Understanding the Long Term Effects of an Invasive Species.

The introduction of non-native species to an area can effect many of the processes that keep that area in balance this includes evolution, shifts in species composition, accumulation of materials and interactions with abiotic variables, these processes may increase,decrease, or qualitatively change the impacts of an invader through time (Strayer, et al. 2006). The effects of the non-native species change over time. With many scientists refering to the time directly after the non-natice species has taken ahold of a new environment as the 'acute' phase, the phase where the native species incur the most damage. This is then followed by a 'chronic' phase where various ecological and evolutionary processes come into play.

 The invasion curve of the long-term effects of invasive species.

Source: senrm.sa.gov.au. Assessed on the 13th of April 2014.

Invasive species have large effects on native biodiversity, cause hundreds of billions of dollars in economic damages, and complicate the management of natural ecosystems around the world, their effects are pervasive and varied, changing variables such as the genetics and population size of individual species, diversity and structure of communities, disturbance regimes and biogeochemical cycles (Strayer, et al. 2006).

Previous attempts to explain the ecological effects of an invader have focused on two attributes: its functional distinctiveness (i.e. how much its characteristics such as nitrogen fixation, flammability, phenology, chemical defenses and diet differ from those of species already in the community) and its abundance (Vitousek, 1990). The data collected in Strayer, 2006; shows that both evolutionary and ecological processes can change the abundance and function distinctiveness of a species over a period of time. This change allows for the native species to be able to slightly diminish the effects of the non-native species. This 'third' attribute (time) needs to be heavily considered when looking and understanding the long term effects of an introduced species.

The 4 main changes in an environment after the introduction of a non-native species are:
(1) Changes in the species that invades.
(2) Changes in the biological community that is invaded.
(3) Cumulative changes in the abiotic environment that is invaded.
(4) Interactions between the invading species and other variables that control the ecosystem.
(Strayer, et al. 2006)

A species can change through time by acclimatization, including shifts in gene expression, resource allocation, or morphology and physiology within the lifespan of an individual. Such changes can influence many community and ecosystem processes (Eviner and Chapin, 2003). After an invasive species arrives in a new region, evolution should tailor it to better fit the physicochemical environment and biota that it encounters, increasing its local population size and spread, and thereby its impacts (Strayer, et al. 2006). Predators, parasites, and diseases of the invader, for which the invader is a valuable resource, might arrive or proliferate to take advantage of the invader, thereby reducing its population size or distribution (Parker, et al. 1999). Analogous changes that moderate the impact of invaders can occur within the species of the community that is invaded, either as a result of genetic or phenotypic changes (Strayer, et al. 2006).

References:

Eviner, V.T. and Chapin, F.S. III (2003) Functional matrix: a conceptual framework for predicting multiple plant effects on ecosystem processes. Annu. Rev. Ecol. Syst. 34, 455–485.

Parker, I.M. et al. (1999) Impact: toward a framework for understanding the ecological effects of invaders. Biol. Inv. 1, 3–19.

Strayer, D.L., Eviner, V. T., Jeschke, J.M. & Pace, M.L. (2006) Understanding the Long-Term effects of Species Invasions. TRENDS in Ecology and Evolution. vol. 21, No. 11. pg. 645 - 651.

Vitousek, P.M. (1990) Biological invasions and ecosystem processes: towards an integration of population biology and ecosystem studies. Oikos 57, 7–13.