ORIGINAL ARTICLE Venation patterns of Bursera species Jacq. ex L. (Burseraceae) and systematic significance A. R. Andre´s-Herna´ndez • David Espinosa • M. Eugenia Fraile-Ortega • Teresa Terrazas Received: 8 December 2011 / Accepted: 12 June 2012 / Published online: 12 July 2012 Ó Springer-Verlag 2012 Abstract The taxonomy of the genus Bursera has been traditionally supported by morphological characters such as fruit form, bark and leaves. Nonetheless, leaf architec- ture, another important source of phylogenetic information, has not been well studied in this group. For this purpose, venation patterns of 30 species of the genus Bursera in Mexico were studied. Clarified leaves allowed finding four types of venation patterns: brochidodromous and eucamp- todromous in complex B. simaruba (section Bursera); a cladodromous pattern in fragilis, microphylla and fagaro- ides groups (herein informally called group Quaxiotea (section Bursera), and semicraspedodromous in section Bullockia species. Only bipinnated species of section Bullockia showed a brochidodromous venation pattern. Furthermore, section Bullockia and complex Simaruba presented reticulate tertiary veins, whereas the group of Quaxiotea species presented a ramified pattern in the ter- tiary veins and tracheoblasts. Keywords Architecture Á Bursera Á Burseraceae Á Leaf Á Systematics Á Venation patterns Introduction The genus Bursera was divided into two groups (Engler 1883; Bullock 1936) based on the number of fruit valves, two or three. McVaugh and Rzedowski (1965) recognized these two groups as two sections, considering a larger number of characters: number of valves, well-developed cataphylls, or inconspicuous cataphylls and type of bark. In this way, Bursera section Bursera includes species with three-valvate fruits, underdeveloped cataphylls present and papering, peeling off bark, whereas Bursera section Bul- lockia includes species with fruits with two valves, well- developed cataphylls and not papering peeling off bark. Although B. mirandae belongs to section Bullockia, it presents exfoliating bark, but such exfoliation is observed as longitudinal stripes instead of peeling papiraceous like the typical bark of section Bursera. On the other hand, a few species from section Bursera (B. paradoxa and B. palaciosii) show smooth, but not exfoliating bark. Molecular phylogenetic analyses (Becerra 1996, 2003; Becerra and Venable 1999; De-Nova et al. 2012) supported the monophyly of the genus Bursera consisting of two major clades; these agree with the two sections recognized by McVaugh and Rzedowski (1965). Contrarily, Weeks et al. (2005) claimed the genus is paraphylletic; their molecular analysis supports monophyly only if the genus Commiphora is included as a sister group of section A. R. Andre´s-Herna´ndez (&) Escuela de Biologı ´a, Universidad Auto´noma de Puebla, Blvd. Valsequillo y Av. San Claudio Edificio 112A, Ciudad Universitaria Col. Jardines de San Manuel, C.P. 72570 Puebla, Mexico e-mail: arahdm@yahoo.com.mx D. Espinosa Laboratorio de Biologı ´a Comparada, UMIEZ–Facultad de Estudios Superiores ‘Zaragoza’, Universidad Nacional Auto´noma de Me´xico, Batalla de 5 de mayo s/n, Col. Eje´rcito de Oriente, Iztapalapa, 09230 Me´xico, D.F., Mexico M. E. Fraile-Ortega Departamento de Biologı ´a, Universidad Auto´noma Metropolitana-Iztapalapa, Iztapalapa, Apartado postal 55-535, 09340 Me´xico, D.F., Mexico T. Terrazas Instituto de Biologı ´a, Universidad Nacional Auto´noma de Me´xico, Apartado postal 70-233, 04510 Me´xico, D.F., Mexico 123 Plant Syst Evol (2012) 298:1723–1731 DOI 10.1007/s00606-012-0673-x