Tag Archives: competition

The Healthy Male Wins the Mate

Guest post by Miguel Gómez-Llano (Image Credit: Sharp Photography, CC BY-SA, Image Cropped)

Male-Male Competition Causes Parasite-Mediated Sexual Selection for Local Adaptation (2020) Gómez-Llano et al., The American Naturalist, https://doi.org/10.5061/dryad.cjsxksn35

The Crux

The natural world changes constantly: temperatures fluctuate, predators and parasites enter into the ecosystem, and the landscape itself could change (looking at you, Yellowstone). These changes mean that organisms are under a constant pressure to adapt to local conditions. Due to this pressure, one of the biggest questions for conservation biology is if species are able to adapt fast enough to keep up with environmental changes. Sexual selection is thought to promote rapid adaptation to such environmental changes, but most of the evidence comes from laboratory studies.

Our study looked at adaptation to one of nature’s ubiquitous pressures: parasitism. We were interested in the strength of selection by parasites and if there was subsequent adaptation by the host in a wild population.

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Don’t Compete If You Don’t Want to Get Eat(en)

Image Credit: Judy Gallagher, CC BY 2.0, Image Cropped

Predators weaken prey intraspecific competition through phenotypic selection (2020) Siepielski, Hasik et al., Ecology Letters, https://doi.org/10.1111/ele.13491

The Crux

We are all familiar with predator-prey relationships in nature, those in which one organism (a predator) kills and consumes another (the prey). Besides these direct effects on prey via consumption, predators can also impose indirect effects on their prey. An indirect effect is one in which the predator changes some aspect of the prey, such as their behavior or the way that they look, but these changes are brought about just by the predator being around. These predator-mediated effects are known to affect the relationships between prey organisms themselves, such as how prey organisms compete with one another, whether its for food, mates, or other resources.

Predators are known to affect how active their prey are, and this selection on activity results in a trade-off between how much prey can grow and their risk of predation. Being more active can allow you to find and eat more food, but that also means that a potential predator is more likely to see you. Today’s paper used larval damselflies and their fish predators to study how selection of fish on their damselfly prey based on the damselfly activity rates affected competition between the damselflies.

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The Kids Are Not OK: Causes of Infanticide in Female Mammals

The Bonnet Macacque, one of the 89 species in which females have been shown to commit infanticide (Image Credit: Vino Rex, CC BY 2.0, Image Cropped)

The evolution of infanticide by females in mammals (2019) Lukas & Huchard, Philsophical Transactions of the Royal Society – Biological Sciences, https://doi.org/10.1098/rstb.2018.0075

The Crux

The practice of male mammals killing their rival’s cubs has been well-documented by wildlife biologists. The image of a male lion striding away from a pride with a dead cub in his mouth is quite haunting (spare a though for Scar’s kids when Simba takes over again). But infanticide by female mammals has received less attention.

Whilst males generally only kill young to ensure they have more access to mates, the motivations behind infanticide in females are more complex. It ultimately comes down to resource competition, but the resources themselves are myriad – milk, availability of space, care from more than one ‘parental’ figure (allocare), and social status. These four resources make up the competing hypotheses as to why females commit infanticide. This week’s researchers wanted to know what factors of a species biology increased the likelihood of a mother to kill an infant of the same species.

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The Roles of Aquatic Predators

Image Credit: Neil Hammerschlag, Oregon State University, Image Cropped, CC BY-SA 2.0

Ecosystem Function and Services of Aquatic Predators in the Anthropocene (2019) Hammerschalg et al., Trends in Ecology and Evolution, https://doi.org/10.106/j.tree.2019.01.001

The Crux

Aquatic predators play an important role in many ecosystems, and are often among the more charismatic species in the ecosystem. Because of this, they are often the target of conservation for ocean management bodies worldwide. This paper aims to provide a synthesis of the ecosystem services that aquatic predators provide in marine and freshwater ecosystems worldwide. Below, we’ve chosen 4 of the more interesting and important roles to go into.

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How Different is Too Different?

This Peruvian warbling-antbird must walk a fine line between being different enough from its competitors to reproduce successfully, while staying similar enough to be able to recognize and outcompete the same competitors (Image Credit: Hector Bottai, Image Cropped, CC BY-SA 4.0).

Range-wide spatial mapping reveals convergent character displacement
of bird song (2019)
Kirschel et al., Proc B, https://dx.doi.org/10.1098/rspb.2019.0443

The Crux

In nature, many different organisms can be found in a single location, and sometimes those organisms are closely related to one another. When this happens, classical evolutionary theory predicts that these closely related species should differ in some ways, so as to differentiate members of their own species from others and avoid the costs associated with breeding with a mate that will not produce any viable offspring. This is called character displacement, and there are many examples of this in nature where two different species may be very similar when they live in different places (allopatry), but when they live in the same place (sympatry) they will differ in appearance, behavior, or the exact part of the local habitat that they live in (see Niche Partioning below).

A specific form of character displacement, called agonistic character displacement, occurs when traits or behaviors associated with competition differ between closely related species living in the same area. This is thought to reduce the costs of wasting energy on competing with an organism that you don’t really “compete” with. Agonistic character displacement can, however, result in greater similarity of traits when similar species live together, but previous studies in this area have not accounted for other causes of this similarity. Today’s authors wanted to do just that. Read more

Keep Your Eyes Open

Image Credit: ulleo, Pixabay licence, Image Cropped

Natural selection favors a larger eye in response to increased competition in natural populations of a vertebrate (2019) Beston & Walsh, Functional Ecology, doi: 10.1111/1365-2435.13334

The Crux

Studying the evolution of traits in response to selection pressure often helps us understand why species look and act the way they do. Selection pressure can include the need to find food before other members of your species, or the need to escape predation.

But what happens when improving your ability to obtain resources also means you’re more vulnerable to predation? Which will win out? This paper looks at a small species of freshwater fish, Rivulus hartii, and determines which of the two pressures contributes most to the evolution of the size of their eye.

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The Ecology of a Mermaid

Image Credit: The Little Mermaid, 1989

Adam regales us with one of the weirdest stories I’ve ever heard, and in case you were wondering, yes we do talk about how mermaids have sex. Jesus. Also there’s some cool ecology. Like how did mermaids evolve? Was it from a mutated baby tossed overboard? Probably not.

05:19 – Mermaids in Cinema
16:35 – Ecology of the Mermaids
33:25 – Mermaid Copulation (you were warned)
38:07 – The Mermaids vs. Jaws

You can also find us on iTunes and Google Play.

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, Image Cropped)

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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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, Image Cropped)

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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Victory May Not Guarantee Survival in Species Conflicts

Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet?
Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet? (Image Credit: Daiju Azuma, CC BY-SA 2.5, Image Cropped)
Insight into invasion: Interactions between a critically endangered and invasive cray fish (2018) Lopez et al., Austral Ecology, doi:10.1111/aec.12654

The Crux

When we talk about invasive species, often the first thing that pops into our minds are things like feral cats, wild pigs, vicious newcomers that wipe out species or transform vast areas. But often what we focus on less are species which arrive and simply outcompete the locals.

The yabby (Cherax destructor) is one such invader. An Australian species, it has been introduced to new waterways through the country and is now threatening other species, including the Falls Spiny Crayfish (Euastacus dharawalus) in eastern New South Wales, Australia. The introduction of the yabby has resulted in a decreasing habitat range for the crayfish, but what sort of mechanisms are causing this? This experiment aimed to document interactions between the two species.

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