1. Reading assignments: ecological impacts Invasives and fire: –D’Antonio and Vitousek 1992. Biological invasions by exotic grasses, the grass-fire cycle, and global change. Annual review of Ecology and Sytematics 23:65-87. –Brooks et al. 2004. Effects of invasive alien plants on fire regimes. BioScience 54: 677-688. Ecosystem changes: –Crooks 2002. Characterizing ecosystem-level consequences of biological invasions: the role of ecosystem engineers. Oikos 97:153-166.

2. 3)Impacts a)Ecological ii)Ecosystem functions Ecosystem engineers: What are they?

3. 3)Impacts a)Ecological ii)Ecosystem functions Ecosystem engineers: What are they? Alter ecosystem physical processes (water use, N cycling) Change habitat structure (more complexity, less complexity) Effects cascade through community

4. 3)Impacts a)Ecological ii)Ecosystem functions Overview Specific examples: General compilation From Crooks (2002)

5. Modified from D’Antonio and Hobbie in Sax et al. 2005 Invasive plants Altered litter quality Altered microbial activity Altered root exudation N fixation Altered microclimate Altered microbial community Altered NPP Altered timing of uptake N loss Fire Altered composition N cycling and pools Effects on Nitrogen

6. 3)Impacts a)Ecological iii)Threatened & endangered species Overview ~409 animals and 598 plants are federally listed species in US

7. 3)Impacts a)Ecological iii)Threatened & endangered species Overview ~409 animals and 598 plants are federally listed species in US 294 (29%) threatened by direct effects of invasive species (IUCN)

8. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Effects can be by: Direct species replacement Indirect through effects on community structure or function

9. 3)Impacts a)Ecological iii)Threatened & endangered species : IUCN database Overview Effects can be by: Direct species replacement Indirect through effects on community structure or function Worldwide Extinctions: 104 records of extinctions directly due to invasives 88 animals (many birds, NZ and HI) 16 plants Endangered and vulnerable: 1317 directly due to invasives

10. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: King Ranch bluestem Bothriochloa ischaemum (Caucasian bluestem) brought in to southern Great Plains (NM, OK, TX) from Russia in 1929 C 4 perennial bunchgrass: establishes readily from seed long growing season tolerates heavy grazing fair forage quality forms dense sod in mature pastures

11. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: King Ranch bluestem Bothriochloa ischaemum (Caucasian bluestem) brought in to southern Great Plains (NM, OK, TX) from Russia in 1929 C 4 perennial bunchgrass: desirable forage species Seeded extensively (for example, ~2 million acres in western OK)

12. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: King Ranch bluestem Bothriochloa ischaemum (Caucasian bluestem) brought in to southern Great Plains (NM, OK, TX) from Russia in 1929 C 4 perennial bunchgrass: desirable forage species Seeded extensively But extremely invasive: Spread along highways into native areas (cemetaries, native grasslands) Difficult to control Threatens federally listed endangered plant Ambrosia cheiranthefolia (south Texas ambrosia)

13. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: Hawaii 80-90 native plant species extinct 270 plant species listed as threatened or endangered 94 noxious weeds, many more alien species

14. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: California Seabloom et al (2006) examined distribution of 834 exotic plants in CA. Multivariate analyses (CCA, SEM)

15. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: California Seabloom et al (2006) examined distribution of 834 exotic plants in CA. Multivariate analyses (CCA, SEM) exotic/invasive species tightly linked to distribution of imperiled species (regression, CCA)

17. 3)Impacts a)Ecological iii)Threatened & endangered species Overview Specific examples: California Seabloom et al (2006) examined distribution of 834 exotic plants in CA. Multivariate analyses (CCA, SEM) exotic/invasive species tightly linked to distribution of imperiled species (CCA) Human activities facilitate initial invasion but exotics spread ahead of front of human development into areas with high numbers of threatened plants (SEMs)

18. 3)Impacts a)Ecological iii)Threatened & endangered species Not a lot of evidence for extinctions (Gurevitch and Padilla 2004) But: ‘Winners and Losers’ in anthropogenic biotic homogenization (McKinney and Lockwood 1999) Invasive plants are ‘winners’ ‘losers’ are species whose numbers/range decline Geographically restricted natives with specific habitat requirements = high extinction rates

19. 3)Impacts a)Ecological iii)Threatened & endangered species Not a lot of evidence for extinctions (Gurevitch and Padilla 2004) But: ‘Winners and Losers’ in anthropogenic biotic homogenization (McKinney and Lockwood 1999) Invasive plants are ‘winners’ ‘losers’ are species whose numbers/range decline Geographically restricted natives with specific habitat requirements = high extinction rates Traits of ‘winners’ r selected Widespread Rapid dispersal High variability Generalist Human commensalism Traits of ‘losers’ K selected Rare Slow dispersal Low variability specialist Maladapted to humans

20. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem

21. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem Ecological impacts typically involve: (1) nutrients/water flow; (2) primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics

22. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem Ecological impacts typically involve: (1) nutrients/water flow; (2) primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics Effects observed as: Species replacements (direct/individual or large scale, w/ or w/o interactions with other factors such as fire)

23. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem Ecological impacts typically involve: (1) nutrients/water flow; (2) primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics Effects observed as: Species replacements (direct/individual or large scale, w/ or w/o interactions with other factors such as fire) Ecosystem functions (C sequestration, N fixation, fire frequency/intensity)

24. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem Ecological impacts typically involve: (1) nutrients/water flow; (2) primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics Effects observed as: Species replacements (direct/individual or large scale, w/ or w/o interactions with other factors such as fire) Ecosystem functions (C sequestration, N fixation, fire frequency/intensity) Loss of native species (threatened or endangered species) Often in conjunction with human-caused habitat change

25. 3)Impacts a)Ecological Summary Only a small percentage (0.1%) of introduced plants become a problem Ecological impacts typically involve: (1) nutrients/water flow; (2) primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics Effects observed as: Species replacements (direct/individual or large scale, w/ or w/o interactions with other factors such as fire) Ecosystem functions (C sequestration, N fixation, fire frequency/intensity) Loss of native species (threatened or endangered species) Often in conjunction with human-caused habitat change Especially on islands Especially rare/specialized species More evidence for population reduction than for extinction (e.g. Harrison et al 2006)