Merremia discoidesperma: Its taxonomy and capacity of its seeds for ocean drifting

Abstract

Merremia discoidesperma (Donn. Sm.) O’Donell (Mary’s-bean) is a rarely collected and inadequately described high climbing woody liana of Chiapas, Mexico; Guatemala; Costa Rica; Hispaniola; and Cuba. There is only one record of this species being cultivated and this from Guanajuato, Mexico in 1894, though seeds are used in folk remedies. These seeds are topographically unlike other known convolvulaceous seeds, thus permitting their positive identification. Because seeds remain buoyant for more than three years in seawater, those produced in the Caribbean and Atlantic drainage region may be transported by the Gulf Stream System as far north as the Norwegian coast, a distance of about 9,500 km. Seeds produced in the Pacific drainage region from Chiapas, Mexico south to Costa Rica may be transported by the North Pacific Equatorial Current as far west as Wotho Atoll in the Marshall Islands, a distance of about 11,000 km. Records of drifting and subsequent stranding of these and other tropical New World disseminules are supported by drift bottle studies and drift debris records in the Atlantic Ocean. In the Pacific Ocean region distribution of stranded Mary’s-bean seeds is supported by a similar distribution of New World pumice. There is an indication in the literature that Mary’s-bean seeds may drift to the Philippines. The record from Wotho Atoll to Norway constitutes the widest drift range of any seed or fruit which has been documented. Other tropical disseminules may drift as far or farther, but their origins cannot be ascertained with certainty. The plant is described, its synonyms listed, and its distribution as well as the distribution of its stranded seeds recorded.