Hybrid fitness decides how a hybrid zone ends
- The idea
- Predict
- See it
- Why
- Check
The idea
“Lots of hybrids means the two will merge, or the hybrids will become a new species.”
A zone full of hybrids looks like a new species being born. The ending depends on how many offspring those hybrids leave.
The short version
The mistake: Lots of hybrids means the two will merge, or the hybrids will become a new species.
What's actually true: How a hybrid zone ends depends on how fit the hybrids are, and a hybrid species also needs a barrier from both parents.
- In a hybrid zone, two diverging populations meet and mate. Hybrid fitness is how many offspring the hybrids leave.
- Less fit hybrids make choosy mating pay, so barriers strengthen. That's reinforcement. Hybrids as fit as their parents let the two fuse.
- Hybrids that do well only inside the zone keep it stable. A hybrid species also needs a barrier from both parents.
On the exam: Ask how fit hybrids are. Lower means reinforcement, equal means fusion, better only in the zone means stable.