Charles Elton's legacy of invasion ecology is 50 years old. He brought together previously disparate themes like biogeography, conservation biology, and population ecology to show the global scale and implications of biological invasions. While Elton had limited direct influence, he was a prophet who mapped new research directions. Invasion ecology has since improved conceptual frameworks and global coverage. However, there remains a mismatch between current research outputs and the most pressing management issues faced, like prevention, early detection and control. New partnerships are needed to better link invasion ecology with other disciplines and ground management options firmly in risk analysis.

1. The Environment Institute
Where ideas grow
Professor David Richardson
50 years of invasion ecology – the legacy of Charles Elton

2. 50 years of invasion ecology – the legacy of Charles Elton
David M. Richardson

4. Lygodium microphyllum (Old World climbing fern), Florida

5. Mimosa pigra, northern Australia

6. Acacia saligna Acacia cyclops
South
African
fynbos
Pinus pinaster Hakea sericea

7. Nile perch, Lates niloticus,
Lake Victoria

9. (2000) BioScience

10. Global human population
Global human population
Source: Wikipedia

11. Kareiva et al. (2007) Science

12. International shipping has increased by a
factor of 10 over the last few decades

13. Totally new vectors & pathways

14. Air transport
Billion passenger km
3000
2500
2000
1500
1000
500
0
1950 1970 1990

15. Massive habitat transformations and
alterations to prevailing disturbance regimes

16. Afforestation with alien trees
(including agroforestry)

17. Increasing use of alien plants in horticulture…
the never-ending search for novelties
Nurseries - new arrivals
originate from a wider source
www.tubsandshrubs.co.uk http://www.plantnurseries.us
area than early introductions
& they tend to arrive via more
direct routes and in bigger
numbers than in the past
http://www.mountainmeadowfarm.org
Image: Jeff Greenberg

18. Pet trade!!

19. Residence time
Propagule pressure

21. Factors implicated in global amphibian declines

22. WHAT IS INVASION ECOLOGY?
• The study of the human-mediated introduction
of organisms, especially introductions to areas
outside the potential range of given organisms
as defined by their natural dispersal
mechanisms and biogeographical barriers.
• Addresses all aspects relating to the
introduction of organisms, their ability to
establish, naturalize and invade in the target
region & their interactions with resident
organisms in their new location.
• Considers costs and benefits of their
presence and abundance with reference to
human value systems.

23. INVASION ECOLOGY – KEY PHASES
•Pre-Elton (<1950)
•Elton (1950s – early 1980s)
•Scope (mid 1980s – late 1990s)
•Today (>2000) Ricciardi & MacIsaac
(2008)

24. Charles Darwin (1809-1882)
„… floras gain by naturalization,
proportionally with the number of the
native genera and species far more in
new genera than in new species‟ (Darwin
1859).
(Darwin 1839)

26. Pyšek et al. (2008) Diversity and Distributions
Invasion rate of Heracleum mantegazzianum in the Czech Republic.

27. Billion passenger km
3000
2500
2000
1500
1000
500
0
1950 1970 1990

28. 1926
1958
Charles Elton (1900-1992)

31. Whytham Woods, Oxfordshire, UK
“Investigations of the role of competition, predation, and abiotic stress in
shaping natural communities were a staple for previous generations of
ecologists”. [Bruno et al. (2003) Trends in Ecology and Evolution].

32. “Biotic resistance”

33. Robert M. May (1936 - )
Robert H. MacArthur (1930 – 1972)

34. International Conference on Mediterranean-Type Ecosystems (MEDECOS)
Stellenbosch, South Africa 1980

35. International Programme on the Ecology
and Management of Biological Invasions
Three main questions:
1) Which species invade?
2) Which habitats are most susceptible to
invasion?
3) Do we know enough to manage #1 and #2?

36. Jim Brown
Simon Levin
Mick Crawley
Paul Ehrlich
Mark
Williamson Dan
Simberloff
Hal Mooney
Stuart Pimm

37. 1989

38. Mark Williamson
1996

40. The Norway/UN
Conference on Alien
Species
Trondheim, Norway
July 1996
GISP
•Human dimensions
•Ecology of introductions
•International pathways
•Management tools
•Country case studies
(1998) •Where to from here?

41. The Global Invasive Species Programme (Phase 1)

42. Naturalized/
Introduced
invasive

43. Status of taxa
GEOGRAPHIC
ENVIRONMENTAL (LOCAL)
casual
REPRODUCTIVE
alien
DISPERSAL
ENVIRONMENTAL (DISTURBED HABITATS)
naturalized
ENVIRONMENTAL (NATURAL HABITATS)
invasive
Richardson et al. (2000) Diversity and Distributions

44. Status of taxa
GEOGRAPHIC
ENVIRONMENTAL (LOCAL)
Traits of the organism
casual
REPRODUCTIVE
The naturalization – invasion process
alien
DISPERSAL
ENVIRONMENTAL (DISTURBED HABITATS)
naturalized
“Invasiveness”
ENVIRONMENTAL (NATURAL HABITATS)
invasive

45. The naturalization – invasion process
ENVIRONMENTAL (DISTURBED HABITATS)
ENVIRONMENTAL (NATURAL HABITATS)
Traits of the organism “Invasiveness”
ENVIRONMENTAL (LOCAL)
REPRODUCTIVE
GEOGRAPHIC
Features of the environment DISPERSAL “Invasibility”
alien
naturalized
Status of taxa
casual
invasive

46. The naturalization – invasion process
ENVIRONMENTAL (DISTURBED HABITATS)
ENVIRONMENTAL (NATURAL HABITATS)
Traits of the organism “Invasiveness”
ENVIRONMENTAL (LOCAL)
REPRODUCTIVE
GEOGRAPHIC
Features of the environment DISPERSAL “Invasibility”
alien
naturalized
Status of taxa
casual
invasive

47. Beginning with Elton
(1958), community
susceptibility to invasion
has largely been treated
as a yes/no issue:
communities are either
deterministically
resistant or susceptible
to the invasion of a
particular species (A).
Realistically, however,
communities vary
continuously in their
susceptibility to invasion,
making invasion success
a probabilistic process
(B)
D‟Antonio et al. (2001) Journal of Mediterranean Ecology

48. The naturalization – invasion process
ENVIRONMENTAL (DISTURBED HABITATS)
ENVIRONMENTAL (NATURAL HABITATS)
ENVIRONMENTAL (LOCAL)
Pollinators
REPRODUCTIVE
GEOGRAPHIC
DISPERSAL
Seed dispersers!
Morella faya invading lava flows; Hawaii
alien
Mycorrhizal
naturalized
Status fungi
of taxa Nitrogen-fixing bacteria
casual
invasive

49. Rejmánek et al. (2005)
Marcel Rejmanek Pulling together the threads – towards a causal explanation for invasiveness

50. •Invading species must have
access to available resources
(light, nutrients, water, etc)
Fluctuating
resource •An invading species will be
availability theory more successful at invading a
of invasibility community if it does not
encounter intense competition
(Davis et al. 2000) for these resources from
resident species.
•Experiments and long-term
monitoring studies - fluctuation
in resource availability = the key
factor controlling invasibility

51. Elton’s legacy?

52. Elton’s legacy?
“To us, the overriding feature of Elton‟s book, and the primary reason for its landmark
status in invasion ecology, is simply that it brought together previously disparate
themes (biogeography, conservation biology, epidemiology, human history,
population ecology, and others) to show the true global scale and the severe and
escalating implications of biological invasions for life on earth. He placed the
phenomenon in the context of ecological understanding of the time, and provided a
map for new research directions.”

53. Elton’s legacy?
“Elton and his monograph, in fact, had
limited influence on the development of
invasion biology – he was a prophet
rather than a founder...”
Dan Simberloff (in press)

55. BROW – Silky smooth
EYES – Wide open
MOST IMPORTANT –
Big baby cheeks
NOSE – Long and straight
LIPS – Juicy but not too much
JAW – Defined and angular SKIN – Plumped; nothing taut
OVERALL – Heart-shape
effect

56. SCIENCE
Improved
conceptual
frameworks
Naturalized/
Introduced
invasive

57. SCIENCE
Better global
coverage
Trends in Ecology & Evolution 23 237-244 (2008)

58. Conflict resolution
Most pressing Eradication?
management
Early detection Restoration
issues
Prevention Containment, control & mitigation
Monitoring
Integrated land management
MISMATCH! SCIENCE
Tenuous links Besides a better
between current understanding of the
research output and “nuts & bolts”, a greater
most pressing focus research on key
management issues management issues
Vectors Homoclime Autecology Population Impact assessment
& analysis (biocontrol) dynamics
“Invasion pathways Control & restoration ecology
ecology” Bioclimatic
modelling alien Landscape ecology
Cost-benefit analysis naturalized
Status of taxa
casual
invasive

59. Needed!
New
partnerships
SCIENCE
Better links with a
wide range of other
disciplines

60. Consideration of management options – firmly grounded in
risk-analysis/risk-management

62. ENVIRONMENTAL (DISTURBED HABITATS)
ENVIRONMENTAL (NATURAL HABITATS)
COMPONENTS OF
THE LAG PHASE
DISPERSAL
PATHWAYS
ENVIRONMENTAL (LOCAL)
REPRODUCTIVE
GEOGRAPHIC
DISPERSAL
IMPACTS
Pollinators
DISPERSAL PATHWAYS alien
naturalized
Status of taxa
casual
invasive

63. Thanks for your attention!

64. The Environment Institute
Where ideas grow
Next Seminar: 18 September
Professor Alan Cooper
Environmental genomics