Glossary of genetics and evolutionary biology

This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics.

It has been designed as a companion to Glossary of cellular and molecular biology, which contains many overlapping and related terms; other related glossaries include Glossary of biology and Glossary of ecology.

Also called functionalism.Also called geographic speciation, vicariance, vicariant speciation, and dichopatric speciation.Also called an ancestral character, primitive character, or primitive trait.Also called positive assortative mating and homogamy.Also testcrossing.Also simply called the Dobzhansky–Muller model.Also called a monophyletic group.Also convergence.Also crossing and outbreeding.Also Darwinian theory and Darwinian evolution.Also derived character, advanced character, and advanced trait.Denoted in shorthand with the somatic number 2n.Also positive selection.Also negative assortative mating and heterogamy.Also diversifying selection.Also divergence.Also gene amplification.Sometimes used interchangeably with genetic variation.Also called allelic drift or the Sewall Wright effect.Also genetic draft and the hitchhiking effect.Also DNA testing and genetic screening.Sometimes used interchangeably with genetic variation.Sometimes used interchangeably with genetic diversity and genetic variability.Denoted in shorthand with the somatic number n.Also inheritance.Also hybrid vigor and outbreeding enhancement.Also homologs or homologues.Also lateral gene transfer (LGT).Also incrossing.Also introgressive hybridization.Also called the last universal cellular ancestor or simply the last universal ancestor.Also pedigree.Also called lineage-branching.Plural loci.Also environmental genomics, ecogenomics, and community genomics.Also point-nonsense mutation.Also nonsynonymous substitution or replacement mutation.Also ontogenesis and morphogenesis.Also outcrossing or crossbreeding.Also maximum parsimony.Also polypheny.Also multifurcation.Also genetic bottleneck.Also prosposito for a male subject and prosposita for a female subject.Also neotype.Also purebreed.Also complex trait.Also refuge.Also called network evolution.Also reversion.Also Fisherian runaway.Also selection pressure.Denoted in shorthand with a + superscript.

In allopatric speciation , a population becomes separated by a geographic barrier and reproductive isolation results in two separate species.
An apomorphy is a derived trait present in one or more members of a clade but not the common ancestor; a plesiomorphy is an ancestral trait present in the common ancestor of the clade and possibly some or all of its descendants.
In centrifugal speciation , the range of an original population (green) expands and then contracts, leaving an isolated fragment population behind. In the absence of interbreeding, the central population (changed to blue) becomes reproductively isolated over time.
Gene flow is the transfer of alleles from one population to another population through the interbreeding of individual organisms belonging to the populations.
In the Kaneshiro model of peripatric speciation , a sample of a larger population results in an isolated population with less males containing attractive traits. Over time, choosy females are selected against as the population increases. Sexual selection drives new traits to arise (green), thereby reproductively isolating the new population from the old one (blue).
Parapatric speciation can occur when the members of a population subject to a selective gradient of phenotypic or genotypic frequencies (a cline ) experience different selective conditions at each end of the gradient ( divergent selection ). Reproductive isolation occurs upon the formation of a hybrid zone. In most cases, the hybrid zone is eliminated due to a selective disadvantage, which effectively completes the speciation process.
In peripatric speciation , a small population becomes isolated on the periphery of the central population evolving reproductive isolation (blue) due to reduced gene flow .
A phylogenetic tree depicting the evolutionary relationships between the three domains of life ( Bacteria , Archaea , and Eukaryota ) and the major clades within them. The root of the tree symbolizes that all extant life on Earth descended from a single common ancestor .
Reinforcement assists speciation by selecting against hybrids .
Reproductive character displacement sometimes occurs when two allopatric populations come into secondary contact . Once in sympatry , changes can be seen in mating-associated traits only in the zone of contact. This is a common pattern found in speciation by reinforcement .
In a ring species , individuals are able to successfully reproduce and exchange genes with members of their own species in adjacent populations occupying a suitable habitat around a geographic barrier. Individuals at the ends of the cline are unable to reproduce when they come into contact.
The four outcomes of secondary contact :
1. An extrinsic barrier separates a species population into two but they come into contact before reproductive isolation is sufficient to result in speciation. The two populations fuse back into one species.
2. Speciation by reinforcement.
3. Two separated populations stay genetically distinct while hybrid swarms form in the zone of contact.
4. Genome recombination results in speciation of the two populations, with an additional hybrid species . All three species are separated by intrinsic reproductive barriers. [ 31 ]