Tag Archives: disturbance

Do Disturbances Promote Biodiversity in the Presence of an Invasive Species?

Image Credit: Paresh Poriya, CC BY 4.0, Image Cropped (also not featuring tunicates)

Testing ecological theories in the Anthropocene: alteration of succession by an invasive marine species (2021) Christianson et al., Ecosphere, https://doi.org/10.1002/ecs2.3471

The Crux

Ecological disturbances, such as fire, floods, or storms, might seem like a catastrophe at first glance, but often they open up space for new species to take the place of dominant ones, creating a more diverse ecosystem. When a disturbance occurs matters as well – if a storm hits right before a particular species starts to reproduce, that species could take advantage of the extra space and become dominant in a short time.

In the 1970s, John Sutherland and Ronald Karlson tested this theory, looking at the invertebrate community of a coastal dock in North Carolina, USA. They found that which species dominated depended on when the community began to grow (a proxy for when disturbance opened up new space).

The area has since seen the introduction of an invasive species of tunicate, Clavelina oblonga. This week’s authors wanted to test whether the original patterns seen in the 1970s still showed up in the presence of the invader.

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The Elusive Climax

Image Credit: ForestWander.com CC BY-SA 3.0 US, Image Cropped

Somewhere in my education, I distinctly remember a video that explained ecosystem succession moving towards a climax condition. The film depicted the gradual filling of a lake and subsequent encroachment of saplings as the system aged towards its inevitable end as a hardwood forest in the eastern United States. I remember thinking even then, “but where do lakes come from?” I couldn’t work out how there could be a mosaic of habitats if there was a steady progression towards a single endpoint.

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