On the identity of Helianthemum mathezii and H. pomeridianum (Cistaceae)

The original description of Helianthemum mathezii regarded the species to be a therophyte. However, the detailed observation of the holotype of H. mathezii, as well as newly collected specimens from the type locality, does not support its condition of annual plant. Further study has led to the conclusion that all these plants can readily be identified as H. pomeridionum; the descriptions of H. mathezii and H. pomeridianum are equivalent except for the habit, being the former annual and the latter suffniticose. We show in this study that H. mathezii is to be considered a synonym of H. pomeridianum, and report a new locality of H. pomeridianum in Morocco. Also, we provide the first chromosome count for this species (2n = 22) which emphasizes the close relationship of H. pomeridianum to II. subgen. Plectolobum.