Invasive species II: management Bio 415/615

Questions 1. What is the ‘homogeocene’? 2. When is the best time to ‘stop’ an invader, in terms of management cost and success? 3. Why do Barney & DiTomaso (2008 Bioscience) suggest domestication of plants for biofuels creates a greater invasion risk than food crop domestication? 4. What did the Cactoblastis moth do to prickly pear cacti in Australia?

What harm do invaders cause?

Melaleuca in S Florida Transpiration higher Lower water table Hotter fire Deeper burn in organic matter, more severe effects

Plant to Plant: Direct Effects Competition for resources, space Growth, repro. Hybridization Reproduction Plant to Plant: Indirect Competition for pollinators, dispersers Reproduction Introduction of disease to native spp Survival Ecosystem Effects Change in Processes Growth, repro. Disturbance, hydrology, food webs, nutrient cycling Invasive Plant Effects in Natural Areas

Economic & other impacts to human well-being Forestry, agriculture Boating, fishing, swimming, water supply Allergies, toxins Fire: human life and property Cost of control Environmental cost of toxic chemical use Nature Conservancy suggests annual costs of invaders are about 5% of world economy; in US $120billion/yr Land ‘infested’ with invaders take up space of CA?

The Homogeocene Globally, species diversity is going down. Locally, species diversity is going up. What does this mean for communities?

Rahel 2000 Science 288: % Introduced

Rahel 2000 Science 288: AllExtirpationsIntroductions

Non-indigenous birds in Hawaii Lockwood Biol. Invasions 8:

Invasion hypotheses: What to do? Innate biology: Weediness, competitiveness, tolerance, preadaptation: Enemy release/Biotic resistance: Community invasibility: diversity, productivity, disturbance: Availability: Rapid evolution:

Invasion hypotheses: What to do? Innate biology: Weediness, competitiveness, tolerance, preadaptation: SOME SPP ARE INVASIVE, PROHIBIT THROUGH RISK ASSESSMENT, DEVELOP STERILE CULTIVARS—YES Enemy release/Biotic resistance: MANY SPP ARE INVASIVE, ESPECIALLY THOSE WITH HIGH GROWTH RATES AND HIGH RESOURCE DEMANDS, ASSESS ROLE OF ENEMIES—YES, but research is demanding Community invasibility: diversity, productivity, disturbance: SOME COMMUNITIES ARE INVASIBLE, MANAGE AGAINST INVASION, MANAGE AGAINST DISTURBANCE AND HIGH RESOURCE LEVELS, MANAGE FOR HIGH NATIVE RICHNESS—SOMETIMES, but not always feasible (disturbance, low richness, high resources are natural, too) Availability: MOST SPP ARE INVASIVE, REDUCE AVAILABILITY—YES Rapid evolution: RESTRICT GENETIC DIVERSITY—YES, but seems unlikely given horticultural interest in selection

Other Countries Eradication USA Traditional Strategies for Invasive Species Prevention Preclearance Exclusion Detection Containment Control

Management costs accumulate: Prevention Early detection, narrow window near entry point for eradication Controlling in selected locations Bearing the cost of change

Prevention: Australian Weed Risk Assessment Pheloung et al. (1999) tested the WRA against 370 plants present in Australia; rate of rejection of invaders was 100% and rate of false positives was low (7%)

INVASIVES ARE A SMALL % OF EXOTICS INVASIVES ARE A SMALL % OF SALES --Florida data from Lippincott & Hall 1996 Taxa% Exotics in cultivation25,000-- Naturalized1,0004 Weedy7503 Possible natural area impacts Sold in the trade today Economically important (33%/40)

Islands and eradication of exotics Krajick Science 310:

Eradication over large areas

Classical Biocontrol: Cactoblastis on Opuntia Damage to Opuntia by Cactoblastis larvae, pad destroyed, plant open to infection Female Cactoblastis ovipositing on Opuntia, linear egg mass attached to a cactus spine

Following this stunning success, C. cactorum has been widely used to control Opuntia spp. around the world. Before Cactoblastis After Cactoblastis This lodged the idea of biological control of weeds in the minds of scientists and launched succeeding programs.