How does a species become invasive? Invasive Species How does a species become invasive?

Invasion ecology ‘ We must make no mistake, we are seeing one of the great historical convulsions in the world’s fauna and flora.’ Elton, 1958

DEFINITIONS indigenous = native to a particular place biogeography = the branch of biology that studies the geographical distribution of organisms Biogeographical studies = native and introduced populations of the same species are compared community studies = non-indigenous species (NIS) are compared with native counterparts

Threats to biodiversity (Earth, 2018) Current rate of species extinction is 1000X to 10,000X the natural rate over the past several billion years Most serious threats to biodiversity stem from human population growth, consumption levels, and mobility HIPPO

Threats to biodiversity (Earth, 2018) Habitat Loss Industrial activities Agriculture Aquaculture Mining/resource extraction Deforestation Water extraction Settlement patterns

Threats to biodiversity (Earth, 2018) Invasive Species Predation Parasitism Diseases Competition Modify habitat Disrupt important interactions

Threats to biodiversity (Earth, 2018) Pollution Toxic chemicals Eutrophication—too much of a good thing Dead zones Bioaccumulation POPs—persistent organic pollutants Plastics

Threats to biodiversity (Earth, 2018) Population, human 1800 < 1 billion Today almost 7.5 billion Increased Land use, resource use, pollution

Threats to biodiversity (Earth, 2018) Overharvesting Hunting Gathering Fishing, including bycatch

What’s the problem with invasive species??? Causes of Global Species Endangerment What’s the problem with invasive species??? All Species Marine Species Lawler et al. (2006), Frontiers in Ecology & the Environment

Negative Impacts of Invasive Species Ecosystem Level Impacts Disturbance Regimes Hydrology: Alterations of Water Regimes Geomorphological processes (erosion, sedimentation) Soil chemistry Community or Population Level Impacts Habitat structure Community composition Resource competition Population reductions, eliminations Genetic Impacts

Economic Impacts Along with irreplaceable losses to biodiversity - Billions $$$ per year from Lost agricultural productivity Lost forest productivity Lost recreational opportunity Pimental et al. 2005. Ecological Economics 52:273-288.

How do they get here? Intentional Exotic plant species for ornamental/agricultural uses Accidental Ship’s ballast Contaminants in crop seed Stow-aways on ships/airplanes Release pets

The Enemy Release Hypothesis (ERH) Relates the success of non-indigenous species (NIS) to reduced control by enemies Pathogens Parasites Predators Studies are split Biogeographical analyses show a reduction in the diversity of enemies in the introduced range compared with the native range Community studies imply no significant enemy differences between natives and invasives Too simple to describe processes at work?

Evolution of Increased Competitive Ability hypothesis (EICA) Blossey & Nötzold (1995) Observations Usually a lag period between time of introduction & point at which it is considered invasive Invasive plants seem to be more virulent in habitats into which they have been introduced (as compared with their native habitats) Presumed a sort of naturalization through modification Predicts that much of the invasive potential of an invasive species is derived from its ability to evolve to reallocate its resources

Evolution of Increased Competitive Ability Hypothesis (EICA) As applied to plants – Under identical growing conditions, species will produce more biomass in an area where it has been introduced vs. in its native range. Invasive species will exhibit lower herbivore defense rates in introduced range than in native range. A species is not as fit (in its native habitat) at the time of introduction vs. when it becomes invasive. Blossey and Notzold. 1995. Journal of Ecology 83(5):887-889.

Novel Weapon Hypothesis Suggests that the success of some invaders is due to the novelty of their competitive, defensive, or predatory traits (Callaway & Ridenour, 2004). Native species may have no evolutionary experience with, and therefore may be extremely susceptible to, allelopathic or defensive compounds produced by invaders

So…which is it??? Very different species as invaders Very different native habitats Cause of invasiveness varies depending on individual factors