Diversity of reproduction Asexual reproduction Parthenogenesis Hermaphrodites Sequential hermaphrodites - protogyny (F M) or protoandry (M F) Sexual.

Diversity of reproduction Asexual reproduction

Parthenogenesis

Hermaphrodites

Sequential hermaphrodites - protogyny (FM) or protoandry (MF)

Sexual reproduction

Male/female reproductive strategy

Asymmetrical gamete size (anisogamy) means the sex with smaller gametes should usually compete for access to the sex with larger gametes.

This results in greater variation among males than among females for reproductive success.

Males should, therefore, fight over females and females should select for resources

Sexual selection - The advantage which certain individuals have over others of the same sex and species, in exclusive relation to reproduction (Darwin, 1871)

A form of natural selection that occurs when individuals vary in their ability to compete with others for mates or in their attractiveness to members of the opposite sex.

As with natural selection, sexual selection leads to genetic changes in the population over time

Intrasexual selection Competition for copulation

Dominance

Alternatives:• friendship with females

• male coalition

• female mimicry

• satellite males

• forced copulation

Competition for fertilization

Sperm competition

Physical, chemical, mate guarding, etc

Competition after fertilization

Bruce effect

Infanticide

Female choice Unequivocal female preference, not a re

sult of male competition

Choice based on "genetic quality“

runaway selection — Fisher

good genes (survival skill)

handicap principle — Zahavi

rare male effect

Choice based on 'non-genetic' benefit

resource defense

parental ability

Mating systems: monogamy, polygyny, polyandry, promiscuity

Cooperation or mutualism-- a mutually helpful action

Reciprocal altruism (reciprocity)-- a helpful action that will be repaid in the future by the recipient

Altruism-- helpful behavior that raises the recipient's direct fitness while lowering the donor's direct fitness

Kin selection

A form of selection in which alleles differ in their rate of propagation because they influence the survival of kin who carry the same allele

Indirect fitness-- the genes contributed by an individual indirectly by helping non-descendant kin, in effect creating relatives that would not have existed without the help

inclusive fitness-- the sum of an individual's direct and indirect fitness

B/C > 1/ r or rB - C > 0

Cooperative breeding a social systems in which some group

members defer their own reproduction, even as adults, and help care for the young of a few breeding individuals

Helpers are typically (but not always) related to breeders and are often individuals that do not disperse instead aid in the rearing of their siblings

found in only about 3% of birds and mammals (roughly 200-300 bird species and about 120 mammal species)

Helper's duties--feeding, carrying, huddling, babysitting, grooming, defense, teaching, incubation, etc.

Do helpers really help?

Increase breeding success

correlation approach

exp. removal of helper

Increase number of breeding free females from caring fledgling

Increase breeder survivorship

Social behavior Societies--groups of conspecifics organized

in a cooperative manner Evolutionary advantages of living in groups

Protection from physical factors

Protection against predator

Assembling for mates

Finding resources, beater effect, overwhelm prey

Group defense of resources Division of labors among specialists Richer learning environment for young

that develop slowly, social facilitation

Cooperative defense against predator Increase vigilance, alarm Dilution effect Selfish herd hypothesis Mobbing, fight back

Evolutionary disadvantages of group living

Increase competition

Increase chances of spreading diseases and parasites

Interference with reproduction

Reduce fitness due to inbreeding

Attracting predators

Eusocial insect

cooperative care of young reproductive castes

overlap between generations

Possible explanations for worker sterility

Kin selection – haplodiploidy

But, they are more closely related to their own male offspring (r = 1/2) and their nephews (r = 3/8) than their brothers (r = 1/4). Therefore, expect workers to lay unfertilized eggs

If mothers are polyandrous (mate multiple times), then workers may be more closely related to their brothers than to half-nephews (r=1/8).

Expect workers to kill unfertilized eggs laid by other workers. Example: honeybees and yellowjackets are polyandrous and have low levels of worker reproduction

What about diploid eusocial animals (e.g. termites, naked mole rats)?

One proposed hypothesis is that these populations undergo cycles of inbreeding. With high levels of inbreeding-mother-son and sister brother can rapid approach r>3/4 for both males and females.

But high levels of inbreeding can lead to inbreeding depression

Thus inbreeding might alternate with some dispersal.

A rare disperser morph is found in mole rats: it is fatter, attempts to disperse in captive settings, solicits mating with non-colony members. Once settled reverts to xenophobia and loses fat stores