evolution iii - contents sexual selection vs. natural selection male and female strategies...
TRANSCRIPT
![Page 1: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/1.jpg)
Evolution III - contents
• Sexual selection vs. natural selection
• Male and female strategies
• Alternative mating tactics
![Page 2: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/2.jpg)
Sexual dimorphism
• The large, male California sea lion, is distinctive from the surrounding, smaller females (from Kardong).
![Page 3: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/3.jpg)
Sexual dimorphism• e.g. in peacock
![Page 4: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/4.jpg)
•
![Page 5: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/5.jpg)
Sexual selection
• Differential reproduction owing to variation in the ability to obtain mates (as opposed to natural selection, which is related to the differential survival of individuals in nature, depending on non-sex related traits) – see Futuyma – Evolutionary Biology
![Page 6: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/6.jpg)
Males are often less selective than females
Australianjewel beetle
maletoad
![Page 7: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/7.jpg)
Biologists exploiting animal desire
• sea
elephant
![Page 8: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/8.jpg)
Anisogamy - Sperm and oocyte of hamsters (enlarged 4000 times – from
Alcock)
![Page 9: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/9.jpg)
Differential reproductive success in males and females
• Female oocytes are a limited reproductive resource, whereas male sperm is not
• Therefore, males have the potential to sire many more offspring than females
• In humans, the male world record is held by Moulay Ismail the Bloodthirsty (Sultan of Morocco 1672-1727), who is said to have fathered 888 children
• Men produce between
100 and 300 million
sperm per day.
![Page 10: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/10.jpg)
Female reproductive success in humans
• According to Guinness World Records 2001, the highest officially recorded number of children born to one mother is 69. This was the first wife of Feodor Vassilyev (1707-1782) of Shuya, Russia. Between 1725 and 1765, in a total of 27 confinements, she gave birth to 16 pairs of twins, seven sets of triplets, and four sets of quadruplets. 67 of them survived infancy.
![Page 11: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/11.jpg)
Females must be more choosy because
• costs of producing female gametes are higher
• costs of pregnancy are higher (e.g. in mammals)
• females often invest more into parental care
• costs of mating with partner of poor genetic quality are higher in females
![Page 12: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/12.jpg)
Thus, a general pattern across the animal kingdom is
• males compete for females and try to mate with as many as possible (emphasis often on quantity)
• females are choosy and try to find the highest quality partners (emphasis on quality)
![Page 13: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/13.jpg)
How to impress females
• 1. look nice
![Page 14: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/14.jpg)
How to impress females
• 2. bring them presents
(as e.g. in scorpion flies (right)
and Bittacus (below))
![Page 15: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/15.jpg)
How to impress females
• 3. offer yourself as a present (e.g. preying mantids, some spiders: females cannibalise
males during or after mating –
thus detracting attention
from other possible sex
partners. also you give your
body as a resource for offspring)
![Page 16: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/16.jpg)
How to impress females• 4. sing them songs (picture from Alcock)
Number of songs in repertoire
Days to finding partner
European warblers
![Page 17: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/17.jpg)
If none of this works - cheat
• Satellite strategies – younger or “weaker” males often position themselves strategically near an attractive male, then sneaking up on females when the large male is un-attentive or otherwise engaged
Great Plains toads,longhorn sheep, horseshoe crabs
![Page 18: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/18.jpg)
Alternative male mating tactics
• different males in the same species use different strategies to gain access to females
• satellite strategies are one example
![Page 19: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/19.jpg)
Alternative male mating tactics – “rape”
• In scorpion flies, some
males will not bring
presents, but mate with
unwilling females.
Usually “losers”,
fertilisation success
typically low.
![Page 20: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/20.jpg)
FIGURE 7.12 Barn Swallows (Kardong, after Andersson, Moller)
Females often prefer exaggerated male traits
![Page 21: Evolution III - contents Sexual selection vs. natural selection Male and female strategies Alternative mating tactics](https://reader030.vdocument.in/reader030/viewer/2022032707/56649e4b5503460f94b3f22f/html5/thumbnails/21.jpg)
Why do females prefer exaggerated male traits?
• “Good genes hypothesis” – extravagant traits indicate biological fitness (because less fit males would be less able to afford such traits).
• One special case of this hypotheses is that such traits indicate ability to cope with parasites.
• “Runaway selection hypotheses” – females prefer sexually attractive traits which they pass on to sons, which makes sons more fit (but only because the sons in turn will also be more attractive to females).