Category Archives: Paper of the Week

Out of Time

Phenological asynchrony: a ticking time-bomb for seemingly stable populations? (2020) Simmonds et al., Ecology Letters, https://doi.org/110.1111/ele.13603

Image Credit: Ian Kirk from Broadstone, CC BY 2.0, Image Cropped

The Crux

When we think of climate change we tend to think about extreme weather events and melting ice caps, but the way in which our environment is changing is giving the planet more than just unseasonal weather. Phenology (the timing of biological events in nature) dictates when an organism begins a given part of its life cycle, and changes in phenology are one of the most frequent responses to climate change. Take bees and flowers; bees feed on the flowers of certain plant species, and in turn spread the plants’ pollen for them. They both depend on the other being around at the same time, and if flowers bloomed too early, or if the bees came around before the flowers were “ready” for them, both parties would suffer.

Such a mismatch is known as an asynchrony, and it is hypothesized to cause population declines due to the harmful impacts on one or more of the interacting species involved (see another recent post to understand how the loss of one or more interactions can lead to cascading effects throughout a local community). While many theoretical models have investigated these processes, today’s authors wanted to combine such models with long-term data on the phenology and population size of great tits (Parus major). Great tits rely on a small period of insect abundance to feed their young, and as such the more closely they can match the needs of their young to the abundance of insect populations the more they will increase their fitness.

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How Influential is the Platypus in Freshwater Dynamics?

Image Credit: Maria Grist, CC BY-SA 4.0, Image Cropped

Platypus predation has differential effects on aquatic invertebrates in contrasting stream and lake ecosystems (2020) McLachlan-Troup, Scientific Reports, https://doi.org/10.1038/s41598-020-69957-1

The Crux

A trophic cascade occurs when a predator’s effects of its prey goes on to affect ‘lower’ levels of that ecosystem. A great example is the effect that sea otters have on kelp: the sea otters prey extensively on sea urchins, which in turn increases the populations of kelp, which the sea urchins prey on. While this is a result of direct predation by otters, often this can occur through a prey species changing its behaviour to avoid the predators.

Yet most ecosystems are more complex than a simple three-level trophic system. Cascades are therefore more likely to occur when the ecosystem is less complex, or when there are well-defined relationships between species, as a result of a predator having preferred prey species or only a few groups of species making up an ecosystem.

This week’s authors investigated how the platypus (our recently-found-to-be-fluorescent friend) influences the abundance and species richness of invertebrates across both rivers and lakes, and whether it’s capable of affecting an ecosystems algae and sediments as well.

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Like a House of Cards

An empirical attack tolerance test alters the structure and species richness of plant–pollinator networks (2020) Biella et al., Functional Ecology, https://doi.org/10.1111/1365-2435.13642

Image Credit: Adamantios, CC BY-SA 3.0, Image Cropped

The Crux

Put simply, ecosystem function is the process that control how nutrients, energy, and organic matter move through an environment. Think about a forest. You have small plants that are eaten by small animals, small animals that are eaten by larger animals, and those larger animals are eaten by even larger animals. When those animals die, they are broken down and consumed by scavengers, fungi, and bacteria. These processes result in a continuous flow of nutrients and energy through the ecosystem. However, if one link (organism) in this chain breaks (goes extinct), the ecosystem could lose its function, and other species that depend on this cycle could go extinct as well.

The way in which a given ecosystem reacts to or recovers from any negative impact that it sustains is key to understanding how ecosystems function. Classically, this is tested with attack tolerance tests, in which all species on a given trophic level are removed and the ecosystem is then monitored to see how/if it maintains its function. In studies of plant-pollinator networks, this is usually modeled with computers, but studies which use natural systems are lacking. Today’s authors wanted to use a natural plant-pollinator system to see what happens.

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Reframing Evolution to Focus on the ‘Stupid, Icky And Small’

Endless forms most stupid, icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life (2020) Jesse Czekanski‐Moir & Rebecca J. Rundell, Ecology & Evolution, https://doi.org/10.1002/ece3.6892

The Crux

When we think about evolution, too often our perception is that it drives species towards larger, more complex, more beautiful forms. It’s driven by popular media in part, but also by the way we teach it and the organisms we choose to focus on. This goes right back to early conceptions of evolution, with Darwin’s seminal text The Origin of Species referencing “endless forms most beautiful and most wonderful”, instead of “most basic and abhorrent”.

But the authors of today’s paper want to challenge that preconception of evolution as favouring larger or more complex or beautiful organisms, and they have some truly magnificent examples to do so with.

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New Neighbors

Interspecific competition slows range expansion and shapes range boundaries (2020) Legault et al., Proceedings of the National Academy of Sciences, https://doi.org/10.1073/pnas.2009701117

Image Credit: CISRO, CC BY 3.0

The Crux

Climate change has resulted in multifarious changes in the natural world, not the least of which being where one can find a given species. Because areas are growing warmer, some species are shifting their habitats to stay within the type of environment that they like. The thing about shifting habitats though is that a species that shifts is likely to run into/need to compete with another species that is already there. Competition affects the growth and dispersal of organisms, so it follows that this should have an effect on the ability of a given species to shift or expand its range. However, most studies do not take competition into account when predicting range expansion.

A classic example in the scientific literature that did take competition into account was that of the gray squirrel invasion of Britain. Gray squirrels invaded and subsequently displaced the native red squirrels, but competition appeared to have no influence. Instead, a pathogen appeared to be the likely cause of the contraction of the red squirrel range. This example, however, comes from an observational study of a single replicate. Today’s authors instead conducted a manipulative lab experiment to test for the effects of competition on range expansion.

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Working Together

Ant collective behavior is heritable and shaped by selection (2020) Walsh et al., The American Naturalist, https://doi.org/10.1086/710709

Image Credit: Землеройкин, CC BY-SA 4.0

The Crux

Working together to achieve a common goal is nothing new to us. We as humans are famously social organisms that not only crave interactions with others, but quite often succeed due to the way that we work together. Interestingly, we tend to work well when we have some form of organizations or leadership, but there are other animals that do not require such leadership. This so-called “collective behavior” is the behavior of a group that emerges without a form of central control. Think of a large school of fish avoiding a predator at the same time, or birds flocking together and flying through the sky. All of this happens as a result of those animals interacting with one another, not because there is some boss animal telling them to do it.

Not surprisingly, groups of animals will vary in their exact method of collective behavior. It’s assumed that this variation is largely dependent on natural selection, but there isn’t actually much that is known about it. For this variation in behavior to have been the result of natural selection, the variation itself has to be advantageous and heritable, meaning that it is better to have the variation and you can then pass it on to your offspring. Today’s authors wanted to measure just that.

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Forecasting Worldwide Alien Invasions

Image Credit: Bernard Dupont, CC BY-SA 2.0, Image Cropped

Projecting the continental accumulation of alien species through to 2050 (2020) Seebens at al., Global Change Biology, DOI: 10.1111/gcb.15333

The Crux

A by-product of globalisation is that over the coming decades, no matter how many episodes of Border Patrol get recorded, new species are going to find their way into new habitats and potentially become invasive alien species, exerting negative effects on the locals. We’ve seen this in the past, and I’ve beaten many a dead horse writing about these species on this site.

What this paper set out to find is whether or not we can predict at what scale this trend will increase.

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Assessing the Impact of the Newly Introduced European Flounder

Image Credit: Tiit Hunt, CC BY-SA 3.0, Image Cropped

Guest Post by Theresa Henke

First record of niche overlap of native European plaice (Pleuronectes platessa) and non-indigenous European flounder (Platichthys flesus) on nursery grounds in Iceland (2020) Henke et al., Aquatic Invasions, In Press

The Crux

Determining whether or not an introduced species is invasive is important, as it determines whether or not management steps need to be taken to slow or eliminate any negative impacts it might have on the local ecosystem. In Iceland, 15 introduced species have been recorded over the past decades but only six of them are currently classified as invasive or potentially invasive. One of these potentially invasive species is the European flounder (Platichthys flesus), a flatfish commonly found in coastal waters of Europe. The flounder is a catadromous fish, meaning it spawns in marine habitats but has the ability to survive in freshwater streams as well.

In 1999, the flounder was firstly identified in Icelandic waters in the southwest of the country. Since then it has rapidly spread clockwise around the country. Currently, it can be found in every part of Iceland, mostly in estuaries but also up in rivers and lakes. Juvenile flounder can be found on nursery grounds in shallow, brackish waters where they overlap with juvenile European plaice (Pleuronectes platessa). Plaice is a commercially important flatfish species native to Iceland. Despite the knowledge of the flounder’s arrival in Iceland in 1999, not much research has been conducted on the impact of this potentially invasive species.

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If It Ain’t Broke, Don’t Fix It

Image Credit: Goutham89, CC BY-SA 4.0

The evolution of crocodilian nesting ecology and behavior (2020) Murray et al., Ecology and Evolution, https://doi.org/10.1002/ece3.5859

The Crux

One goal of evolutionary ecology is to understand the links between microevolution and macroevolution, meaning evolution in the short term (multiple generations) and how that scales up to the long term (millions of years). In macroevolution, a group of organisms is thought to be successful if it not only exists for a long period of time, but if it also boasts a large number of species. With those criteria in mind, crocodilians (alligators, crocodiles, gharials, and caimans) are one of the most successful lineages to have ever existed on the planet. Though they may not be the most diverse group of organisms with only 25 species, they have been around for about 100 million years. To put that into perspective, dinosaurs went extinct about 65 million years ago, meaning that the crocodilians not only lived with dinosaurs, but they survived the mass extinction that the dinosaurs didn’t.

This longevity as a lineage raises some questions as to what it is about the crocodilians that made them so successful, when their cousins the dinosaurs died out. An interesting aspect of crocodilians is that there is very little variation among these organisms, as they are all generalist carnivores, live aquatic lives, exhibit mating vocalizations, their sex is determined by the temperature of their eggs (see Did You Know?), and they care for their eggs and young. Despite these similarities, there are some notable differences in the reproductive ecology and behavior of the different species, specifically how they build and care for their nests. Because of these differences, the authors of today’s study asked if variation in how crocodilians reproduce may have been the cause of their success.

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Releasing the Devil

Conservation trade-offs: Island introduction of a threatened predator suppresses invasive mesopredators but eliminates a seabird colony (2020) Scoleri et al., Biological Conservation, https://doi.org/10.1016/j.biocon.2020.108635

The Crux

Invasive species are a nightmare for local wildlife wherever they are, but on islands they’re even worse. Introduced predators can wipe out entire populations of species, as Tibbles the cat and his fellow feral buddies demonstrated in the extreme when they drove the Lyall’s wren extinct. On coastal islands this is a recurring theme. An invasive ‘mesopredator’ – like the American Mink in Europe or the cat in Australia – is introduced and quickly goes to work, often on small mammals, birds, reptiles and amphibians alike.

Sometimes, but not always, introducing a top predator to an area can suppress the activities of the mesopredator. They can outcompete the mesopredator for resources, or begin to prey on them. The problem is, that if that top predator goes after the same food as the mesopredator, the local prey species suffer either way.

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