Ring Species
Ring Species: A Catalyst for Speciation
After spending time on the Galapagos Islands studying the origin of various species, former divinest Charles R. Darwin proposed the evolutionary theory of natural selection, a mechanism by which advantageous variations in a population are preserved while unfavorable variations are lost (Berkeley, 2008). As a result of these variations, some individuals are better acclimated to their environment than others. This results in the better-suited individuals outcompeting the less fortunate individuals for resources, and eventually causes genetic types to replace others. Natural selection is ultimately a process that can lead to the evolution of species (Zimmer, 2013).
One key aspect of natural selection is that it can create variation across the geographical range of a population by the transfer of alleles. This is known as gene flow, and according to scientist James Mallet, “gene flow is caused by…the movement or dispersal of whole organisms or genomes from one population to another.” The rate at which alleles move between populations and the amount of gene flow that occurs depends on how far individual organisms travel (Mallet).
Although gene flow is pivotal in creating genetic variation between populations, it is also essential that sexually reproducing species remain somewhat distinct from one another. In order to ensure this, reproducing species demand isolating barriers, in which both extrinsic (geographic) and intrinsic (reproductive) factors reduce gene flow from the individuals of other species (Zimmer, 2013). Both geographic and reproductive isolation can eventually lead to “isolation by distance” introduced by Sewall Wright in 1943 to describe “the accumulation of local genetic differences under geographically restricted dispersal.” This can occur when two populations of a species evolve away from each other at a faster rate than gene flow can connect them. This ultimately results in the continuous divergence of a
After spending time on the Galapagos Islands studying the origin of various species, former divinest Charles R. Darwin proposed the evolutionary theory of natural selection, a mechanism by which advantageous variations in a population are preserved while unfavorable variations are lost (Berkeley, 2008). As a result of these variations, some individuals are better acclimated to their environment than others. This results in the better-suited individuals outcompeting the less fortunate individuals for resources, and eventually causes genetic types to replace others. Natural selection is ultimately a process that can lead to the evolution of species (Zimmer, 2013).
One key aspect of natural selection is that it can create variation across the geographical range of a population by the transfer of alleles. This is known as gene flow, and according to scientist James Mallet, “gene flow is caused by…the movement or dispersal of whole organisms or genomes from one population to another.” The rate at which alleles move between populations and the amount of gene flow that occurs depends on how far individual organisms travel (Mallet).
Although gene flow is pivotal in creating genetic variation between populations, it is also essential that sexually reproducing species remain somewhat distinct from one another. In order to ensure this, reproducing species demand isolating barriers, in which both extrinsic (geographic) and intrinsic (reproductive) factors reduce gene flow from the individuals of other species (Zimmer, 2013). Both geographic and reproductive isolation can eventually lead to “isolation by distance” introduced by Sewall Wright in 1943 to describe “the accumulation of local genetic differences under geographically restricted dispersal.” This can occur when two populations of a species evolve away from each other at a faster rate than gene flow can connect them. This ultimately results in the continuous divergence of a
References: Allozyme. (2005, October). Biology Online. Retrieved from http://www.biology-online.org/dictionary/Allozyme Caucho & Baum, (2012). The Caribbean slipper spurge Euphorbia tithymaloides: the first example of a ring species in plants Charles Darwin (1809 - 1882). BBC News. BBC News. 2012. Retrieved from <http://www.bbc.co.uk/history/historic_figures/darwin_charles.shtml> Hausdorf, B. (2011). Progress toward a general species concept. Irwin, D. E. (2002). Ring species: Unusual demonstrations of speciation Wake. (1997). Incipient species formation in salamanders of the ensatina complex Wake, D. B., and C. J. Schneider. (1998). Taxonomy of the plethodontid salamander genus Ensatina Wake, D. B., & Yanev, K. P. (1986). Geographic variation in allozymes in a "ring species," the plethodontid salamander (2001). Biologist 's uncover Darwin 's 'missing evidence ' for divergence of species in a warbler 's song (2008). Understanding evolution. University of California Museum of Paleontology, Retrieved from <http://evolution.berkeley.edu/evolibrary/article/0_0_0/devitt_02> (2012)