Grant & Grant
Figures
Figures
What are the key takeaways from Fig. 2 (pg. 132)?
Evolutionary trees of Darwin's finches. Lower tree is more accurate because of its asymmetry where main trunk splits.
Define allopatry and sympatry. What is their importance in studying adaptive radiation?
Allopatry - a population or species that is physically isolated from other similar groups by an extrinsic barrier to dispersal
Sympatry - a population or species that occurs in the same place at the same time
Important for understanding the beginnings and progression of adaptive radiation.
What are the key takeaways from Fig. 1 (pg. 2)?
A. Aligning Darwin's finch and zebra finch genome. Shows that genomes of both species are in same order
B. 28 SNPs most likely to be involved in beak/body size differences btw 3 finch species
C. Difference in nucleotide diversity between the 28 loci and non-associated regions for 3 species. Shows that our 28 loci are associated
D. Variance in allele frequency btw species for all 3 species. Shows how similar they are to each other
What is adaptive radiation and why are Darwin's finches so good for studying them here?
Adaptive radiation = "rapid morphological and ecological diversification from a common ancestor" (from intro).
Darwin's finches are great for studying this due to the fact that:
1. no species has gone extinct from human causes (that is known)
2. species has currently and historically received gene flow from each other
3. diversification has been linked to one key, survival based trait (beak size)
This Grant and Grant paper was written for American Scientist, a bimonthly science magazine. How did it differ from other papers we read? Did you like it? Do you think it was effective?
Every person on your team must share!
What is we value and respect all opinions in this classroom. Full points!
What are the key takeaways from Fig. 4 (pg. 134)?
Shows allopatric model of speciation in 3 steps. Grants acknowledge that this model (when applied to Darwin's finches) is wrong.
What are the two errors in the Grants' allopatric speciation model they first proposed in 1981?
1. Speciation does not require a population to recolonize an island where their ancestors lived, even if they have diverged enough to permit coexistance.
2. Cannot assume that all islands existed at the beginning of the adaptive radiation or that the ecosystems were as complex as modern day.
What are the key takeways from Fig. 2 (pg. 3)?
Shows how similar the haplotypes of Darwin's finches are compared to G. magni at each loci using allele frequency. Also uses PCA to compare species' beak size.
Blue is no difference in allele frequency.
Define what a haplotype is and why it's helpful for studying evolutionary differences between species.
A haplotype is an area on a genome that tends to be inherited together. It is easy to see genetic differences between species in these areas and see how similar they are compared to a common ancestor.
What implications do the Rubinetal paper have for future conservation efforts, in island ecosystems and in general?
Every person on your team must share!
What is we value and respect all opinions in this classroom. Full points!
What are the key takeaways from Fig. 5 (pg. 135)?
Curve showing the number of extant finch species and islands across time. Presence/absence of islands is important for understanding adaptive radiation in a changing environment.
What were the 4 questions raised by adaptive radiation that the Grants' posed? Ask one of these questions about a Galapagos species and try to answer it :)
Origins: Where did the ancestors come from, when and how?
Speciation: How and why are new species formed?
Diversity: Why are there number of species?
Disparity: Why are these species as different, or as similar, as they are?
What are the key takeaways from Fig. 3 (pg. 5)?
A. Full genome phylogenetic tree of Darwin's finches to examine divergence of haplotypes. Shows different genotypes at locus 24.
B. Shows time that each of our 28 loci diverged from a common ancestor.
C. Fraction of hybridization from G. magni to G. prop on each locus.
What's up with these 28 loci that they found? List some important things to note.
The 28 loci are 28 haplotypes that show phenotypic diversity among the species of Darwin's finches. They have been shown to be enriched with genes that code for beak development.
What metaphor for adaptive radiation do the Grants' suggest at the end of their article and WHY? Do you like this representation over the old one?
Every person on your team must share!
What is we value and respect all opinions in this classroom. Full points!
What are the key takeaways from Fig. 8 (pg. 137)?
Why is the radiation of Darwin's finches unique compared to other island species, like the Hawaiian honeycreepers?
Youth and rapid diversification. Incredibly short doubling time of 3/4 of a million years.
What are the key takeaways from Fig. 4 (pg. 6)?
A. 3 possible topologies. Top 1 is the only one consistent with the phylogeny they created.
B. Shows why Top 1 is the most likely phylogeny and that the placement of G. magni is inconsistent with species tree.
C. Topology weightings according the 3 possible topologies in 100 SNPs on chromosome 1A.
How does hybridization and introgression play a role in their findings?
Distinct combinations of haplotypes throughout the genome of multiple finch species show that hybridization and introgression occurred rather frequently.
What was the most difficult part of reading the Rubinetal paper? What suggestions or changes would you make?
Every person on your team must share!
What is we value and respect all opinions in this classroom. Full points!
What are the key takeaways from Fig. 9 (pg. 138)?
Shows expected and observed morphological diversification in finches as compared to the 3D adaptive landscape.
(hint: think about song)
How do cues that guide mating decisions diverge in incipient species and lead to reproductive isolation?
Alt: How do songs and responses to them diverge in incipient species?
What are the key takeaways from Fig. 5 (pg. 7)?
Why does it make sense for these haplotypes to be enriched with beak growth and development genes in the context of evolution?
Beak size, shape and width are vital for survival, and are heavily acted up by selection. Thus, they are what is most likely to contribute to the differences between species.
How does this Grant & Grant paper relate to the other (many) Grant & Grant papers we've read during this program?
Every person on your team must share!
What is we value and respect all opinions in this classroom. Full points!