Tag Archives: phylogeny

If It Ain’t Broke, Don’t Fix It

Image Credit: Goutham89, CC BY-SA 4.0

The evolution of crocodilian nesting ecology and behavior (2020) Murray et al., Ecology and Evolution, https://doi.org/10.1002/ece3.5859

The Crux

One goal of evolutionary ecology is to understand the links between microevolution and macroevolution, meaning evolution in the short term (multiple generations) and how that scales up to the long term (millions of years). In macroevolution, a group of organisms is thought to be successful if it not only exists for a long period of time, but if it also boasts a large number of species. With those criteria in mind, crocodilians (alligators, crocodiles, gharials, and caimans) are one of the most successful lineages to have ever existed on the planet. Though they may not be the most diverse group of organisms with only 25 species, they have been around for about 100 million years. To put that into perspective, dinosaurs went extinct about 65 million years ago, meaning that the crocodilians not only lived with dinosaurs, but they survived the mass extinction that the dinosaurs didn’t.

This longevity as a lineage raises some questions as to what it is about the crocodilians that made them so successful, when their cousins the dinosaurs died out. An interesting aspect of crocodilians is that there is very little variation among these organisms, as they are all generalist carnivores, live aquatic lives, exhibit mating vocalizations, their sex is determined by the temperature of their eggs (see Did You Know?), and they care for their eggs and young. Despite these similarities, there are some notable differences in the reproductive ecology and behavior of the different species, specifically how they build and care for their nests. Because of these differences, the authors of today’s study asked if variation in how crocodilians reproduce may have been the cause of their success.

Read more

How Form Defines Function

Image Credit: Francesco Veronesi, CC BY-SA 2.0, Image Cropped

Macroevolutionary convergence connects morphological form to ecological function in birds (2020) Pigot et al, Nature Ecology & Evolution, https://doi.org/10.1038/s41559-019-1070-4

The Crux

There are an astounding amount of different forms that the animals on our planet take. Likewise, there are a multitude of diverse functions that animals serve in the environment, such as that of a herbivore, a predator, or scavenger. In some cases it’s a clear link between the form of a given animal and its function in the environment, like that of the beak of a hummingbird that allows it to feed on nectar and their role as a pollinator. But whether or not there is a reliable way to predict the function of an animal based off of its form is has been the subject of considerable controversy.

Deciding on how many morphological traits to use to predict ecological function is a difficult prospect. One could argue that it’s impossible to pick a finite number of traits, as there are infinite possible niches that organisms can fill so there’s no way that a set of traits could fill those infinite possible niches. Mapping animal form to function has major implications for quantifying and and conserving biodiversity, and the authors of today’s paper wanted to to determine just how many traits are needed to do that.

Read more

Subspecies – Do We Need Them?

Image Credit: billp1969, Pixabay licence, Image Cropped

You might have come across the word “subspecies” when reading about biodiversity, but what does the term actually mean? And do we really need a more precise classification beyond species? There is unfortunately no consensus about this. Ask 5 biologist and you’ll get at least 10 different answers. So let’s have a look at why it’s such a complicated issue.

Read more

Whales Are Fish: Weird Perspectives on Classification

You would think that after researching how a species will react to climate change, which individuals are more likely to avoid predators, and what its DNA says about its evolutionary history, simply classifying what species an animal is would be pretty simple. Unfortunately that’s not the case. I distinctly recall being given the runaround by my primary school teacher when asked to define what a mammal was (according to the internet a coconut qualifies, so maybe that debate’s not over yet).

Read more

Going Beyond Range Size in Analysing Extinction Risk

Animals of wildly different sizes may have different likelihoods of extinction, but it could all depend on their range sizes (Image Credit: Harvey Barrison, CC BY-SA 2.0, Image Cropped)

Constraints on vertebrate range size predict extinction risk (2019) Newsome et al., Global Ecology and Biogeography, http://doi/epdf/10.1111/geb.1309

The Crux

To act to prevent a species going extinct, we have to know that it’s at risk of extinction. Ecologists and conservationists simply don’t have the time or resources to make sure that all species remain safe. So having reliable methods of predicting species extinction risk is crucial.

On a global scale, the relationship between a species size and the area that it is found in (geographical range) has been studied intensively since ecology’s inception, both in existing and prehistoric species. Initial research showed that in general, the larger a species is, the larger its range size needed to be, with large species that had relatively smaller range sizes more prone to extinction. However more recent work has shown (naturally) that there are exceptions to this, with mammals viable range size actually decreasing up to a certain ‘breakpoint’, after which the size grows again.

Read more

Birds are Reptiles

When one looks at birds like this puffin, it can be hard to reconcile its cute appearance with its place in the animal kingdom. The thing is, this adorable puffin has something in common with a rattlesnake, in that it’s a reptile (Image credit: Ray Hennessy, Unsplash licence, Image Cropped).

You read that correctly, birds are reptiles. Now, I can hear you saying “but we learned that they are a different group of organisms, and that reptiles are just those scaly animals that have cold blood?” While reptiles don’t have cold blood per se, some of them DO have feathers. And can fly. In this post I hope to convince you of the fact that the puffin pictured above, and all of its avian relatives, belong with the snakes, lizards, crocodiles, and turtles in the reptile group.

Read more

The Chilly Cradle of Life

Species richness is much higher in waters near the equator, but do we see that in a phylogenic tree?

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)

An inverse latitudinal gradient in speciation rate for marine fishes (2018) Rabosky et al., Nature  doi:10.1038/s41586-018-0273-1

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.

Read more