Tag Archives: fungus

The Key Component

Host availability drives the spatiotemporal dynamics of interaction metapopulations across a fragmented landscape (2020) Opedal et al. 2020, Ecology. https://doi.org/10.1002/ecy.3186

Image Credit: Ferran Turmo Gort, CC BY-NC-SA 2.0, Image Cropped

The Crux

Ecology is all about understanding how biotic and abiotic factors interact within environments. Biotic factors are those that involve living organisms such as prey availability/resource abundance (i.e., the availability of food and resources?), competitor density, or predator density. Abiotic factors, however, are those that involve non-living aspects of the environment, such as rainfall or temperature. Studying how these various factors interact with one another allows researchers to better understand how and why ecological dynamics vary across a changing landscape.

One really cool thing about ecological dynamics is that they can play out across trophic levels, meaning something happening at the level of the resource (such as grass) can then result in changes at a higher trophic level, such as that of the consumer (deer) or predator (wolf). While there has been an enormous amount of work dedicated to understanding how these species interactions affect the species involved, much less is known about how these dynamics play out across a natural landscape. Today’s authors used a well-known model system (see Did You Know?) to study just that.

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The Enemy of My Competitor is My Friend

Image Credit: Andreas Kay, CC BY-NC-SA 2.0, Image Cropped

Specifc parasites indirectly influence niche occupation of non‑hosts community members (2018) Fernandes Cardoso et al., Oecologia, https://doi.org/10.1007/s00442-018-4163-x

The Crux

One of the oldest questions in community ecology is why do some species seem to co-occur with one another, while others don’t? Two hypotheses have been put forward to explain why this happens: environmental filtering and niche partitioning. Environmental filtering is when some abiotic feature of a given environment – such as the temperature or oxygen levels – prohibits some species from ever living in the same location as another. A very broad (and overly simplistic) example of this is that you would never see a shark living in the same habitat as a lion, because the shark needs to live in the ocean and the terrestrial Savannah of Africa where lions are found “filter” the sharks out. Niche partitioning, on the other hand, involves species adapting to specialize on a given part of the environment, thus lessening competition for a niche by dividing it up. You can see this with some of Darwin’s Finches, which adapted differently-sized beaks to feed on differently-sized seeds. They all still eat seeds, but they are not eating the same seeds. 

Interactions with other organisms, either direct or indirect, can also influence which species co-occur. If one species can out-compete another, they likely won’t be able to co-occur because the better competitor will take most of the resources, forcing the other out. This can all change, however, if a third organism affects the competitive ability of the superior competitor, allowing the inferior competitor to persist despite its lesser ability.

Today’s authors used two spider species to study community assembly and how it may be affected by a fungal parasite. Chrysso intervales (hereafter inland spiders) builds webs further away from rivers, while Helvibis longicauda builds webs close to the river (hereafter river spiders). Interestingly, only the river spiders are infected with the fungal parasite, thus they investigated how interactions between the two spiders may be mediated by this fungal parasite. Read more