Hybrid zone dynamics are influenced by genotype-specific variation in life-history traits: Experimental evidence from hybridizing Gambusia species

Evolution
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Abstract

Results from two experiments are presented that contrast differences in life-history traits and population dynamics between two species of live bearing fishes (Gambusia affinis and G. holbrooki) that hybridize across portions of the southeastern United States. Progeny from parental holbrooki and holbrooki-affinis F1 crosses exhibited larger lengths at birth, at 15 days, and matured earlier, and at larger size than did progeny from parental affinis and affinis-holbrooki F1 crosses. Comparisons of experimental populations of affinis, holbrooki, and mixed (affinis + holbrooki) species composition followed over two years revealed that affinis populations consistently exhibited smaller population size, lower carrying capacity, lower recruitment, and larger over-winter mortality than did holbrooki or mixed populations. Evidence for density-dependent reductions in fecundity and concomitant increases in juvenile mortality rates were observed in all populations, but were most pronounced for affinis populations. Genotype-specific differences in life-history traits appear to confer differential advantage to offspring of parental holbrooki origin and F1 progeny of holbrooki maternal parentage given the resource availability and the age structure and densities experienced during these experiments. Results have direct implications regarding the rate and direction of evolution within hybrid zones formed by these two species.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Hybrid zone dynamics are influenced by genotype-specific variation in life-history traits: Experimental evidence from hybridizing Gambusia species
Series title Evolution
DOI 10.2307/2410075
Volume 47
Issue 2
Year Published 1993
Language English
Publisher Society for the Study of Evolution
Contributing office(s) Alaska Science Center
Description 15 p.
First page 632
Last page 646
Country United States
State South Carolina