Tag Archives: ecology

Introduced Species Might Restore Ecological Functions Lost During The Ice Age

Image Credit: hbieser, Pixabay Licence, Image Cropped

Introduced herbivores restore Late Pleistocene ecological functions (2020) Lundgren et al., PNAS, https://doi.org/10.1073/pnas.1915769117

The Crux

The fauna of the Pleistocene (also known as the Ice Age) was not that dissimilar to the communities of animals which inhabit our planet now. However, many more large land mammals inhabited all kinds of ecosystems. By the end of the Pleistocene, many of them were extinct, mainly due to climate change impacts (glaciers got larger and restricted their ragne) and prehistoric human impacts like over-hunting, habitat alteration, and introduction of new diseases. The decline of large-bodied herbivores in the Late Pleistocene (LP from here on) led to many ecological changes including reduced nutrient cycling and dispersal, reduced primary productivity, increased wildfire frequency and intensity, and altered vegetation structure. These changes have become our norm.

Scientists usually study species introduction under the premise that they are ecologically novel. However, the introduction of large herbivores has been found to drive changes in the environment, potentially restoring or introducing novel ecological functions similar to pre-extinction Late Pleistocene conditions. This week’s researchers wanted to investigate what sort of role introduced mammals played in restoring ecological interactions by investigating their functional similarity with LP species.

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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

Biotic Interactions: Not All They’re Cracked Up to Be?

Image Credit: Danyell Odhiambo/ICRAF, CC BY-NC-SA 2.0

Local Adaptation to Biotic Interactions: A Meta-analysis across Latitudes (2020) Hargreaves et al., The American Naturalist, https://doi.org/10.1086/707323

The Crux

Local adaptation is a process whereby individuals native to a given area are better-suited to live in that environment than foreign individuals, and those local individuals will out-compete foreign individuals. This adaptation to local conditions can range from a predator that is better at finding and catching prey, to a plant that is more efficient than another at taking nutrients from the soil, or to a host that has evolved defenses against a local parasite. Despite a wealth of literature and science that has been dedicated to the study of local adaptation, it is not clear what it is about the environment that commonly drives it.

Early studies of local adaptation measured abiotic (non-living) factors like temperature and the amount of light, but this ignores the fact that all environments include biotic factors like other species and any interactions with them. A small amount of studies have shown that biotic interactions (i.e. interactions with other species) can drive local adaptation, but there isn’t a consensus on how common of a pattern that is. Today’s authors used a meta-analysis of previous studies to test how these biotic interactions affect local adaptation. Read more

The 2020 Oikos Write-Up: Ecology in the Anthropocene

My lord Iceland is gorgeous. There could not have been a better setting for the 2020 Nordic Oikos Society’s Annual Meeting. Driving through deserts of snow that ring of the kind of quiet isolation you’d expect from a town in a depressing British murder mystery was a wonderful experience.

As was the conference itself, of course. So let’s recap some of my highlights from this year’s meeting, titled ‘Ecology in the Anthropocene’.

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Biological Invasions & The Witcher

Image Credit: The Witcher, 2020

Science and movies often don’t go well together*. It’s no-one’s fault. Science can often be boring and riddled with uncertainties, and movies and TV require plot advancement and definitive results.

But you know what’s a scientific fact? That Henry Cavill’s chin can cut diamond, and if you thrust him into a cosplay outift he probably already had at home and send him out to slaughter a bunch of CGI monsters you’ll get something that is at the very least mildly enjoyable. And if you’re an invasion ecologist who runs a podcast looking at the ecology of movie monsters, mildly enjoyable monsters are enough to dedicate a blog post to.

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How Form Defines Function

Image Credit: Francesco Veronesi, CC BY-SA 2.0, Image Cropped

Macroevolutionary convergence connects morphological form to ecological function in birds (2020) Pigot et al, Nature Ecology & Evolution, https://doi.org/10.1038/s41559-019-1070-4

The Crux

There are an astounding amount of different forms that the animals on our planet take. Likewise, there are a multitude of diverse functions that animals serve in the environment, such as that of a herbivore, a predator, or scavenger. In some cases it’s a clear link between the form of a given animal and its function in the environment, like that of the beak of a hummingbird that allows it to feed on nectar and their role as a pollinator. But whether or not there is a reliable way to predict the function of an animal based off of its form is has been the subject of considerable controversy.

Deciding on how many morphological traits to use to predict ecological function is a difficult prospect. One could argue that it’s impossible to pick a finite number of traits, as there are infinite possible niches that organisms can fill so there’s no way that a set of traits could fill those infinite possible niches. Mapping animal form to function has major implications for quantifying and and conserving biodiversity, and the authors of today’s paper wanted to to determine just how many traits are needed to do that.

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The Why and How of Genetic Diversity

Whilst cichlid fish might look incredibly diverse, they are actually all relatively genetically similar. So how do we define genetic diversity, and how do we conserve it? (Image Credit: Emir Kaan Okutan, Pexels Licence, Image Cropped)

Biodiversity has become an immensely popular buzzword over the last few decades. Yet the concept of genetic diversity has been less present in everyday ecological conversations. So today I want to go through why genetic diversity is important, how we define it, and why there is often controversy about its application in conservation science. Read more

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