Invasive species Flashcards
Stephens Island Wren
Galbreath & Brown 2004 Notornis
Stephens Island, New Zealand
1984, 10 specimens brought in by lighthouse cat
Cats established thereafter (10’s)
Cats drove wren extinct
Angel de la Guarda Deer Mouse
Vázquez-Domínguez et al. 2004 Oryx
Isla Estanque, Mexico Abundant 1995 1 x domestic cat 1998 ~100 scats collected 90% contained deer mouse hair No deer mice 98, 99, 01 CR elsewhere
Steadman 1995 Science
The loss of birdlife in the tropical Pacific may exceed 2000 species (the majority of which were species of flightless rails)
Duncan et al. 2013 PNAS
983 species extinct in the pacific
We calculate that human colonization of remote Pacific islands caused the global extinction of close to 1,000 species of nonpasserine landbird alone; nonpasserine seabird and passerine extinctions will add to this total.
Pacific Island extinctions
Mostly wholly or partly due to introduced predators
Cats, rats, pigs, snakes
Avian malaria
+Hunting by man
+Habitat conversion
What do extinctions mean for ecosystem functioning?
Functional consequences on Guam
Caves et al.,
Brown tree snake
Introduced late 1940’s
Near-complete loss native forest birds by late 1980’s
Functional consequences on Hawaii - Avian malaria
52 endemic species at European contact
Third gone extinct, many others critical
Cox & Elmqvist 2000
Conserv Biol
Extinction of Hawaiian Lobelia
Cascading extinction of 31 species Hawaiian Lobelia in last century
As a result, 31 species of the Cam- panulaceae have gone extinct in the last century (K. Wood, personal com- munication). Reduction in the popu- lation sizes of native Campanulaceae and loss of the plants as a nectar source has in turn affected relic pol- linator populations, causing evolu- tionary changes in beak morphology (Smith et al. 1995; Buchman & Nab- han 1996).
Introduced species
An introduced species is one that: Lives outside of its native range Arrived by human activity Deliberate – garden plants Accidental – ballast in ships How big is the problem?
Global exchange and accumulation of non-native plants
13,168 plant species
Invasive species
“From Russian beetles to giant African snails, the U.S. is under assault—and it’s costing us billions”
Are introduced species that spread to: Damage environment Economy Human health Plants, animals or diseases
Assembled all costs in USA, UK, Australia, South Africa, India & Brazil
Crop, forestry & livestock pests, + human disease
US$ 314 billion / year
Implications for conservation
Dramatic extinction from introduced predators on islands Major issues on continents: Chytridmycosis Cane toads Nile perch
Chytrid is dispersed by frog trade?
Schloegel et al., 2012
Hybrid genotypes of amphibian chytridiomycosis associated with the bullfrog trade
South African clawed frog
Global pet & zoo trade
Biomedical sciences
Tested 145 specimens at California Academy of Sciences
4% infected with chytrid
Scale of problem?
Smith et al. 2009 Science
Live animals imported to USA between 2000-06 = 1.5 billion
Global estimates >1 billion / year
Invasive cane toads cause mass mortality of freshwater crocodiles in tropical australia
Letnic et al., 2008
Nile Perch in Lake Victoria
Introduced late 50s Explosive increase 80s Fish yield increased 3- to 4-fold Fisheries biologists consider this a success What about conservation biologists?
> 300 species endemic cichlid
Destruction of endemic species flock: decline of cichlids of lake victoria
Extrapolations suggest ~200 species disappeared or threatened with extinction
Implications for conservation
Dramatic consequences of introduced predators on islands
Also major issues on continents:
Chytridmycosis
Cane toads
Nile perch
Key question:
How to manage invasive species to prevent conservation losses?
Managing invasiveness
Area and growth, carrying capacity and control costs
(1) Prevention is better than cure
(2) Predict invasive species
Remotness promotes biological invasions on islands worldwide
Moser et al., 2018
. While isolation has shaped natural colonization of islands for millions of years, globalization in trade and transport has led to a breakdown of biogeographical barriers and subsequent colonization of islands by alien species. Using a large dataset of 257 subtropical and tropical islands, we show that alien richness increases with increasing isolation of islands. This pattern is consistent for plants, ants, mammals, and reptiles, and it cannot simply be explained by island economics and trade alone. Geographical isolation does not protect islands from alien species, and island species richness may reach a new dynamic equilibrium at some point, likely at the expense of many endemic species.
Models using biological attributes could not predict invasiveness of species pairs
European range predicted invasiveness of 70% of species pairs
Big range =
wide environmental tolerances
165 species pairs 1 invasive in New Brunswick, Canada 1 congeric species not invaded Three biological characters Lifeform, stem height, flowering period European geographic range
Predicting the Australian weed status of southern african plants
Best predictors were:
Weed status in s. Africa
Climatic range in s. Africa
congeric weeds in s. Africa
But only good predictors when present >140 yrs
No clear synthesis for targeted quarantine or eradication of newly introduced species
Plants at highest risk of becoming invasive:
Aquatic or semi-aquatic
grasses, nitrogen-fixers
climbers, clonal trees
Only 25% invaders are serious agri-weeds
No clear synthesis for targeted quarantine or eradication of newly introduced species
(3) Eradication of invasives
Goats on Galapagos
‘Judas’ goats
Carrion et al.
11 million dollars
Rodents on Oceanic Islands
“Galapagos to poison 180 million invasive black rats”
Nov 15, 2012
House mouse, Gough Island, eating Tristan Albatross (CR) chick
Those birds do not evolve to have defence
Rodenticides used in 284 island eradications
Eradications from 284 islands (47,628 ha)
35 others failed (mostly mice)
Cost per hectare 3-2000 dollars
(4) Local control of invasives
Scotch Broom removal
Milo McIver State Park, USA
Limited resources or infestation preclude eradication
Control by reducing density
Manual (digging, pulling)
Mechanical (cutting, girdling)
Prescribed fire
Chemical control (pesticides, herbicides)
Biological control (grazers, introductions??)
Allows other species to survive (thrive?)
Are many non-natives so bad?
Gnangara Pine Plantation, WA Why are pines a problem? Aquifers supply Perth 38% water loss to pines Solution? Clear the plantations Carnaby’s Black Cockatoo Use pines for 6-month non-breeding season Seeds 27% more nutritious than native seeds What should be done???
Java sparrow
Highly threatened by cagebird trade
64 locations studied 109 individuals at 17 sites
Introduced populations: Hawaii Philippines China (100-10,000 breeding pairs, BPs) Taiwan (<100 BPs) Japan (<10,000 BPs) Survival of Java sparrow in the ‘wild’ most likely in novel locations
Novel ecosystems
Definition: Development of ecosystems that differ in composition and/or function from ‘native’ systems
Inevitable consequence of rapid human-induced changes to species distributions and environments
Complex management & ethical dilemmas
Novel ecosystems damage native fauna
Vs. benefits to threatened species
Recovery of ecosystem goods & services
Whether & how to act is emerging field
Summary
Invasives driven 1,000’s extinctions Prevalent globally Cause billions in economic costs Difficult to predict invasives Hard / expensive to eradicate them Local control often only option Mankind rapidly creating novel ecosystems Complex conservation dilemmas
