Invasive species: the worst case?

Benthic fauna 97% by number exotic

99% by biomass exotic

Biological invasions (Lec16)

ImpactsWhich species invade?Which communities are invaded?

ReadingsInvasional meltdown hypothesis

Management - Biological Control (Lec17)

SOME DEFINITIONS

Indigenous/native species - a spp found within its native rangeNon-indigenous/introduced species - a spp introduced to areas beyond its native range by human activity

Established - a spp with a self-sustaining population outside its native range

Invasive species - a non-indigenous spp that spreads from the point of introduction and becomes abundantNon-invasive species - a non-indigenous spp that remains localised within its new environment

Introduced species are common

Pine trees in Africa

African dung beetles in Australia

Australian Possum in New Zealand

New Zealand snails in North America

What proportion of species in BC are introduced?

%VASCULAR PLANTS 21FRESHWATER FISH 15MAMMALS 8REPTILES 27AMPHIBIANS 10

How serious is the problem in BC?

Most major agricultural pestseg apple clearwing moth

50% of weedsBC lists 47 noxious weeds.eg yellow starthistle Japanese knotweed

Check outE Flora BC Invasive species Page

What are the impacts of invasions?

Economic + cows, potatoes, oysters

- zebra mussel, gypsy moth, purple loosestrife

Public health - malaria - cholera pandemic

- avian flu?

Biodiversity - impacts on SAR

25% endangered species

31% threatened species

16% special concern species COSEWIC

IMPACTS OF INTRODUCED SPECIES

1. PREDATION

Nile Perch - - introduced to Lake Victoria in 1980 - caused extinction of many endemic cichlid fish

Seehausen et al 1997 Cons Biol 11:890-904

IMPACTS OF INTRODUCED SPECIES

1. PREDATION

Red Fox - introduced in 1855- linked to declines of ground nesting birds, many small mammals, turtles

Removal and rock wallabies in WA

1. PREDATION - the rosy wolfsnail Euglandina

The introduced predator from se USAIntroduced to Hawaii, Society Islands, Mascarene Islands, Seychelles

WHY?Brought in to control African giant snailAchatina fulica

ConsequenceHawaii15/20 endemic Achatinella spp.Society Islands56/61 endemic partulids extinct

IMPACTS OF INTRODUCED SPECIES

2. COMPETITION

Zebra musselFirst found in Great Lakes in 1988Small - 2.5 cm longHigh densities - 15000/m2

Unionid mussels - 297 endemics

40-75% spp extirpated or of special concern

>60% cases due to zebra mussels

IMPACTS OF INTRODUCED SPECIES

2. COMPETITION - Himalayan balsam

Introduced to Europe 100 yrs agoNectar produced at very high rateBumblebees visit 4X

more frequently

IMPACTS OF INTRODUCED SPECIES

2. COMPETITION - Himalayan balsam

Competes with natives for services of pollinators

IMPACTS OF INTRODUCED SPECIES

3. GENETIC - california tiger salamander

Native decliningCongener used as baitReleasedGenetic study - 6 ponds - all had hybrids

- no “pure” individuals in 50%

IMPACTS OF INTRODUCED SPECIES

3. GENETIC - the introduced mallard threatens

Endemic Hawaiian Duck NZ Grey duck

Endemic florida mottled duck

IMPACTS OF INTRODUCED SPECIES

4. HABITAT ALTERATION -

Beaver1946 - 50 to Argentina2006 - 115,000

Dominant tree spp - all Nothofagus

Regeneration dependant on seedlings

Beaver limit regeneration, deforest riparian habitat

IMPACTS OF INTRODUCED SPECIES

5. HABITAT ALTERATION - Yellowstone NP

New Zealand snail1994 - introduced2006 - 20K-500K /m2

Impact - consumes 75% GNP of the system - is 97% of primary consumer biomass - produces 2.5X total animal waste in

control stream - increases nutrient cycling - on native spp. unknown

IMPACTS OF INTRODUCED SPECIES

CAN BE NEGLIGIBLE

Crested mynahIntroducedBecame common in sw BCNow extinct

European cranefly1960’s pest in Vancouver2006 - non-pest status

Species imported into new area

Survives transport and introduction

Fails in transport

Establishment

Fails to establish

Spread

Noninvasive

Invasive

INVASIONS - a sequence of unfortunate events

Filters apply at each stage

1. Biogeographic - physical barriers2. Physiological - match between species and

climate

3. Biotic - Interaction with native species

The tens rule of invasions Williamson and Fitter (1996)

1 in 10 species imported survive --> introduced1 in 10 species introduced ---------> established1 in 10 species established --------> invasive (ie pest)

KEY QUESTIONS

What features of the invading species predict establishment and expansion?

What characteristics of a community favour invasions?

Why do species have a large impact?

What features of the invading species predict establishment and expansion?

Your Predictions

What features of the invading species predict Establishment and invasion success (expansion)?

Mammalian introductions into Australia

40 spp 30 genera 14 families

What features of the invading species predict Establishment?

Mammalian introductions into Australia

Establishment - 23 of 40 spp became established Numbers of individuals releasedLocation - greater area of climatically suitable habitatSpecies - larger overseas range size

ExpansionNumber of introductionsLocation - greater area of climatically suitable habitatSpecies - body size (smaller)

- lifespan (shorter)- fecundity (higher)- diet (Carnivore>Omnivore or herbivore)

What characteristics of a community favour invasions?

Predictions

1. The habitat is hospitable

2. There is “niche space available”

so species-rich communities are less vulnerable

= the biotic resistance hypothesis Elton (1958)

and disturbed communities are more vulnerable

Q. Explain why?

Invasions in streamside tussock communities

Natural data Exp’tal data

Q. Does this support the biotic resistance hypothesis?

Plant invasions in S African reserves

Q. What does this suggest?

Which communities are most vulnerable?

Hospitable habitatsResource rich systems

- combining biotic resistance+disturbance

Fig 9.14

Why do species have a large impact?

High impact invaders Can be plants, animals or microbesAct as predators, herbivores, parasites/disease

But are oftenKeystone predatorsEcosystem engineersFilling an empty niche

CONCLUSIONS

Species invasions Are CommonBut impacts vary from negligible to severe

Establishment increases with numbers released

Invasiveness (pests/weeds)is hard to predict

Risk varies with species-richness, resource availability and disturbance

What can you do? See E Flora BC Invasives page

NEXT - management and biological control