Aquatic Invasive Species

Native Species

species that evolved in the local environment or that dispersed to the environment by natural means

Native Communities generally

evolve together.

Species evolve or arrive to fill

open niches, or roles, in the ecosystem

Populations and communities are

generally stable over time

Exotic Species

a species transported by humans outside its natural range and iontroduced into a new environment - aka alien species, non native species, non indigenous species

Invasive

an exotic species that persists and reproduces in its new environment and spreads greatly in distribution (may negatively impact new environment or human interests)

Transport of a species beyond its normal range by human actively

Intentional, Accidental, Incidental

Intentional

Stocking, Biological control, Aquarium releases

Accidental

Escapes, Ballast water, stock contaminants

Incidental

interconnected waterways, dams, aquarium and ornamentals trade

Establishment

Introduced species develops a reproducing population

Filters

conditions that prevent species from establishing

Environmental Filters

Temperature, Light, Water availability, shelter, salinity, water chemistry

Biotic Filters

Predators, Food availability, Parasites and pathogens, Competition

Spread

expansion of the area the newly established species occupies (depends on how well the newly established species reproduces and disperses)

Reproduction success depends on how the species

interacts with its environment and the native community

Traits that allow species to reach new habitats

Persistence in temporary environments, Resistance to drying, Dormant stages

Traits that allow species to succeed in new habitat

Asexual reproduction, Rapid growth and reproduction, Trophic generalist, Broad environmental tolerance

Impacts (impacts AIS)

significant negative impacts to the environment, economy, and human health

Environmental (impacts AIS)

Native species loss, foodweb disruptions, loss in production or nutrient cycling, habitat degradation

Economic (impacts AIS)

Property values, drinking water quality, food supply

Health

Pathogen prevalence

Why are invasions successful

Invader traits meet ecosystem traits

Invader traits

1. Traits that allow species to reach new habitats

2. Traits that allow species to succeed in its new habitat

Ecosystem traits

1. Biotic resistance

2. Invasional meltdown

3. Propagule

Hypotheses that have been supported in some but not all cases

Biotic resistance, Invasional meltdown, Propagule pressure

Biotic resistance

The biodiversity of an ecosystem allows it to resist invasion

Diverse communities have strong interspecies interactions

• Competition

• Predation/herbivory

• Parasitism

Invasional meltdown

Previous invasions lead to more invasions

Direct or indirect positive interactions among invasive species is more common than negative interactions

Propagule Pressure

Propagules are units that are able to reproduce

• Individuals (asexually reproducing)

• Fragements

• seeds

Two Components

1. Propagule size: the number of individuals arriving during an introduction event

2. Propagule number: the number of introduction events

Very few insects are invasive overall…

mostly just fish

AIS

vertebrates and mollusks over represented, insects under-represented

How do invasives impact natural communities?

They compete with organisms for food, space, and other resources.

They eat native organisms (predation, herbivory)

Change physical and/or chemical characteristics of the environment

Impacts on the community often depend on

the trophic role of the invasive species

Invasive Macrophytes

Fast growing plants that spread by fragmentation, increasing plant biomass but often inedible to herbivores. They outcompete native plants, reduce biodiversity, form dense monocultures, trap sediments, slow currents, and alter water conditions like depth, temperature, and light.

Impacts of macrophytes

They change ecosystems by altering physical structures, harming fisheries, reducing fish populations, blocking boats, obstructing navigation, raising flood risks, lowering property values, and boosting pest breeding.

Direct or indirect positive interactions among invasive species is

more common than negative interactions

Ecosystem engineering

changing the physical structure

Invasive mollusks (mussels, clams)

filter algae from water, deposit waste in sediments, attach to hard surfaces, reproduce rapidly, have microscopic larvae, and tolerate various environments.

Gastropods (snails)

feed on algae from lake and stream bottoms (benthos) and consume aquatic plants, impacting ecosystems

Invasive predatory fish

Reduce prey diversity and numbers, especially targeting vulnerable species, leading to ecosystem imbalances.