Pacific Island Ecosystems at Risk (PIER)

Opuntia robusta


Note:  Risk assessment prepared for Australia

Information on Risk Assessments

        Opuntia robusta
A. Biogeography/     wheel cactus
  historical     P&C
1 Domestication/ 1.01 Is the species highly domesticated? Y
  cultivation 1.02 Has the species become naturalised where grown? Y
    1.03 Does the species have weedy races? N
2 Climate and 2.01 Species suited to Australian climates (0-low; 1-intermediate; 2-high) 1
  Distribution 2.02 Quality of climate match data (0-low; 1-intermediate; 2-high) 1
    2.03 Broad climate suitability (environmental versatility) Y
    2.04 Native or naturalised in regions with extended dry periods Y
    2.05 Does the species have a history of repeated introductions outside its natural range? Y
3 Weed 3.01 Naturalised beyond native range Y
  Elsewhere 3.02 Garden/amenity/disturbance weed  
  (interacts with 2.01 3.03 Weed of agriculture Y
  to give a weighted 3.04 Environmental weed Y
  score) 3.05 Congeneric weed Y
B. Biology/Ecology    
4 Undesirable 4.01 Produces spines, thorns or burrs Y
  traits 4.02 Allelopathic  
    4.03 Parasitic N
    4.04 Unpalatable to grazing animals Y
    4.05 Toxic to animals  
    4.06 Host for recognised pests and pathogens Y
    4.07 Causes allergies or is otherwise toxic to humans  
    4.08 Creates a fire hazard in natural ecosystems  
    4.09 Is a shade tolerant plant at some stage of its life cycle N
    4.10 Grows on infertile soils Y
    4.11 Climbing or smothering growth habit Y
    4.12 Forms dense thickets Y
5 Plant 5.01 Aquatic N
  type 5.02 Grass N
    5.03 Nitrogen fixing woody plant N
    5.04 Geophyte N
6 Reproduction 6.01 Evidence of substantial reproductive failure in native habitat N
    6.02 Produces viable seed. Y
    6.03 Hybridises naturally  
    6.04 Self-compatible or apomictic  
    6.05 Requires specialist pollinators  
    6.06 Reproduction by vegetative fragmentation Y
    6.07 Minimum generative time (years) 3
7 Dispersal mechanisms 7.01 Propagules likely to be dispersed unintentionally (plants growing in areas with much vehicle movement) Y
    7.02 Propagules dispersed intentionally by people N
    7.03 Propagules likely to disperse as a produce contaminant N
    7.04 Propagules adapted to wind dispersal Y
    7.05 Propagules water dispersed Y
    7.06 Propagules bird dispersed  
    7.07 Propagules dispersed by other animals (externally) Y
    7.08 Propagules survive passage through the gut  
8 Persistence 8.01 Prolific seed production (>2000/m2) N
  attributes 8.02 Evidence that a persistent propagule bank is formed (>1 yr)  
    8.03 Well controlled by herbicides N
    8.04 Tolerates, or benefits from, mutilation or cultivation Y
    8.05 Effective natural enemies present in Australia N
      Outcome: Reject
      Score: 20
  Statistical summary   Biogeography 8
  of scoring   Score partition:                       Undesirable attributes 6
      Biology/ecology 6
      Biogeography 9
      Questions answered:                       Undesirable attributes 8
      Biology/ecology 18
      Total 35
      Agricultural 14
      Sector affected:                                   Environmental 13
      Nusiance 0
   A= agricultural, E = environmental, N = nuisance, C=combined  

Risk assessment prepared by Rod Randall

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This page new 25 January 2001.