Abstract Detail

Conservation Biology

Rybicki, Nancy [1], Striano, Elizabeth [2], Thum, Ryan [3].

An investigation of a cryptic introduction of Water Chestnut (Trapa sp.) in the Potomac River Watershed, Virginia.

The Eurasian Water Chestnut (genus Trapa) is a non-indigenous species of floating aquatic plant in North America that impedes growth of native submerged aquatic vegetation through shading.  A key characteristic in differentiating species in this genus is the number of barbed horns (0, 2, 3 or 4) projecting from the fruit and its width.  Populations of a Trapa sp. with a four-horn fruit (Trapa natans L.) have been established in the Northeast United States since the 1800s.  No other Trapa taxa have been reported in the US.  In 2014, Trapa sp. was found growing in the tidal Potomac River in Virginia for the first time since the costly eradication of T. natans from this river in the 1940s.  We compared the two-horn Trapa sp. characteristics with existing colonies of T. natans in Maryland and with the worldwide literature on Trapa spp. and we investigated its local distribution and mode of dispersal. This Trapa sp. has a medium size, 2-horned fruit that differs significantly from the historically reported large, 4-horned fruit of T. natans.  In a comparison of the ITS DNA sequences of two- versus four-horned Trapa collected in 2014 we found that the two morphotypes exhibited a fixed difference for a single nucleotide indel, further suggesting these as closely-related but distinct taxa.  Genetic characteristics did not differ at the chloroplast trnLf region. A literature review of Trapa species showed that the fruit morphology of Virginia Trapa sp. was not different from the 30 to 50 mm wide, two-horned species, T. japonica, described in Japan, Korea, and Taiwan.  However, T. japonica appears to be synonymous with about six other names by which the species may be known and that differed depending on the country and taxonomic reference used.  A survey of local waterways and investigation of earlier reports of T. natans in Virginia showed that Trapa sp. with two horns was spreading between 2000 and 2015 among ponds and a reservoir on four separate tributaries in the Potomac River watershed and into tidal water. Local seed dispersal has likely occurred by hydrologic transport and epizoochary on geese as evidenced by observations and photographs. Natural resource managers in North America should become familiar with this previously unreported taxon.  More work is needed to understand distinctions among Trapa spp. and to determine if ecosystem response and best management practices may differ between taxa.

1 - US Geological Survey, 12201 Sunrise Valley Dr, Reston, VA, N/A, 20192, USA
2 - A Green Footprint LLC, Fairfax Station, VA, 22039, USA
3 - Montana State University's Plant Sciences Department Bozeman, MT 59717

Keywords:
Trapa japonica
Trapa natans
Aquatic and Riparian
taxonomy
invasive species
morphology.

Presentation Type: Poster
Session: P, Conservation Biology Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PCB012
Abstract ID:733
Candidate for Awards:None