On the relative eve of such an amazing time in our history as the 200th anniversary of the births of both Charles Darwin and Abraham Lincoln (two of my favorite people, born on the same day - February 12, 1809 - mind you) and in light of my own birthday (February 2nd - mark your calendars!) AND the inauguration of President Barack Hussein Obama, who may do wonders for Science in America, I felt it fitting to talk about evolution.
Yes, for the two of you who may be sincerely interested, I thought I would give a brief description of what it is that has brought me (us) to Scandanavia - my research.
I have begun my research in Evolutionary Genetics with the goal of getting a PhD in 3 short, busy years. I was selected along with eight other early stage researchers (ESRs) from across Europe and Asia under a Marie Curie grant, funded by the EU, to study the process of speciation. I am the only American in the group.
http://speciation.group.shef.ac.uk/itn/
Speciation is the process by which new species are formed. Typically, it involves some sort of barrier to gene flow - usually a geographical one - that allows two or more populations of a single species to diverge genetically as they evolve in habitats that differ ecologically. Different local ecologies means different selective pressures ("natural selection") and, thus, different local adaptations for each group. For instance, one population may be exposed to different predators, temperatures, or host plants (as is often the case in insects) than the other. This means that the two populations will evolve and adapt to the specific challenges they face.
You can also think about the African ancestor to modern humans, separated from other similar populations (which would become our ape relatives) by ecology (i.e., "apes" in the forest, "humans" on the savannah) or by sheer distance, as the human predecessors began to move out of Africa an inhabit every (expletive!) inch of the globe. (I read recently that the population size of our ancestors before leaving Africa was a mere 5,000 strong.)
Along with adaptation by natural selection, different mutations accumulate and genetic drift progresses in a different fashion in each population. With enough time - usually millions of years - substantial genetic differences build up until, at some point, the two populations are so far different from one another that they can no longer interbreed; this is the prerequisite for species formation and existence, according to the biological species concept, or BSC. The BSC defines a species as a group of interbreeding individuals which are fertile among themselves, but not with any other groups. (What about lions and tigers, right?)
Whereas my Master's work was on two desert Drosophila species, my work in Finland will focus on the boreal "fruit fly", Drosophila montana. This species has adapted to live in the cold of the northern latitudes and can be found near the arctic circle, close to 66ºN latitude, where temperatures can dip down to -50ºC. That's -58ºF - pretty amazing for an insect! It's range extends across the northern hemisphere throughout Europe, Asia, and North America and it is generally associated with water - beaver dams in particular. Populations in our lab include flies from Finland, Canada, and high elevation sites in Colorado.
These flies overwinter as adults. This means the few short months of warmth that they experience are vital to their survival. During the warmest parts of the year, adult flies emerge from "hibernation" (called "diapause" in insects) and look for mates. Mating season is short, typically only a few weeks, and the rest of the warm season is time enough for the larvae (maggots, you might call them) to feed, grow, form a pupal case, and emerge as winged adults. There is usually only one generation per year, which means the newly emerged adult flies that survive to see the onset of winter must go dormant and wait until the following spring to find a mate.
In the first phase of my research, I will be looking to see if sexual isolation has arisen between populations from Oulanka, Finland (in the north) and those from Vancouver, BC. In other words, are these populations in the early stages of speciation? I will run mating trials where mature, adult flies of each population will be allowed to choose between their own and foreign members of the opposite sex. If mating is non-random (in other words, if they choose their own type over members of the other populations) then it is an indication that they are indeed diverging and possibly becoming new species. The small amount of work that has been done already in our lab suggests that they are not sexually isolated, however, all mating trials performed up to this point have been "no-choice" by design. In other words females (who generally do the choosing in Drosophilids) are confined with either a similar or a foreign male, and then scored as to whether copulation (mating) occurs.
So a guy walks into a bar...and there's only one girl there. (Who do YOU think he'll choose?)
I should start my experiments within the next month or so and I am looking forward to the work. I will also do some genetic work with microsatellites to determine if female flies who have been multiply inseminated can "choose" whose sperm they use to produce offspring, and whether there is a connection between chromosomal inversions and sexual isolation (I can see your hand wafting over your head now).
One great thing about this study is that it will include fieldwork. As I learned at the University of Arkansas under the direction of Dave Stahle climbing ancient bald cypress in the swamps of south Arkansas and Bill Etges in the Sonoran desert collecting flies for my Master's work, fieldwork is one of my favorite things. Now, instead of going into pristine, undisturbed landscapes in search of old-growth trees and cactophilic fruit flies, I'll be going into pristine, undisturbed landscapes in the warm boreal spring in search of beaver dams and Drosophila montana, although I'm sure I'll pay plenty of attention to the trees too...
Onward,
Jackson
Thanks, now I get it!
ReplyDeleteLove, Mom