Table 2.

The research questions addressed and summarized findings regarding the three Phragmites lineages in the four study regions.

	Chesapeake Bay	St Lawrence River	Utah	Gulf Coast
Regional climate (www.worldclimate.com; data from nearby meteorological stations)	Jan max/min = 5 °C/−5 °C; July max/min = 31 °C/19 °C; Average rainfall = 105 cm; Baltimore, MD	Jan max/min = −6 °C/−14.7 °C; Julymax/min = 26 °C/16 °C; Average rainfall = 76 cm; Montreal, Trudeau Airport, QC	Jan max/min = 3 °C/−7 °C; July max/min = 34 °C/17 °C; Average rainfall = 100–200 cm; Salt Lake City, UT; multiple nearby alpine sites for precipitation	Jan. max/min = 16 °C/6 °C; July max/min = 32 °C/23 °C; Average rainfall = 158 cm; Plaquemines Parish, LA
1. What is the regional and continental significance of the region's wetlands?	Fisheries including blue crab; migratory (Atlantic Flyway) and resident bird habitat	Drinking water; habitat for birds, fish, and other wildlife including many at-risk species	Critical migratory bird habitat on Pacific and Central Flyway, particularly for a region with a semiarid environment where wetlands are scarce	LA contains 40–45 % of the US's wetland habitats; an important stopover for birds on the Mississippi Flyway
2. What are the known or perceived negative or positive impacts of P. australis invasion?	Negative impact: Aggressive spread; recent study documenting no native plant diversity in P. australis stands Positive impact: May act as a sediment trap, buffering wetlands from sea-level rise	Negative impact: Large monospecific stands raise concerns about consequences for ecosystem function and wildlife habitat Positive impact: May be efficient at removing nutrients from agricultural run-off in ditches	Negative impact: Perceived but not documented loss of diverse habitat for migratory birds Positive impact: Unknown	Negative impact: Can negatively affect bird habitats; with progressive invasion of interior marshes, may cause loss of wildlife habitat Positive impact: Can help prevent marsh subsidence by capturing sediment and protecting interior marshes from tropical storm events and oil spills
3. In what habitats do you find the different P. australis lineages?	Introduced: fresh to brackish wetlands; associated with developed and agricultural land-use Native: rivers and creeks on eastern shore of Chesapeake Bay	Introduced: ditches; newly exposed shores; and managed, disturbed or restored wetlands Native: freshwater wetlands of the St Lawrence River (low marsh and areas with fewer human impacts)	Introduced: fresh to brackish wetlands; on sandy beaches, in seasonally flooded areas, and in semi-permanently flooded wetlands with emergent vegetation; disturbed habitats such as ditches and roadsides Native: along rivers and streams, in seeps or near hot springs, and usually away from the major lakes and cities; widespread but not dense	Introduced: mostly in Balize Delta, where it is the dominant vegetation in wetlands with depths <1 m Berlandieri: on roadsides, waste areas/lowlands adjacent to estuarine wetlands, and most wet soils in general, but usually not in standing water; in Balize Delta - sporadically on spoil banks and elevated splays
4. When and how did introduced P. australis first invade and spread?	Little documentation except rapid spread shown in Rhode River 1970–present day	Present for more than 96 years but spread rapidly with the creation of new habitat associated with the highway network in 1960–70s	First herbarium record in 1993; spread rapidly post-flooding of Great Salt Lake in 1980s	Introduced >90 years ago; arrival and spread likely related to major storm events and anthropogenic impacts from canal construction and dredging
5. How fast is introduced P. australis expanding within the region?	Number of patches in Rhode River increased 40× and area covered increased 25× over a 40-year period	Mean dispersal events for the establishment of new patches estimated at 27–77 m year−1 in linear habitats (roadside and agricultural ditches)	No published data	No published data. Ongoing studies looking at annual growth and spread of individual clones with different water depths and salinity levels
6. Is there evidence for multiple introductions of P. australis?	Most likely explanation given the high levels of genetic diversity	Most likely explanation given the high levels of genetic diversity	Most likely explanation given the high levels of genetic diversity	Yes, because there are multiple sublineages of introduced P. australis
7. Do the mechanisms of spread differ among the lineages?	Introduced: seeds very important within and between watersheds, and even within patches Native: no data	Introduced: seeds more important than previously thought Native: no data	Seeds much more important for introduced than native	Introduced: reliance on sexual reproduction varies between sublineages Berlandieri spread is almost entirely vegetative
8. Is introduced P. australis replacing the other lineages?	Not documented; co-occur only in some areas	Possibly at regional scale based on herbarium specimens; however monitoring at the boundary between native and introduced patches did not show clear replacement of one by the other	Not documented but historic native populations were found to still exist in a recent field survey; co-occur in a number of locations so native may get replaced in the near future	Not documented in the Balize delta (berlandieri does not play a significant role in deltaic wetlands); in competition study in a restoration, berlandieri was replaced by introduced P. australis
9. What are the major vegetation types that P. australis is replacing?	Iva frutescens (marsh elder), Spartina patens (salt meadow cordgrass), Spartina cynosuroides (big cordgrass), Schoenoplectus americanus (common threesquare), Distichlis spicata (saltgrass), and Typha angustifolia (narrowleaf cattail)	Has been associated with habitats supporting species such as Typha spp. (cattails), Carex lacustris (hairy sedge), Sparganium eurycarpum (broadfruit bur-reed), and Calamagrostis canadensis (bluejoint). Introduced P. australis outcompetes Typha spp. in roadside habitats but no other systematic documentation of vegetation replacement	Schoenoplectus maritimus (alkali bulrush), S. acutus (hardstem bulrush), Typha spp. (cattails), and mudflat species such as Distichlis spicata (saltgrass)	In interior marshes of the Balize Delta, Schoenoplectus deltarum (delta bulrush), Sagittaria latifolia (broadleaf arrowhead), and Sagittaria platyphylla (delta arrowhead) are being invaded by introduced P. australis; but overall, there is a lack of historical data