BIOA01H3 Lecture 12: BIOA01 – Lec 12- Speciation & Variation

• School: UTSC
• Department: Biological Sciences
• Course: BIOA01H3
• Professor: Maydianne Andrade

Document Summary

Physical barrier divides a pop. (no gene flow) Founder effects can cause initial stages of divergence. Mutations can give rise to different alleles in groups. Selection & drift can lead to independent changes in allele frequencies in groups. Specialization or genetic changes in subgroups reduce gene flow: host races, chromosomal mutations, polyploidy, chromosome rearrangements. 1. 1allopatric speciation: vicariance e. g. , ref fishes (wrasse) in caribbean sea & pacific ocean. Formation of isthmus of panama (~3mya) = vicariance event for marine animals. Closely related species found on pacific & caribbean side. Split + local adaptation & divergence: dispersal. Dispersal among islands can lead to repeated divergence. Timing of dispersal & divergence can be dated (fossil record, molecular clocks) Can lead to origin of a species cluster = group of closely related species or subspecies descended from a recent common ancestor e. g. , hawaiian drosophila (800 species) e. g. , kingfishers on mainland new guinea.