Tag Archives: dynamics

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

The Challenges Facing Community Ecology

Community ecology, as a relatively new discipline, is fraught with challenges. Here, we look at why an hour spent talking about those challenges may make you feel like the PhD student pictured above (Image Credit: Lau Svensson, CC BY 2.0, Image Cropped)

Anyone who has forayed any small distance into academia will probably understand the following quote by Aristotle.

“The more you know, the more you realize you don’t know.”

According to Stewart Lee, participating in further education means embarking on a “quest to enlarge the global storehouse of all human understanding”. This might be true, yet venturing into academia also means that the more answers you learn to challenging scientific questions, the more questions get opened up. It’s the circle of academic life.

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Why Warmer Winters Don’t Always Help Geese

Image Credit: MaxPixel, CC0 1.0, Image Cropped

Contrasting consequences of climate change for migratory geese: Predation, density dependence and carryover effects offset benefits of high-arctic warming (2019) Layton-Matthews et al., Global Change BiologyDOI: 10.1111/gcb.14773

The Crux

Most of us know that climate change will bring warmer, shorter winters to most parts of the world. For many species in areas like the Arctic, it would be easy to interpret this as a good thing – plants grow earlier, so animals get more food, right? Naturally it’s never that simple. Many herbivorous species have evolved in sync with climate cycles so that their reproduction peaks when food becomes available. If season start dates change, these species may not be able to change their own cycles in time. Additionally, what happens if populations of their predators suddenly boom?

Today’s authors wanted to know what role a warming climate played in the population fluctuations of migratory barnacle geese (Branta leucopsis).

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Andrew Hendry: The Changing Views and Speeds of Evolution

The word evolution generally conjures images of millenia-long timescales. Maybe the 15 million years it took for whales to evolve, or the 2.5 million years it took to get from Australopithecus to modern humans. But over the last few decades, scientists have begun to realise that some forms of evolution can take place over much shorter timescales. Leading this field has been Professor Andrew Hendry, author of Eco-Evolutionary Dynamics, a “masterful, comprehensive synthesis treating most of today’s hot topics in ecology and evolution”.

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