Changing with the Climate

Signatures of local adaptation along environmental gradients in a range-expanding damselfly (Ischnura elegans) (2018) Dudaniec et al., Molecular Ecology http://doi:  10.1111/mec.14709

An immature female blue-tailed damselfly (Ischnura elegans) (Image Credit: Charles J Sharp, CC BY-SA 4.0)

The Crux

Terrestrial organisms aren’t always stationary entities, they often move around the landscape searching for food, potential mates, or more ideal environments. Over time, these movements may introduce the species into new environments, as some change allows the species to expand their historical range.

An interesting aspect of this shifting of the species range is how the organisms at the edge of the distribution are maladapted to the novel environments, as most of the species will be adapted to conditions at the core of the species range. To overcome this, they must adapt to the new conditions. Successful adaptation is dependent on changes in gene frequencies away from the historical genotypes, with an increase in genes that promote survival in the new habitats. The authors in this study used molecular techniques to identify genes that new environments might select for.

When the Food Comes to You

Long-distance migration of prey synchronizes demographic rates of top predators across broad spatial scales (2016) Ward et al, Ecosphere, DOI: https://doi.org/10.1002/ecs2.1276

Disconnected Orca populations often use the same food source. So can this lead to similar demographic rates? (Image Credit: publicdomainpictures.net, CC0 Public Domain)

The Crux

Populations that experience some kind of connection are classified as “meta-populations”, as they are all interconnected in some way and can influence one another. Although these populations may be geographically and reproductively isolated, meaning that they are in different places and the organisms from the different populations don’t breed with one another, certain environmental factors may cause these populations to grow or shrink in similar ways.

The key to understanding how this synchrony between the varying populations happens is understanding what connects them. Killer whale (orca) populations in the northeast Pacific Ocean inhabit three distinct areas, with orcas from the northern and southern populations never coming into contact with one another. They do, however, feed on the same salmon populations that migrate from where the southern population lives to the where the northern lives. The authors wanted to find out if this connection via a food source could result in the demographic rates of these distant populations syncing up.

Grazers as Managers

Livestock grazing regulates ecosystem multifunctionality in semiarid grassland (2018) Ren et al., Functional Ecology, DOI: http://doi.org/10.1111/1365-2435.13215

A lamb, one of the many different kinds of grazers on our planet (Image Credit: Wikimedia Commons, CC 2.0)

The Crux

Grassland is the most common type of land cover on our planet, and about one third of the Earth’s population depends on these ecosystems to survive. Grasslands are not only the most common terrestrial ecosystem, but they are also some of the most vulnerable to degradation.

Sustainable grazing practices on these ecosystems are incredibly important when trying to maintain or improve the health of the many organisms that call grasslands home. The challenge with maintaining ecosystem multifunctionality is that trade offs between different functionalities are common, making it difficult to accomplish every goal at once. When managers try to maximize the productivity of a system this may reduce the overall diversity, as this often involves promoting the dominant plant species at the expense of every other species. The authors of this study were interested in determining the effects of grazing on environmental multifunctionality, so they analyzed what impact grazers had on multiple traits of the grassland ecosystem.

Taken For a Ride

Mind Control: How Parasites Manipulate Cognitive Functions in Their Insect Hosts (2018) Libersat et al., Frontiers in Psychology 9.

This parasitic fungus takes over the brain and then ejects its spores out of the ant’s head (Image Credit: Penn State, CC BY-NC 2.0)

The Crux

The field of neuro-parasitology is a relatively new field in biology and deals with the study of parasites that manipulate the nervous system of their hosts for their own gain (usually at the expense of the host). The authors of this review focused on host-parasite interactions between insect hosts and their myriad of parasites, due not only to most studies in this field being done with insects, but also the fact that most animals on the planet are in fact insects.

The Chilly Cradle of Life

An inverse latitudinal gradient in speciation rate for marine fishes (2018) Rabosky et al., Nature 559

Species richness is much higher in waters near the equator, but do we see that in a phylogenetic tree? (Image Credit: Rich Brooks, CC BY 2.0)

The Crux

The tropical regions of the Earth are the most species-rich and diverse ecosystems on the planet, with this diversity and species-richness declining as you move further and further from the equator. One hypothesis explaining this is that speciation rates are simply higher in the tropics, meaning that more species are evolving in a given time in the tropics than anywhere else. To test for this, the authors used the largest phylogenetic tree available and analyzed speciation rates (how many new species evolve from older species) per million years.

Snakes Spreading Seeds

Seed ingestion and germination in rattlesnakes: overlooked agents of rescue and secondary dispersal (2018) Reiserer et al., Proceedings of the Royal Society B: Biological Sciences, 285(1872)

The sidewinder rattlesnake, one of many snakes that inadvertently transports seeds by swallowing small herbivores (Image Credit: Brian Gratwicke, CC BY 2.0)

The Crux

Plants depend on outside forces to disperse their seeds away from the parent plant, and the most common way is via a process called zoochory, where animals spread the seeds. This can be due to seeds being stuck onto the fur of an animal, animals taking and storing the seeds in a different location, or when an animal eats the fruit and later defecates the seeds.

One indirect way in which seeds are dispersed is when a predator, such as a coyote, raptor, or bobcat, consumes an animal (like a mouse) that had seeds in its stomach or cheek pouches. Rattlesnakes commonly consume small rodents that carry seeds in cheek pouches, and though these snakes are known to eat these seed-carrying animals, their own role in seed dispersal remains largely unknown. In order to learn more, the researchers in this study dissected museum specimens to search for secondarily-consumed seeds.

Fortune Favors the Bold Spider

Selection for Collective Aggressiveness Favors Social Susceptibility in Social Spiders (2018) Pruitt et al., Current Biology 28(1)

Leadership can play an important role of a population dynamics, but is it the strength of the leaders or the willingness of the followers that has more influence? (Image Credit: Bernard Dupont, CC0)

The Crux

Socially-influential leaders can have a large effect on the actions of any group. Think of that one person in your life that everyone looks to when it’s time to make a decision; whether it’s something trivial like where to go for dinner, or something more important like whether or not to take that job on the other side of the country, these individuals make a large impact in their social circles. This can also be seen in the natural world, like the alpha of a wolf pack, or the matriarchs of an elephant troop or an orca pod. These focal individuals greatly influence the actions and success of their groups.

In order to determine not only how important these influential individuals are, but also how much the “social susceptibility” of the followers matters, the researchers in this paper used a species of social spider in two different habitat types. By using both arid and wet environments and analyzing both sides of the influence coin, this study was able to accurately determine the importance of both influencing and being influenced in different ecosystems.

Scared to Death

Fear and lethality in snowshoe hares: the deadly effects of non-consumptive predation risk (2018) MacLeod et al., Oikos 127(3)

Fear itself of a predator is enough to reduce populations of a snowshoe hare, show Macleod at al. (Image Credit: Dave Doe, CC BY 2.0)

The Crux

When we think of a predator-prey relationship, many colorful examples of charismatic animals come to mind: the lion and the wildebeest, the orca and the seal, the owl and the mouse. We think of these organisms locked in an endless battle, with one needing to catch and eat, the other to escape and live. While these are definitely interesting and important aspects of the predator-prey relationship, prey species need to worry about more than just being eaten. These “non-consumptive effects” play into what is called the Ecology of Fear.

This study was an attempt to show that the perceived risk of predation itself was enough to reduce survival in prey species. Unlike previous studies on this question, MacLeod et al. were the first to conclusively show this effect in mammals.

Water Pollution Allows Unhealthy Males to Breed More

Reversed parasite-mediated selection in sticklebacks from eutrophied habitats (2010) Heuschele & Candolin, Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-010-0937-9

Normally three spined sticklebacks are less likely to find a mate when they are affected with parasites, but does this change with eutrophication? (Image Credit: Sam Perrin, NTNU)

The Crux

We’ve all heard the stories of turtles choking on plastic bags, or birds swallowing sporks. Algae grows out of control due to chemicals being added to the water, which changes the native habitat. For fish like sticklebacks, where males compete for the attention of females, the loss of visibility has the potential to be a problem for the females. Male sticklebacks defend a territory, develop a bright red spot, and fight other males. The long and short of it is that the bigger, stronger, and prettier fish mate more and the weaker and uglier fish don’t. One thing that weaker males tend to have more of than stronger males are parasites, which isn’t a surprise as a parasite’s entire existence revolves around surviving at the expense of whatever organism is unfortunate enough to have them.

Understanding how eutrophication affects female choice in relation to parasites, and thus the reproductive dynamics of this system, is quite important. This paper tries to map that out, using the Baltic Sea around Southern Finland. This experiment is well-suited to the problem, as there has already been evidence for algal growth changing the dynamics of stickleback reproduction.

Getting Better May Get You Eaten

Immune response increases predation risk (2012) Otti et al., Evolution 66

Fighting off an infection can use up valuable energy, and also change behaviour, which can lead to enhanced risk of predation (Image Credit: Gilles San Martin, CC BY-SA 2.0)

The Crux

Parasites and diseases cause a lot of problems for their hosts, stealing resources like blood, food and energy. But fighting off parasites is also a costly process, so hosts have to walk the thin line between using just enough resources to fight off the parasite and using too many, leaving them with nothing. The amount a host invests in their immune response will depend on the specific environment that they live in. For example, in an environment where resources are plentiful, a host may decide that it is worth shaking off a parasite or disease. In areas where resources aren’t, they may choose to save energy.

Introducing predation to a situation further complicates things. Having a lot of predators around naturally means energy conservation becomes even more important. This study examines the risk of predation for an organism that is fighting off an infection.