Tui Chub and the Genetics behind Understanding Them

The following blog is for tracking genetic findings concerning the MTC. First some vocabulary:

• loci - Plural of locus, a site or position on a chromosome where a particular gene or DNA sequence resides. Often used interchangeably with the term 'gene', but locus is more generic.
• ESU - evolutionarily significant unit, a distinct kind (species or subspecies)
  
• AFLPs - amplified fragment length polymorphisms
  
• allozyme - is one of several possible forms of an enzyme, a product of a particular allele at a given gene locus, with different genetic backgrounds, allowing genetic variation between individuals, subspecies or specieis to be deduced.
• basepair - Two of the building blocks of DNA held together by weak bonds. In a DNA molecule, adenine always bonds with thymine (AT), and cytosine always bond s with guanine (CG).
  
• microsatellite - A short sequence of DNA, usually 1 to 4 basepairs (a unit of DNA), that is repeated together in a row along the DNA molecule. There is variation from individual to individual in the number of repeats. There are many places in any organism's genome or DNA that contain microsatellites.
• intraspecific - Term that means "within one species."
• interspecific - Term that means "between two or more different species."
• hybrid - an organism that is the offspring of genetically dissimilar parents or stock.
• introgressive - Infiltration of the genes of one species into the gene pool of another through repeated back-crossing of an interspecific hybrid with one of its parents.
• non-introgressed - not showing an infiltration of genes from one species into the gene pool of another (i.e. between Mohave tui chub and Arroyo Chub)
• backcrossing - To cross (a hybrid) with one of its parents or with an individual genetically identical to one of its parents.
• genetic proximity -
• sympatric - Populations of two or more organisms or species that inhabit the same or overlapping geographic area.
• allopatric - Living in another region; said of populations of species which occupy ranges in different places on the earth's surface such that gene flow between them would be restricted or absent.
• morph - A Morph or morphotype, meaning "form" (from the Latin morpha), is a zoological term that describes local populations or subpopulations of a single species of animal that are phenotypically or behaviourally distinct from the larger population as a whole.
• fixation index (F_ST) is a measure of population differentiation based on genetic polymorphism data (such as SNPs or microsatellites).
• subpopulations - A well-defined set of interacting individuals that compose a proportion of a larger, interbreeding population.
• bottleneck - When a condition or event kills a significant percentage of a population and the survivors of such a bottleneck become the ancestors of future generations (and the genetic characteristics of those who do not survive are deleted from the racial heritage) leaving the surviving population with only the alleles of the survivors.
• founder - an individual(s) drawn from a source population that contribute genetically to the derived subpopulation.

---------------------------------------

The following abstract can be found at http://www.desertfishes.org/meetings/2006/DFC_Program_2006_Abstracts_2_sided.pdf

Genetic structure and management history of Mohave tui chub (Siphateles bicolor
mohavensis)

Chen, Yongjiu*1; Parmenter, Steve2; May, Bernie3. (1-North Dakota State University, Department of Biological Sciences; 2-California Department of Fish and Game; 3-The University of California, Davis, Department of Animal Science).

The Mohave tui chub (Siphateles bicolor mohavensis) is the only fish native to the Mojave River, California. Mass intergeneric hybridization with introduced arroyo chubs (Gila orcutti) displaced tui chubs from the Mojave River in the 1930s. Mohave tui chubs persisted in one relictual population, Mohave Chub Spring (MC Spring), from which three refuge populations were derived. Employing 12 microsatellite DNA loci, our study characterized genetic diversity of populations of Mohave tui chub, and examined the taxonomic status of the cyprinid fish common in the Mojave River today. We found only unhybridized arroyo chubs in the Mojave River, and unhybridized Mohave tui chubs in the refugial populations. Population substructure is evident among the four Mohave tui chub populations. Contrary to our expectation, the source population at MC Spring has significantly fewer alleles and lower heterozygosity than populations historically derived from it. Our findings suggest that genetic drift due to a small effective population size in MC Spring has reduced genetic diversity in the five decades since the original transplants were made. A bottleneck of 10 individuals during the founding of the Camp Cady population is reflected in significantly lower genetic diversity and divergence of that population from all others. Two additional refuges possess significantly higher levels of diversity, Lake Tuendae and China Lake. We recommend instituting artificial gene flow to rebuild genetic diversity in MC Spring and Camp Cady, and to better conserve allelic diversity in the species as a whole. New populations established in the future should be derived from Lake Tuendae and China Lake.

To be continued...