BIOL 2040 Lecture Notes - Lecture 14: Coevolution, Herbivore, Greenish Warbler
27 Apr 2018
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Lecture 14 - Phylogenies (end), Speciation
April 10, 2018
7:24 PM
Are large tests an adaptation to large social groups in bats?
• There is a positive correlation between testes mass and social group size
o This can be misleading - use phylogeny trees to check
A confounded correlation
• Hypothetically - if there was a split in bat social groups, where one population grew to have larger
testes and happened to have an increased testes size, and the other population that continued to
have small population size and happened to have a decreased testes size, it would look like bat
social group size and mass of testes are correlated
• We could get the correlation even if testes size and group size aren't related to each other
Phylogenetically independent contrasts
find more resources at oneclass.com
find more resources at oneclass.com
• A method that uses phylogenetic information to transform mean values for a set of species into
values that are statistically independent and identically distributed
o We use the mean values at each node to plot a graph
• We look at the differences that had evolved from the node and we would plot the differences
o Ex. what are the differences between P and Q?
• These nodes gives us the information on independent contrasts
• You take the differences at the divergent nodes to look for a relationship
The data on bat testes
• One group had a smaller group size but larger body mass and smaller testes, compared to the
larger group size that had a smaller body mass, but had larger testes
• Independent contrast has a stronger correlation for group size vs. testes size, but the correlation
isn't as strong as compared to the raw data
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Are large tests an adaptation to large social groups in bats: there is a positive correlation between testes mass and social group size, this can be misleading - use phylogeny trees to check. The data on bat testes: one group had a smaller group size but larger body mass and smaller testes, compared to the larger group size that had a smaller body mass, but had larger testes. Independent contrast has a stronger correlation for group size vs. testes size, but the correlation isn"t as strong as compared to the raw data. Independent contrast - asking the question of if one change correlated with another change in a different species at the same node. Beetles (order coleoptera) are the most speciose group on earth - over 300,000 species: why, herbivorous beetle species. In all 5 nodes - feeding on angiosperms is common: something about feeding on plants must be driving speciation.
