2)How are they located? Perception is that the problem is getting worse. Is there data to support the perception? Can we answer basic questions: Across and within what specific political boundaries are invasions occurring? How abundant are the invaders? Which areas or habitats are next at risk? Are invaders populations expanding, static, contracting? Primary reference: Mack in Mooney & Hobbs (2000)

2)How are they located? a)Eyewitness accounts Darwin in 1833 during trip through the Argentinean pampas “… very many (probably several hundred) square miles are covered by one mass of these prickly [variegated thistle] plants, and are impenetrable to man or beast. Over the undulating plains, where these great beds grow, nothing else can now live.”

2)How are they located? a)Eyewitness accounts Darwin during trip through the Argentinean pampas in 1833 “… very many (probably several hundred) square miles are covered by one mass of these prickly [variegated thistle] plants, and are impenetrable to man or beast. Over the undulating plains, where these great beds grow, nothing else can now live.” Evidence for presence of invader and that was a problem But oQualitative, not quantitative oOften unverified oLack accurate temporal scale oLack accurate spatial scale oBiases of observer

2)How are they located? a)Eyewitness accounts b)Herbarium records Epilobium hirsatum entered US by 1829 in Rhode Island. Invasion mapped according to collection locations (Mack in Mooney & Hobbs 2000).

2)How are they located? a)Eyewitness accounts b)Herbarium records Kochia scoparia 1 st collected in SE Wyoming Invasion mapped by county (Mack in Mooney & Hobbs 2000).

2)How are they located? a)Eyewitness accounts b)Herbarium records Pluses Can go back a long time Verifiable record Often supplemented with floristic surveys, pioneer journals, etc. But Collection date ≠ appearance date Collected once ≠ persisted Wrong ID by original collector Wrong label information What does absence mean?

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Modern, gird-based – Elodea canadensis and E. nuttallii in the Netherlands. Dutch began systematic surveys in 1902 on a 5 km x 5 km grid (Mack in Mooney & Hobbs 2000).

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Modern, grid-based: Pluses Systematic, topographic grid-based (known spatial scale) Data at regular time intervals (known time scale) But Primarily western Europe Large grid size: can still get gaps

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Modern, permanent plots – Hieracium lepidulum in New Zealand from (Mack in Mooney & Hobbs 2000).

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Modern, permanent plots: Pluses Reliable, quantitative data Data at regular time intervals (known time scale) Both presence and absence information But Primarily developed countries Still get gaps Labor intensive Costly

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Paleoecological methods – Pollen diagrams for central Arizona over last ~3000 years (Jackson in Luken & Thieret 1997).

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys Paleoecological methods: Pluses Can yield important information oMajor invasions after Polynesians settled Oceana oMajor invasions after Europeans settled New World oSome species previously thought to be aliens are not But Often coarser taxonomic resolution Coarser temporal scale Coarser spatial scale

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys d)Deliberate searches Examples: Russian thistle (Salsola kali) in northern Great end of 1800’s by USDA Yellow star thistle (Centaurea solstitialis) in California in ’s of invaders in South Africa from 1979 – 1993 by roadside surverys

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys d)Deliberate searches Pluses Often intensive time and space data But Single species Problem already exists

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys d)Deliberate searches e)Remote sensing Mimosa pigra in Australia over 5 years from aerial photos (Mack in Mooney & Hobbs 2000).

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys d)Deliberate searches e)Remote sensing Pluses Lots of potential for excellent spatial and temporal resolution But Identifying 1 invader with a background of many natives

2)How are they located? a)Eyewitness accounts b)Herbarium records c)Systematic floristic surveys – best right now d)Deliberate searches e)Remote sensing – best in future