management unit
A local population that is managed as a unit due to its demographic independence.

marginal overdominance
Greater fitness of heterozygous genotypes, which are not the most fit in any single environment, due to an organism’s interactions with multiple environments that each favor different alleles.

match probability (MP)
The probability of sampling an individual with an identical multilocus genotype to the one already sampled (“in hand”).

maternal effects
The influence of the genotype or phenotype of the mother on the phenotype of the offspring. Because it has no genetic basis, maternal effects are not heritable.

maximum likelihood
A statistical method of determining which of two or more competing alternative hypotheses (such as alternative phylogenetic trees) yields the best fit to the data.

maximum likelihood estimate (MLE)
A method of parameter estimation that obtains the parameter value that maximizes the likelihood of the observed data.

MCMC
Markov chain Monte Carlo. A tool or algorithm for sampling from probability distributions based on constructing a Markov chain. The state of the chain after many steps is then used as a sample from the desired distribution. Sometimes called a random walk Monte Carlo method.

MDS
Multidimensional scaling. A statistical graphing technique used to represent genetic distances between samples in two or three dimensions, and thereby visualizing similarities and differences between different groups or samples.

Mendelian segregation
The random separation of paired alleles (or chromosomes) into different gametes.

meristic character
A trait of an organism that can be counted using integers (e.g., fin rays or ribs).

metacentric
A chromosome in which the centromere is centrally located.

metapopulation
A collection of spatially divided subpopulations that experience a certain degree of gene flow among them.

metapopulation scale
The spatial scale at which individuals migrate between local subpopulations, often across habitat that is unsuitable for colonization.

microchromosomes
Small chromosomes found in many bird species which, unlike heterochromosomes, carry functional genes.

microsatellite
Tandemly repeated DNA consisting of short sequences of one to six nucleotides repeated between approximately five and 100 times. Also known as VNTRs, SSRs, or STRs.

migration
The movement of individuals from one generically distinct population to another resulting in gene flow.

minimum viable population (MVP)
The minimum population size at which a population is likely to persist over some defined period of time.

minisatellite
A tandemly repeated sequence of approximately 10–100 nucleotides that are 500 to 30,000 base pairs in length.

mitochondrial DNA (mtDNA)
A small, circular, haploid DNA molecule found in the mitochondria cellular organelle of eukaryotes.

ML
See maximum likelihood.

MLE
See maximum likelihood estimation.

molecular clock
The observation that mutations sometimes accumulate at relatively constant rates, thereby allowing researchers to estimate the time since two species diverged (TMRCA).

molecular genetics
The branch of genetics that studies the molecular structure and function of genes, or that (more generally) uses molecular markers to test hypotheses.

molecular mutations
Changes to the genetic material of a cell, including single nucleotide changes, deletions, and insertions of nucleotides as well as recombinations and inversions of DNA sequences.

monoecious
A plant in which male and female organs are found on the same plant but in different flowers (for example maize).

monomorphic
The presence of only one allele at a locus, or the presence of common allele at a high frequency (>95% or 99%) in a population.

monophyletic
A group of taxa that include all species, ancestral and derived, from a common ancestor.

monophyly
The presence of a monophyletic group.

monotypic
A taxonomic group that encompasses only one taxonomic representative. The reptile family that contains tuatara (Sphenodontia) is currently monotypic.

morphology
The study of the physical structures of an organism, including the evolution and development of these structures.

MP
See match probability.

MRCA
Most recent common ancestor. In cladistics, the organism at the base of a clade, from which that clade arose.

mRNA
Messenger ribonucleic acid.

MSD
Multiple factor sex determination.

mtDNA
See mitochondrial DNA.

MU
See management unit.

mutagenesis
The natural or intentional formation of mutations in a genome.

mutation
An error in the replication, or transmission, of DNA that cause a structural change in a gene. See also molecular mutations.

mutational meltdown
The process by which a small population accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which leads to further accumulation of deleterious mutations. A population experiencing mutational meltdown is trapped in a downward spiral and will eventually go extinct.

MVP
See minimum viable population.