|SREL Reprint #0979|
and Genetic Characteristics of Dispersal in the Mosquitofish, Gambusia affinis
Analysis of 3,271 mosquitofish was conducted during a single dispersal
event in a small thermally-impacted reservoir to characterize both demographic
and genetic traits of dispersing fish. Males
dispersed in much larger numbers than females or juveniles.
Mean lengths of fish were greatest at distances farthest from homesites.
Pregnant females which dispersed carried significantly more fetuses than
non-dispersers, a direct result of their larger size. Genotype frequencies of four enzyme loci of dispersing fish
were non-randomly distributed throughout the pond and significant clines of gene
frequencies with distance from the major refuge were found.
Associations of genetic distance values and geographical distances
between collections sites were non-significant for some loci, indicating fish
were not distributed in a pattern based on random intermixing of refuge groups.
Refuge fish (N=368) were also collected after
dispersal. Males represented very
small percentages of post-dispersal refuge populations. Changes in allele frequencies of refuge fish of ten percent
and greater occurred during the dispersal event at some sites.
Wright’s F-coefficients indicated that increased genetic heterozygosity
and population differentiation occurred both within and among refuge groups
after dispersal. Dispersal, as documented here for Gambusia affinis,
is proposed to be selectively advantageous for species which occupy temporally
and/or spatially fluctuating environments.
SREL Reprint #0979
Brown, K.L. 1985. Demographic and genetic characteristics of dispersal
in the mosquitofish, Gambusia affinis (Pisces: Poeciliidae). Copeia