Abstract
From a total of 524 microsatellite loci considered in nearly 40 000 individuals of 78 species, freshwater fish displayed levels of population genetic variation (mean heterozygosity, h=0·46, and mean numbers of alleles per locus, a=7·5) roughly similar to those of non‐piscine animals (h=0·58 and a=7·1). In contrast, local population samples of marine fish displayed on average significantly higher heterozygosities (h=0·79) and nearly three times the number of alleles per locus (a=20·6). Anadromous fish were intermediate to marine and freshwater fish (h=0·68 and a=11·3). Results parallel earlier comparative summaries of allozyme variation in marine, anadromous, and freshwater fishes and probably are attributable in part to differences in evolutionarily effective population sizes typifying species inhabiting these realms.
Highlights
The term microsatellites refers to a class of co-dominant DNA markers which are inherited in a Mendelian fashion
The salient finding of this literature review is that local population samples of marine fishes tend to display, on average, significantly higher heterozygosities and numbers of alleles per locus than do freshwater fish
All mean estimates of within-population microsatellite variation summarized here are far higher than those recorded in earlier allozyme surveys
Summary
The term microsatellites refers to a class of co-dominant DNA markers which are inherited in a Mendelian fashion. Microsatellite loci are widely dispersed along and among chromosomes, and each locus is characterized by a known DNA sequence. These sequences consist of both unique DNA (which defines the locus) and of repetitive DNA motifs (which may be shared among loci). The repetitive elements consist of tandem reiterations of simple sequence repeats (SSRs) and are typically composed of two to four nucleotides such as (AC)n or (GATA)n where n lies between 5 and 50. Following the discovery of microsatellite DNA markers about a decade ago (Litt & Luty, 1989; Tautz, 1989; Weber & May, 1989), thousands of these loci have been described in diverse eukaryotic organisms, including humans (Dib et al, 1996)
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