Natural selection stabilizes at local optima, as armor-plate shifts in sticklebacks show

Evidence

Such is the nature of most natural selection. Populations adapt to surrounding conditions until they reach a local optimum. Environments may change and, when they do, selection kicks in once again favoring new trait sizes or colors that work better in the new surroundings. But these shifts also are expected to stabilize. Ocean sticklebacks have sported three long spines and fifty-two armor plates for hundreds of thousands of years. When some of these fish found themselves dumped into freshwater habitats, natural selection in their new environment led to a rapid shift from three spines to one, and from many armor plates to few (fourteen plates). But once these populations reached their new optimum, the change in armor stopped. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 180

Categorization

• XREF: connects to: Oscillating directional selection can produce net evolutionary stasis; Rising predator pressure quickly enlarged lake stickleback armor; Oscillating selection can produce stasis despite strong directional pressure — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 701 (+6 more)

Related

• Rising predator pressure quickly enlarged lake stickleback armor (similarity 0.93)
• Oscillating directional selection can produce net evolutionary stasis (similarity 0.89)
• Stickleback fossils document armor gain and loss across one hundred thousand years. (similarity 0.88)
• Weapons shrink when predator pressure falls and armor gets costly. (similarity 0.88)
• Oscillating selection can produce stasis despite strong directional pressure (similarity 0.83)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.83)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.82)
• Natural selection usually favors modest weapon size because cost offsets benefit (similarity 0.82)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.81)
• Sexual selection stays directionally constant while physical natural selection oscillates (similarity 0.81)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.80)
• Species with huge weapons often show weak current selection on them. (similarity 0.80)
• Armor evolution tracks a benefit-cost trade-off identical to that shaping animal weaponry (similarity 0.80)
• Variation in animal weapon size is explainable by species ecology and behavior. (similarity 0.79)
• Ambush predators evolve large weapons because they strike rather than chase prey (similarity 0.79)

Broader Connections

• Weapon size in animal species is under stabilizing selection, not open-ended directional selection #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 850
• Armor evolution tracks a benefit-cost trade-off identical to that shaping animal weaponry #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 62
• Natural selection usually favors modest weapon size because cost offsets benefit #corroborates (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 21