Behavioral Ecology - Sexual Selection

What are two definitions for sexual selection?

1) A difference, among members of the same sex between the average mating success of individuals with a particular phenotype versus individuals with other phenotypes

2) Selection for traits within a sex specifically related to reproductive success

What is the difference between intrasexual and intersexual selection

1) Intra: “Male-male competition

2) Inter: “Female choice”

What is isogamy?

When gametes are the same size (occurs in many unicellular organism)

What is anisogamy?

When gametes differ in size, one large and one small (occurs in nearly all sexually reproducing multicellular plants and animals)

What is the main difference in gamete production between males and females?

Males can produce a lot of gametes (energetically cheap), whereas females are limited in gamete production (energetically expensive)

In intrasexual selection…

Males with the greatest size, strength, or best-developed weapons get the highest mating success

How can elaborate male traits hinder survival?

Allow for increased reproductive success with females, but at the cost of other survival

Ex: Male barn swallows with elongated tail feathers have increased mating with females, but catch less prey

What is the good resources/direct benefits hypothesis?

Females choose specific traits because they are signal/cues about the resources males will provide that will increase their reproductive success

Ex: Male sedge warblers with larger song repertoires feed their nestlings more

What are the good genes/indirect benefits hypotheses?

1) Fisher: Females gain attractive sons. More attractive mates have more attractive young; the hypothesis is only about attractiveness, not about quality

2) Zahavi: Good genes for sons and daughters. More attractive mates are higher genetic quality, and offspring will be of higher genetic quality; genes for survival and reproduction rather than genes just for attracting females