Speciation Flashcards
1
Q
Speciation
A
- bridge between pop evolution and taxonomic diversity
- organism diversity is due to cladogenesis
- usually too fast for fossil record but to slow for study; largely inference based
- different animals undergo independent divergence, maintaining separate identities/evolutionary tendencies
2
Q
Species Classification Function
A
- COYNE & ORR (2004); species let us:
1. Systematically classify organisms.
2. Correspond discrete similar organism groups.
3. Understand natural discrete organism clusters.
4. Represent evolutionary history products.
5. Apply study to largest possible organism variety. - necessary for understanding within/between pop variation and sibling species
3
Q
Sibling Species
A
- advocates of biological species concept accept genetic “leakage” between species
- ie. carrion/hooded crow often mistaken as same species as produce hybrids
4
Q
Linnaean Classification
A
- all species have a name conforming to binomial/trinomial system (ie. genus/species)
- ie. giraffe (“giraffa camelopardalis”) = animalia/chordata/mammalia/artiodactyla/giraffidae/giraffa/cameloparalis/reticulata, etc.
5
Q
Biological Species Concept (BSC)
A
- MAYR (1942); a species is a group of fertile individuals bared from interbreeding with similarly physiological groups (lest risking parental incompatibility/hybrid sterility) due to reproductive isolation
6
Q
BSC: Issues
A
- hybrids do occur (ie. ligers/phickens)
- some males (ie. hybrid flycatchers) are even fertile, though females aren’t
7
Q
Phenotypic Species Concept (PSC)
A
- a species is a group of organisms sufficiently similar to one another/different from other species
8
Q
PSC: Issues
A
- variation between populations occur
- ie. latitudinal variation occurs in white-tailed deer
- CLINE = gradual character change in allele frequencies over geographic distance
9
Q
PSC-I: Bergmann’s Rule
A
- BERGMANN (1874)
- “… within broadly distributed taxonomic clades, pops/large species are found in cold regions, while pops/small species are found in warmer regions…”
- ie. seagull; wingspan decreases further south in Europe it’s found since less body surface is needed to maintain warmth/travel to the South for the winter as they’re already there
10
Q
New Species Formation
A
ALLOPATRIC
PERIPATRIC
PARAPATRIC
SYMPATRIC
11
Q
NSF: Allopatric
A
- geographic; pops of same species isolates into new ones
- ORIGINAL POP: full
- INITIAL SPECIATION STEP: halved via barrier
- REPRODUCTIVE ISOLATION EVOLUTION: develops in isolation
- NEW SPECIES AFTER EQUILIBRIATION OF RANGES: overlaps
12
Q
NSF: Peripatric
A
- closely related species in isolated into nearby unconnected area
- ORIGINAL POP: full
- INITIAL SPECIATION STEP: new niche enters externally
- REPRODUCTIVE ISOLATION EVOLUTION: in isolated niche
- NEW SPECIES AFTER EQUILIBRIATION OF RANGES: overlaps born
13
Q
NSF: Parapatric
A
- adjacent ranges w/narrow contact zone so species form new area
- ORIGINAL POP: full
- INITIAL SPECIATION STEP: new niche enters internally
- REPRODUCTIVE ISOLATION EVOLUTION: in adjacent/internal niche
- NEW SPECIES AFTER EQUILIBRIATION OF RANGES: divides w/overlap
14
Q
NSF: Sympatric
A
- evolution of new species within same habitat due to reproductive isolation
- ORIGINAL POP: full
- INITIAL SPECIATION STEP: genetic polymorphism
- REPRODUCTIVE ISOLATION EVOLUTION: within pop
- NEW SPECIES AFTER EQUILIBRIATION OF RANGES: divides w/overlap
15
Q
NSF: Allopatric (Examples)
A
- IE. birds of paradise; free to evolve and mix w/few preds in Papua New Guinea
- IE. Galapagos finches; adaptive radiation in response to different food types (ie. nuts/fruit) on various Galapagos islands, requiring different beaks
16
Q
NSF: Peripatric (Examples)
A
- similar to allopatric BUT one pop is much smaller
- IE. polar bears VS brown bears; polar matriline traced for hypothetical relationship between browns; little known about polars due to climate crisis; hybridization occurred in Ice Ages; divided by drastic climate dispersal events; breeding left strong print
17
Q
NSF-PERI: Matriline
A
- line of descent from female ancestor to descendant; individuals in all intervening generations are mothers
18
Q
NSF: Parapatric (Examples)
A
- IE. huge salamander variation (aka. ring species); maybe ancestral species was northern but pops expanded south down San Joaquin valleys
19
Q
NSF-PARA: Ring Species
A
- extreme forms don’t interbreed in region of new species formation overlap
- prove INTRASPECIFIC differences can be big enough for INTERSPECIFIC differences = natural variation can generate whole new species
- IE. new yellow-legged gull from herring gull; looks similar w/smaller wingspan/different legs/leaner build
20
Q
Nature Packaging Concept
A
- nature is always discretely packaged in tight forms
- if full range according to time/space is studies, apparent boundaries become fluid
21
Q
NSF: Sympatric (Examples)
A
- species overlap
- IE. cichlid diversity; second set of jaws overlaps within multiple fish
22
Q
Separation Maintenance
A
- LIFE CYCLE affected by PRE/POST-ZYGOTIC BARRIERS
23
Q
SM: Life Cycle Affected By PZ Barriers
A
- IE. hamsters; fitness of zygote A impacts number of zygotes in next gen according to current gamete contributions in A
- PRE = between adult A and mate; prevent further zygote production
- POST = between zygote A and development; prevent birth
24
Q
SM: Pre-Zygotic Barriers
A
- prevent/reduce likelihood of gamete transfer to members of another species; ie. PRE-MATING PRE-ZYGOTIC BARRIERS - LIMITED DISPERSAL - ISOLATING (ECOLOGICAL) BEHAVIOUR POST-MATING PRE-ZYGOTIC BARRIERS - GAMATE ISOLATION
25
SM: Post-Zygotic Barriers
- consist of reduced survival/reproductive rates of hybrid zygotes; ie.
HYBRRID UNVIABILITY/STERILITY
26
SM: PRE-Z: PRE-M: Limited Dispersal
- IE. grandparents having been born within 80km of each other; choosing mater based on proximity/clusters immediately available
27
SM: PRE-Z: PRE-M: Isolating Behaviour
- IE. blue-footed booby; mate recognition systems consist of displays/responses to signal potential mates
- female usually doesn't respond to inappropriate signals
28
SM: PRE-Z: POS-M: Gamete Isolation
- scheme of fertilization combining invertebrate/mammalian attributes
- caused via whether sperm sticks to proteins on egg surface for penetration; protein divergence causes it
- failed union of different species' gametes; important in externally fertilising species (ie. marine invertebrates)
29
SM: PRE-Z: POS-M: Gamete Isolation (Process)
- VACQUIER (1995); process is:
1. Sperm chemotactically attracted to egg.
2. Sperm binds to egg envelope.
3. Acrosome reaction; externalises contents of acrosomal vesicle.
4. Sperm holes egg envelope; reaches egg cell membrane.
5. Membranes of 2 cells fuse; restore diploid genome; activate development.
30
SM: POS-Z: Hybrid Unviability
- often have lower survival rates that "full species"
| - mortality intrinsic during embryogenesis due to developmental issues
31
SM: POS-Z: Hybrid Sterility
- mature survival but lack of viable gamete production
- HALDANE'S RULE (1922); "... when in the offspring of 2 different animal races, a sex is absent/rare/sterile, it's the heterozygous/heterogametic sex..."
32
SM: Breaking the Barriers
- species barriers broken via experimental crossing
| - DIGBY (1912); crossed primula flowers; most were sterile but some weren't; had double chromosomes (polyploidy) in turn
33
Modern Speciation
- occurs daily
- ie. all peasant colourations are "phasianus colchicus" regardless of variations/migration patterns; all have same roots but speciation is constantly changing them/adding more collorations/characteristics based on new migratory areas
34
MS: Co-Evolution
- IE. pheasants and their belly bugs differentiating together based on changed environments
35
SUMMARY
- species are variously defined; may arise due to pops of founder species isolating GEOGRAPHICALLY (allopatric/peripatric/parapatric) or BHEAVIOURALLY (sympatric)
- post-isolation; despite re-encountering, new species remain reproductively isolated due to ingrained adaptation of breeding
- speciation is a constantly ongoing process
