Lecture 22 & 23 & 24: Species and Speciation Flashcards
Define the morphological species concept.
Species are distinguished by morphological differences.
Define the biological species concept.
Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.
Define the phylogenetic species concept.
a single lineage of ancestor-descendant populations which maintains its identity from other such lineages.
Define a ring species
a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two “end” populations in the series, which are too distantly related to interbreed, though there is a potential gene flow
What are the four premating/prezygotic reproductive isolating mechanism?
- Ecological isolation
- Temporal isolation
- Mechanical isolation
- Ethological isolation
What are the four postmating/postzygotic reproductive isolating mechanisms?
- Gamete incompatibility (prezygotic)
- Hybrid inviability
- Hybrid sterility
- F2 breakdown
What is ecological isolation?
When two species are unable to mate because they occupy different ecologies.
What it ethological isolation?
When two species are unable to make because the have different mating behaviors.
What is temporal isolation?
When the reproductive timing of species are not in synch.
What is mechanical isolation?
When species are morphologically incompatible.
Define sibling species.
Species that are close relatives to one another.
Define cryptic species.
Species that are not easily distinguished, but are true species.
What is hybrid inviability?
When the embryo of two species doesn’t live.
What is hybrid sterility?
When hybrids develop, but are sterile and thus cannot reproduce.
What is F2 breakdown?
When the F1 generation is fertile, but thee next generation (F2) are sterile or have reduced fitness?
What is the allopatric model of speciation?
When there are extrinsic barriers to gene flow that cause species to differentiate by having isolating mechanism evolve.
Understand reproductive isolation vis Dobzhansky-Muller Incompatibilities.
Species split into two and each have a different mutation that causes hybrid lethality and sterility when future generations meet.
What is the reinforcement model?
Similar to the allopatric model, but when species come back into secondary contact it imposes selection for isolating mechanism. Hybrids are less fit, and there is selection against those hybrids.
Define character displacement.
Is the accentuation of characters where species overlap, but minimized in places where they do not. This will decrease the number of individuals who mate with the wrong individuals.
Define heterospecific.
belonging to the same species.
Define conspecific.
belong to different species.
What is the sympatric model of speciation?
Divergence without obvious geographic barrier. Selection on habitat survival genes and associated selection of mating genes.
Be able to distinguish the genetic differences between species from the genetic basis of species isolation.
Slide 39
How is reproductive isolation correlated with genetic distance?
Reproductive isolation is positively correlated with genetic distance (opposite of similarity). With greater genetic distance (DNA divergence and time of separation) the greater reproductive isolation.
Understand the effect of the X-chromosome in hybrid sterilitty
F1 and backcrosses between two fly species show the “poisonous” X-autosome interactions. When X from one species is present with autosomes from the other species, sperm motility is reduces (sterility).
What is Halden’s rule?
In hybrid crosses between differentiated forms, the heterogametic sex has lower fertility or viability. Implies incompatabilities between sex chromosomes and autosome from diverged populations.
Understand the relationship between sexual selection and speciation.
Sexual selection can drive speciation.
Understand the relationship between ecological factors as species diversity
Ecological factors may promote and limit species diversity.