recent microsatellite markers have suggested that these may be a single entity. Considering geographical data and the isolation of populations, we hypothesised that the different morphospecies could form two entities, corresponding to the north and centre of the Sierra Madre Oriental. This hypothesis was tested by morphological observations, chloroplast comparisons and phylogenetic analyses of plastomes, angiosperm DNA plastid barcodes and Magnolia-specific plastid DNA barcodes from hypervariable regions. Phylogenetic results from plastomes and angiosperm DNA plastid barcodes refute the multispecies hypothesis and show that the six morphospecies of this complex inhabiting the S