Ch. 24: Speciation

Development of a new species, source of diversity, can happen abruptly or gradually.

Biological species, Morphospecies, Phylogenetic species

Individuals between one or more populations that have the potential to interbreed in nature and produce fertile offspring

Act prior to formation of a zygote, blocks mating/fertilization

Act after formation of zygote, prevent hybrid zygote from developing or hybrid adult from reproducing

Species that breed at different times

Species occupy different habitats within a geographic area, rarely encounter one another

Courtship rituals and behaviors that attract mates, including visual recognition, songs, or dance

Matings fail because eggs and sperm are incompatible

Matings fail because mate and female reproductive structures are incompatible

gene mix impairs hybrid development

Fertile f1, but sterile f2. Corn hybrids have higher growth in F1, lower growth/fitness in f2 due to crossing-over events

Geographically isolated populations never have an opportunity, cannot test in fossil species, majority of species are asexual

Individual lineages differ in size, shape, or other morphological feature (typically arise after population isolation)

Widely applicaple, easy to apply

Polymorphic and cryptic species, taxonomic pickiness

1. populations genetically isolated
2. genetic differences gradually accumulate between the 2 populations
3. reproductive isolation evolves

1. Disruptive selection (external forces)