Molecular markers for comparative studies of variation in ecology and systematics

Abstract

Variation in the organisms comes as consequence of ontogenetic, environmental
or genetic changes. Polymorphism is the discontinuous genetic variation associated with non-sexual
processes. Polymorphism may or may not be conspicuous and results from changes in the DNA due mutations
or recombination. Variation at the individual, population or species level allows to find inherited attributes
(morphological or molecular) that show if the variants under study belong or not to the same organism,
population or species. The presence of these shared attributes distinguishes the ontogenetic, population or
historical individuality. This manuscript describes molecular markers used to sample variation within and
among populations for ecological or systematic studies. Methods to obtain markers from proteins are
reviewed first, followed by those from nucleic acids. Some of these molecular markers'are: immunological
essays, isozyme electrophoresis, restriction fragment length polymorphisms, random amplified polymorphic
DNAs, mini and microsatellites. single strand conformation polymorphism and DNA sequencing. Available
molecular markers have helped solve diverse ecological and systematic problems, like: parentage, diversity,
hybridization, geog'raphic variation, speciation and phylogeny, among others. These markers can be explored
in any gene or gene product from any organism.