GE CLST 70B Lecture Notes - Lecture 11: Species Complex, Guppy, Asexual Reproduction
17 Feb 2017
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The fact that female seahorses compete for mates contradicts bateman"s principal. Bateman"s principal is a good rule of thumb, but there are many exceptions. Offspring quality can be just as important as quantity. Paternal care is common in gobies: male sand gobies eat their developing babies, when density of eggs is high, males eat more eggs, low oxygen puts all eggs @ risk, eliminating some helps the rest survive. 1:1 male:female ratio is typical expectation for mendelian inheritance of sex chromosomes. Easy to imagine that mutations can also lead either x or y sperm to be more successful, skewing the ratio. However, sex ratios are always close to 1:1. Frequency-dependent selection: traits are only favored when they are rare, polymorphism. Side-blotched lizard example: orange beats blue, blue beats yellow, yellow beats orange, rock paper scissors of natural selection, as soon as one becomes rare, it also has an advantage.
