Species interactions have predictable impacts on diversification (2021) Zeng and Wiens, Ecology Letters. https://doi.org/10.1111/ele.13635
Image Credit: MacNeil Lyons/NPS, CC BY 2.0
No organism on the planet lives in complete isolation from other organisms. Many organisms serve as a food source for others, and even apex predators have to compete for their food. Species interactions like predation, competition, and parasitism directly impact organisms in their daily lives, but there is also a possibility that these same species interactions have had an impact on much longer timescales. That is, species interactions may have had a direct effect on the diversity of life on our planet.
Species interactions have been previously shown to affect diversification rates (see Did You Know?), so the question that today’s authors asked was whether there is a general trend to the effects of species interactions on diversification rates? Specifically, do species interactions with negative fitness (such as being killed by a predator) impacts decrease diversification rates, and do species interactions with positive fitness (such as successfully parasitizing a host) impacts increase diversification rates?
High parasite diversity accelerates host adaptation and diversification (2018) Betts et al., Science. https://doi:10.1126/science.aam9974
Image Credit: Dr. Graham Beards, CC BY-SA 3.0
Host-parasite relationships are often thought of or depicted in a pairwise structure. That is, one host is attacked by one parasite, without an acknowledgement or consideration of how complex the relationship can be. For example, hosts are often attacked by more than one type of parasite, and the parasites themselves have to compete with one another for resources from the host. Because parasites are costly for a host, the hosts benefit from evolving resistance to the parasites. It follows that the more parasites a host is attacked by, the higher the benefit of evolving resistance, so we’d expect to see more resistance in hosts that are attacked more often. This should then result in differential evolutionary rates among hosts, which would then result in greater evolutionary divergence (see Did You Know?)
To test this idea, the authors of today’s study used a bacterium (Pseudomonas aeruginosa) and five lytic viral parasites (hereafter bacteriophages). These bacteriophages reproduce within host cells until they eventually cause the host to burst, killing the host (think of the chestburster in Alien, but a LOT of them). Because their reproduction results in the death of the host, lytic parasites impose a very strong selection pressure on hosts, making this a perfect host-parasite system to test the above prediction.
The discovery of ‘lesbian’ seagulls in California in the 1970s shook outdated beliefs that homosexuality was unnatural. Since then, scientists have documented cases of homosexuality in hundreds more species (Image Credit: JanBirdie, Pixabay licence)
Darwin’s work on evolution, natural selection and “survival of the fittest” is probably the most well-known scientific hypothesis out there.
Survival of the fittest means that the “fittest” have the highest reproductive success – whether that is achieved by roaring the loudest, building the most beautiful nest, camouflaging the best, or performing the most impressive mating dance. Passing on their genes to the next generation is what makes an individual successful in this context.
A flatworm (Pseudocerus liparus) crawling on a sponge – passing through a forest of hydroids and tunicates. (Image credit: Christa Rohrbach, CC BY-NC-SA 4.0)
Last week I posted an article about fascinating creatures that escape death almost completely, including the famous “immortal jellyfish” (link below). Yet while the jellyfish’s attitude to aging is awe-inspiring, its existence poses a more obvious, yet perplexing question: why do we age?
The hydromedusa of Podocoryna borealis. (Image credit: Lara Beckmann, NorHydro, CC BY-SA 4.0)
Our existences are often centered around the hope that we will live a long and fulfilled life. At the same time, while we aim to grow old, many of us abhor the aging process, dreaming of remaining young and healthy for as long as possible. It explains why we are so fascinated by the concept of immortality. Think of vampire stories, constant quests for the fountain of youth, or even the newest anti-aging products in the drugstore next door. But apart from the few extra years we gain nowadays through modern medicine and improved life circumstances, many of us can’t extend our lives much further.
We share this fate with many other animals that go through the stages of birth, growth, reproduction and death. But despite that, we don’t need to rely on science-fiction to get a glimpse of everlasting life: some organisms on our planet don’t follow these stages and some cheat it altogether – escaping death almost completely.
This is a cat bent on the apocalypse (Image Credit: Sa Ka, Pixabay licence, Image Cropped)
I like to think that when people visit Ecology for the Masses, they come to quench their insatiable curiosity about the ecological world and all its mysteries, and just want a well-reasoned, accessible answer to their issues (and also to figure out whether birds are reptiles of course).
Evolution and maintenance of microbe-mediated protection under occasional pathogen infection (2020) Kloock et al., Ecology and Evolution, https://doi.org/10.1002/ece3.6555
Image Credit: Zeynep F. Altun, CC BY-SA 2.5, Image Cropped
Microbes are everywhere in nature, and I don’t just mean out in the wild. They live inside of every plant and animal, including humans. These microbes can be harmful, beneficial, or do nothing to their hosts. When they help us, microbes take part in what’s called “defensive mutualism”, which is where they help their hosts fight off parasites. Benefiting from this mutualistic relationship depends on whether or not there are parasites around to defend against, as microbial defense mechanisms can harm not only the parasite but also the host itself.
For this symbiotic relationship to continue and not be selected against over time, the benefits of hosting the microbe must outweigh the costs. This is all well and good when there are always a lot of parasites to defend against, but that is not always the case. Today’s authors wanted to test how changes in parasite pressure over time affected the relationship between a defensive microbe and its host.
Endless forms most stupid, icky, and small: The preponderance of noncharismatic invertebrates as integral to a biologically sound view of life (2020) Jesse Czekanski‐Moir & Rebecca J. Rundell, Ecology & Evolution, https://doi.org/10.1002/ece3.6892
When we think about evolution, too often our perception is that it drives species towards larger, more complex, more beautiful forms. It’s driven by popular media in part, but also by the way we teach it and the organisms we choose to focus on. This goes right back to early conceptions of evolution, with Darwin’s seminal text The Origin of Species referencing “endless forms most beautiful and most wonderful”, instead of “most basic and abhorrent”.
But the authors of today’s paper want to challenge that preconception of evolution as favouring larger or more complex or beautiful organisms, and they have some truly magnificent examples to do so with.