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.

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?

Melaleucain S Florida

• Transpiration higher

• Lower water table• Hotter fire• Deeper burn in

organic matter, more severe effects

Plant to Plant: Direct EffectsCompetition for resources, space Growth, repro.Hybridization Reproduction

Plant to Plant: IndirectCompetition for pollinators, dispersers ReproductionIntroduction of disease to native spp Survival

Ecosystem EffectsChange 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 2000Science 288:854-856

% Introduced% Introduced

Rahel 2000Science 288:854-856

AllAllExtirpationsExtirpationsIntroductionsIntroductions

Non-indigenous birds in HawaiiLockwood 2006. Biol. Invasions 8:449-457.

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

USATraditional 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

http://www.daff.gov.au/ba/reviews/weeds/system/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 cultivation 25,000 --

Naturalized 1,000 4

Weedy 750 3

Possible natural area impacts 125 0.5

Sold in the trade today 40 0.16

Economically important 13 0.05 (33%/40)

Islands and eradication of exoticsKrajick 2005. Science 310:1410-1413.

Eradication over large areas

Classical Biocontrol: Cactoblastis on Opuntia

Damage to Opuntia by Cactoblastis larvae,pad destroyed, plant open to infection

Female Cactoblastis ovipositingon 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 mindsof scientists and launched succeeding programs.