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Colonization by Mosquitofish (Gambusia affinis) of a Great Plains River Basin

Karen L. Brown
Copeia
Vol. 1987, No. 2 (May 13, 1987), pp. 336-351
DOI: 10.2307/1445769
Stable URL: http://www.jstor.org/stable/1445769
Page Count: 16
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Colonization by Mosquitofish (Gambusia affinis) of a Great Plains River Basin
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Abstract

Mosquitofish have rapidly colonized the Arkansas River basin in Kansas during the past 50 yr. Fish were collected from creeks in the basin to compare genetic and demographic characteristics of populations taken from relatively earlier and more recently established areas. Mean population levels of genetic variation were not significantly lower in more recently colonized areas, a result unexpected if initial founder events are important. In this case, multiple insemination of females and differential selection of colonizers may have decreased the eroding effects of founder events on genetic variation. Heterogeneity of genotypic and demographic frequency distributions was most common among populations in newly established areas, a finding attributed to non-random movement and/or survivorship of individuals involved in the colonization process. Male and female colonization patterns differed across the basin. Male heterozygosity values were significantly less than female and juvenile heterozygosities at all collection sites, indicating either differential mortality of heterozygous males or dispersion of them from creek populations. Males also exhibited a greater degree of genetic differentiation between sites within the basin, a finding which further supports the contention that males incur a greater selective force during colonization than females. The noted success of this species as a colonizer in many diverse aquatic habitats can be attributed to increased colonization capabilities of females in comparison to males and to the fact that single females who are multiply inseminated are able to seed new habitats with a genetically diverse group of offspring.

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