Biology › Section J · Evolution › Topic J.3
Reconnection and rates of speciation
A split between species is rarely final at first. The two lineages may keep meeting at the edges - a hybrid zone - where the fate of their offspring decides everything: divergence reinforced, species fused back together, or an uneasy balance. And the pace of splitting itself has two tempos, gradual drift and punctuated bursts, with the environment conducting.
In this topic
- Speciation is not a clean cut
- The hybrid zone
- Reinforcement: bad hybrids widen the gap
- Fusion: good hybrids merge the branches
- Stability: the uneasy balance
- Two tempos of speciation
- The environment sets the tempo
- Worked example: predicting hybrid zone outcomes
- Worked example: the snails in the shrinking lake
- What both models share
- Common mistakes to avoid
- Key takeaways
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