The Big Picture
In our context, this is essentially a scale issue of time or space or both.
Remember that if you are analyzing multiple groups that vary across time and space, you need to be sure that you are examining phenomena do not vary in that way (or at least vary in a compatible and predictable way) or the analysis doesn't make much sense. You will see later in the course that this simple assumption is often violated in biogeographic studies and that this often results in truly unfortunate consequences.
MICROEVOLUTION
vs.
MACROEVOLUTION
It isn't a contest - they are both part of the whole story.
Local processes lead to regional or global ones sometimes (diversification
of a particularly successful group).
Large scale parameters influence the evolution of many groups over
a large area sometimes (K/T boundary).
The two work in concert through NATURAL SELECTION.
We can think of Natural Selection as the force that effects all organisms. Those that do better are selected for, those that do worse are selected against. Natural selection is the process by which those that are selected against are weeded out. Even the best adapted organisms can be selected against when their environment changes.
EVOLUTION is change over time. Microevolution is change at the local (usually population) level. This can be as subtle as genetic drift (the random flow of genetic differences) or as striking as a massive and highly successful mutation. Founder effect - islands.
Genetic
Drift - a brief demonstration.
You
can do your own genetic drift simulations here.
Macroevolution is the term we use to describe the large scale changes that we see, usually over long periods of time or over large numbers of clades. As we saw with the Vrba paper, large scale changes are always occurring and are (for the most part) explainable. At long time scales we can see patterns such as PUNCTUATED EQUILIBRIUM. We will discuss this more next time as it relates to assumptions in how we discover phylogenies.
Now that you've learned the generalities and some terminology, we'll discuss some specific examples (mostly from the book) in class.
Watch for these terms that refer to the spatial proximity of lineages diverging in speciation events.
ALLOPATRIC
PARAPATRIC
SYMPATRIC
And these terms:
COMPETITION
ADAPTIVE RADIATION
VICARIANCE