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Received Oct 11; Accepted Nov 2. Abstract We tested the hypothesis that mate choice is responsible for countergradient variation in the sexual coloration of Trinidadian guppies Poecilia reticulata.
The nature of the countergradient pattern is that geographical variation in the carotenoid content of the orange spots of males is counterbalanced by genetic variation in drosopterin production, resulting in a relatively uniform pigment ratio.
A female hue preference could produce this pattern, because hue is the axis of colour variation most directly affected by the pigment ratio.
To test this hypothesis, we crossed two populations differing in drosopterin production and produced an F2 generation with variable drosopterin levels.
When the carotenoid content of the orange spots was held constant, female guppies preferred males with intermediate drosopterin levels. This shows that females do not simply prefer males with greater orange spot pigment content; instead, the ratio of the pigments also affects male attractiveness.
To our knowledge, this is the first direct evidence for a hypothesized agent of countergradient sexual selection. Introduction Countergradient variation is a geographical pattern in which environmental variation in a trait is masked by genetic variation, resulting in reduced phenotypic variation across environments electronic supplementary material, figures S1 and S2 [ 12 ].
The most commonly described cases involve diminished variation in body size or development time across altitudinal or latitudinal gradients [ 3 ]. Countergradient variation patterns have been documented in numerous species reviewed in Conover et al.
Countergradient variation is usually hypothesized to arise from selection opposing the influence of the environmental gradient on the development of the trait i.
In this paper, we report the results of an experiment designed to investigate a hypothesized mechanism of countergradient selection on the sexual coloration of male guppies Poecilia reticulata.
Male guppies have complex and highly polymorphic colour patterns that typically include orange spots [ 78 ]. Drosopterins are synthesized de novo from carbohydrates and amino acids, whereas tunaxanthins are obtained by metabolic conversion of ingested carotenoids [ 10 ]. The primary source of carotenoids for guppies is unicellular algae [ 11 ].
In the upper reaches of Trinidad's watersheds, algae production is light-limited [ 11 ]. Algae availability generally increases in the downstream direction, as streams widen, creating larger gaps in the forest canopy [ 1112 ].
Population comparisons along this gradient showed that the mean carotenoid content of the orange spots increases asymptotically with algal carotenoid intake [ 13 ].
Nevertheless, the ratio of carotenoid and drosopterin pigments remains relatively constant across sites owing to correlated variation in drosopterin production [ 14 ]. A common garden experiment showed that interpopulation variation in drosopterin production is largely genetic [ 14 ].
This is a countergradient pattern in which genetic variation in drosopterin production counteracts the effects of the carotenoid availability gradient on the pigment composition of the orange spots [ 14 ].
Two alternative explanations for the countergradient pattern that do not require countergradient selection have been ruled out [ 14 ]. First, production costs might constrain guppies to produce less drosopterins at sites with lower food algae availability. This hypothesis was ruled out by showing that food limitation in the laboratory does not affect drosopterin levels in the orange spots.
Second, if female guppies prefer males with brighter colours in darker environments, then this might select for reduced pigment deposition at darker sites see Marchetti [ 15 ].
This hypothesis was rejected by showing that drosopterin production correlates better with carotenoid intake than with ambient light levels, and that orange spot brightness is only weakly correlated with ambient light. The basis of our countergradient selection hypothesis is as follows.
Tunaxanthins and drosopterins have different absorbance spectra; hence, the shape of the orange spot reflectance spectrum depends on the ratio of the two pigments [ 9 ].
To human eyes, the orange spots appear yellower less red as the carotenoid: While variation in total pigment content affects the chroma colour saturation and, to a lesser extent, the brightness total reflectivity of the orange spots, the axis of colour variation that is most directly affected by the pigment ratio is the hue [ 14 ].
Researchers often treat hue as a categorical variable yellow, orange, red, etc.
Environmental effects on social interaction networks and male reproductive behaviour in guppies, Poecilia reticulata. W. WishlowInteraction of endocrine and experiential factors in regulation of sexual-behaviour in female guppy Poecilia reticulata. Behaviour, 48 (), pp. Such a possibility warrants further examination. Breden F. Phenotypic differentiation in female preference related to geographic variation in male predation risk in the Trinidad guppy (Poecilia reticulata). Behav Ecol Sociobiol. ; – Jun 15, · Correlated Evolution of Female Mating Preferences and Male Color Patterns in the Guppy Poecilia reticulata. Anne E. Houde1, John A. Endler2. 1Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 2Department of Biological Sciences, University of California, Santa Barbara, CA Cited by:
How guppies perceive hue is not known. Nevertheless, it is reasonable to hypothesize that a female mate preference based on hue is responsible for the observed countergradient variation pattern [ 1416 ]. That is, the relatively constant pigment ratio observed across populations in nature might have resulted from females choosing males based, in part, on the hue of their orange spots.
For simplicity, we call this the hue preference hypothesis, although as will become clear shortly, this name should not be taken too literally. Our basic approach to testing the hue preference hypothesis was to allow female guppies to choose among males with different carotenoid: To obtain a robust test of this prediction, it was important to control the pigment ratio experimentally.
The simplest way to control the pigment ratio would be to raise males on different dietary carotenoid levels.
However, previous research using this method showed that females prefer males raised on the highest carotenoid level, whether the males come from high-drosopterin populations or low-drosopterin populations [ 1718 ].Female mating preference for bold males in the guppy, Poecilia reticulata J G Godin, L A Dugatkin Proceedings of the National Academy of Sciences Sep , 93 (19) ; DOI: /pnas Sperm transfer through forced matings and its evolutionary implications in natural guppy (Poecilia reticulata) populations JONATHAN P.
EVANS. A subsequent examination of each female in the laboratory under low-power magnification confirmed our original choice of females. Mitochondrial DNA sequence variation among natural populations of.
May 07, · Our results support the hypothesis that a female mate preference is responsible for countergradient variation in the sexual coloration of male guppies. The key result was that, when male carotenoid levels were controlled experimentally and statistically, female guppies preferred males with intermediate drosopterin levels (figure 1).Cited by: Use of digitally modiﬁed videos to examine female mate preference for orange spot coloration of males in the guppy, Poecilia reticulata Aya Sato and Kenji Karino*.
Jun 15, · Correlated Evolution of Female Mating Preferences and Male Color Patterns in the Guppy Poecilia reticulata. Anne E. Houde1, John A. Endler2. 1Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 2Department of Biological Sciences, University of California, Santa Barbara, CA Cited by: Two experients were conducted to determine the effect of male color phenotype present during development on the mate choice of adult female guppies.
Females were raised with either a colorful male, non-colorful male, or no male, and then measured for choice of a colorful or non-colorful male in a two-stimulus visual choice test.