Identification and Taxonomic Status of Cordylanthus tenuis SUBSP. Pallescens (Orobanchaceae)

Abstract Cordylanthus tenuis subsp. pallescens, Pallid Bird's-beak, is a rare plant of the Mount Shasta area of northern California. Recent reports of dozens of populations outside its limited expected range, observations of plants with morphology intermediate to other subspecies of C. tenuis, and populations that seemed to include individuals of more than one subspecies, raised questions about its rarity and taxonomic validity. Examining populations in the field suggested that many reported populations were misidentified because they were based on a single trait, often foliage color. The name C. t. subsp. pallescens should be restricted to populations in which all or most plants have the combination of traits expected of this taxon, including yellow-green foliage, four to eight flowers per cluster, and short, mostly non-glandular calyx hairs. In the context of other variation recognized at the subspecies level in C. tenuis, recognizing C. t. subsp. pallescens taxonomically is a reasonable choice, despite...