Animal Behavior Exam 2

sexual selection

a form of natural selection proposed by Charles Darwin, where individuals with certain inherited traits are more successful at obtaining mates and reproducing

intrasexual selection

competition between members of the same sex (usually males)for access to mates, resulting in traits like size, strength, or weapons

intersexual selection

one sex choosing mates based on desirable traits resulting in ornaments or displays

• direct contests over access to females

• dominance ranks

• territory holdings

• sperm competition

Male intrasexual selection

• who will mate

• which sperm will fertilize

• how much to invest in offspring afterwards

Female intersexual selection

• intrasexual = male-male competition

• intersexual = female mate choice

intersexual vs intrasexual selection

• nuptial gifts

• sexual suicide

• parental care

direct benefits of mate choice

• contain gifts that improve germ storage

• bitter compounds that reduce predation

Nuptial gifts

Fecundity

biological potential or physical capacity to reproduce

sexual suicide

male sacrifices himself to be cannibalized by female

copulation

physical act of sexual union, specifically the insertion of the male reproductive organ into the female's, for transferring sperm and ensuring fertilization

• higher offspring genetic quality

• increased inclusive fitness

Indirect benefits of female mate choice

• increase offspring’s genetic quality

• traits that are honest indicators of male genetic quality

• males are genetically compatible

Good genes hypothesis (indirect benefits)

• direct benefits: parental care

• indirect benefits: parasite resistance genes

Good genes hypothesis: Sticklebacks

• had men and women wear t-shirts to sleep in and rank other shirts based on “attractiveness of smell”

• optimal mating choice = someone with different MHC genes since offspring with more diverse MHC complexes are correlated with fitness

Good genes hypothesis: sweaty t-shirts

ridiculously extreme trait with no survival advantage other than female preference

runaway sexual selection

• large females have larger fecundity

• females who have eaten recently are less likely to cannibalize

Why do male praying mantis prefer larger females

allows females to be available and fertile since they don’t have to spend time nursing offspring

Why do gelada monkeys commit infanticide

females abort infants if new male takes over since infanticide hurts her reproductive rate

Counterstrategies to infanticide

Male bed bugs pierce female’s abdominal wall and inseminate directly into her body cavity

Traumatic insemination

• Time

• Energy

• Lost opportunity

• Exposure to predation

Costs of female mate choice

female dolphins have vaginal folds, position female in determines if females can be fertilized

Copulatory choice

• cryptic female choice

• control of fertilization

Post-copulatory mate choice

cryptic female choice

bias sperm use in favor of specific males, allowing them to influence paternity even after mating with multiple partners

• cost: predator locates you

• benefit: save your kin

Cost and benefits of alarm calls

nepotism hypothesis

favoring family or kin in hiring, promotion, or resource allocation

inclusive fitness

an organism's total genetic success, measured by the sum of its direct fitness (producing its own offspring) and its indirect fitness (helping relatives raise offspring who share the same genes)

kin selection

traits of an individual that enhance the fitness of relatives can be favored even if they reduce its direct fitness

rB > C (relatedness x benefit > cost) OR

Hamilton’s Rule

F_Tot = F_D + F_I

inclusive fitness

probability that 2 individuals share a random gene at the same locus identical by descent (IBD)

r (diploid relatedness)

r_XY = Σ (1/2)^L_XY ,L_XY = number of links that create the shortest path between X and Y

Generational distance method

Phylogeny argument: Females had 2 advantages over males:

1. Parental care tendencies

2. Began evolving stingers initially ovipositors which became prey paralyzers

Why only female workers in haplo-diploid communities?

1. Division of labor

2. Overlap of generations

3. Cooperative work for the colony

Haplodiploidy and eusociality

clumped food sources and nests make finding mates difficult, high level of intebreeding make them mimic haplo-diploid situation with high relatedness

Bartz theory for termite eusociality

Food is clumped so getting to food resources may expose them, cover wood with dirt before safely foraging

Predation theory for termite eusociality

human menopause and long post-reproductive lifespans evolved because grandmothers enhanced their inclusive fitness by helping to feed and care for grandchildren

grandmother hypothesis

• helps maximize inclusive fitness

• depends on relatedness to social group

• older females are repositories for ecological knowledge

• helps offspring when resource availability fluctuates

• reproductive conflict

Menopause

• anti-predation

• improved foraging efficiency

• defense of resources

• aerodynamic/hydrodynamic

• homeothermic

• improved care of offspring

• information sharing

benefits of group living

• competition for food, mates, nest sites, materials, limited resources

• risk of infection via disease/parasites

• exploitation of parental care

• infanticide

• conspicuous

Costs of group living

• dilution

• detection

• defense

• deterrence

• confusion

Antipredatory benefits of group living