Show Me The Science Month Day 5

Speciation Genetics is, in a sense, an oxymoron. Genetics is the study of heritable characteristics, but the researchers who study speciation genetics are looking for genes that cause inheritance to fail. They are looking for the genetic incompatibilities that keep species apart.

Speciation is about how a population of similar, interbreeding organisms becomes two or more populations so different from each other that they no longer form a common gene pool. Species' differences can be extremely subtle. In fact, an evolutionary process of speciation means that there must be a point at which the physical differences between two species is hard to discern, as well as a point when two populations aren't quite different species, but well on their way to becoming separate. At some point, when one gene pool splits into two, genetic incompatibilities arise that make cross-breeding between two populations a doomed enterprise.

What kinds of genetic incompatibilities first arise in the process of speciation? What types of genes are involved? A paper in the January 16th issue of Science reports on the discovery of a 'speciation gene' keeping two mouse sub-species from producing viable offspring.

Show Me The Science Month Day 4

How did we become human? You can ask the same question in a slightly different way: how did we become different from chimps?  Although the common ancestor that we shared with chimps 5-7 million years ago was not itself a chimp, it probably resembled modern-day chimps much more than it resembled us. Both humans and chimps have been changing under evolutionary pressure since our lineages split, but humans have obviously picked up traits that make us stand out from other modern apes, most notably our intelligence.

Show Me The Science Day 3

Reproduction involves some tricky trade-offs for all species, and anyone who has watched a David Attenborough film knows that you can find a wide range of reproductive strategies in nature. Some animals spend their energy producing hundreds or thousands of offspring and leave them to fend for themselves. Others, like whales and humans, produce only a few offspring but expend an enormous amount of resources trying to give those offspring the best chance in life possible.

Plants face a similar trade-off. They can choose to produce many energetically cheap small seeds, or fewer, more expensive large seeds. A recent paper in PLoS Genetics takes a look at one of the genes involved in seed size evolution. They study naturally-occurring genetic variation in found in this gene, and the relationship of that genetic variation to seed size in the domesticated tomato and its wild relatives.

Variation in Seed Size, Figure 1 from Orsi and Tanksley