Tag Archives: herbivory

After The Hare Comes The Tortoise: Monitoring The Effect Of A Deliberately Introduced Reptile

Image Credit: Yulia Kolosova, CC BY 4.0, Image Cropped

Impacts of herbivory by ecological replacements on an island ecosystem (2022) Moorhouse-Gann et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14096

The Crux

Turning an ecosystem that has been ruined by humans back into a thriving natural world is a long, difficult task, but it is possible. One method for making it easier is re-introducing species that we’ve wiped out. Often the reintroduction of the functions that these species perform helps restore many other species, and helps the ecosystem returns to a more ‘natural’ state.

But what happens when a really key species has gone extinct? One way of solving this conundrum is introducing a similar species that performs the same function. This sounds like a good workaround, but introducing a non-native species might have unexpected ecological repercussions.

This week’s researchers were based on Round Island, in Mauritius, where two species of giant tortoise (the saddle-backed and the domed Mauritius giant tortoise) had gone extinct. A third species, the Aldabra giant tortoise, was introduced in 2007. The main point of concern on the island is that the tortoise diet may overlap with that of a vulnerable species, the Telfair’s skink. This week’s team wanted to find out whether the tortoise was helping or hindering the island.

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Better Means Faster

Species interactions have predictable impacts on diversification (2021) Zeng and Wiens, Ecology Letters. https://doi.org/10.1111/ele.13635

Image Credit: MacNeil Lyons/NPS, CC BY 2.0

The Crux

No organism on the planet lives in complete isolation from other organisms. Many organisms serve as a food source for others, and even apex predators have to compete for their food. Species interactions like predation, competition, and parasitism directly impact organisms in their daily lives, but there is also a possibility that these same species interactions have had an impact on much longer timescales. That is, species interactions may have had a direct effect on the diversity of life on our planet.

Species interactions have been previously shown to affect diversification rates (see Did You Know?), so the question that today’s authors asked was whether there is a general trend to the effects of species interactions on diversification rates? Specifically, do species interactions with negative fitness (such as being killed by a predator) impacts decrease diversification rates, and do species interactions with positive fitness (such as successfully parasitizing a host) impacts increase diversification rates?

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Cool As A Moose?

Guest post by Katariina Vuorinen

Cool as a moose: How can browsing counteract climate warming effects across boreal forest ecosystems? (2020) Vuorinen et al., Ecology, https://doi.org/10.1002/ecy.3159

The Crux

When temperatures increase, trees grow more. When a moose struts in and eats the twigs, trees grow less. So, if we just have enough moose around, climate warming won’t be able to increase the growth rate of trees. This is what we call the “cooling” effect. Rather simple – and cool – story, right?

However, every ecologist knows that the biological theatre is more complex than this. What if snow protects saplings against browsing? What if changes in temperature affect moose in such a way that they will not feed on trees in the same way as they used to? What if trees’ response to moose is actually different depending on whether it is warm or cold? In complex ecological systems, tree growth is determined in an intricate network of interactions, where the story line is so mind-bogglingly complicated that it seems almost impossible to say what is actually going on.

Luckily, it’s not quite impossible. In this paper, we set out to model those intricate networks, taking into account everything from the climate, the tree species, the effect of time, to the presence of herbivores and their browsing intensity, in an attempt to disentangle that complex biological theatre.

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