Category Archives: Paper of the Week

Getting Older is Favored in Choosy Species

One of the timeless (get it?) questions in biology is why did we evolve to age? What benefit is there to getting older and deteriorating before we die? (Image Credit: medienluemmel )

Evolution favours aging in populations with assortative mating and in sexully dimorphic populations (2018) Lenart, P. et al., Scientific Reports, 8,

The Crux

We as humans are familiar with aging as the slow deterioration of our bodies and minds over time, and we can see this in other animals as well (think of the old family dog with white around its muzzle). The interesting thing is that not every species ages in the way that we do, that is to say that they stay forever “young” until they die. In a biological sense that means that while these organisms can and do die, their risk of death remains the same throughout the course of their lives. This would be akin to your grandparents, in their old age, having the same risk of death as you during the prime of your life. Or, conversely, you being just as likely to die in your sleep as a senior citizen.

The authors of this study note that, while theories for the evolution of aging abound in the scientific literature, they are not broadly applicable and some of them even require the existence of aging for the evolution of aging to even happen. They wanted to find out in what situations aging individuals could outcompete non-aging individuals, and vice-versa.

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The Effects of City Life On a Species’ Body

Species like the anole exist in natural and urban environments. So how does where they live affect their body shape? (Image Credit: RobinSings, CC BY-SA 4.0)

Linking locomotor performance to morphological shifts in urban lizards (2018) Winchell, K. et al., Proceedings of the Royal Society of Biological Sciences, 285,

The Crux

We know that human construction leads to displacement of many species, regardless of the ecosystem. But just because we put up a city, doesn’t mean that all the species that lived there go disappear. Some stay and adapt to their new surroundings. Understanding how certain types of organism respond to new environments is important when considering our impact on a species.

Today’s paper looks at the response of lizards, in this case anoles, to living in the city. The authors wanted to find out, among other things, whether individuals of the selected species showed different locomotive abilities on natural and man-made surfaces based on whether or not they came from the city or the forest, and whether these corresponded to morphological differences.

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It’s All in Your Mind

Rodents and primates are periodically cited as some of the more intelligent animals on the planet, but it turns out that the large brains that these mammals possess have evolved more than once in their history. (Image Credit: Arjan Haverkamp CC BY-SA 4.0 

Encephalization and longevity evolved in acorrelated fashion in Euarchontoglires but not in other mammals (2018) DeCasien, Alex R., Evolution, DOI: doi:10.1111/evo.13633

The Crux

Some of the most striking footage from documentaries like the recent “Blue Planet II” involve organisms that display remarkable intelligence (the octopus that uses shells to disguise itself and hide from its shark predators was a particular favorite of mine). As humans, we sometimes assume that we have the best brains on the planet and have somewhat of a monopoly on intelligence, so it’s always fascinating and maybe even surprising to see other animals using their own brains to solve problems. In mammals, brains that are larger than expected have evolved more than once, which is somewhat of a surprise given how costly a big brain is. For example, your brain needs 20% of the oxygen that your body uses, so one out of every five breaths is exclusively for your brain.

Larger brains are also correlated with longer lives, relative to the group that the organism in question belongs to. Historically, studies on brain size and longevity have been dominated by primate species, so the concern was that this long life/large brain trend may only be a primate trend, instead of generalizable to all mammals. The authors of this study wanted to analyze this trend across more mammal groups, in addition to studying the relationship between larger brains and longer lives.

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Bigger is Not Better

Not all GPS coordinate data are created equal, and some of it may actually be meaningless. (Image Credit: Daniel Johansson, CC BY-NC 2.0)

The smartphone fallacy – when spatial data are reported at spatial scales finer than the organisms themselves (2018) Meiri, S., Frontiers of Biogeography, DOI:

The Crux

One of the greatest annoyances when using museum specimens, old datasets, or large occurrence databases (such as GBIF) is when the locality of an occurrence is only vaguely described, and the coordinate uncertainty is high; “Norway” or “Indochina” doesn’t really tell you much about where that specific animal or plant was seen. Luckily, the days where such vague descriptions were the best you could get are long gone, as most of us now walk around with a GPS in our pockets, and even community science data can be reported very accurately, and more or less in real-time.

However, we have now encountered the opposite problem: the reported coordinates of organisms are often too precise to be realistic, and in the worst-case scenario, they might be borderline meaningless. The author of this study wanted to highlight how this advance in technology coupled with our eagerness to get more accurate data and results have made us too bold in our positional claims.

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Populations Can’t Grow without Homes

Sea otters are one of many charismatic species found along the California coast, yet recovery doesn’t seem to be helping them. Is it something about their habitat that is preventing population growth? (Image Credit: “Mike” Michael L. Baird, CC BY 2.0)

Gaps in kelp cover may threaten the recovery of California sea otters  (2018) Nicholson et al., Ecography, DOI:10.1111/ecog.03561

The Crux

In the 18th and 19th centuries, the fur trade was a massive industry in North America. As a result, many species were hunted and trapped to near extinction. The California sea otter (Enhydra lutris) was reduced in population to less than 50 total individuals. The enactment of the Internation Fur Treaty allowed the species (and others) to come back from the brink of extinction, and they now number over 3200 individuals and are spread across 525km of the California coast. Interestingly, although the population is recovering, it has not bounced back as quickly as other protected mammals living in the same habitat. The California sea lion, for example, has a maximum population growth rate more than twice that of the sea otter (11.7% compared to 5%).

Despite the remarkable recovery of the species, the sea otters occupy less than a quarter of their historic range and have not expanded along the coast in 20 years. The authors of this paper wanted to investigate what it is about the sea otters and their habitat that is slowing this population’s growth rate and spread along the coast.

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Dingoes May Not Be the Answer to Australia’s Cat Problem

Dingoes are Australia’s largest native predator. but are they capable of suppressing feral cat populations? (Image Credit: Bernard Dupont, CC BY-SA 2.0)

Diet of dingoes and cats in Central Australia: does trophic competition underpin a rare mammal refuge? (2018) McDonald et al., Journal of Mammalogy, DOI:10.1093/jmammal/gyy083

The Crux

Feral cats are a huge problem for wildlife in plenty of continents. However, there’s nowhere they have had quite so severe an effect as in Australia. Mammals between 50g and five kilos have seen huge reductions in numbers, and many species have gone extinct. Yet there are some areas in Australia which appear to present refuges for native mammals, so it’s crucial to understand the mechanisms behind these areas.

The MacDonnell Ranges in South Australia are home to large dingo populations, which prey on the local kangaroo species. Dingoes can also suppress cat populations through direct predation. The purpose of this paper was to investigate to what degree dingo and cat diets overlap, to see whether the presence of dingoes contributes to the formation of a refugee for native mammals.

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If You Can’t Stand the Heat, Get Out of the Pond

Dragonflies like this Western Pondhawk female are particularly vulnerable to warming due to climate change. (Image Credit: Eugene Zelenko, CC BY-SA 4.0)
Simulated climate change increases larval mortality, alters phenology, and affects flight morphology of a dragonfly (2018) McCauley et al., Ecosphere, doi:10.1002/ecs2.2151

The Crux

Climate change is something that we hear about on a daily basis. The dire warnings tend to concern sea levels rising and temperatures varying so much that we have more intense and deadly storms than before, but these are all direct effects of the climate. Another thing that climate change can do is have indirect effects on organisms.

Organisms with complex life cycles spend the juvenile part of their lives in one environment before moving on to the adult stage in another environment. The researchers in this study wanted to know how simulated climate change during the juvenile stage of the organisms lifetime could affect the adult stage.

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