Sunday, June 9, 2013

The term, ‘living fossil’ was initially coined by Charles Darwin to describe creatures that existed for several millions of years in the fossil record, but had changed very little in that time. Famous examples include the coelacanth and the lungfish. Conventionally, sturgeon are considered to be included in this group. But a new study shows that when it comes to change in body size over time, sturgeon have actually been evolving faster than most other fish.

The study, which was published in Nature Communications, shows that sturgeons have evolved a huge variety of sizes, from dwarf sturgeon the size of a bass and some species that can be as big as a car. This is just one result obtained in the study, which looked into the rate of species formation and anatomical variation in fish. To do so, an evolutionary tree linking 7,864 species of fish was assembled. The tree graphed DNA sequence data and body-size information for each species. The researchers actually had to develop brand new programs to process the huge data sets!

Using the raw data and the computer programs, the researchers studied ‘the correlation between how quickly new species form and how rapidly they evolve new body sizes’. Sure enough, a strong correlation was found between species variation and body size evolution across ray-finned fish. Up till now, the evidence for this was largely anecdotal. So, while palaeontologists noticed that groups of organisms with more species tended to have greater anatomical variation, the theory was never rigorously tested.

The fish can mostly be organized into two groups. The first group of fish, which includes the gar, forms species very slowly and has very little variation in body size. The other group, which includes salmon and trout, has fast species formation and a large range of body sizes.

In the words of the lead author, "We're basically validating a lot of ideas that have been out there since Darwin, but which had never been tested at this scale due to lack of data and the limits of existing technologies."

But you’re forgetting the sturgeon! The sturgeon is anomalous in that it does not conform to the general pattern. So, even though there are only 29 species worldwide, their body size is highly varied. Pfft… Hipsters!

Read all about it: http://bit.ly/13JKWXt
Image URL: http://bit.ly/11nblY5

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