Format: ORAL

Gerardo Hernndez-Vera1*, Marco Ibarra-Martnez1,2, Jos A. Vzquez-Garca1, Eduardo Ruiz-Snchez1, Marco Cerna2, Miguel A. Muiz-Castro1, Arturo Snchez-Gonzlez3 *Corresponding author. E-mail: gerardohvera@hotmail.com

1 Centro Universitario de Ciencias Biológicas y Agropecuarias (CUCBA), Instituto de Botánica, Universidad de Guadalajara. Zapopan, Jalisco, México. 2 Carrera de Biotecnología de los Recursos Naturales, Universidad Politécnica Salesiana. Quito, Ecuador. 3 Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de Hidalgo. Pachuca, Hidalgo, México.

In Mexico there are approximately 40 species of the genus Magnolia (Magnoliaceae), five of them included in the Sect. Macrophylla: M. alejandrae, M. dealbata, M. nuevoleonensis, M. rzedowskiana and M. vovidesii. Although most of these are threatened and some have sociocultural importance, its evolutionary history and the biogeographical events underlying their diversification and distribution are still unknown. In the present study, we analyse sequence data from four cpDNA regions (trnH-psbA, ORF350, trnK-matK and trnL-rpl32) of Magnolia species Sect. Macrophylla distributed in Mexico in order to: (1) infer their phylogenetic relationships, (2) assess its genetic diversity and population structure, (3) evaluate possible signatures of demographic expansion and (4) infer its temporal and geographical origin. Bayesian inference and maximum likelihood analyses corroborated the monophyly of Sect. Macrophylla. Interspecific relationships were not resolved and M. alejandrae and M. nuevoleonensis were recovered as a single monophyletic group. The highest genetic diversity was found in populations of M. dealbata, M. alejandrae and M. nuevoleonensis. Bayesian Skyline Plots and mismatch distribution analyses indicate that, overall, the studied populations are in a process of demographic expansion, particularly, the populations of M. alejandrae and M. nuevoleonensis. Analyses of genetic and phylogeographic structure indicate that geography has played a fundamental role in shaping the genetic structure of Magnolia Sect. Macrophylla in Mexico.Based on molecular clock analyses, initial diversification of Sect. Macrophylla is estimated to have occurred ca. 16.1 Ma, whose ancestral area probably included the Sierra Madre Oriental, Sierra Madre del Sur and Trans-Mexican Volcanic Belt. Given that the origin of the Section broadly coincides with the climatic changes of the middle Miocene and with the emergence of the Trans-Mexican Volcanic Belt,these events could have played a fundamental role in the diversification of Magnolia Sect. Macrophylla in Mexico.