Quiz 6 (Species Concepts, Speciation Modes) Flashcards
How were species determined pre-evolutionary theory?
Species were determined by their appearance (phenetic species concept)
How were species categorized according to phenetic species concept?
A representative specimen was chosen and organisms would be compared to it to visually determine if the organism was of the same species (typological approach)
How were species distinguished from each other in post-darwinian phenetics?
As many traits as possible were measured on multiple organisms
Cluster statistics were used to distinguish one species from another
What is the problem with using cluster statistics?
There is no biological explanation for why, it is completely subjective since species are determined visually
What is the horizontal species concept?
Species are defined at a moment in time; comparing populations
What is the vertical species concept?
Species are defined from the time of their inception until they speciate (speciation events)
What is the biological species concept?
A horizontal species concept
Species are defined by if an interbreeding group of organisms are reproductively isolated from other organisms
What are the key points of BSC?
Rooted in population genetics
There is a common gene pool that ties the members of the species together
Members of multi-cellular organisms look similar because they have developmental genetics similar enough to maintain viability & fertility
What are the 2 reproductive isolating mechanism categories?
Prezygotic: prevent interbreeding before a zygote forms
Postzygotic: prevent individuals from successfully interbreeding after a zygote is formed
What is geographic isolation?
A prezygotic isolation mechanism
There is geographic barrier causing populations causing populations to not be able to reproduce
What is ecological isolation?
A prezygotic isolation mechanism
Populations have different habitat preferences
ex: lizards that live in trees vs. lizards on land
What is temporal isolation?
A prezygotic isolation mechanism
Populations mate during different seasons or different times of day
What is behavioral ioslation?
A prezygotic isolation mechanism
Populations have different behaviors
What is mechanical isolation?
A prezygotic isolation mechanism
Populations attempt to mate but their parts don’t fit right so there is not fertilization
What is gametic isolation?
A prezygotic isolation mechanism
Populations are able to mate however the chemical signals of the egg aren’t recognized by the sperm so a zygote isn’t created
What is Hybrid Inviability?
A postzygotic isolation mechanism
The F1 generation dies due to incompatible developmental programs
What is Hybrid Sterility?
A postzygotic isolation mechanism
The F1 generation is sterile
What is Hybrid Breakdown?
A postzygotic isolation mechanism
Genetic failure in the F2 generation
How does Hybrid Breakdown work?
Species 1 has interacting loci on 2 pairs of chromosomes
Species 2 does not
F1 generation is created and the necessary interacting loci are present
However, due to random assortment during meiosis, some gametes do not have the necessary interacting loci which can have deleterious affects
What is the recognition species concept (RSC)?
A horizontal species concept
Group of organisms that have a shared mate recognition system (SMRS) which they use to identify appropriate mates
What is RSC good for?
Animals with specialized mating rituals for mate choice
What is RSC not good for?
Organisms that release gametes in water/ air
Organisms that use others to move their gametes
How does RSC and BSC compare and contrast?
Both rooted in population genetics
Species are defined by their gene pool
BSC is isolating, RSC is cohesive
Which species concept is right?
It depends on the cost to individuals
Species with a low mating cost, species that lack perceptual systems for mate recognition: BSC
Species with a high mating cost: RSC
What is the cladistic species concept?
A vertical species concept
Lineage of interbreeding organisms that begins when the parental lineage is divided into 2 species and ends when extinct
What are the 3 major modes of speciation based on geographic relationships?
Allopatric
Parapatric
Sympatric
What is allopatric specitation?
Members of a population are separated by a geographical barrier
What is large scale (vicariance) allopatric speciation?
A large population is divided into 2 large sub-populations due to oceans, mountains, plate tectonics (vicariance events)
What evolutionary forces would we expect to genetically differentiate them?
Most likely selection because of the population size especially if conditions are different in the regions (different selection pressures)
Drift less likely because drift has a larger effect in smaller populations
Could genetic incompatibility arise at a single locus?
No, wouldn’t bring about complete isolation
Could 2-loci cause genetic incompatibility (Dobzhansky-Muller incompatibilities)?
Yes, if new mutations arise in 2 populations & they go to fixation then hybridize, the new genotype (a,b) could potentially be fatal & cause isolation
What are peripheral isolates in allopatric speciation?
The range in which a species lives expands when conditions are favorable and contracts when they are not
Peripheral isolates are sub-populations that survive even when conditions are unfavorable & are separated from the main population
How does the founder effect form peripheral isolates?
Small amounts or even a single gravid female (extreme) immigrate to a new habitat
What makes peripheral isolates differentiate?
Selection: if the environment is different from the main population & if there is enough genetic variation in the isolated population
Drift: depends on the size of the isolate since drift has larger effects in smaller populations & how long it stays small
What evidence is there for allopatric speciation?
The Dodd Experiment:
Mating preference came about when there was selection for a new diet;
pre-zygotic isolation developed pretty quickly
Unsure if drift has a role due to not being tested
Same pattern seen in other studies (11/14)
Developmental biases causing this
