Category Archives: Paper of the Week

Are Animals Doing the Wrong Thing?

The great tit (Parus major) needs to gain more than 10 % of its body weight in pure fat every evening, in order to survive a cold winter night (Image Credit: Ian Frank, CC BY 2.0)

Short-term insurance versus long-term bet-hedging strategies as adaptations to variable environments (2019). Haaland, T.R. et al., Evolution, 73, 145-157.

The Crux

Why do animals behave the way they do? Behavioral ecology is a field of research trying to explain the ecological rationale of animal decision making. But quite often, it turns out the animals are doing the ‘wrong’ thing. Why don’t all animals make the same choice, when there clearly is a best option? Why do animals consistently do too little or too much of something?

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Finished Before You Even Started

Predators are known to affect prey while they are adults and juveniles, but what about when they haven’t even hatched yet?  (Image Credit: Bernt Rostad, CC BY 2.0)

Predation risk affects egg mortality and carry over effects in the larval stages in damselflies (2018) Sniegula et al., Freshwater Biology, p. 1-9

The Crux

In the natural world, one of the most dangerous things that a prey animal has to worry about is a predator. These organisms depend on the prey for their sustenance, and as such have become very good at finding ways to eat them. These are known as direct effects, as a predator eating prey is a direct interaction.

Another aspect of the predator-prey relationship is that of indirect effects, or effects that a predator has on prey that don’t involve it eating the prey animal. These can include predator-induced changes in the prey’s behavior, immune function, or even survival. These indirect effects are usually studied in prey species that are adults or juveniles, but the authors of today’s paper were interested in what indirect effects predators had on the eggs of prey species.

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Mapping Species Distribution with Citizen Science

 Community, or citizen, science is a huge, often untapped data source for ecologists. So what are the pitfalls of using it? (Image Credit: Jacob W. Frank, CC BY 2.0)

Occupancy models for citizen-science data (2018) Altwegg & Nichols, Advances in Modelling Demographic Processes, 10, p. 8-21

The Crux

Species distributions maps are great. I remember rifling through animal encyclopedias as a kid, checking out the distributions of my favourite animals, just assuming that people knew exactly where to find all these organisms. But the reality is that figuring out exactly where species live is extremely difficult.

It’s made easier, however, by the use of citizen (or community) science. This occurs when volunteers involve themselves in projects in which they observe and report the presence or absence of a species in a given area, which is then used to determine a species’ distribution. This data is obviously incredibly useful to any ecologist, but it comes with some drawbacks. This paper attempts to summarise those drawbacks and outline ways to work around them.

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Blending In

In nature, it often pays to blend in to your background, especially if you’re a prey species like the deer mice used in this study. (Image Credit: David Cappaert, CC BY 2.0)

Linking a mutation to survival in wild mice (2018) Barret et al. Science, 363, p. 499-504.

The Crux

A big part of ecological studies involves investigating how certain traits or behaviors work (adapted) or don’t work (maladapted) in a specific environment, while scientists who study genetics may investigate specific parts of the DNA that are under selection for specific values of a given trait. Surprisingly, not many studies investigate these two aspects of natural selection simultaneously, instead they will attribute selection to a specific trait value without knowing the genetic mechanisms behind it.

The authors of this study used a well-studied model system of deer mice (Peromyscus maniculatus) to link these two aspects of ecology together, tying a mutation in a gene that codes for coat color into selection in the wild. The study took place in the Sand Hills of Nebraska, a relatively young region (in geological terms) where these mice are expected to have recently adapted to the environment due to strong selection for traits that promote their survival.

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The Motivation Behind Migration

Species like this red-crowned crane perform yearly migrations, but how do they weigh up the costs and benefits? (Image Credit: Alistair Rae, CC BY-SA 2.0)

Where the wild birds go: explaining the differences in migratory destinations across terrestrial bird species (2018) Somveille, Manica & Rodrigues. Ecography, 42, p. 225-236.

The Crux

Migratory birds make up a huge chunk of the world’s bird life, yet there are still a lot of gaps in our knowledge concerning why they migrate to the areas they do. There’s a variety of potential benefits to migration, from remaining within a comfortable temperature range or a preferred habitat, to gaining access to areas that have a surplus in resources, to escaping competition with resident species. However, migration also results in increased mortality due to the amount of energy it takes. This week’s study tried to analyse the drivers of migration, and what trade-offs were made between migration’s potential benefits and costs.

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The Root of Disease

Fields full of herbaceous plants such as these can be incredibly diverse and complicated ecosystems, and the multitudes of species that inhabit them can influence the magnitude of disease that the organisms that inhabit it may encounter (Image Credit: LudwigSebastianMicheler , CC BY-SA 4.0)

Past is prologue: host community assembly and the risk of infectious disease over time (2018) Halliday, F.W. et al., Ecology Letters, 22, https://dx.doi/10.1111/ele.13176

The Crux

Everything in ecology is based around the environment that a focal organism inhabits, including the interactions it has with other organisms and the non-living aspects of the habitat itself (temperature, water pH, etc.). That being said, it’s no surprise that disease dynamics are likely to depend on the environment that a host inhabits, and that the environment itself is a product of what came before. That is to say, the group of organisms that originally populate a given ecosystem can have an effect on how that ecosystem will look in the future (lakes with freshwater mussels will have clearer water than those without).

The scientific literature is full of experiments, observations, and hypotheses about which environmental conditions lead to fluctuations in disease dynamics. As such, it is difficult to come to a consensus with a “one-size-fits-all” rule for disease dynamics and community structure. The authors of today’s study used a long-term experiment to determine what exactly moderates disease over time.  Read more

Restoring Biodiversity Through Species Interactions

When species like this toucanet are lost, the interactions that they are a part of are lost too. So how can we restore them? (Image Credit: Jairmoreirafotografia, CC BY-SA 4.0)

Estimating interaction credit for trophic rewilding in tropical forests (2018) Marjakangas, E.-L. et al., Philosophical Transactions of the Royal Society of Biology, 373, https://dx.doi/10.1098/rstb.2017.0435

The Crux

We have reviewed more than enough papers on biodiversity loss to entitle us to skip the whole “losing species is bad” spiel (see here, here and here). But what we haven’t talked about is that when some species are lost, specific interactions that those species participate in disappear from an ecosystem. Those interactions range from the minute to the crucial. One such crucial example is that of seed dispersal, whereby specific plants rely on specific animals to disperse their seeds, thus maximising biodiversity in other parts of the forest and creating a positive feedback loop.

Naturally, conservationists will want to reintroduce animals to propagate some of these reactions. But as is always the case in conservation, maximising return is absolutely essential when you’re faced with limited resources and a lot of ground to cover. Today’s authors wanted to develop a system for maximising the effect of species reintroduction.

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