Archive for the ‘evolution’ Category

First Post – Where does D. melanogaster come from?

June 20, 2008 Leave a comment

For the first post, I will begin with a short statement of what I forsee for this blog. I am a graduate student in evolutionary ecology / genetics / development, and likely will have many science oriented blog posts. Though other tidbits are likely to show up here as well. I think that there are both selfish and altruistic reasons to have a blog. Selfishly, I think that writing more about science is going to help me to wrap my head around complex ideas, and really focus my thoughts. Altruistically, one of the most important, yet sadly neglected, aspects of science is communication with non-scientists. I hope that non-scientists as well as scientists will find my blog of interest.

Ok. On to the science.

I recently finished up an evolutionary physiology project using the workhorse of genetics – Drosophila melanogaster . I will begin by saying that one of the first things I told my PhD advisor when I arrived in graduate school was that there are only a few aspects of research that I did not want to pursue, and the first was that I really did not want to work with Drosophila thinking that most Drosophila research is of the type “Gene X binds with Gene Y under some highly unnatural condition”. Turns out one of my projects has focused on highly adaptive traits in natural populations of melanogaster. Oh well, back to the science.

D. melanogaster is a cosmopolitan fruitfly – it is found in all biogeographic regions of the planet, and is one of only two species of the genus that has successfully colonized both tropical and temperate regions (the other speices is D. simulans – a close relative of melanogaster). D. melanogaster is highly commensal with humans, being transported all over the globe through modern commerce. Because of its relationship with humans, its likely high migration rate, and likely high rate of transient individuals, population genetic studies have been difficult. Therefore the biogeographic history of the species is not well worked out.

It is widely accepted that D. melanogaster originated in East Africa mainly due to two the fact that majority of closely related drosophilids are endemic to Africa, and most of the polymorphism in non-African populations of the species can be found in African populations. Migration patterns into Eurasia were likely ancient as the flies could move across land the whole way, whereas migration into the Americas and Australia seems to have happened with the arrival of humans with commerce in these locations on the order of several hundred years ago. Population genetic and Phylogeographic studies of non-African populations have been difficult due to the species’ relationship with humans, its high level of global migration, and the recent colonization (D. melanogaster into North America have been its first description on the continent in 1862 (in Cuba) and many later published reports of them throughout the Americas by the 1880s.

I am not sure if there is a better way to date the arrival of D. melanogaster into North America due to the complications of the population genetics within the species. For now we are just left with the descriptions at the end of the 19th century. Regardless, it is safe to say that D. melanogaster colonized the Americas in the recent past.