Chromosome numbers in Chihuahuan Desert Cactaceae. III. Trans‐Pecos Texas

Abstract

Chromosome numbers are reported for 112 collections of Cactaceae, including 102 collections of Opuntia. Reports are presented for 33 species in five genera and a total of 36 taxa. Two specimens were sterile. Emphasis was given to the documentation of intraspecific ploidy-level consistencies and differences, because of the current poor state of knowledge about the populational integrity of chromosome numbers in Trans-Pecos cacti and because information about ploidy levels is taxonomically significant particularly in certain genera of Cactaceae. First reports are presented for six taxa, including Opuntia aureispina (2n = 11 II), O. tortispina (2n = 33 II), and Ancistrocactus tobuschii (2n = 11 II). Chromosome numbers are now known for all but one or two of the ∼104 currently recognized cactus taxa in Trans-Pecos Texas.