Lecture 24 - Evolution of Biodiversity Flashcards
What are the two methods to study long-term diversification trends?
Fossil data: Provides direct but incomplete evidence.
Molecular phylogenies: Offers estimates of divergence dates and speciation rates.
How does biodiversity vary in space and time?
Not even in space: Biodiversity hot spots differ geographically.
Not even over time: Historical data shows fluctuating species diversification.
What is the distribution of biodiversity across the tree of life?
Biodiversity is not evenly distributed. Examples:
1,500 species of Rodentia
9 species of Pholidota
What is the formula for species diversification rate?
Diversification rate (D) = Speciation rate (S) - Extinction rate (E).
What is a phylogenetically independent contrast?
A method to compare traits in sister clades where one clade has the trait, and the other does not.
What is the correlation between herbivory and species richness?
Herbivorous clades, like weevils, have ~10× more species than their non-herbivorous sister clades.
Plants with herbivory defences (e.g., extrafloral nectaries) are also more species-rich.
What is co-speciation?
Co-evolution of host and symbiont lineages, e.g., Buchnera aphidicola and aphids.
Requires congruence in phylogenies of host and mutualist.
What is the “pull of the present”?
An upward trend in recent diversification due to speciation events appearing closer to the present.
How do we interpret the slopes in lineage-through-time plots?
A steep slope indicates rapid diversification.
A flat slope indicates slow diversification or extinction.
How can sexual conflict affect diversification?
Traits like mating behaviour or reproductive roles may lead to higher diversification rates in species with intense sexual competition.
What does the sister clade comparison suggest about sexual conflict?
Positive association between sexual conflict and species diversification.
What scenarios are common for parasite speciation?
Co-speciation
Host-switching
Independent speciation
What does imperfect co-speciation look like in hosts and parasites?
Host and parasite phylogenies are partially congruent but include mismatches, e.g., “missing the boat” or host extinction.
What are possible reasons for the slowdown in diversification?
Limited ecological niches.
Evolutionary constraints on speciation rates.
How is diversification rate calculated from phylogenies?
Using dated molecular phylogenies to estimate the rate of lineage accumulation over time.
