short season of growth. Cushion plants have been described as ecosystem engineers because of their ability to locally maintain increased moisture and soil temperatures below the cushion ±15 °C (±27 °F) relative to adjacent soil temperatures. Some, specifically Mulinum leptacanthum and Oreopolus glacialis, have been positively identified as species that alter the macronutrient concentrations in the soil. These attributes allow other species to more easily colonize the harsh environments that cushion plants inhabit. Species richness is therefore demonstrably increased where cushion plants have colonized. Diversity The cushion plant form is not endemic to any single area or plant family. About 338 species worldwide in 78 genera in areas ranging from Tasmania, New Zealand, and Tierra del Fuego to the arctic tundra of Svalbard have convergently evolved the same plant form in response to similar environmental conditions. Thirty-four diverse plant families, such as Apiaceae, Asteraceae, Caryophyllaceae, Donatiaceae, and the Stylidiaceae, include cushion plant species. References External links TASMANIAN TREASURES-Cushion Plants Subshrubs Plant morphology Plant life-forms Evolutionary ecology