Warm-up List and explain the three ways in which sympatric speciation occurs.

Important dates 1. Exam is this Tuesday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test. 2. Finish Clover Case Study for bonus on exam. Due Tuesday, 9-16 before exam. 10% points extra credit. 3. Lab Write-up due Thursday, September 18 You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday this week. Write up will be in your lab notebook. 4. Binder check on exam day

Sympatric (“Same Country”) Speciation In sympatric speciation, speciation takes place in geographically overlapping populations Could occur via: 1)Polyploidy 2)Habitat differentiation 3)Sexual selection

Polyploidy Polyploidy is the presence of extra sets of chromosomes due to accidents during cell division Polyploidy is much more common in plants than in animals

Habitat Differentiation Sympatric speciation can also result from the appearance of new ecological niches For example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees ◦Native habitat: hawthorne tree ◦Apple tree introduced by Europeans

Sexual Selection -Sexual selection can drive sympatric speciation -Sexual selection: type of selection in which individuals with certain inherited traits are more likely than others to obtain mates -Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake Victoria, which led to about 600 species of cichild within the one lake speciation

Figure Normal light Monochromatic orange light P. pundamilia P. nyererei EXPERIMENT

Hybrid zones reveal factors that cause reproductive isolation A hybrid zone is a region in which members of different species mate and produce hybrids Hybrids are the result of mating between species with incomplete reproductive barriers

Patterns Within Hybrid Zones A hybrid zone can occur in a single band where adjacent species meet ◦For example, two species of toad in the genus Bombina interbreed in a long and narrow hybrid zone

Figure EUROPE Yellow-bellied toad, Bombina variegata Fire-bellied toad range Hybrid zone Yellow-bellied toad range Fire-bellied toad, Bombina bombina Frequency of B. variegata-specific allele Yellow-bellied toad range Hybrid zone Fire-bellied toad range Distance from hybrid zone center (km)

Hybrid Zones over Time When closely related species meet in a hybrid zone, there are three possible outcomes: ◦Reinforcement of reproductive barriers by less fit hybrids ◦Fusion ◦Stability

Reinforcement: Strengthening Reproductive Barriers The reinforcement of barriers occurs when hybrids are less fit than the parent species Over time, the rate of hybridization decreases

Fusion: Weakening Reproductive Barriers -If hybrids are as fit as parents, there can be substantial gene flow between species -If gene flow is great enough, the parent species can fuse into a single species

Figure Normal light Monochromatic orange light P. pundamilia P. nyererei EXPERIMENT

Figure Pundamilia nyererei Pundamilia pundamilia Pundamilia “turbid water,” hybrid offspring from a location with turbid water

Stability: Continued Formation of Hybrid Individuals When hybrid populations are stable because they are as fit or fitter than the parent populations

Speciation can occur rapidly or slowly and can result from changes in few or many genes

The Time Course of Speciation Broad patterns in speciation can be studied using the fossil record, morphological data, or molecular data

Patterns in the Fossil Record The fossil record includes examples of species that appear suddenly, persist essentially unchanged for some time, and then apparently disappear Niles Eldredge and Stephen Jay Gould coined the term punctuated equilibria to describe periods of apparent stasis punctuated by sudden change The punctuated equilibrium model contrasts with a model of gradual change in a species’ existence

Figure (a) Punctuated pattern Time (b) Gradual pattern

Speciation Rates The punctuated pattern in the fossil record and evidence from lab studies suggest that speciation can be rapid ◦For example, the sunflower Helianthus anomalus originated from the hybridization of two other sunflower species

Studying the Genetics of Speciation A fundamental question of evolutionary biology persists: How many genes change when a new species forms? Depending on the species in question, speciation might require the change of only a single allele or many alleles ◦For example, in Japanese Euhadra snails, the direction of shell spiral affects mating and is controlled by a single gene

Morphological evidence for speciation? Examples we’ve discussed so far?

From Speciation to Macroevolution Macroevolution is the cumulative effect of many speciation and extinction events The interval between speciation events can range from 4,000 years (some cichlids) to 40 million years (some beetles), with an average of 6.5 million years

Important dates 1. MasteringBiology HW due this Friday night, 11:59 PM! 2. Exam is Monday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test. 3. Finish Clover Case Study for bonus on exam. Due Monday, 9-15 before exam. 10% points extra credit. 4. Lab Write-up due Thursday, September 18 You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday next week. Write up will be in your lab notebook.

Important dates 1. Exam is this Tuesday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test. 2. Finish Clover Case Study for bonus on exam. Due Tuesday, 9-16 before exam. 10% points extra credit. 3. Lab Write-up due Thursday, September 18 You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday this week. Write up will be in your lab notebook. 4. Binder check on exam day