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Kim Dej

Lecture 31 November-22-11 3:26 PM Mechanisms of Speciation Figure 16-1. Quickthink: Consider the situation wherein you conducted a phylogenetic systematic analysis on 14 populations amount 6 species, ABCDEF. Try to explain possible events as to what happened at B4. Possibly the species is just misclassified. things that look alike are classified in the same taxa Phylogenetic Species We can build phylogenetic trees and expect all species fall out into a clade If we found one of the members to fall out in a sister group, then we'd have to reconsider the species (i.e. like B4) phylogenetic species - elephants They separated African savannah species and African forest into two different species. Some morphological differences, however, cladogram was constructed by genetic data. Important for conservation work b/c it matters whether one collection of organisms are two species or one species. --stop gene flow -- no longer can interbreed, b/c they've diverged too much in their traits Allopatric = ancestral population, and then something breaks them apart, like the changing direction of a river and so species cannot mix anymore. They are separated by Everything else in between is just a shade of these two geography. Sympatric = the two groups are still in contact, in overlapping geography, and they interact with each other, however, they are still able to differentiate, and after a significant time they become two separate species physical - dispersal, vicariance A mainland and an island, and some organisms can be transported to the island. The net result is that one population is separated to the other. Enough to disrupt gene flow provided they don't go back and forth. Vicariance: Same result, but due to a breaking up for a land mass, or changing direction of a river, etc geographical - dispersal and colonisation Hawaiian fruitflies -- huge variety of shapes, colours, size, etc. They all live in the Hawaiian islands, and they are volcanic and very young. The oldest island is shown on the left, newer ones on the right. Each fly species live on a separate island, and so it's found that dispersal and colonization of islands are shown by the phylogenetic tree. geographical - vicariance Snapping shrimp: Different sized So we have genetic data. Pacific and claws -- snap their claws to create Caribbean populations are sister soundwave that confuses prey. groups. Meaning they are more closely related to those on the other side of Populations are on the pacific and the landmass (even though they are Caribbean side -- separated. further away) The ones on the Pacific side look like those on the Caribbean side, and so morphologically we may try to classify them as the same taxa, but b/c they are separated by land mass we don't. We may not know that though. Bottleneck: Where a population undergoes a great narrowing (decrease), and then traits diverge quickly under conditions of drift natural selection Took Hawthorn flies into the lab, and simulated the temperatures. Maggot flies, can live on one of two types of fruits. Apples and One week of warm temperatures Hawthorn trees. Apples mature is typical of what they experience in the wild. Mature in cooler earlier in the season, and so those flies experience warmer temperatures. Apples experience conditions. very warm temperatures because fruit mature in late July. The fly lay eggs in the fruit. These two types of trees are found Individuals in the Apple race fly together, but the species are have a difference than hawthorn flies distinct. There's genetic evidence to suggest that selection is causing each population to stay on their own fruit. Two sister species of drosophila sexual selection species -- d. heteroneura and d. silvestris. Heteroneura males engage in head-butting to compete Heteroneura Silvestris Heteroneura, as heads are wider, females prefer them mo
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