Mark Alan Hershkovitz

Cistanthe philhershkovitziana Hershk. was described from the north-central Chilean coast in 2018. Based on the apparent absence of plants during drought years, it was described as the only species of C. sect. Cistanthe with a putatively annual life history (~therophytic life form). The species occurs primarily in coastal habitats, but also in some seasonally moist sites up to perhaps 50 km inland. Its range spans ca. 600 km of latitude, ca. 28–33S. Detailed reinvestigation especially of the southernmost populations in Chile’s perennially humid southern Central Littoral Zone (CLZ) demonstrates that this species is a facultative annual, viz. a perennial that flowers from seed during its initial seasonal cycle, in this case ca. 10–12 weeks after germination. Here, I suggest that most species of C. sect. Cistanthe have this facultative capacity. However, unlike the other species, C. philhershkovitziana is cryptophytic, which contributes to its appearance as annual. Moreover, the plants are comparatively short-lived. Plants of C. philhershkovitziana grow in seasonally dry sites, and seeds germinate in response to precipitation, whether the typical Mediterranean climate winter rains or irregular rains that arrive during other seasons. Phenology thus is mediated primarily by hydration and less so by temperature and light, and phenology varies both interannually and locally. Southern CLZ populations mostly comprise primarily first and second-year individuals, and caudices rarely survive more than three years. High mortality here owes to a variety of site-specific circumstances. In northern Chile, high mortality probably owes the inability of the young caudices to withstand multi-year droughts. The largely unreported incidence of the facultative annual condition among Montiaceae and angiosperms in general is likely to be consequential to interpretation of life history/form and phenological macroevolution and ecology.