Chapter 11: Fornications of Kings Kirsten and Sam
Good Morning! Who s ready to learn about some incest? Discussion: Social reactions to incest vs. animal world incest- talk away! - Zoos - Dog breeds - Loss of habitat - Game of Thrones
Acarophenax mahunkai Fornicating with sister in the womb when the belly burst and all his sisters left him in their mother s corpse Males in species such as this are usually short lived and puny, some even lack mouths
Inbreeding depression-reduced vigor of inbred children compared to outbred Issues with Incest Due to recessive genes Recessive genes- the overridden copy of a gene from either the mother or father effects don t show unless individual inherits two copies Can be deadly! More likely to now work properly Family members genetically more similar, so odds of uniting two copies of harmful recessive genes rise
Animal In Favor of Incest: Hermaphrodites Commit self-fertilization egg and sperm shifting inside The Exception -->Earthworm folds in on itself 80% Flowering plants Flowers with both male and female parts Making both male and female flowers simultaneously ¾ self-fertilize once in awhile
Any Child is Better than None Offspring of selfing hermaphrodites are even more vulnerable to inbreeding depression Any child is better than none Emergency Selfing White-lipped snail If no mate appears it will start selfing Inclination to self-fertilize should depend on the balance between inbreeding depression and opportunities for mating with others
Nonhermaphrodites: Humans Hawaiians, Egyptians, and Incas brother sister mating was mark of divinity Royal families of divine ancestry mimicking ancestoral behavior Unsure to what extent inbreeding depression occurred Consequence of social stratification Common in Europe where women not permitted to marry men of lesser rank than themselves
Nonhermaphrodites: Insects,Mites,and Pinworms Many insects and mites and all pinworms have few recessive genes no inbreeding depression! Haplodiploidy: (more Harmful common) recessive genes never have chance to accumulate Females are diploid and receive two copies of each gene, one from each parent Males are haploid and hatch from unfertilized eggs, receiving only one copy of genes from their mother Males have no fathers and females don t need to mate to produce sons Parental Genome Elimination: (less common) Males come from fertilized eggs, but in early development father s genes destroyed Causes males to have one set of genes Ex: Button beetle and wasps
Mites and Orgies Mites as a group tend to have disproportionate sex ratios and commonly have many more females than males Skewed ratios are often a trademark of close incest: Having a couple males is plenty if there is no competition for mates since the only females present are all mothers or sisters Paternal Genome Elimination: Some mites (and a few insect species) go through a process that kills the male portion of the diploid mite resulting in an offspring that was once diploid but becomes haploid early in embryonic development Basically the males are there to provide sperm and that s it
Sex Ratios Scleroderma immigrans (a wasp) will mate with her sons and grandsons Female button beetles will sometimes lay haploid male eggs simply to provide themselves with fertilization and then lay diploid female eggs instead- males live for a very short period of time and are few and far inbetween Wood lemmings have a maverick chromosome that skews the population to be seventy percent female
Outbreeding Depression Mangrove fish only vertebrae know to self-fertilize hermaphrodite mangrove sih are incapable of spawning with one another Only spawn with pure males Outbreeding depression- sometimes unions between distantly related individuals produce offspring who has a poor chance of surviving or reproducing, than offspring of more closely related parents
WHAT?!...HOW?! Genes of partners cannot act effectively together mare + jackass = mule May indicate populations are diverging into separate species odd and even year salmon in a river External environment individuals evolve features to cope with local conditions mating with individual from elsewhere may break favorable gene combinations
Some Professional Advice You are damned if you inbreed and damned if you outbred Documented cases of outbreeding depression are far fewer than inbreeding depression Inbreeding depression drives evolution of mechanisms to stop mating with relations Mechanisms to avoid outbreeding are unknown and is probably just a cause of mating patterns Guess who!