Based at the Moffitt Cancer Center, Florida, Cancer Ecology is a small research group led by David Basanta. We are mathematical modellers who work with biologists and clinicians, trying to understand the ecology of tumors and the evolutionary dynamics of cancer progression and resistance to treatment.

What is a species?

Trait distribution

With the increasing focus on the role of intra tumour heterogeneity in cancer, figuring out the types of tumour cells in a cancer becomes more important. But whereas we have a good idea of what a species is when it comes to sexual organisms, this question is harder when dealing with asexual ones.
One approach is to look at the genetic differences between two cells. If the differences are small then we can say that they belong to the same species. The problem with that is that genetic differences may not mean much. From the evolutionary point of view what matters is the phenotype: the way the cell looks, behaves and interacts with other cells and the environment.
This is closer to what we do with sexual species. If two individuals of different gender can mate and have offspring that can also mate then they are considered to be part of the same species.
Tamir Epstein is a research scientist with a PhD in physics and whose work involves him jumping between Princeton and Moffitt. He raised this issue and suggested an approach that I am trying to explore here.
If you start a colony of cells in a petri dish starting from one single cell there will be a lot of traits where the cells will be slightly different from the original one. We can describe this with a distribution like the one in the figure at the top of this post.
So here is a possible definition of species for asexual organisms courtesy of Tamir and (and myself to a smaller measure through the discussion): two organisms belong to the same species if for a relevant number of traits they can lead to the same distribution. That is, if you take two cells, place them under the same circumstances and let them grow, the resulting distributions should be identical.
I am guessing this is a start. In reality it is quite likely that finding two cells that can lead to equal distributions of traits will be tough so a degree of flexibility migh be necessary.

Blame journals for bad science

Blame journals for bad science

Guns, germs, steel...and fashion

Guns, germs, steel...and fashion