Impact of Invasive species on Biodiversity

Sneak peek to my essay and a recap from our loss of biodiversity presentation!

Biodiversity is the genetic, taxonomic and ecosystem variety in living organisms of a given area, environment, ecosystem or the whole planet. (McAllister, 1991)

Loss of Biodiversity if the current extinctions due to anthropogenic activity (Diamond, 1989). These activities include: transporting invasive species, habitat destruction, habitat fragmentation, over-exploitation and secondary effects or “chains of extinction”. These activities are reducing species richness, genetic variation or richness in ecosystem types. Main focus of this post will be on the impact of invasive species.

What are invasive species?

“Invasive species are organisms (usually transported by humans) which successfully establish themselves in, and then overcome, otherwise intact, pre-existing native ecosystems.”

Invasive plant species are thought to pose large threat to native biodiversity, and a meta-analysis of local-scale studies done by researcher Powell et al. confirm this view. However they also suggest that plant invaders rarely cause regional extirpations or global extinctions, causing us to question whether invasive species have a big influence on native biodiversity. -IUCN/SSC (Species Survival Commission) Invasive Species Specialist Group

What effects did invasive plants have on plant species richness?

g5

Figure obtained from a paper by Martin et al, 2009 the figure shows the correlation between reduction in species richness vs. species similarity. The x-axis simply shows the overall reduction of species between 2 plots (invaded and uninvaded). The y-axis shows the similarity between the plant species in the two plots being compared. The graph shows us that there are fewer species in the invaded plot in comparison to the uninvaded plot. As you can see the more similar the two plots were the higher the species richness, showing us that the introduced species in out-competing the native plant species.

Do all invasive species impact biodiversity?

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Figure obtained from a research paper by Martin et al, 2009. This figure shows the impact of individual invading neophytes on the number of species, the Shannon Diversity Index was used to produce the graph. As we can see 11 out of the 13 species had an impact on species richness. Thus the decrease in species richness in invaded plots depended on the identity of the invading species. Showing us that not all invasive species have an impact on biodiversity, however a large portion of them did.

Does plant invasion effect biodiversity across spatial scales?

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Obtained from a meta-analysis paper by Powell et al. shows a negative relationship between the log spatial scale on the x –axis against the log response ratio effect size, Ir, between invaded and uninvaded plots. (Ir= ln(uninvaded species richness)- ln(invaded species richness)). Each point represents a case study of invasive species effects on plot level. The fitted regression includes all study types, including both observational (comparing plots with and without invaders) and experimental (removal and addition) studies. Circles represent observational, triangles removal and squares addition.

As observed regardless of the type of study the slope in negative indicating that the negative influence of invasive species decreased with increased spatial scale.

Do invasive species have the same impact on species richness at both a local and regional scale?

graph

Obtained from a meta-analysis paper by Powell et al. Figure on shows the invader effect on the loss of native species richness at a local scale and regional scale, the results were based on a patch-occupancy model.  Shows uninvaded plot has a higher species richness compared to the invaded plots at a local scale (α) however at a regional scale (ϒ) both invaded and uninvaded plots have the same species richness. According to Powell et al. the result is explained by the presence of few rare (low occupancy) species, which were thus unlikely to be lost from all patches in the presence of invasive species. This result was consistent with trends they observed in literature, whereby the dramatic local-scale effects of invasive species do not scale up to regional-level effects on species richness of extinctions.

Future Direction

  • Verify that plants you are buying for you yard/ garden are not invasive
  • When boating, clean your boat thoroughly before transporting it to a different body of water
  • Clean your boots if you do hiking in a new area to get rid of seeds and weeds
  • Don’t pack plant species of any kind when travelling from place to place
  • Volunteer at a local park and help remove or identify invasive species
  • Help educate other about invasive species

 

Resources

  • Diamond, J., Ashmole, N., & Purves, P. (1989). The Present, Past and Future of Human-Caused Extinctions [and Discussion]. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences,325(1228), 469-477. Retrieved from http://www.jstor.org/stable/2396936
  • Hejda, M., Pyšek, P., & Jarošík, V. (2009). Impact of invasive plants on the species richness, diversity and composition of invaded communities. Journal of Ecology, 97(3), 393–403. https://doi.org/10.1111/j.1365-2745.2009.01480.x
  • McAllister DE. (1991) What is biodiversity? Can. Biodiv. 1, 4-16. [1.2]
  • Powell, K. I., Chase, J. M., & Knight, T. M. (2011). A synthesis of plant invasion effects on biodiversity across spatial scales. American Journal of Botany, 98(3), 539–548. https://doi.org/10.3732/ajb.1000402
  • Society, T. R., Transactions, P., Society, R., & Sciences, B. (n.d.). Downloaded from http://rstb.royalsocietypublishing.org/ on November 9 , 2015.
  • Van Kleunen, M., Weber, E., & Fischer, M. (2010). A meta-analysis of trait differences between invasive and non-invasive plant species. Ecology Letters, 13(2), 235–245. https://doi.org/10.1111/j.1461-0248.2009.01418.x
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About nadunik

Originally Sri Lankan, I was raised in Botswana in Africa and I am currently an international student in Canada. I am a Biology major and I love every aspect of Biology and truly enjoy my lab work!
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