Introduction

Notholaena aschenborniana is widespread in Mexico, and enters the United States in southern Arizona and western Texas (where it is rare: S1 in Arizona and S2 in Texas; NatureServe, 2008). It is restricted to rocky habitats, usually on limestone. All populations studied to date are triploid (they have three complete chromosome sets) and reproduce asexually through apogamy (the sporophytes produce unreduced spores, which develop into triploid gametophytes, which then produce a new sporophyte directly from their vegetative tissue, without sexual reproduction; Windham, 1993a; Windham and Yatskievych, 2003)