Isolation and Speciation Macroevolution in action!
Formation of a new species… what is a “Species”? Many definitions of species exist Morphological – based on finding physical/structural similarities Advantages: applies to both sexual/asexual organisms Disadvantage: subjective Ecological – based on the niche of an organism (its role in ecosystem) Phylogenetic – based on an animal’s ancestry/genetic history Compare physical characteristics/molecular similarities Paleontological – focus on morphologically-discrete species known only from the fossil record
Biologic Species concept Defined as: Population/group of populations that can successfully interbreed, producing viable, fertile offspring Speciation often requires major genetic changes Hinges on reproductive isolation – something that keeps two groups that would normally interbreed from doing so
Allopatric vs. Sympatric Speciation Allopatric - “away from one’s fatherland” Physical barrier divides 1 population into two Mountains, channels, islands, rivers, lava flows, etc. Leads to a divergence of the gene pool through mutations, selection, etc. If enough time passes, will likely be unable to mate if reintroduced
Sympatric Speciation Species evolves while alongside its fellow organisms. How? Polyploidy Habitat differentiation Sexual selection Reminder: zygote = fertilized egg
Reproductive Isolation Leads to speciation… …By preventing gene flow among populations Prezygotic Isolation – prevents fertilization Mechanical Habitat Behavioral Mating songs Temporal Gametic Polyploidy (plants)
Mechanical
Habitat
Behavioral
Temporal
Gametic
Post-Zygotic Isolation Fertilization has occurred, but the hybrid isn’t viable, can’t reproduce Reduced hybrid inviability – development/survival of hybrids is impaired Reduced hybrid fertility – hybrids fail to produce functional gametes Hybrid breakdown – offspring of hybrids are feeble/infertile
Some examples of hybrids that are infertile (sterile) Cool stuff! (Male partner listed first)
Camel + Llama =
Cama
Tiger + lion =
Tiglon!
Lion + tiger =
Liger
Zebra + horse =
Zebroid
Donkey + horse =
Mule
Horse + Donkey =
Hinney
False Killer Whale + Dolphin
Wolphin
Leopard + Lion =
Leopon
Grizzly + Polar Bear
Grolar/ Pizzly
Goat + Sheep =
Geep
Cattle + Bison=
Beefalo
Human + Chimpanzee =
Humanzee?