Speciation Flashcards
What defines a species?
Taxanomic, ‘biological’, evolutionary - Each has a part to play
Please explain the Phenetic / taxanomic species concept?
The smallest group of natural populations permanently separated from other by discontinuity in biotype series (phenotypes dont combine) - Breeds within its own limits - Almost all species recognised like this
Please explain the biological species concept?
Groups of actually or potentially interbreeding populations which are reproductively isolated from other groups.
Explain the phylogenetic species concept
Smallest cluster of individuals within which there is a paternal pattern of ancestry and descent - Would lead to sub-species become species
What are some problems with the species concept in total?
Hybridisation, Inbreeding, Asexual reproduction, Autopolyploidy, Chromosomal rearrangements (polyploids)
What is the problem with species concept and inbreeding
Species can produce whole population of just one phenotype - If populations differ they can resemble species - Not usually permanently distinct
What is the problem with agamospermous groups?
Last ability to have sex
What are the problems with autopolyploids?
Look identical but aren’t - could be diploid, triploid, tetraploid…..
What is the best species definition?
Species are groups of morphologically similar individuals held together due to a combination of: - natural selection, gene flow and genealogical history
What are the mechanism contexts for speciation?
-Geographical / space - Time / speed (of speciation) - Genome - Ecology
What are the two main lineages of speciation?
Lineage-fusion processes Lineage-splitting processes
What are possible mechanisms for lineage-splitting processes?
Geographical isolation - genepool fragmentation and divergence Ecological isolation - habitat, temporal, breeding, floral divergence Genomic isolation - chromosomal rearrangemnt –> cross incompatibility, reduced fitness of hybrids
How does allopatric (geographical) speciation occur?
Varied genepool –> differentiation of genepool –> physical separation of two or more large groups of the ancestral species –> divergence occurs –> uniform natural selection
How does peripatric speciation occur?
Dispersal or evolution of one population of main genepool during range contraction
Divergence of new population away for ancestral species
Define parapatric speciation:
When two population which are on the border / immediately adjacent diverge.
Divergence of a continous genepool
Define sympatric speciation:
When a new species evolves from the ancestral species whilst still occupying the same geographical area.
Summarise the differences between the types of speciation
Explain regional speciation in terms of allopatric and parapatric models.
Divergence in geography thought to be primary reason.
Collective divergence- mediated by:
- unform natural selection
- geneflow between populations of diverging race, mutations spread due to adaptive value
Evidence for regional speciation:
Itermediates are common in many species
Partial reproductive isolation may occur between conspecific geographical reas
No qualitative difference for trait distiinguishing between geographical area.
Evidence against regional speciation
Regional genepools are usually subdivided into genetically different populations.
- Gene flow too limited to permit genepool to evolve as a race.
- Selection often causes migration opposed to evolution
- No proven examples of speciation on a regional scale.
Explain local speciation- peripatric and sympatric models.
If all changes that occur with speciation occur locally then a new species can evolve by common descent if distinctive features are passed on.
Tempo and size of population can also vary
Does it depend on longevity?
single isolated populations are often not long lived enough to undergo speciation and are more likely to go extinct.
What are meta-populations?
Cluster of neighbouring populations connected by frequent geneflow (including dispersal)
- longer lived than local populations
- Peripatric speciation possible?
What mechanisms can lead to breeding system divergence?
Inbreeding produces two different populations
How can floral divergence lead to speciation
Pollinators and flowers co-evolve
Pollinators and flower become specific to one another
Single gene may control flower colour –> what pollinators are attracted –> what diversity is produced
Two different pollinators acting on one species could lead to reproductive isolation and speciation
- DIfferent pollinators select for different variants (amount of yellow on flower)
Summarise what speciation can involve:
