Week 4. More Selection and Speciation

September 18th: Levels of Selection and Speciation.

Natural selection alters the genetic makeup of a population. The fundamental premise of Darwinian selection is that natural selection acts on the individual, but in recent years, a number of authors have argued that selection might act at a different levels. We will come back to this point later in the semester, but lets bring it up here while we are talking about selection.

For a time Ernst Mayr's formulation of the biological species concept clarified a vexing question for evolutionary biologists. However, evolutionary biologists continue to debate, and search for "the magic compeling definition of speicies" Hey 2001. While we will not cover the full spectrum of this debate, we must address the mechanisms by which new species arise in order to appreciate the role that animal behavior may play in this process.

Sinervo Chapter 4 & 5

for more on species concept see Hey (2001) The mind of the species problem. TREE 7:326-329
for a different twist read West_Eberhard (2005) Developmental plasticity and the origin of species differences. PNAS 102:6543– 6549.

September 20th: Sexual Selection and Matechoice

Charles Darwin distinguished sexual selection as variance in the number of mates.
"Sexual selection depends on the success of certain individuals
over others of the same sex, in relation to the propagation of the
species; while natural selection depends on the success of both
sexes, at all ages, in relation to the general conditions of life. "
—Charles Darwin, 1871

Sexual selection takes two major forms: intrasexual selection (most commonly seen as 'male–male competition') in which members of the less limited sex (typically males) compete aggressively for access to the limiting sex (typically females), and intersexual selection (also known as 'mate choice', most commonly 'female choice') in which males compete with each to be most attractive to females. As we will see later in the semester, these roles are reversed for some species. For today, we will consider cases in which Sexual Selection and Natural Selection may act in opposing directions.

Sinervo chapter 3 & 10
Moller, AP (1989) Viability costs of male tail ornaments in a swallow. Nature 339: 132-5.
Evans, MR (1998)Selection on swallow tail streamers. Nature 394: 233-34.
Moller, AP (1999) Moller (1999) scientific correspondence Nature 397: 115.
Anderson, M & Simmons, L.W. (2006)Sexual Selection and Mate Choice. TREE 21:296-302.

Chenworth & Blows (2006) Dissecting the comlex genetic basis of mate choice. Nat. Rev Genet. 7:682-692