Category Archives: Paper of the Week

The Cost Of Small-Scale Hunting On A Big-Scale Bird

Achieving international biodiversity targets: learning from local norms, values and actions regarding migratory waterfowl management in Kazakhstan (2022) Jones et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14198

The Crux

Some species that we consider local treasures have ranges that extend over vaste swathes of the planet, and some of these make use of those entire ranges. This is probably most obvious in bird species. Some of the locals that have been popping up in my neighbourhood as spring kicks off have been spending the winter on the other half of the planet, and have made use of countless other locations on their journeys between the two endpoints.

This makes conservation a headache. Just because a species is beloved and protected at one end of its range doesn’t mean it’s afforded the same luxury at another end. Even if the species is internationally recognised as threatened, that doesn’t mean every location it visits will respect – or even be aware – of this status. That means that to protect migratory species, we need to figure out the most important parts of their ranges, and work with the people who live there to ensure the birds persist. Today’s paper is an investigation into how effective this sort of work could prove in the future.

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Your Immune Defenses Are What You Eat

Condition‐dependent immune function in a freshwater snail revealed by stable isotopes (2022) Seppälä et al., Freshwater Biology, link to article

Image credit: Bj.schoenmakers, CC0, via Wikimedia Commons

The Crux

There are myriad factors at play when it comes to parasitic infections, but the primary physiological barrier for the parasite is the immune function of host organisms. Despite its importance and usefulness, the immune function is costly to maintain. Building and effectively using immune defenses relies on the host being able to secure enough food to properly fuel its defenses. As a result, individuals in poor condition are more susceptible to parasites. Building off of that, if the conditions in a given area are poor/worsening, then an entire population of organisms may be vulnerable to disease outbreak.

Many studies have investigated the dependence of immune function, including one of my own, but many of those studies take place in lab settings where the food given to a host is carefully controlled. While there are obvious benefits to controlling experimental conditions, it can be hard to generalize the findings of a lab study to the natural settings that organisms actually live in. Today’s authors utilized an observational study of a freshwater snail (Lymnaea stagnalis) to better relate host condition in nature to immune function.

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Avoiding Collisions With Trains By Fleeing… Onto The Tracks?

Image Credit: Clément Bardot, CC BY-SA 4.0, Image Cropped

Ungulates and trains – factors influencing flight responses and detectability (2022) Bhardwaj et al., Journal of Environmental Management, https://doi.org/10.1016/j.jenvman.2022.114992

The Crux

Trains are one of the most climate-friendly ways to cross long-distances. Whether it’s people heading off on holiday or transporting food, clothing or other goods, it’s a (usually) cheap and low-emissions method of travel.

Yet train-animal collisions can be a massive problem for wildlife. Deer in Europe, bears in North America, and elephants in India are three of the many, many groups of species that suffer mortalities every year when they’re hit by trains. The collisions aren’t exactly friendly to the trains either, with many drivers suffering from trauma and repairs often need to be made (granted, not as bad as being run over).

Understanding more about animal behaviour in the face of a train can help us figure out how to prevent these collisions. Today’s authors enlisted the help of Swedish train drivers in an attempt to understand how animals behave when confronted with an oncoming mass of metal.

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Can You Afford to be Picky?

The better, the choosier: A meta-analysis on interindividual variation of male mate choice (2022) Pollo et al. , Ecology Letters, https://doi.org/10.1111/ele.13981

Image credit: barloventomagico, CC BY-NC-ND 2.0

The Crux

Choosing who to reproduce with (mate choice – see Did You Know?) is a major player when it comes to the evolution of a species, yet it can be tough to know when individuals (and which individuals) should be choosy in their partners. A general trend is that when there are a plethora of potential mates available, too many for a given animal to mate with, they must make decisions on who to mate with. For many species, females tend to be the choosy sex, given the limited number of reproductive resources that are available to them (i.e., eggs) and how many males are usually available to mate.

Despite this commonality of female mate choice, male mate choice is also widespread in the animal kingdom. It is therefore important to know how different factors affect how a male chooses his mates. One factor that may play a key role is male quality, or the ability of a male to acquire mates. It could be that males that vary in their quality also vary in how picky they are. Today’s authors used a meta-analysis, or a “study of studies”, to understand how males make their decisions.

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Why A Big Brain Means A Longer Life (For Parrots)

Image Credit: Patrick Kavanagh, CC BY 2.0, Image Cropped

Coevolution of relative brain size and life expectancy in parrots (2022) Smeele et al., Proceedings of the Royal Society Biological Sciences, https://doi.org/10.1098/rspb.2021.2397

The Crux

Figuring out what exactly drives a species’ lifespan has proved more of a puzzle than it might at first seem. Sure, we can look at a single species and provide a few reasons for why it might live as long as it does, but finding predictable patterns relating different factors to life expectancy (let’s say longevity from here) is a little complex.

Take brain capacity for instance. There are three mostlymain theories (which are all somewhat linked) as to how brain capacity affects longevity. The cognitive buffer hypothesis suggests that the ability to solve puzzles granted by a larger brain enables a species to survive situations that other species couldn’t, giving them a longer lifespan. The expensive brain hypothesis suggests that a brain takes up more energy, therefore slowing growth and extending longevity. And the delayed benefits hypothesis suggests that a larger brain capacity allows for more skilled food-finding techniques, resulting in higher diet quality, less adult deaths, and most importantly, the ability for a longer learning period from their parents, resulting in more skill transfer.

Parrots are very smart creatures, almost on the same level as primates when it comes to relative brain size. Today’s authors wanted to test for links between brain capacity and longevity in parrots, and see if their findings lined up with any of the three hypotheses.

What They Did

The team drew their longevity data from Species 360, an organisation which collects information from conservation bodies worldwide. They used life expectancy as their measure of longevity, and compared it to relative brain size, as well as other features like body mass, latitudinal range and diet, which have been shown to affect longevity before.

The authors also tested a few other models which included measurements of developmental time and parental investment to see if either of these had an impact. Either being important could shed light on whether or not the expensive brain or delayed benefits hypothesis play a part in development.

Did you Know: Parrots As Invaders

Their bright colours and intelligence make parrots an inherently charismatic species, one we often sympathise with when we hear of their threatened status and degraded ecosystems. But some species of parrot are biting back, with rose-ringed parakeets (pictured below) now a damaging invasive species in much of Europe. A warming climate and rising numbers will likely only see their range expand.

Read More: Polly Want A City? Population Boom Sparks Call For Cull Of London’s Invasive Parakeets

What They Found

As suspected, larger parrot species tended to have longer lives. But larger relative brains also led to longer lives, though it wasn’t as large a contributor as body size was. The other parameters, including those related to diet, developmental time and parental investment, didn’t have a meaningful effect on parrot longevity in these models.

One added tidbit – the Cacatua, a genus which includes the sulphur-crested cockatoo (pictured above) were the longest lived birds, with the Large Fig Parrot of South East Asia coming in last, with a life expectancy of under two years.

Rose-ringed, or ring necked parakeets, which are causing a stir in European cities as their ivnasive populations expand (Image Credit: TheOtherKev, Pixabay licence)

Problems

Testing hypotheses in science is made easier by the fact that often they’re mutually exclusive, and concluding that research supports one hypothesis is often a direct result of rejecting another. Yet the researchers today were testing three hypotheses that were certainly not mutually exclusive, which really muddies the waters, and makes teasing the effects apart a little difficult.

So What?

The fact that diet and developmental factors had no effect here is interesting, as at least the delayed benefits hypothesis suggests that better diet may lead to longer lives. The expensive brain hypothesis also suggests that increased brain capacity contributes to a longer life by extending development time, so it’s odd that development time had no effect on longevity.

Ultimately the research here doesn’t disprove any of the theories, and perhaps shows most proof for the cognitive buffer hypothesis, suggesting that increased problem-solving abilities can contribute to longer lifespans. Since longer-lived species are often more likely to be threatened, their increased intelligence could be used as a conservation tool, seeing as we humans are often more enamoured with more intelligent species.


Dr. Sam Perrin is a freshwater ecologist who completed his PhD at the Norwegian University of Science and Technology who loves parrots almost enough to wish they would stop messing about and just invade Norway. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.

Getting Hot Hot Hot

How melanism affects the sensitivity of lizards to climate change (2022) Mader et al. , Functional Ecology, https://doi.org/10.1111/1365-2435.13993

Image credit: Tony Rebelo, CC BY-SA 4.0, via Wikimedia Commons

The Crux

Climate change is a fact of life. Every day we uncover more of the negative effects it will have on the various animals, plants, and fungi in the natural world. Species range contractions are one such effect, and they occur when the area that a given species normally occupies shrinks. They are directly linked to a species’ risk of extinction, with this risk growing as a species inability to adapt to new environments grows. Though the theory sounds logical, many of the exact mechanisms behind range contractions are still unknown.

Ectotherms are organisms that depend on the surrounding environment to regulate their own body temperature, making them particularly vulnerable to climate change. Many different biological mechanisms are involved in regulating temperature, but the ability to reflect solar radiation is a key player. Indeed, the ability of organisms to reflect solar radiation (aka energy from sunlight) is part of the thermal melanism hypothesis (see Did You Know?). Melanistic (darker) organisms may be favored under climate change, due to the protection against UV radiation provided by melanin. However, melanistic individuals are more prone to increased heating, which can be bad. Today’s authors sought to understand how climate change would affect melanistic organisms.

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Making Food Webs Out Of (Almost) Nothing At All

Food web reconstruction through phylogenetic transfer of low-rank network representation (2022) Strydom and Bouskila et al., Methods in Ecology and Evolution, https://doi.org/10.1111/2041-210X.13835

The Crux

Understanding food webs (and more generally how different species interact) is important in helping us to understand ecological processes, but sampling (observing) interactions in the field is pretty challenging. Observing a parrot? Simple. Observing a possum? No problem. Observing a parrot evicting a possum from a tree-hollow? Rarer.

This means that data on species interactions is sparse. But we do have data for some regions, and things like computers and fancy maths (think machine learning) at our disposal. Which leads to the question: can we learn something from the places for which we do have interaction data and ‘transplant’ this knowledge and create an interaction network for a region with no data at all?

The focus here is to try and use predictive methods to help and at least give us a idea of who might potentially be eating who and use this to construct a metaweb (a full list of potential interactions) for a region that has plenty of species data, but no species interaction data.

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Why Are There So Many Species?

The causes and ecological context of rapid morphological evolution in birds (2022) Crouch & Tobias, Ecology Letters, https://doi.org/10.1111/ele.13962

Image credit: Andrej Chudý , CC BY-NC-SA 2.0

The Crux

One of the biggest questions facing evolutionary ecologists is why some groups of organisms contain SO MANY species, while others are relatively sparse in comparison. We’ve discussed adaptive radiations on Ecology for the Masses before, which is when a burst of speciation occurs within a group, with new species adapting to fill new ecological niches. It could be that the reason for such uneven groups is that some clades, or related groups of organisms, are more prone to such adaptive radiations than others. If this is true, it would mean that such clades experience not only an increase in the number of lineages (species) that they contain, but also the number of traits they exhibit.

Increases in the speciation rate and trait evolution are the hallmarks of adaptive radiations, but they may not occur at the same time, which can lead to some different outcomes. Clades may diversify rapidly, without really evolving new traits, and this is known as a “non-adaptive radiation“. In contrast, a lineage may quickly evolve new traits without speciating, which is known as an “adaptive non-radiation“. To understand the causes and context of such evolutionary scenarios, today’s authors studied the history of bird evolution.

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The Lazy Bird Gets the Worm

A fine-scale analysis reveals microgeographic hotspots maximizing infection rate between a parasite and its fish host (2021) Mathieu-Bégné et al., Functional Ecology, https://doi.org/10.1111/1365-2435.13967

Image credit: Viridiflavus via Wikimedia Commons, CC BY-SA 3.0

The Crux

Interactions between hosts and parasites can be broken down into two broad stages: the encounter filter and the compatibility filter. The encounter filter determines whether a parasite actually comes in contact with a host, through either a spatial or temporal overlap. After the encounter filter comes the compatibility filter, the stage at which a parasite either successfully infects a host and takes the resources needed, or is successfully repelled by the host. Though the encounter filter must come before the compatibility filter, most studies tend to focus on the compatibility filter. Yet for a parasite to successfully encounter a host, many obstacles must first be overcome.

Parasites tend to be very small, and hosts tend to be rare. Furthermore, many hosts move around the environment and/or are only available to a parasite at specific times of the year. Finally, in many cases the environment that a single host can occupy is huge. With all of these difficulties facing parasites, it is not surprising that they have evolved many different strategies to effectively find hosts.

However, some species don’t appear to display these strategies. For them to succeed, it is possible that they distribute themselves in a non-random (see Did You Know?) fashion in the environment, clumping together to form “hot-spots” of infection. Other studies have investigated this “hot-spot” phenomenon before, but tended to focus on larger spatial scales, anywhere from hundreds to thousands of meters. Today’s authors wanted to understand if investigations at much smaller spatial scales (i.e., ~10 meters or less) could provide further insight into the spatial aggregation of parasites.

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How Invasives Get In Your Head (And Your Poop)

Image Credit: Hedera Baltica, CC BY-SA 2.0, Image Cropped

Invasive alien species as an environmental stressor and its effects on coping style in a native competitor, the Eurasian red squirrel (2022) Santicchia et al., Hormons and Behaviour, https://doi.org/10.1016/j.yhbeh.2022.105127

The Crux

We know that human activities can cause enormous stress for local species, and the introduction of invasive species is one of the most harmful stressors on a global basis. We know that new, harmful species can cause local extinctions, but how does their introduction affect the locals on a behavioural level?

Grey squirrels were introduced to Europe last century and have been spreading since, displacing the native red squirrels and wiping them out in many areas. This week’s authors wanted to know exactly how red squirrels’ behaviour changed when the grey squirrels were introduced, by looking in detail at the behaviour of red squirrles in both invaded and non-invaded areas, and seeing if they could see evidence of these changes in the expression of hormones (more on this in Did You Know).

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