Tag Archives: speciation

Simulating the Evolution of Life in South America

Modeling the ecology and evolution of biodiversity: Biogeographical cradles, museums, and graves (2018) Rangel et al., Science, 244, DOI: 10.1126/science.aar5452

The Crux

Understanding the processes which drive biodiversity worldwide is never more crucial than now, in a world where biodiversity is shrinking rapidly. Biogeography, the study of species distributions, has come a long way, but there are still a lot of problems that need solving, including improving our understanding of the interactions between factors like climate change, dispersal abilities, fragmentation and species competition, to name a few.

This paper attempted to analyse some of the effects of those factors in concert, by producing a simulation of the evolutionary process in the world’s most biologically diverse continent, South America.

What They Did

South America was chosen not only for its biodiversity, but for its place as the home of the Andes, a mountain range which is not only a huge source of climatic variation, but a huge dispersal barrier for many species.

The researchers simulated everything to do with a species life history over an 800,000 year period. This included for instance whether or not its dispersal ability allowed it to survive habitat fragmentation, or whether it was able to evolve fast enough to survive climatic changes.  The simulation used no ‘real’ data whatsoever, instead the parameters used to run the simulation were randomised based on biogeographical principles. The simulations were also run over a gradually topographically smoothed version of South America, which emphasised the effect that the wide variations in climate produced by the Andes have on increasing species diversity.

Did You Know: Islands in the Tropics

Island biogeography studies the distributions of species on islands, which often show trends in species richness and composition that vary wildly from the mainland. However many of the trends seen in islands can also be seen in mountain areas, as species which require higher altitudes to exist face the same issues dispersing between areas of similar altitude as do species attempting to move from island to island. Cool mountain forests in the otherwise dry Great Basin in the USA and the higher, less tropical peaks of the Anders are great examples of this, with many species isolated in these mountaintops.

What They Found

The simulations bore a strong resemblance to current species patterns in South America, lending credibility to these results. The simulations were most sensitive to the location of the ‘founder species’, with the effect of temperature, speciation and extinction on a species varying depending on where it first appeared. The species ability to evolve quickly also affected the models, with high rates of evolution promoting the dominance of relatively few species, and low rates producing high extinction. Overall species diversity declined as the topographical variation of the Andes was reduced, confirming the role of a varied climate as a driver of species diversity.


Increasing rates of evolution in the simulations prevented high levels of species extinctions, but increasing them too much resulted in a few species dominating the rest (Image Credit: Santiago Ron, CC BY-ND 2.0)


Whilst this paper is undoubtedly cool, I want more information on its application to species fluctuations today. Is something that doesn’t take into account the rapid human-driven change we’re seeing today useful in predicting species distributions in such an immediate future?

So What?

Models like this are frankly astonishing. They give hope that one day we won’t necessarily need mountains of data to provide simulated forecasts of the consequences of our immediate actions on the planet. Having seen co-author Carsten Rahbek speak on the challenges in modelling recently, I hope that advances in this field will help us isolate regions and species in dire need of conservation.

Demonstrating Adaptive Evolution in Parasites

Host defense triggers rapid adaptive radiation in experimentally evolving parasites (2019) Bush et al., Evolution Letters, p. 1-9

The Crux

Adaptive radiation is a fascinating ecological concept, one with which anyone who knows the tale of Darwin’s finches will be familiar with. The basic premise is that an organism may evolve different forms (and ultimately become different species) in response to pressures exerted upon them.

But whilst this may have been observed in many vertebrates, it’s often overlooked in parasites, whereby host defenses can prompt divergence in parasite morphology. Today’s paper wanted to test the two basic concepts of evolution. 1) Can host defenses prompt physical changes in parasites? 2) Are these changes heritable?

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The Ecology of a Mermaid

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.

How to Ecology Your Dragon

In our second week on the dragons of Dreamworks’ How to Train Your Dragon trilogy, we have a flamin’ good time discovering why those dragons are WAY too wacky, exactly how much intraspecies predation goes on in Berk and why you should really make up your mind about domestication.

03:49 – Vikings in Cinema
10:57 – Ecology of the Dragons
29:17 – Toothless vs. the Furious Five

You can also find us on iTunes and Google Play.

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.

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