Predation and the persistence of melanic male mosquitofish (Gambusia holbrooki)

Abstract

The empirical reasons for the persistent rarity of a genotype are typically complex and tedious to identify, particularly in nature. Yet rare morphs occur in a substantial fraction of phenotypic polymorphisms. A colour polymorphism has persisted for decades in the eastern mosquitofish, yet why this is so remains obscure. Here, I report the results of (1) intensive sampling at 45 natural sites to obtain the frequency distribution of the melanic (black) mosquitofish morph in Florida, (2) predation trials, conducted independently in mesocosms, with three different predatory species and (3) two mark‐recapture studies, conducted in nature. This work (1) documents the rarity of melanic mosquitofish in nature, (2) demonstrates that melanic males experience a selective advantage over silver males in the presence of predators, (3) indicates no difference in the colour morphs‘ survival at a natural site essentially devoid of these predators, although suggesting a higher rate of recapture for melanic males at a site rife with predators. Overall, selective predation appears to contribute to the persistence of the melanic morph, despite its rarity in nature.

Susceptibility of Transgenic and Wildtype Zebra Danios, Danio rerio, to Predation

“…Their eyes contain rods and cones (Heidinger 1976), and they have a visual range similar to humans (Horth 2004). Thus, largemouth bass should have been able to visually discriminate between the red transgenic zebra danios and the wildtype zebra danios on the basis of color.…”

“…(2) native to North America and common worldwide 3 ; (3) abundant in nearby streams and lakes; and (4) have been consumed by largemouth bass in previous predator-prey research, e.g., Goodyear (1972), Kania and O'Hara (1974), Woltering et al (1978), Sass and Motta (2002), Horth (2004).…”

“…Largemouth bass, Micropterus salmoides, was chosen as the predator, because (1) it is a major freshwater piscivore (Howick and O'Brien 1983;Horth 2004); (2) although native to the eastern USA (Robbins and MacCrimmon 1974;Heidinger 1976) it is common worldwide, including North America (Robbins and MacCrimmon 1974;Heidinger 1976); (3) it is a diurnal, visual predator that can detect differences in color and pattern in small, prey fish (Horth 2004); (4) it eats a wide variety of vertebrates and invertebrates (Heidinger 1976); and (5) it has been one of the most frequently used predators in previous predator-prey experiments, e.g., Sullivan et al (1978), Savino and Stein (1982), Schramm and Zale (1985), Webb (1986), Theodorakis (1989), Knight and Gido (2005), and in nearly 25% (9 of 37) of the studies reviewed by Mesa et al (1994).…”

Melanin pattern morphs do not differ in metabolic rate: implications for the evolutionary maintenance of a melanophore polymorphism in the green swordtail, Xiphophorus helleri

“…Differences in thermoregulation and predation risk among melanophore morphs have not yet been investigated in Xiphophorus (but see Horth 2004) but there is some evidence that melanin patterns function as signals in a social context in Xiphophorus. The vertical bar pattern of male Xiphophorus multilineatus appears to function as a signal to both rivals and potential mates (Morris et al 1995).…”

Consistent Frequency of Color Morphs in the Sea Star Pisaster ochraceus (Echinodermata:Asteriidae) across Open-Coast Habitats in the Northeastern Pacific1

“…Alternative hypotheses with empirical support based on selective mechanisms include (1) nonrandom mating due to sexual selection or signaling to prevent inbreeding (Houde 1987, Galeotti et al 2003; (2) apostatic selection, in which rare morphs are more successful in hunting prey or avoiding predators through the disruption of search images or advertisement of distastefulness (Allen 1988, Gillespie and Oxford 1998, Horth 2004; (3) disruptive selection through crypsis in heterogeneous backgrounds or physiological adaptation to spatially or temporally variable environments (Nevo 1973, Hairston 1979, Etter 1988; and (4) balancing trade-offs among these agents. Mechanisms invoking plasticity include the roles of (1) color plasticity in response to environmental factors (Wente and Phillips 2003); (2) dietary differences resulting in phenotypic differences (Tlusty and Hyland 2005); and (3) ontogenetic color change (Booth 1990).…”