Habitat Isolation
2 species live in the
same area, occupy
different habitats rarely
encounter each other
garter snakes
Temporal Isolation
2 species breed at
different times of the
day or seasons
Eastern and Western
Spotted Skunks
Behavioral Isolation
Signals to attract mates
are often unique to a
species
fireflies
Mechanical Isolation
Closely related species
attempt to mate, but
are anatomically
incompatable
flowering plants with
pollination barriers
Gametic Isolation
Sperm and egg must
recognize each other
fertilization of fish eggs
Prezygotic Barriers
Postzygotic Barriers
Reduced Hybrid
Viability
Reduced Hybrid
FertilityHybrid
Breakdown
Hybrid Breakdown
abort development of
hybrid at some
embryonic stage
Meiosis doesn't
produce fertile gametes
in vigorous hybrids
First generation hybrids are
fertile, but they can't
produce fertile offspring in
the next generation
subspecies of
salamanders
horse + donkey = sterile
mule
rice, cotton
(f1 fertile, but not f2)