Idiosyncrasies of Cistanthe ipniana Hershk. (C. sect. Rosulatae; Montiaceae)

Mark Alan Hershkovitz

Cistanthe ipniana Hershk. [C. sect. Rosulatae (Reiche) Hershk.; Montiaceae] was described briefly based on collections from Huasco Province, Atacama Region, Chile. The species is distinctive in having flower morphology essentially identical to that of C. litoralis and C. longiscapa, to which it is very closely related genetically, but a distinctive vegetative form identical to that of C. thyrsoidea (Reiche) Peralta & D.I.Ford of the more distantly related C. sect. Thyrsoideae Hershk. Although sympatric, there is no evidence for potential or historical gene flow between these species. Additional collections and observations of collected plants cultivated ex situ permits a more detailed description of the species, taking into account variation, fruit and seed characters, and senescence behavior. The floral bracts in C. ipniana are described as being not only unique to this among all Cistanthe species, but remarkably similar to the floral bracts of some more remotely related Philippiamra Kuntze and Calyptridium Nutt. species (Cistantheae; Calyptridinae). But the latter taxa have much smaller flowers. The similarities in vegetative habit and distinctive floral bracts of C. ipniana to remotely related Cistantheae is attributed to convergent evolution, and the difference between these traits in C. ipniana and its closest relatives is attributed not to some sort of “adaptive” evolution that might be presumed by mainstream evolutionary biology, but to evolutionary “natural drift” and its corollary, the Principle of Evolutionary Idiosyncraticity.