Purple Cushion

Purple cushion evolved in cold, windy habitats in southern Darwin. A simple mutation has allowed more extreme branching, giving the organism a compact, cushion-like appearance. This allows better protection against wind, desiccation, and radiation. While the shallow, nodule-bearing roots of its ancestor are still present, more of the underground biomass is dedicated to a taproot for anchoring and access to water in drought conditions. The reduced nitrogen access and harsh habitat cause this organism to grow very slowly, reaching full size after many decades or centuries. Reproduction is nearly unchanged, but reproductive appendages are less conspicuous and grow close to branch tips rather than the basal stems.

While nitrogen fixation in the root nodules is reduced compared to its ancestor, the immediate vicinity of the organism is still enriched over many years and the compact branch structure provides ideal sites for other flora to grow around, underneath, and within the branches. This can create small islands of fertility and biodiversity in an otherwise barren landscape.