A Look at Invasive Species

Python Explodes After Eating Alligator October 5, 2005 MIAMI, (AP) Alligators have clashed with nonnative pythons before in Everglades National Park. But when a 6-foot gator tangled with a 13-foot python recently, the result wasn’t pretty. The snake apparently tried to swallow the gator whole — and then exploded. The gators have had to share their territory with a python population that has swelled over the past 20 years after owners dropped off pythons they no longer wanted in the Everglades. The Asian snakes have thrived in the wet, hot climate.

Why are species declining? Percentage of threatened / endangered species in the U.S. imperiled by: Habitat degradation and loss - 85% Invasive species - 49% Pollution - 24% Overexploitation - 17% Disease - 3% Dave Wilcove et al. 1998 BioScience

Definitions: Introduced (non-native, exotic) - species introduced deliberately or accidentally from somewhere else Domestic/Feral (released pets, livestock and game animals) - can spread disease, compete with native species Invasive species - species that spread subsequent to establishment usually at some cost.

Transport of Invasive Species Introduced deliberately: game animals domestic animals plants for agriculture Accidental: ballasts of ships unprocessed wood fruit shipments by-pass natural barriers escapees (from zoos)

Snake Escape Makes Zoo Squirm MARCH 28, 2011 An Egyptian cobra was still on the loose at the Bronx Zoo Sunday after slithering out of its enclosure Friday afternoon. Zoo keepers shut down the Reptile House "until further notice" to look for the venomous 20-inch snake. Officials said the cobra's reclusive nature meant it posed little danger to the public.

Movement of/ increased exposure to exotic species includes pathogens!! Emerging Infectious Disease – never known before or absent for 20 years Schistosomiasis, AIDS, SARS, etc.

“Forecast and control of epidemics in a globalized world “Forecast and control of epidemics in a globalized world.” Hufnagel et al. PNAS 2004

Why study biological invasions? Consequences threaten biodiversity costly widespread

Estimated annual costs associated with non-native species: Group costs (in millions) Plants (purple loosestrife, weeds) 34,000 Mammals (feral pigs, rats) 37,000 Birds (pigeons, starlings) 2,000 Fishes 1,000 Arthropods (ants, termites, other pests) 19,000 Mollusks (zebra mussel, asian clam) 1,200 Microbes (plant pathogens, animal disease) 41,000 All organisms over $136 billion per year Source: Pimentel et al. 2000 BioScience

Why study biological invasions? Unique opportunities for basic research community ecology animal behavior evolution

Hypotheses for the success of introduced species: Escape from natural enemies predators, parasites, disease Increased competitive ability outcompete native species Pre-adapted to disturbed environments

Characteristics of invasive species general diet and habitat requirements high abundance small body size high reproductive potential (r-strategy) good competitors social / gregarious

(different characteristics may be important at different stages) Stages of invasion 1. Opportunity (transport) 2. Establishment 3. Spread (different characteristics may be important at different stages)

Cane toads Native to Central and South America Introduced to Australia to control insects pests in sugar cane Milky secretions are highly toxic. Kill dogs, cats and native animals including snakes and crocodiles.

Monster cane toad found in Australia Mar 28, 2007 SYDNEY (Reuters) - A huge cane toad the size of a small dog has been captured in the Australian tropical city of Darwin, startling environmentalists who are fighting to stop the poisonous amphibians spread across the country. "It's a monster toad," said Paul Cowdy from FrogWatch which captured the cane toad on Monday night. "We've never seen a cane toad this big," he said on Tuesday. "It's a male and normally females are bigger." Cane Toad Video

How do they impact native species? Can be predators, competitors, parasites, diseases. Can hybridize with native species. Can modify habitat. Can promote spread of other invaders. Ultimately…displace native species

Argentine ants disrupt ant-mediated seed dispersal. Dendromecon rigida - tree poppy (Papaveraceae) Source: Carney, Byerley & Holway. 2003.Oecologia

What makes certain ecosystems vulnerable? Diverse, undisturbed communities have few invaders “Biotic resistance” Disturbed habitats have more invaders Human residential areas: many European species that are commensal with humans Islands: little history with competitors, predators, parasites, or diseases

Over 2,000 species of birds have gone extinct on islands as a result of habitat loss and the introduction of predators and parasites. Hawaii: Habitat loss, malaria, rats and mongoose

How do we control invasive species? In urban and agricultural areas pesticide/herbicide use still common Natural enemies - Biological Control Manage the landscape to minimize disturbance Turn off the water; landscape with native plants

Results of pesticide use Killed native competitors May select for resistance Health risks for people

Biological Control: The use of one species to control another. Usually a specialist predator or parasite of an invasive species. Needs to be species specific or could cause even worse problems.

Photo: Alex Wild Phorid flies (Pseudoacteon tricuspis) parasitize fire ant workers, eventually causing them to lose their heads

Prevention Education is key Research is still needed - generalities? Monitoring programs - early detection Prevent establishment - quarantine Increased communication among agencies Increase regulations

A Closer Look at Zebra Mussels

How did Zebra Mussels enter the US? Zebra Mussels, once native to Europe, were ingested into the freshwater ballast compartments on transoceanic vessels and made way to the Great Lakes. The mussels entered and enough survived to colonize and reproduce.

What is ballast water and how are exotic species introduced What is ballast water and how are exotic species introduced?   Ballast water- is water that is added to commercial ships that lack cargo to enhance stability. The water is then stored in compartments and along with the larva of the Zebra Mussel and other microorganisms are taken on as well. During the journey, lack of sunlight and food may kill the majority of organisms, yet some survive. When in port, cargo is added to the ship and the ballast water is pumped out. Along with it, the mussel larva adaptable for reproduction.

Ballast Water Dispersal

Detroit, MI 1988

Reasons For Rapid Spread 2 Categories: Natural Mechanisms Water currents Birds Insects Other animals Human Mediated Mechanisms Artificial waterways Ships and other vessels Fishing activities Amphibious planes Recreational equipment

However, the most effective and dominant dispersal mechanism is: -Via natural dispersal of their planktonic veliger stage which occurs rather early in their development. This is accomplished mainly by currents which carry them.

Life Cycle-(generalized) Reproduce via ‘Broadcast Spawning’: Broadcast Spawning- the female mussel releases her egg in the water to be met by the male sperm. They fuse to form gametes. Life-Cycle Characteristics/Success- Female may release up to 1 million eggs Egg release is dependent on water temp. Must be above 12 degrees C Optimal temperature- 28 degrees C

1988

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2003

Ecological Impacts: A number of ecological impacts exist due to zebra mussel invasion. These impacts can be further divided into two different types: Abiotic Ecological Impacts Biotic Ecological Impacts And both are responsible for economic disturbance wherever Zebra Mussels are present or near by.

Abiotic Factors: The leading abiotic impact that Zebra Mussels have on recently invaded waters is:  Mussel Biofouling Temporary Marine Structures: Buoys Navigational aids Fishing nets watercraft Permanent Marine Structures: Pilings Bridges Docks

Removal From A Well Biofouling of a marine Structure Clogging a Pipeline Crayfish Attachment

Abiotic Damage (cont’d) More dramatic in an economic sense: Power Plant Structures/Water Plants - Crib structures - Trash bars - Screen houses - Steam condensers - Heat exchangers Water Line Water Pumps- 11,000 gal/min Clogging of A Cooling Structure

Example: Monroe, MI   “The town of Monroe, MI lost its water supply for three days due to massive numbers of Zebra Mussels clogging the city’s water-intake pipeline. Since then, water users such as power companies, steel plants, city water suppliers, and golf courses, have had to retool their water-intake systems”                                                                                                                                                                         

Flow Into A Power Plant

Biotic Ecological Impacts:   In General, a large range of life in freshwater systems is affected. Large decrease in phytoplankton biomass Cyanobacteria blooms Zooplankton populations affected, either directly or indirectly  Dramatic reduction in food availability for fish

Not all negative however for living organisms: The invasion by Zebra Mussels has definitely disturbed natural populations with its induction in 1988 in The United States. Recent studies reveal that Zebra Mussels are beneficial as both water filtering devices and a source of food for some fish as well. An estimated filtration rate of 1 L/day has been determined for each adult mussel. With reproduction by the thousands to millions, this amount of filtering is beneficial for water clarity.   Primarily Walleye and Yellow Perch within the Great Lakes have been recorded to have traces of Zebra Mussels within their digestive tracts.

Economic Impact:   As with certain instances like the town of Monroe, MI, Zebra Mussels are having large scale affects on the economy. Continual damage is taking place and a large amount of money is needed for clean up and natural conservation of existing species. Within the next 10 years, The US Department of Fisheries and Wildlife estimates around five billion dollars for Zebra Mussel control and containment in just the Great Lakes region and Canada alone.

Future/Containment:   Perhaps the most popular conservation organization today is The 100th Meridian Initiative. This group attempts to accomplish a number of things to keep the spread of Zebra Mussels from continuing, such as: An attempt to keep the westward spread of the Zebra Mussel past the 100th meridian of The US. (Roughly Past The Mississippi)   They believe the spread is a result of launching personal watercraft and non-commercial boats in and out of lakes and streams. To avoid this they believe in random boating inspections, surveys, and perhaps the most worthwhile, education on the species.