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
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.
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.
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
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.
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.
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 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.