A new ancestral diploid species of echinocereus endemic to southwestern utah and northern arizona

Echinocereus relictus B. Wellard is a newly described diploid (2n=22) species that is the presumed ancestor of the tetraploid (2n=44) E. engelmaniii. Echinocereus engelmannii subsp. engelmannii represents both diploid and tetraploid cytotypes. Diploid individuals are endemic to a narrow section of southwestern Utah and northwestern Arizona and have noted similarity with the formerly endangered E. engelmannii var. purpureus. The distributional range of the diploid and tetraploid plants was mapped using cytogeography. Morphological data collected from ten populations (5 diploid, 5 tetraploid) were correlated with ploidy and analyzed using discriminant function analysis. The cytogeographic and discriminant function analysis results support the distinction of the diploid as new species which is a likely ancestor to the widely distributed tetraploid Echinocereus engelmannii subsp. engelmannii. E. relictus (syn. E. engelmannii var. purpureus) occurs in a rapidly expanding urban area, and its conservation status needs to be evaluated.