Same Diet, Different Lineage
Two closely related bat species both eat insects and share intact chitinase genes. Their common ancestor was also insectivorous. What explains this similarity?
What is shared ancestry/homology
This enzyme helps digest starch and is often expanded in frugivores
What is amylase?
This taste receptor is often lost in strict carnivores
What is the sweet receptor (T1R2)?
Two species share a trait because their common ancestor had it. This is called ___
What is shared ancestry/homology?
A digestive enzyme gene shows very few amino acid changes across 60 million years of bat evolution, regardless of diet
What is purifying selection
A nectar-feeding bat in the Americas and a nectar-feeding bat in Africa evolved from insectivorous ancestors in separate clades. Both show increased sugar transporter expression, but via different mutations
What is convergent evolution
Loss of this gene would reduce the ability to digest insect exoskeletons
What is chitinase?
Giant pandas have lost this taste receptor due to bamboo specialization
What is the umami receptor (T1R1)?
A trait appears similar but evolved for different functions
What is analogy
After a lineage shifts away from insect consumption, its chitinase gene accumulates stop codons and frameshift mutations
What is relaxed selection
Two frugivorous bat species in the same genus independently increase amylase copy number after diverging from an insectivorous ancestor
What is parallel evolution
Two nectar-feeding mammals show increased expression of sugar transport genes, but via different regulatory mutations. This is an example of _____
What is molecular convergence via different mechanisms?
Multiple nectar-feeding bats show modifications in sweet receptors. What type of selection likely drove this?
What is positive selection?
If two species share identical mutations at the same nucleotide position, what might that suggest?
What is possibly shared ancestry?
A sugar metabolism gene in nectar-feeding bats shows dN/dS > 1 along branches corresponding to dietary shifts
What is positive selection
Two separate clades evolve frugivory shortly after ecological opportunity arises. Multiple dietary niches diversify from an insectivorous ancestor. What macroevolutionary process best explains this pattern:
── Insectivore (Clade C)
────┤
│ └── Frugivore (Clade A)
Ancestral ─┤
Insectivore │ ┌── Frugivore (Clade B)
└─────┤
└── Insectivore (Clade D)
What is adaptive radiation?
A gene is pseudogenized in multiple carnivorous mammals due to reduced carbohydrate intake. What evolutionary force likely relaxed selection on this gene?
What is relaxed purifying selection?
If two species lose bitter receptors independently, what pattern would you expect in their mutations?
What is different inactivating mutations in the same gene?
A gene is lost in multiple species due to random drift in small populations. Is this convergence?
What is No; it is independent neutral evolution (genetic drift), not adaptive convergence.
Two species maintain multiple alleles of a taste receptor gene at intermediate frequencies within populations
what is stabilizing selection
Two species appear to share a genetic variant associated with a dietary trait. However, the gene tree does not match the species tree.
What evolutionary process could explain this pattern?
What is incomplete lineage sorting?
Why might regulatory evolution be more common than coding changes in dietary adaptation?
What is:
allows for functional changes in metabolism without altering the structure of proteins
minimizes negative effects on other bodily processes
lower deleterious impact
How could you test whether a taste receptor change is adaptive rather than neutral?
What is:
dN/dS ratios
Functional assays
Expression studies
Correlation with dietary shift timing
What statistical evidence would strengthen a claim of convergent molecular evolution?
What is:
significant excess of identical amino acid substitutions over neutral expectations
high ratios of convergent to divergent sites
strong correlations between phenotypic similarity and molecular distance
A gene shows random variation across lineages, with no association to diet and dN/dS ≈ 1
What is neutral evolution (genetic drift)