Pollinia Removal and Suspected Pollination of the Endangered Ghost Orchid, Dendrophylax lindenii (Orchidaceae) by Various Hawk Moths (Lepidoptera: Sphingidae): Another Mystery Dispelled

Abstract

The ghost orchid, Dendrophylax lindenii (Lindl.) Bentham ex Rolfe (Orchidaceae), is a rare, leafless epiphyte restricted to forests in southernmost Florida and western Cuba. The species' appealing floral display, high public profile, and challenging cultivation contribute to its ongoing removal from the wild by unethical collectors. To effectively conserve this and other native orchids that rely on seed for reproduction, a thorough understanding of natural pollination mechanisms is essential. Digital single lens reflex camera traps were used to survey for potential pollinators visiting D. lindenii flowers on the Florida Panther National Wildlife Refuge during the summers of 2016 to 2018. Based on suspected D. lindenii pollinia affixed to photographed moths, we provide visual evidence that D. lindenii is pollinated by at least 2 large hawk moths (Sphingidae) in southern Florida, which include the fig sphinx moth, Pachylia ficus Linnaeus, and pawpaw sphinx moth, Dolba hyloeus Drury (both Lepidoptera: Sphingidae). Species that were documented probing D. lindenii flowers, but lacked pollinia, included the giant sphinx moth (Cocytius antaeus Drury), banded sphinx moth (Eumorpha fasciatus Sulzer), and streaked sphinx moth (Protambulyx strigilis Linnaeus) (all Lepidoptera: Sphingidae). In addition to the aforementioned species of hawk moths (sphinx moths), the seagrape spanworm moth (Ametris nitocris Cramer; Lepidoptera: Geometridae), palamedes swallowtail (Papilio palamedes Drury; Lepidoptera: Papilionidae), monk skipper (Asbolis capucinus Lucas; Lepidoptera: Hesperiidae), Brazilian skipper (Calpodes ethlius Stoll; Lepidoptera: Hesperiidae), and 3 unidentifiable geometrid moths were observed visiting D. lindenii flowers within the study area. During 2017 and 2018, a total of 21 different visits by Lepidoptera were recorded, and the duration of each visit was rarely longer than 1 s. Hawk moth visits were infrequent, but did show some evidence of clustering by species. Measurements of proboscis lengths of the 2 documented pollinators from museum specimens were of sufficient length (50-100 mm) to probe D. lindenii nectar spurs, further lending support to our field observations. Larval food sources of the 2 confirmed pollinators include plant species native to southern Florida, suggesting that these moths are natural pollinators of D. lindenii. Our findings, although preliminary, provide critically needed baseline information that will augment ongoing conservation efforts in southern Florida aimed at the recovery of D. lindenii.