Species formation

• defined by Linneaus-morphological species concept
• Simply if they look alike they are related
• Morphospecies

• Each species has a history
• --Speciation event (split on tree)
• --Extinction
• --Two daughter species

-male and female of same species look different

-different species are superficially identical but are different

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

Keep sexual lineages seperate

• Lineage splits
• New allele becomes fixed at different loci in each They can hybridize
• Lethal
• Functionallyinferior

• Species similar enough to each other but not of same species, mate to produce offspring
• Offspring are sterile

• interbreeding
• speciation
• Dobzhansky-Muller

• -daughter species
• Over time the species will have different population and become 2 different species

• allopatric
• sympatric

- population of species become geographically isolated and accumulates enough difference through time reproductive isolation and formation of new offspring

• 1.Vicarience
• 2.Founder events-founding pop that splits from parent pop Throughtime founding pop will become its own species

-explosion of many new ecologically diverse species developing in an area in a short period of time from single ancestor

• -speciation occurs in same geographic location
• 1.exploitation of niches- IE chikled fishes
• 2.polyploidy-quickly change in as little as 2 generations Common in plants, rare in animals

• -duplication of set of chromosomes within individuals
• Single species-autopolyploidy
• Two different species- allopolyploidy

• Tetraploids NO w/diploids
• But tetraploids w/ tetraploid complete isolation in 2 generations

Interbreeding of closely related Offspring often fertile bc chromosome pair w/almost identical

• Hybrid zones may form if reproductive isolation is incomplete
• If hybrids are fit, mating occurs with parentals from both pop
• If hybrids less fit, complete isolation evolves Hybridzone- where two distinct pop reproduce regardless Yellowbellied toad- hybrids are abnormal yet wildtype will mate

• Dietary shifts--predatory v herbivorous
• In plants--animalpollinated faster than wind pollinated
• Columbines--longer spurs>shorter => restict # pollinator species

• -before mating or fertilization or formation of zygote
• Spatial isolation
• Temporal isolation
• Mechanical isolation
• Gametic isolation
• Behavioral isolation

• -after mating or fertilization
• Prevents hybrid gametes producing viable offspring
• In play when prezygotic barriers fail

• hybrid zygote abnormality
• hybrid sterility
• low hybrid viability

-zygote will be unfit for reproduction/survival

-parents of different species produce offspring offspring is normal but cant repoduce

-much less fit than parents or purebred offspring

• - speciation exceed extinction rate
• --Occurs following mass-extinction
• --Large number of daughter species from single ancestor