Speciation and Reproductive isolation mechanisms
Species: group of individuals who are able to mate amongst themselves to make healthy
Exceptions: Horses and donkeys mate to make mules
-Hooded crow and carrion crows can make hybrids, but are geographically separated
Reproductive Isolation Mechanisms: factors that does not allow for successful reproduction
Pre zygotic Barriers: prior to when a zygote is formed
-Prevention of Mating: doesn’t allow for having sex
-Behavioral Isolation: each species may use different signals or behaviors to attract mates.
Sometimes they don’t work or are incompatible.
-Birds and frogs sing a song
-Temporal Isolation: mating at the wrong time cannot allow them to mate even though they
could be in the same habitat.
-Flower mating seasons
-Ecological/Habitat Isolation: species occupy different habitats within the same area
wherethey’re separated and cannot mate
-Northwest Garter snakes prefer meadows while common garter snakes are in water all the
Prevention of fertilizing: doesn’t allow for fertilization
-Mechanical Isolation: Different species don’t mate because their genitals aren’t compatible
-Genitals of damsel flies are different from other flies and can only mate with their own
-Gametic Isolation: If gametes from different species do not meet, barriers preventing sperm
and eggs from forming a zygote.
-Sperm might not survive in female, or molecular markers on eggs signal sperms that this
isn’t the right egg, and will ignore it
Post Zygotic Barriers: doesn’t allow for successful growth of the hybrid (refers to offspring
from mating 2 species) -Reduction of Hybrid viability: Fetus forms after fertilization, but followed by spontaneous
abortion due to genetic incompatibility.
-lethal alleles terminates the process
-chromosome number mismatches, first stage of mitosis terminates
-Reduced zygotic barriers: Hybrid offspring could become sterile. Problem because
chromosome number during mating because parental chromosomes differ from other
species or parental species.
-Donkey and horse’s hybrid is sterile
-Hybrid Breakdown: F1 hybrids may work, but F2 hybrids are often always ste