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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #385214

Research Project: Development and Implementation of Biological Control Programs for Natural Area Weeds in the Southeastern United States

Location: Invasive Plant Research Laboratory

Title: The phytogeography and genetic diversity of the weedy hydrophyte, Pistia stratiotes L.

item Madeira, Paul
item Dray, F Allen
item TIPPING, PHILIP - Retired ARS Employee

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2021
Publication Date: 5/12/2022
Citation: Madeira, P.T., Dray Jr, F.A., Tipping, P.W. 2022. The phytogeography and genetic diversity of the weedy hydrophyte, Pistia stratiotes L.. Biological Invasions.

Interpretive Summary: Waterlettuce is a floating aquatic weed long thought to be introduced into Florida and thus subjected to integrated management efforts, including biological controls. Discovery of relatively recent (~12,000 year old) fossils in the sediments of Lake Annie, FL, coupled with biological differences in the plant between locations and differential responses to biological control agents between those same locations suggested the possibility of multiple "types" of waterlettuce in Florida. This study investigated that possibility and found that worldwide there are at least 7 different genetic types, 3 of which are likely different, though visually indistinct, species (called cryptic species). Four of the genetic types occur in Florida. One of these appears likely to be native to the Caribbean (including Florida), while another appears native throughout the Americas. The other two types in Florida are from Asia and South America. Implications for control of this species in Florida are discussed.

Technical Abstract: Pistia stratiotes is a pantropical floating weed that is problematic in many regions of the world, including Florida, USA. Questions regarding the origins and relationships of P. stratiotes populations worldwide, and especially in Florida, prompted a molecular investigation using five chloroplast and one mitochondrial DNA sequences. The data show that P. stratiotes comprises a minimum of seven distinct genotypic clades worldwide, four of which differ enough to possibly represent different species. Florida, which was more heavily sampled than other regions of the world, contains four of the clades - one of which shows evidence of being pan-Caribbean with sufficient variation to suggest regional (including Florida) nativity. A second clade, present in the U.S. Gulf States and California, is also probably native within this range but likely more broadly present throughout the Americas. Another clade, predominant in southern Florida and the St. Johns River, likely originated in South America. Results are discussed in the larger context of the effects of cryptic species on weed management, including biological control efforts.