Diversity of reproduction

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

2. 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.

3. 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)

4. 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

5. Intrasexual selection • Competition for copulation Dominance Alternatives: • friendship with females • male coalition • female mimicry • satellite males • forced copulation

6. Competition for fertilization Sperm competition • Physical, chemical, mate guarding, etc • Competition after fertilization • Bruce effect • Infanticide

7. Female choice • Unequivocal female preference, not a result of male competition • Choice based on "genetic quality“ • runaway selection — Fisher • good genes (survival skill) • handicap principle — Zahavi • rare male effect

8. Choice based on 'non-genetic' benefit • resource defense • parental ability • Mating systems: monogamy, polygyny, polyandry, promiscuity

9. 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

10. 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

11. 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

12. 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

13. 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?

14. Increase breeding success • correlation approach • exp. removal of helper • Increase number of breeding free females from caring fledgling • Increase breeder survivorship

15. 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

16. 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

17. Evolutionary disadvantages of group living • Increase competition • Increase chances of spreading diseases and parasites • Interference with reproduction • Reduce fitness due to inbreeding • Attracting predators

18. Eusocial insect • cooperative care of young • reproductive castes • overlap between generations

19. 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

20. 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

21. 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.

22. 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