Lagenocarpus rigidus (Cyperaceae) may facilitate the establishment of Catasetum gardneri (Orchidaceae) in restinga areas of Northeastern Brazil

Catasetum gardneri is an ornamental orchid endemic to the Brazilian Atlantic Forest that occurs mainly as a terrestrial species in shrubby restinga vegetation, within thicket clumps of Lagenocarpus rigidus (Cyperaceae). We investigated the interspecific relationship between these species and evaluated the abundance and structure of two subpopulations of C. gardneri in two hectares of a fragment of restinga in Bahia State. We found 167 individuals of C. gardneri (104 juveniles and 63 adults) in 3098 thickets of L. rigidus . The abundance of C. gardneri was higher inside the thicket clumps of L. rigidus , specially the larger ones, than on bare sand ( n = 65) and on isolated host plants ( n = 7). We concluded that L. rigidus may act as a nurse plant, facilitating the establishment of C. gardneri . Facilitation by L. rigidus would be related to its leaves — since when dry, they curl up and remain attached to the plant — and leaf sheaths that accumulate on the caudex. These structures likely contribute to minimize abiotic stresses and alter the local availability of resources. These discoveries open new lines of investigation and reveal the possibility of using L. rigidus in population reinforcement, reintroduction or even ex situ cultivation of C. gardneri .