Invasive species: the worst case? Benthic fauna 97% by number exotic 99% by biomass exotic

Biological invasions (Lec16) Impacts Which species invade? Which communities are invaded? Readings Invasional meltdown hypothesis Management - Biological Control (Lec17)

SOME DEFINITIONS Indigenous/native species - a spp found within its native range Non-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 abundant Non-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 PLANTS21 FRESHWATER FISH15 MAMMALS8 REPTILES27 AMPHIBIANS10

How serious is the problem in BC? Most major agricultural pests eg apple clearwing moth 50% of weeds BC lists 47 noxious weeds. eg yellow starthistle Japanese knotweed Check out E 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 caused extinction of many endemic cichlid fish Seehausen et al 1997 Cons Biol 11:

IMPACTS OF INTRODUCED SPECIES 1. PREDATION Red Fox - introduced in 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 USA Introduced to Hawaii, Society Islands, Mascarene Islands, Seychelles WHY? Brought in to control African giant snail Achatina fulica Consequence Hawaii 15/20 endemic Achatinella spp. Society Islands 56/61 endemic partulids extinct

IMPACTS OF INTRODUCED SPECIES 2. COMPETITION Zebra mussel First found in Great Lakes in 1988 Small cm long High densities /m2 Unionid mussels 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 ago Nectar produced at very high rate Bumblebees 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 declining Congener used as bait Released Genetic study - 6 ponds - all had hybrids - no “pure” individuals in 50%

IMPACTS OF INTRODUCED SPECIES 3. GENETIC - the introduced mallard threatens Endemic Hawaiian DuckNZ Grey duck Endemic florida mottled duck

IMPACTS OF INTRODUCED SPECIES 4. HABITAT ALTERATION - Beaver to Argentina ,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 snail introduced K-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 mynah Introduced Became common in sw BC Now extinct European cranefly 1960’s pest in Vancouver non-pest status

Species imported into new area Survives transport and introduction Fails in transport Establishment Fails to establish SpreadSpread Noninvasive Invasive INVASIONS - a sequence of unfortunate events

Filters apply at each stage 1.Biogeographic - physical barriers 2.Physiological - match between species and climate 3.Biotic - Interaction with native species The tens rule of invasionsWilliamson and Fitter (1996) 1 in 10 species imported survive --> introduced 1 in 10 species introduced > established 1 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 released Location - greater area of climatically suitable habitat Species - larger overseas range size Expansion Number of introductions Location - greater area of climatically suitable habitat Species - 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 habitats Resource rich systems - combining biotic resistance+disturbance Fig 9.14

Why do species have a large impact? High impact invaders Can be plants, animals or microbes Act as predators, herbivores, parasites/disease But are often Keystone predators Ecosystem engineers Filling an empty niche

CONCLUSIONS Species invasions Are Common But 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