Ch14
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Define species according to the evolutionary species concept
a lineage of populations that maintains its identity from others & has its own evolutionary fate
Can the evolutionary species concept be used to identify species or understand their boundaries?
No
Define phenetic/morphological species concept
Individuals that cluster in phenotype space can be assigned to the same species
Define biological species concept
Groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups
State the difficulties of using the biological species concept
• hard to apply to extinct animals • does not apply to asexual species • hybridization is happening more often
Define phylogenetic species concept
The smallest monophyletic groups distinguished by a shared derived character
State the difficulties of using the phylogenetic species concept
• Traits used do not need to be ecologically, physiologically, or morphologically significant • Opportunity for over-splitting • some traits may be cause by local adaptation & polymorphic for a given species
Does all 3 concepts agree with one another?
No
List the concepts needed to define species
• evolutionary fate • distinguishable characters • lack of gene flow • shared derived characters
Define allopatric speciation
Speciation caused by geographic isolation ex. snapping shrimp Alpheus
Define parapatric speciation
speciation caused by diverging populations joining at a common border ex. black & red spruce
Are hybrids caused by parapatric speciation always at fitness disadvantage?
No ex. Artemisia tridentata in hybrid zone
Define ring species
species or species complex whose distribution spreads around geographical barriers, or areas of unsuitable habitat *they have some gene flow
Define sympatric speciation
speciation that occurs within the same location ex. cichlids, Amphilophus
Why don’t two separate species merge back together if they overlap in range?
due to prezygotic & postzygotic isolating mechanisms
State the function of prezygotic isolating mechanisms
prevents mating or fertilization
State the function of postzygotic isolating mechanisms
prevents zygote or offspring from surviving
If a barrier disappears & populations come back into contact, what can occur?
blending or reinforcement
List the genetics of reproductive isolation
• Changes in chromosome number • Chromosomal rearrangement • Dobzhansky-Muller hybrid incompatibility • Sex chromosomes & Haldane’s rule
Define Haldane’s rule
If among hybrid offspring one sex is absent, rare or sterile, it will be the heterogametic sex