27: Speciation Flashcards
Speciation
The evolution of two or more distinct species from a single ancestral species.
species
An evolutionarily independent population or group of populations. Generally distinct from other species in appearance, behavior, habitat, ecology, genetic characteristics, and so on.
biological species concept
The definition of a species as a population or group of populations that are reproductively isolated from other groups. Members of a species have the potential to interbreed in nature to produce viable, fertile offspring but cannot interbreed successfully with members of other species.
prezygotic isolation
Reproductive isolation resulting from any one of several mechanisms that prevent individuals of two different species from mating.
postzygotic isolation
Reproductive isolation resulting from mechanisms that operate after mating of individuals of two different species occurs. The most common mechanisms are the death of hybrid embryos or reduced fitness of hybrids.
morphospecies concept
The definition of a species as a population or group of populations that have measurably different anatomical features from other groups. Also called morphological species concept.
polymorphic species
A species that has two or more distant phenotypes in the same interbreeding population at the same time.
cryptic species
A species that cannot be distinguished from similar species by easily identifiable morphological traits.
phylogenetic species concept
The definition of a species as the smallest monophyletic group in a phylogenetic tree.
monophyletic group
An evolutionary unit that includes an ancestral population and all of its descendants but no others. Also called a clade or lineage.
synapomorphy
A shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors. Useful for inferring evolutionary relationships.
subspecies
A population that has distinctive traits and some genetic differences relative to other populations of the same species but that is not distinct enough to be classified as a separate species.
allopatry
Condition in which two or more populations live in different geographic areas.
allopatric speciation
Speciation that occurs when populations of the same species become geographically isolated, often due to dispersal or vicariance.
vicariance
The physical splitting of a population into smaller, isolated populations by a geographic barrier.
biogeography
The study of how species and populations are distributed geographically.
sister species
Closely related species that occupy adjacent branches in a phylogenetic tree.
sympatry
Condition in which two or more populations live in the same geography area, or close enough to permit interbreeding.
sympatric speciation
The divergence of populations living within the same geographic area into different species as the result of their genetic (not physical) isolation.
niche
The range or resources that a species can use and the range of conditions that it can tolerate. More broadly, the role that species plays in its ecosystem.
polyploidy
(adjective: polyploid) The state of having more than two full sets of chromosomes, either from the same species (autopolyploidy) or from different species (allopolyploidy).
autopolyploidy
(adjective: autopolyploid) The state of having more than two full sets of chromosomes (polyploidy) due to a mutation that doubled the chromosome number. All the chromosomes come from the same species.
allopolyploidy
(adjective: allopolyploid) The state of having more than two full sets of chromosomes (polyploidy) due to hybridization between different species.
reinforcement
In evolutionary biology, the natural selection for traits that prevent interbreeding between recently diverged species.
hybrid zone
A geographic area where interbreeding occurs between two species, sometimes producing fertile hybrid offspring.
