Question: Which flower is the most invasive and found in more countries than the other, Rhodanthe or Tansy?

Context paragraphs:
Invasive species in Mexico: Mexico is one of 17 countries characterized as "megadiverse" because of the number of species and the wide variety of aquatic and terrestrial ecosystems present, due to its geography, a convergence of Nearctic and Neotropical regions.  This has favored the existence of a considerable number of habitats with diversely distant species.  Economic, social and cultural exchange between Mexico and other countries has also facilitated the entry of exotic and invasive species.  An invasive species is defined as one native to a particular area that has been introduced into a new habitat, adapting and altering to suit its new conditions.  The definition given by the Convention on Biological Diversity in 2009 is "An exotic species established in habitats and natural or semi-natural ecosystems; it is an agent of change and a threat to native biodiversity".  Invasive species are classified taking into account six criteria of management:

Rhodanthe: Rhodanthe, also known as sunray or pink paper daisy, is a genus of Australian plants in the pussy's-toes tribe within the daisy family.

Red lionfish: The red lionfish ("Pterois volitans") is a venomous coral reef fish in the family Scorpaenidae, order Scorpaeniformes.  "P. volitans" is natively found in the Indo-Pacific region, but has become an invasive problem in the Caribbean Sea, as well as along the East Coast of the United States.  This and a similar species, "Pterois miles", have both been deemed as invasive species.  Red lionfish are clad in white stripes alternated with red/maroon/brown stripes.  Adults in this species can grow as large as 47 cm (18.5 in) in length, making it one of the largest species of lionfish in the ocean, while juveniles are typically shorter than 1 in .  The average red lionfish lives around 10 years.  As with many species within the Scopaenidae family, it has large, venomous spines that protrude from the body, similar to a mane, giving it the common name lionfish.  The venomous spines make the fish inedible or deter most potential predators.  Lionfish reproduce monthly and are able to quickly disperse during their larval stage for expansion of their invasive region.  No definitive predators of the lionfish are known, and many organizations are promoting the harvest and consumption of lionfish in efforts to prevent further increases in the already high population densities.

Nyabing, Western Australia: Nyabing is a small town in the Great Southern region of Western Australia.  The name is of Aboriginal origin and is thought to derive from the Aboriginal word "ne-yameng" which is the name of an everlasting flower "Rhodanthe manglesii."

Tansy: Tansy ("Tanacetum vulgare") is a perennial, herbaceous flowering plant of the aster family, native to temperate Europe and Asia.  It has been introduced to other parts of the world including North America, and in some areas has become invasive.  It is also known as common tansy, bitter buttons, cow bitter, or golden buttons.

Tanacetum camphoratum: Tanacetum camphoratum is a species of flowering plant in the aster family known by the common names camphor tansy and dune tansy.  It is native to the Pacific Coast of North America from British Columbia to California, where it grows in sand dunes and other coastline habitat.  This species may be known by the synonym "Tanacetum douglasii" and is often included in "Tanacetum bipinnatum".  It is a rhizomatous perennial herb with a thick, low-lying stem up to 25 centimeters long, branching to form a mass of vegetation.  It is hairy, glandular, and aromatic, with a camphor scent.  The leaves are up to 25 centimeters long and thick but featherlike, divided into many narrow leaflets on each side of the main rachis.  Each leaflet in turn has many segments along each side, and the segments are usually divided into several small, knobby segments with folded or curled edges.  The inflorescence bears up to 15 flower heads, each about a centimeter wide or slightly wider.  Each head contains many yellowish disc florets and many pistillate florets around the edges.  The latter may have minute ray florets.  The fruit is an achene a few millimeters long which is tipped with a small pappus of toothed scales.

Tansy beetle: The tansy beetle ("Chrysolina graminis") is a species of leaf beetle.  It measures 7.7–10.5 mm in length and has a characteristic bright metallic green colouration.  The common name derives from the tansy plant on which they often feed as both larvae and adults.  In addition to the nominotypical subspecies, which repeats the specific name, "C. graminis graminis", there are five further distinct subspecies of tansy beetle, which, collectively, have a Palearctic distribution, although in the majority of countries where it is found the species is declining.  In the United Kingdom it is designated as 'Nationally Rare' and this localised population, centred on York, North Yorkshire, has been the subject of much recent research.

Nob Hill Nature Park: Nob Hill Nature Park is a 6-acre oak woodland located in St. Helens, Oregon, 30 mi north of Portland, Oregon.  Perched on a basalt bluff, it overlooks the Columbia River, at the point where Multnomah Channel joins the Columbia.  Along with white oak trees, or "Quercus garryana", it also has a wide array of native wildflowers in spring, including camas, trillium, iris and larkspur.  It also has plenty of invasive plants, including blackberry, English ivy, lunaria (or money plant), vinca, mullein, thistle and tansy.  There is a lot of poison oak too, which is commonly found in western oak woodlands.  Long pants, long sleeves and heavy shoes are recommended.

Northern Pacific seastar in Australia: The Northern Pacific starfish, ("Asterias amurensis") is an invasive species in Australia.  The starfish is native to the coasts of northern China, North Korea, South Korea, Russia and Japan and distribution of this species into other countries has increased.  It is on the Invasive Species Specialist Group list of the world's 100 worst invasive species.

Tanacetum huronense: Tanacetum huronense, also known as Lake Huron tansy, is a type of wildflower most commonly found on sand dunes around the Great Lakes.  Lake Huron tansy currently requires conservation measures in some regions.

Supporting paragraphs: Rhodanthe Tansy
Answer: Tansy