S2: W7 (Dr. Hanlie) Flashcards
Galapagos islands?
= a “hotbed” of speciation.
Why are the Galapagos islands a “hotbed” of speciation?
It’s because the islands arose from volcanic islands.
Speciation?
= process by which new species are formed.
Speciation = …?
Cladogenesis.
Modes of speciation? (3)
• Allopatric speciation.
• Parapatric speciation.
• Sympatric speciation.
“Patric”?
= place.
Allopatric speciation process? (4)
• Original population.
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• Barrier formed.
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• Populations in isolation.
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• New distinct species after equilibrium.
Parapatric speciation process? (4)
• Original population.
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• New niche entered.
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• In new niche.
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• New distinct species after equilibrium.
Sympatric speciation process? (4)
• Original population.
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• Polymorphism.
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• Within the population.
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• New distinct species after equilibrium.
Types of speciation in general? (2)
• Allopatric speciation.
• Non-allopatric speciation.
Types of allopatric speciation? (2)
• Allopatric speciation by vicariance/Vicariant speciation.
• Peripatric speciation.
Types of Non-allopatric speciation? (2)
• Parapatric speciation.
• Sympatric speciation.
What causes speciation to occur?
What can happen if drivers disappear?
Hybridization (uncommon).
Vicariant speciation?
= geographic isolation due to a barrier to dispersal & gene flow.
Egs of barriers? (4)
• Uplifting of mountains.
• Continental drift.
• Changes in the flow of rivers.
• Changes in environment (desertification).
Eg of Vicariant speciation?
Panamic porkfish & Porkfish.
• the former lives in the Pacific ocean & the latter lives in the Atlantic ocean.
Peripatric speciation?
= small, isolated population, usually on the periphery of a larger ancestral species gives rise to a distinct species (founder effect).
Peripatric speciation attributes? (2)
• Active dispersal into an area not previously occupied.
• Periphery is isolated.
Egs of Peripatric speciation? (2)
• Hawaiian picture-winged Drosophila.
• Mexican prairie dog.
Egs of Peripatric speciation? (2)
• Hawaiian picture-winged Drosophila.
• Mexican prairie dog.
Explain Hawaiian picture-winged Drosophila?
12 species arose from a single species that migrated from the mainland.
Explain Hawaiian picture-winged Drosophila?
12 species arose from a single species that migrated from the mainland.
Explain Mexican prairie dog? (5)
• Grassland ecosystems.
• Shifts in distribution related to Pleistocene climate change.
• Divergence from C. ludonicianus.
• Climate change promoted biogeographical substructure within Chihuahua descent.
• Population expansion resulted in secondary co tact between lineages of C. ludovicianus.
What happens if separated populations come into contact after removal of barrier? (3)
• If reproductively isolated, no mating/no viable offspring.
• If not completely reproductively isolated, may form secondary hybrid zone where hybrids are sterile/inviable/less fit.
• Reinforcement of NS.
What happens if separated populations come into contact after removal of barrier if reproductively isolated (prezygotic/postzygotic)?
No mating/no viable offspring.
What happens if separated populations come into contact after removal of barrier if not completely reproductively isolated? (2)
• May form secondary hybrid zone.
• Hybrids sterile/inviable/less fit.
Hybrids sterile/inviable/less fit attributes? (2)
• Lower rates of survival.
• Eg due to epistatic incompatibility.
Eg of What happens if separated populations come into contact after removal of barrier?
Green-eyed tree frog.
Explain Green-eyed tree frog? (3)
• Habitat isolation.
• Event = deforestation (remove trees for agricultural areas).
• Evolved 2 different mating calls due to different habitat structure.
Non-allopatric speciation?
= speciation is initiated when there’s incomplete geographic separation of two or more populations of an ancestral species.
Non-allopatric speciation attribute?
Limited gene flow continues to occur between populations, yet there is divergence.
Parapatric speciation?
= populations occur in adjacent regions with different selection pressures (eg in an ecological cline) or where 2 different habitats meet.
Parapatric speciation attributes? (2)
• Gene flow occurs bit “hybrid”.
• Especially if drivers are weak, we can have a zone of hybridization or secondary contact (ecological niche).
Egs of Parapatric speciation? (3)
• Grasses in the vicinity of mines.
• Orchid Satyrium hallackii.
• Carrion crow & hooded crow.
Explain eg 1 of Parapatric speciation? (2)
• Have diverged from neighbouring populations in:
- tolerance to heavy metals.
- flowering time.
- self pollinate more frequently.
• Eurasia (uncontaminated) & Northern Africa (mine waste).
Explain eg 2 of Parapatric speciation? (4)
• Separation by pollinator shift along ecological gradient.
• Different pollinators.
• One hawkmoth & other carpenter bee.
• Proboscis vs spur length.
Explain eg 3 of Parapatric speciation? (2)
• The 2 species of crow meet.
• There’s a primary hybrid zone.
Sympatric speciation?
= occurs when one or more new species arise without geographical segregation of populations.
Sympatric speciation attributes? (6)
• Models postulate disruptive selection (eg in 2 microhabitats), which leads to Intermediate phenotypes (heterozygotes) that have low fitness.
• May involve one or many loci.
• Difficult to prove.
• Occupy different microhabitats which leads to Intermediate phenotypes that have lower fitness.
• Genetic differences result in reproductive isolation.
• Should also be linked to mate selection.
Eg of Sympatric speciation?
Apple maggot fly.
Explain eg of Sympatric speciation? (5)
• Lay eggs on Hawthorn fruit.
• Moved onto apples (shifted host).
• Speciated sympatrically.
• From Hawthorn to apples.
• Timing of fruit mating differs.
What do we use to hypothesize modes of speciation? (3)
• Distribution maps.
• Habitat & body size information.
• Phylogenies.
Drivers of speciation? (6)
• Barrier.
• Geographical distance.
• Ecological.
• Reproduction.
• Genetic isolation (no gene flow).
• Divergences (NS/SS).
Eg of where a competitor caused character displacement in a sympatric population?
Geospiza fortis & G. magnirostris.
Character?
= useful features that help species to exploit resources.
Types of character divergence? (2)
• Character displacement.
• Character release.
Character displacement attributes? (5)
• Due to competition.
• Control.
• Character gets displaced.
• Evolutionary divergence in resource-exploiting traits.
• Caused by interspecific competition.
Chatacter release attributes? (3)
• No competition.
• No control.
• Takes advantage of variety of resources in the absence of competition.
Driver of something?
= what is the underlying cause behind a certain geographical speciation pattern.
General process in terms of character divergence types? (4)
Character release
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Drought/event happens
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Competitor introduced
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Character displacement
Eg of character divergence types?
Geospiza fortis (medium ground finch).
Explain eg of character divergence types? (6)
• Daphne major.
• Absence of small ground finch.
• Medium ground finch.
• Presence of new competitor (large ground finch).
• Same species, different beak size.
• Process:
Character release
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Drought happened (“killed” small beak variant)
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Competitor introduced.
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Character displacement (evolved a medium sized beak to “widen diet”).
Explain Cactus finches? (7)
● Eg of Sympatric speciation.
● Males singing song type A had longer, wider beaks & ate cactus seeds in fruit. Males singing song type B had smaller, narrower beaks & ate insect larvae in cactus pads.
● Divergent selection.
● No two males with the same song type.
● Enforced by continuous climatic changes.
● No assortative mating by females.
● Territorial pattern disappears in wetter year (secondary pattern):
• beak size is now intermediate.
• songs are no longer different.
Cactus finches paper?
Grant & Grant, 1983.
Conclusion of Cactus finches? (2)
● Mate choice is not genetically correlated with the use of a particular niche.
● Drivers were weak & didn’t prevent genre flow.
Explain Warbler finch? (4)
● Ecological adaptation in parapatry (song differences).
● Secondary contact phase (very little discrimination of heterospecific song).
● Two morphologically similar species.
● Occupy similar ecological niches.
Warbler finch paper?
Grant & Grant, 2006.
Explain Grey warbler finch & Green warbler finch? (4)
● Low levels of genetic divergence/genetic distance.
● Positive correlation between genetic distance & differences in maximum elevation (ecological differentiation ).
● Females have chosen to breed on islands with habitats similar to where they were born.
● Phylogram of mtDNA haplotypes & geographical location.
Grey & Green warbler finch paper?
Tonnis et al., 2005.
Grey & Green warbler finch conclusion? (2)
● Genetic relatedness among populations is associated with habitat similarity.
● Habitat choice explains genetic & habitat similarities.
Explain Disa draconis complex species? (6)
● Habitat isolation (2 adjacent in Western Cape).
● Horse fly (mountain form) with short spur length.
● Long-tongued fly (sandplain form) with long spur length.
● Orchid species have different spur length (evolve/diverge as such).
● If a short spur is in an environment with only long-tounged flies, they will evolve long spur length.
● Therefore, long spur goes with Long-tongued fly & vice versa.
Spur?
= part of a flower that allows itself to be pollinated.
Interpreting pattern of speciation from phylogeny attributes? (2)
• Dating the phylogeny relative to understanding the history of the landscape helps (historical biogeography).
• Match phylogeny to distribution OR distribution to phylogeny.
