Aa rosei

Aa rosei is a terrestrial orchid in the family Orchidaceae, order Asparagales, belonging to the Andean genus Aa. The species epithet rosei honors Joseph Nelson Rose, an American botanist of the late nineteenth and early twentieth centuries who made extensive plant collections throughout Mexico, Central America, and South America, contributing to the knowledge of New World plant diversity. Rose worked at the United States National Herbarium and described numerous new plant species from the Americas, making him an important figure in the history of American botany. Aa rosei is a compact herbaceous perennial native to the high-altitude grasslands of the Andes in South America. Like all Aa species, it forms a basal rosette of firm, lance-shaped to elliptic leaves from which an erect flowering stem rises to bear a dense spike of small orchid flowers. The leaves are adapted to the challenging abiotic conditions of high Andean habitats: cold temperatures, strong winds, intense ultraviolet radiation, and thin soils. The small flowers of Aa rosei exhibit the complex floral structures characteristic of all orchids — three sepals, two lateral petals, a specialized lip, and a fused column bearing the reproductive organs. The lip in particular is important for attracting the specific insect pollinators that visit the flowers in the open high-altitude grassland environment. Aa rosei likely occurs in Peru or Bolivia, countries where Rose conducted fieldwork and where the genus Aa has its greatest diversity. Mycorrhizal associations are essential for the establishment and nutrient acquisition of this orchid in the nutrient-poor Andean soils. Habitat loss threatens this and related Andean orchid species.