title: Rapoport's rule: a comparative analysis between South and North American columnar cacti.
authors.affiliation: Centro de Ecología, Universidad Nacional Autónoma de México, Apartado Postal 70-275, 04510-Mexico, D.F., Mexico.
authors.forename: C
authors.initials: C
authors.lastname: Mourelle
authors.forename: E
authors.initials: E
authors.lastname: Ezcurra