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Guppies
Kinds of Guppies Terms modified by Guppies Selected AbstractsRearing Environment Affects the Brain Size of Guppies: Lab-Reared Guppies have Smaller Brains than Wild-Caught GuppiesETHOLOGY, Issue 2 2009James G. Burns Animals bred for captivity often have smaller brains and behave differently than their wild counterparts. These differences in brain size have been attributed to genetic changes resulting from, for example, inbreeding depression and pleiotropic effects of artificial selection for traits such as docility. A critical question, though, is whether these differences in brain size are due to plastic responses to the environment, not just genetic changes. We observed a large reduction in brain size in first generation, lab-reared female guppies compared with wild-caught ones (19% smaller telencephalon, 17% smaller optic tectum). We then reared first-generation, lab-born guppies in environments varying in spatial complexity and size in an attempt to isolate factors that might increase brain size and change temperament, but no significant differences in phenotype were observed. The results of these experiments show that, although the environmental factors responsible for the effect have not been found, even first generation lab-reared individuals can have smaller brains than wild individuals. [source] Premating Avoidance of Inbreeding Absent in Female Guppies (Poecilia reticulata)ETHOLOGY, Issue 7 2006Åslaug Viken The recognition and avoidance of kin during mating can be an important means of reducing the potential for inbreeding depression in offspring. We report here that premating mechanisms to avoid inbreeding, either innate or learnt through juvenile experience, are at best weak in female guppies (Poecilia reticulata). Guppies are small, ovoviviparous, neo-tropical freshwater fish, with a polygamous mating system where males actively court females and females are selective of their mates. In a series of mate-choice experiments, naïve, virgin females of the Quare River population in Trinidad were given a choice between a brother and a non-sib male from the same population. Initially, females were only provided olfactory cues upon which to base their choice and then subsequently both olfactory and visual cues. Despite the females displaying mate choice, we found no evidence of them discriminating between the male types in either experiment. There was thus no indication of inbreeding avoidance, suggesting that experiences after maturation or with mature males (e.g. rare male preference), dispersal and/or post-mating mechanisms may be evolutionarily more important avoidance mechanisms. [source] CROSS-GENERATIONAL ENVIRONMENTAL EFFECTS AND THE EVOLUTION OF OFFSPRING SIZE IN THE TRINIDADIAN GUPPY POECILIA RETICULATAEVOLUTION, Issue 2 2006Farrah Bashey Abstract The existence of adaptive phenotypic plasticity demands that we study the evolution of reaction norms, rather than just the evolution of fixed traits. This approach requires the examination of functional relationships among traits not only in a single environment but across environments and between traits and plasticity itself. In this study, I examined the interplay of plasticity and local adaptation of offspring size in the Trinidadian guppy, Poecilia reticulata. Guppies respond to food restriction by growing and reproducing less but also by producing larger offspring. This plastic difference in offspring size is of the same order of magnitude as evolved genetic differences among populations. Larger offspring sizes are thought to have evolved as an adaptation to the competitive environment faced by newborn guppies in some environments. If plastic responses to maternal food limitation can achieve the same fitness benefit, then why has guppy offspring size evolved at all? To explore this question, I examined the plastic response to food level of females from two natural populations that experience different selective environments. My goals were to examine whether the plastic responses to food level varied between populations, test the consequences of maternal manipulation of offspring size for offspring fitness, and assess whether costs of plasticity exist that could account for the evolution of mean offspring size across populations. In each population, full-sib sisters were exposed to either a low- or high-food treatment. Females from both populations produced larger, leaner offspring in response to food limitation. However, the population that was thought to have a history of selection for larger offspring was less plastic in its investment per offspring in response to maternal mass, maternal food level, and fecundity than the population under selection for small offspring size. To test the consequences of maternal manipulation of offspring size for offspring fitness, I raised the offspring of low- and high-food mothers in either low- or high-food environments. No maternal effects were detected at high food levels, supporting the prediction that mothers should increase fecundity rather than offspring size in noncompetitive environments. For offspring raised under low food levels, maternal effects on juvenile size and male size at maturity varied significantly between populations, reflecting their initial differences in maternal manipulation of offspring size; nevertheless, in both populations, increased investment per offspring increased offspring fitness. Several correlates of plasticity in investment per offspring that could affect the evolution of offspring size in guppies were identified. Under low-food conditions, mothers from more plastic families invested more in future reproduction and less in their own soma. Similarly, offspring from more plastic families were smaller as juveniles and female offspring reproduced earlier. These correlations suggest that a fixed, high level of investment per offspring might be favored over a plastic response in a chronically low-resource environment or in an environment that selects for lower reproductive effort [source] Geographic variation in sperm traits reflects predation risk and natural rates of multiple paternity in the guppyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2010K. E. ELGEE Abstract Guppies (Poecilia reticulata) are models for understanding the interplay between natural and sexual selection. In particular, predation has been implicated as a major force affecting female sexual preferences, male mating tactics and the level of sperm competition. When predation is high, females typically reduce their preferences for showy males and engage more in antipredator behaviours, whereas males exploit these changes by switching from sexual displays to forced matings. These patterns are thought to account for the relatively high levels of multiple paternity in high-predation populations compared to low-predation populations. Here, we assess the possible evolutionary consequences of these patterns by asking whether variation in sperm traits reflect differences in predation intensity among four pairs of Trinidadian populations: four that experience relatively low levels of predation from a gape-limited predator and four that experience relatively high levels of predation from a variety of piscivores. We found that males in high-predation populations had faster swimming sperm with longer midpieces compared to males in low-predation populations. However, we found no differences among males in high- and low-predation populations with respect to sperm number, sperm head length, flagellum length and total sperm length. [source] Adaptive Offspring Sex Ratio Depends on Male Tail Length in the GuppyETHOLOGY, Issue 11 2006Kenji Karino A biased sex ratio in a brood is considered to be an adaptive strategy under certain circumstances. For example, if the expected reproductive success of one sex is greater than that of the other, parents should produce more offspring of the former sex than the latter. A previous study has documented that in the guppy, Poecilia reticulata, the female offspring of males possessing proportionally longer tails exhibit smaller body sizes and show decreased reproductive outputs than those of males having shorter tails. On the other hand, the total lengths of the male offspring of the long-tailed males are larger because of their longer tails; consequently, they exhibit greater sexual attractiveness to females. Therefore, it has been hypothesized that this asymmetry in the expected reproductive success between the male and female offspring of long-tailed males may result in a biased sex ratio that is dependent on the tail lengths of their fathers. This hypothesis was tested in the present study. The results showed that the females that mated with long-tailed males produced more male offspring than those that mated with short-tailed males. Logistic regression analysis showed that the ratio of tail length to the standard length of the fathers is a determinant factor of the sex of their offspring. These results suggest that the manipulation of the offspring sex ratios by parents enhances the overall fitness of the offspring. [source] Male Mate Choice in the Guppy (Poecilia reticulata): Do Males Prefer Larger Females as Mates?ETHOLOGY, Issue 2 2004Emily J. E. Herdman Although females are the choosier sex in most species, male mate choice is expected to occur under certain conditions. Theoretically, males should prefer larger females as mates in species where female fecundity increases with body size. However, any fecundity-related benefits accruing to a male that has mated with a large female may be offset by an associated fitness cost of shared paternity if large females are more likely to be multiply mated than smaller females in nature. We tested the above hypothesis and assumption using the Trinidadian guppy (Poecilia reticulata) by behaviourally testing for male mate choice in the laboratory and by ascertaining (with the use of microsatellite DNA genotyping) patterns of male paternity in wild-caught females. We observed significant positive relationships between female body length and fecundity (brood size) and between body length and level of multiple paternity in the broods of females collected in the Quaré River, Trinidad. In laboratory tests, a preference for the larger of two simultaneously-presented virgin females was clearly expressed only when males were exposed to the full range of natural stimuli from the females, but not when they were limited to visual stimuli alone. However, as suggested by our multiple paternity data, males that choose to mate with large females may incur a larger potential cost of sperm competition and shared paternity compared with males that mate with smaller females on average. Our results thus suggest that male guppies originating from the Quaré River possess mating preferences for relatively large females, but that such preferences are expressed only when males can accurately assess the mating status of encountered females that differ in body size. [source] Rearing Environment Affects the Brain Size of Guppies: Lab-Reared Guppies have Smaller Brains than Wild-Caught GuppiesETHOLOGY, Issue 2 2009James G. Burns Animals bred for captivity often have smaller brains and behave differently than their wild counterparts. These differences in brain size have been attributed to genetic changes resulting from, for example, inbreeding depression and pleiotropic effects of artificial selection for traits such as docility. A critical question, though, is whether these differences in brain size are due to plastic responses to the environment, not just genetic changes. We observed a large reduction in brain size in first generation, lab-reared female guppies compared with wild-caught ones (19% smaller telencephalon, 17% smaller optic tectum). We then reared first-generation, lab-born guppies in environments varying in spatial complexity and size in an attempt to isolate factors that might increase brain size and change temperament, but no significant differences in phenotype were observed. The results of these experiments show that, although the environmental factors responsible for the effect have not been found, even first generation lab-reared individuals can have smaller brains than wild individuals. [source] Premating Avoidance of Inbreeding Absent in Female Guppies (Poecilia reticulata)ETHOLOGY, Issue 7 2006Åslaug Viken The recognition and avoidance of kin during mating can be an important means of reducing the potential for inbreeding depression in offspring. We report here that premating mechanisms to avoid inbreeding, either innate or learnt through juvenile experience, are at best weak in female guppies (Poecilia reticulata). Guppies are small, ovoviviparous, neo-tropical freshwater fish, with a polygamous mating system where males actively court females and females are selective of their mates. In a series of mate-choice experiments, naïve, virgin females of the Quare River population in Trinidad were given a choice between a brother and a non-sib male from the same population. Initially, females were only provided olfactory cues upon which to base their choice and then subsequently both olfactory and visual cues. Despite the females displaying mate choice, we found no evidence of them discriminating between the male types in either experiment. There was thus no indication of inbreeding avoidance, suggesting that experiences after maturation or with mature males (e.g. rare male preference), dispersal and/or post-mating mechanisms may be evolutionarily more important avoidance mechanisms. [source] Male Mate Choice in the Guppy (Poecilia reticulata): Do Males Prefer Larger Females as Mates?ETHOLOGY, Issue 2 2004Emily J. E. Herdman Although females are the choosier sex in most species, male mate choice is expected to occur under certain conditions. Theoretically, males should prefer larger females as mates in species where female fecundity increases with body size. However, any fecundity-related benefits accruing to a male that has mated with a large female may be offset by an associated fitness cost of shared paternity if large females are more likely to be multiply mated than smaller females in nature. We tested the above hypothesis and assumption using the Trinidadian guppy (Poecilia reticulata) by behaviourally testing for male mate choice in the laboratory and by ascertaining (with the use of microsatellite DNA genotyping) patterns of male paternity in wild-caught females. We observed significant positive relationships between female body length and fecundity (brood size) and between body length and level of multiple paternity in the broods of females collected in the Quaré River, Trinidad. In laboratory tests, a preference for the larger of two simultaneously-presented virgin females was clearly expressed only when males were exposed to the full range of natural stimuli from the females, but not when they were limited to visual stimuli alone. However, as suggested by our multiple paternity data, males that choose to mate with large females may incur a larger potential cost of sperm competition and shared paternity compared with males that mate with smaller females on average. Our results thus suggest that male guppies originating from the Quaré River possess mating preferences for relatively large females, but that such preferences are expressed only when males can accurately assess the mating status of encountered females that differ in body size. [source] INDIRECT GENETIC EFFECTS INFLUENCE ANTIPREDATOR BEHAVIOR IN GUPPIES: ESTIMATES OF THE COEFFICIENT OF INTERACTION PSI AND THE INHERITANCE OF RECIPROCITYEVOLUTION, Issue 7 2009Bronwyn H. Bleakley How and why cooperation evolves, particularly among nonrelatives, remains a major paradox for evolutionary biologists and behavioral ecologists. Although much attention has focused on fitness consequences associated with cooperating, relatively little is known about the second component of evolutionary change, the inheritance of cooperation or reciprocity. The genetics of behaviors that can only be expressed in the context of interactions are particularly difficult to describe because the relevant genes reside in multiple social partners. Indirect genetic effects (IGEs) describe the influence of genes carried in social partners on the phenotype of a focal individual and thus provide a novel approach to quantifying the genetics underlying interactions such as reciprocal cooperation. We used inbred lines of guppies and a novel application of IGE theory to describe the dual genetic control of predator inspection and social behavior, both classic models of reciprocity. We identified effects of focal strain, social group strain, and interactions between focal and group strains on variation in focal behavior. We measured ,, the coefficient of the interaction, which describes the degree to which an individual's phenotype is influenced by the phenotype of its social partners. The genetic identity of social partners substantially influences inspection behavior, measures of threat assessment, and schooling and does so in positively reinforcing manner. We therefore demonstrate strong IGEs for antipredator behavior that represent the genetic variation necessary for the evolution of reciprocity. [source] BALANCING SELECTION, RANDOM GENETIC DRIFT, AND GENETIC VARIATION AT THE MAJOR HISTOCOMPATIBILITY COMPLEX IN TWO WILD POPULATIONS OF GUPPIES (POECILIA RETICULATA)EVOLUTION, Issue 12 2006Cock van Oosterhout Abstract Our understanding of the evolution of genes of the major histocompatibility complex (MHC) is rapidly increasing, but there are still enigmatic questions remaining, particularly regarding the maintenance of high levels of MHC polymorphisms in small, isolated populations. Here, we analyze the genetic variation at eight microsatellite loci and sequence variation at exon 2 of the MHC class IIB (DAB) genes in two wild populations of the Trinidadian guppy, Poecilia reticulata. We compare the genetic variation of a small (Ne, 100) and relatively isolated upland population to that of its much larger (Ne, 2400) downstream counterpart. As predicted, microsatellite diversity in the upland population is significantly lower and highly differentiated from the population further downstream. Surprisingly, however, these guppy populations are not differentiated by MHC genetic variation and show very similar levels of allelic richness. Computer simulations indicate that the observed level of genetic variation can be maintained with overdominant selection acting at three DAB loci. The selection coefficients differ dramatically between the upland (s 0.2) and lowland (s, 0.01) populations. Parasitological analysis on wild-caught fish shows that parasite load is significantly higher on upland than on lowland fish, which suggests that large differences in selection intensity may indeed exist between populations. Based on the infection intensity, a substantial proportion of the upland fish would have suffered direct or indirect fitness consequences as a result of their high parasite loads. Selection by parasites plays a particularly important role in the evolution of guppies in the upland habitat, which has resulted in high levels of MHC diversity being maintained in this population despite considerable genetic drift. [source] CROSS-GENERATIONAL ENVIRONMENTAL EFFECTS AND THE EVOLUTION OF OFFSPRING SIZE IN THE TRINIDADIAN GUPPY POECILIA RETICULATAEVOLUTION, Issue 2 2006Farrah Bashey Abstract The existence of adaptive phenotypic plasticity demands that we study the evolution of reaction norms, rather than just the evolution of fixed traits. This approach requires the examination of functional relationships among traits not only in a single environment but across environments and between traits and plasticity itself. In this study, I examined the interplay of plasticity and local adaptation of offspring size in the Trinidadian guppy, Poecilia reticulata. Guppies respond to food restriction by growing and reproducing less but also by producing larger offspring. This plastic difference in offspring size is of the same order of magnitude as evolved genetic differences among populations. Larger offspring sizes are thought to have evolved as an adaptation to the competitive environment faced by newborn guppies in some environments. If plastic responses to maternal food limitation can achieve the same fitness benefit, then why has guppy offspring size evolved at all? To explore this question, I examined the plastic response to food level of females from two natural populations that experience different selective environments. My goals were to examine whether the plastic responses to food level varied between populations, test the consequences of maternal manipulation of offspring size for offspring fitness, and assess whether costs of plasticity exist that could account for the evolution of mean offspring size across populations. In each population, full-sib sisters were exposed to either a low- or high-food treatment. Females from both populations produced larger, leaner offspring in response to food limitation. However, the population that was thought to have a history of selection for larger offspring was less plastic in its investment per offspring in response to maternal mass, maternal food level, and fecundity than the population under selection for small offspring size. To test the consequences of maternal manipulation of offspring size for offspring fitness, I raised the offspring of low- and high-food mothers in either low- or high-food environments. No maternal effects were detected at high food levels, supporting the prediction that mothers should increase fecundity rather than offspring size in noncompetitive environments. For offspring raised under low food levels, maternal effects on juvenile size and male size at maturity varied significantly between populations, reflecting their initial differences in maternal manipulation of offspring size; nevertheless, in both populations, increased investment per offspring increased offspring fitness. Several correlates of plasticity in investment per offspring that could affect the evolution of offspring size in guppies were identified. Under low-food conditions, mothers from more plastic families invested more in future reproduction and less in their own soma. Similarly, offspring from more plastic families were smaller as juveniles and female offspring reproduced earlier. These correlations suggest that a fixed, high level of investment per offspring might be favored over a plastic response in a chronically low-resource environment or in an environment that selects for lower reproductive effort [source] THE EFFECTS OF GENOTYPE, AGE, AND SOCIAL ENVIRONMENT ON MALE ORNAMENTATION, MATING BEHAVIOR, AND ATTRACTIVENESSEVOLUTION, Issue 11 2005Lisa K. Miller Abstract The traits thought to advertise genetic quality are often highly susceptible to environmental variation and prone to change with age. These factors may either undermine or reinforce the potential for advertisement traits to signal quality depending on the magnitude of age-dependent expression, environmental variation, and genotype-age and genotype-environment interaction. Measurements of the magnitude of these effects are thus a necessary step toward assessing the implications of age dependence and environmental variability for the evolution of signals of quality. We conducted a longitudinal study of male guppies (Poecilia reticulata) from 22 full-sibling families. Each fish was assigned at maturity to one of three treatments in order to manipulate his allocation of resources to reproduction: a control in which the male was kept alone, a courtship-only treatment in which he could see and court a female across a clear partition, and a mating treatment in which he interacted freely with a female. We measured each male's size, ornamental color patterns, courtship, attractiveness to females, and mating success at three ages. Size was influenced by treatment and age-treatment interactions, indicating that courtship and mating may impose costs on growth. Tail size and color patterns were influenced by age but not by treatment, suggesting fixed age-dependent trajectories in these advertisement traits. By contrast, display rate and attempted sneak copulation rate differed among treatments but not among ages, suggesting greater plasticity of these behavioral traits. As a result of the different patterns of variation in ornamentation and behavior, male attractiveness and mating success responded to male age, treatment, and the interaction between age and treatment. Neither age nor treatment obscured the presence of genetic variation, and the genetic relationship between male ornamentation and attractiveness remained the same among treatments. Our findings suggest that neither age-dependent variation nor environmentally induced variation in reproductive effort is likely to undermine the reliability of male signaling. [source] This is not déjà vu all over again: male guppy colour in a new experimental introductionJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2007N. KARIM Abstract We use an experimental introduction in nature to examine factors that influence parallel evolution. In 1996, 200 high-predation guppies (Poecilia reticulata) from the Yarra River were introduced into the Damier River, which previously lacked guppies. Eight years later, we quantified the colour of wild-caught guppies (,phenotypic' divergence) and lab-reared guppies (,genetic' divergence) from low- and high-predation environments in both rivers. Phenotypic and genetic divergence between predation environments within the Yarra was evident for black and for orange. Phenotypic divergence within the Damier was parallel to the Yarra for black but not for orange. Genetic divergence was absent between predation environments within the Damier, but was evident when comparing both Damier populations to their Yarra ancestors. The evolution of male colour thus depends on factors other than the simple contrast between ,high' and ,low' predation. We suggest that the parallel evolution of male signalling traits may sometimes first require the parallel evolution of female preferences. [source] Intrinsic reproductive isolation between Trinidadian populations of the guppy, Poecilia reticulataJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2006S. T. RUSSELL Abstract Although Trinidadian populations of the guppy, Poecilia reticulata, show considerable adaptive genetic differentiation, they have been assumed to show little or no reproductive isolation. We tested this assumption by crossing Caroni (Tacarigua River) and Oropuche (Oropuche R.) drainage populations from Trinidad's Northern Range, and by examining multiple aspects of reproductive compatibility in the F1, F2 and BC1 generations. In open-aquarium experiments, F1 males performed fewer numbers of mating behaviours relative to parental population controls. This is the first documentation of hybrid behavioural sterility within a species, and it suggests that such sterility may feasibly be involved in causing speciation. The crosses also uncovered hybrid breakdown for embryo viability, brood size and sperm counts. In contrast, no reductions in female fertility were detected, indicating that guppies obey Haldane's rule for sterility. Intrinsic isolation currently presents a much stronger obstacle to gene flow than behavioural isolation, and our results indicate that Trinidadian populations constitute a useful model for investigating incipient speciation. [source] Sexual colouration and sperm traits in guppiesJOURNAL OF FISH BIOLOGY, Issue 1 2007T. E. Pitcher The relationships among the area, hue, saturation and brightness of orange colouration and sperm traits in the guppy Poecilia reticulata were investigated. Males with greater areas of orange colouration had significantly larger sperm loads, more motile sperm and longer sperm relative to males with relatively little orange colouration. Males with greater areas of orange colouration did not possess more viable sperm than males with relatively little orange colouration. There was no evidence that any of the sperm traits were related to the hue, saturation or brightness of the orange colouration. These results are discussed in the context of the roles that direct and indirect selection might play in maintaining female preference for male guppies with large areas of orange colouration. [source] The effects of carotenoid and food intake on caudal fin regeneration in male guppiesJOURNAL OF FISH BIOLOGY, Issue 4 2006G. R. Kolluru The trade-offs involved in allocating carotenoid pigments and food to healing and regrowing damaged caudal fin tissue v. other functions were examined in guppies Poecilia reticulata, a species in which females prefer males that display larger amounts of carotenoids in their skin. The guppies were derived from four natural populations in Trinidad that differed in resource availability but not predation intensity. Carotenoids, food and site of origin did not affect either absolute or relative fin regrowth, which suggested that fin regeneration in guppies was not constrained by carotenoid availability. It is possible that carotenoid intake influences fin regeneration in the presence of natural stressors such as predators. There was a significant negative interaction between food level in the laboratory and resource availability in the field: males from low-resource-availability sites regrew more fin tissue when raised on the high food level, and males from high-resource-availability sites regrew more fin tissue when raised on the low food level. The direction of this interaction runs counter to theoretical expectations. [source] Why there is better evidence for culture in fish than chimpanzeesJOURNAL OF FISH BIOLOGY, Issue 2003K. N. Laland Fish have comparatively small brains and are not renowned for their intelligence. Yet a series of laboratory experiments on the guppy reveals that they can be surprisingly good at learning from each other, and that social learning processes can mediate behavioural traditions analogous to the tool using traditions of different populations of chimpanzees. Transmission chain experiments have established that arbitrary and even maladaptive information can be socially transmitted among shoals of fish. Studies of behavioural innovation in guppies are strikingly consistent with findings of equivalent studies in primates. There are strong sex differences in innovatory tendencies and social learning abilities in guppies, which also parallel observations of primates. These studies suggest that the adage ,necessity is the mother of invention' may be a characteristic feature of animal innovation. When considered in combination with the findings of transfer experiments carried out on natural populations of fish, it becomes apparent that fish are an excellent model system for studies of animal social learning and culture. [source] The inheritance of heteroplasmy in guppiesJOURNAL OF FISH BIOLOGY, Issue 5 2002J. S. Taylor Guppies Poecilia reticulata from the Rio Grande, Trinidad are heteroplasmic; individuals possess up to nine different-sized mtDNA haplotypes. A PCR survey of mtDNA length variation that included mothers and embryos suggests that a large number of mitochondrial genomes (possibly within a much smaller number of organelles) pass from one generation to the next. [source] Treatment development for systemic Tetrahymena sp. infection in guppies, Poecilia reticulata PetersJOURNAL OF FISH DISEASES, Issue 6 2010M Pimenta Leibowitz Abstract Antibacterial and antiparasitic agents and a cysteine protease inhibitor (E-64) were tested against Tetrahymena infection, a serious problem in guppy production worldwide. Chemicals were tested in vitro by a colorimetric assay for Tetrahymena survival. The most effective were niclosamide, albendazole and chloroquine, with 23%, 35% and 60% survival, respectively, following 2-h exposure to 100 ppm. Longer incubation periods resulted in greater reductions in survival. Niclosamide was further studied in vivo at different dosages, administered orally to Tetrahymena -infected guppies. Mortality rates were significantly lower in all treatment groups; in trial I, 30% and 33% mortality in 5 and 40 mg kg,1 niclosamide-fed fish vs. 59% mortality in controls; in trial II, 35%, 13% and 10% in 50, 100 and 200 mg kg,1 niclosamide-fed fish vs. 64% in controls. The effect of the cysteine protease inhibitor E64 was tested in tissue culture, by measuring histolytic activity of the parasite (Tet-NI) on a guppy-fin cell line, based on cell depletion. Tet-NI feeding activity was significantly reduced following pretreatment with E-64 relative to non-treated Tet-NI. E-64-pretreated Tet-NI was injected i.p. into guppies: recorded mortality rates were significantly lower (35%) than that in non-treated Tet-NI (60%), suggesting inhibition of the parasite's cysteine protease as a possible therapeutic approach. [source] Genome-wide single nucleotide polymorphisms reveal population history and adaptive divergence in wild guppiesMOLECULAR ECOLOGY, Issue 5 2010EVA-MARIA WILLING Abstract Adaptation of guppies (Poecilia reticulata) to contrasting upland and lowland habitats has been extensively studied with respect to behaviour, morphology and life history traits. Yet population history has not been studied at the whole-genome level. Although single nucleotide polymorphisms (SNPs) are the most abundant form of variation in many genomes and consequently very informative for a genome-wide picture of standing natural variation in populations, genome-wide SNP data are rarely available for wild vertebrates. Here we use genetically mapped SNP markers to comprehensively survey genetic variation within and among naturally occurring guppy populations from a wide geographic range in Trinidad and Venezuela. Results from three different clustering methods, Neighbor-net, principal component analysis (PCA) and Bayesian analysis show that the population substructure agrees with geographic separation and largely with previously hypothesized patterns of historical colonization. Within major drainages (Caroni, Oropouche and Northern), populations are genetically similar, but those in different geographic regions are highly divergent from one another, with some indications of ancient shared polymorphisms. Clear genomic signatures of a previous introduction experiment were seen, and we detected additional potential admixture events. Headwater populations were significantly less heterozygous than downstream populations. Pairwise FST values revealed marked differences in allele frequencies among populations from different regions, and also among populations within the same region. FST outlier methods indicated some regions of the genome as being under directional selection. Overall, this study demonstrates the power of a genome-wide SNP data set to inform for studies on natural variation, adaptation and evolution of wild populations [source] Competition as a selective mechanism for larger offspring size in guppiesOIKOS, Issue 1 2008Farrah Bashey Highly competitive environments are predicted to select for larger offspring. Guppies Poecilia reticulata from low-predation populations have evolved to make fewer, larger offspring than their counterparts from high-predation populations. As predation co-varies with the strength of competition in natural guppy populations, here I present two laboratory experiments that evaluate the role of competition in selecting for larger offspring size. In the first experiment, paired groups of large and small newborns from either a high- or a low-predation population were reared in mesocosms under a high- or a low-competition treatment. While large newborns retained their size advantage over small newborns in both treatments, newborn size increased growth only in the high-competition treatment. Moreover, the increase in growth with size was greater in guppies derived from the low-predation population. In the second experiment, pairs of large and small newborns were reared in a highly competitive environment until reproductive maturity. Small size at birth delayed maturation and the effect of birth size on male age of maturity was greater in the low-predation population. These results support the importance of competition as a selective mechanism in offspring size evolution. [source] Active selection for large guppies, Poecilia reticulata, by the pike cichlid, Crenicichla saxatilisOIKOS, Issue 3 2004Jan Johansson Size-selective predation has been proposed to be one important evolutionary force shaping life-history traits in guppies (Poecilia reticulata). Populations living in the presence of the ring-tailed pike cichlid (Crenicichlasaxatilis) are smaller, mature earlier, allocate more energy to offspring and get more and smaller young than guppies in localities without Crenicichla. We investigated if Crenicichlasaxatilis is a size-selective predator, if the selectivity is a result of active choice and if the optimal prey size can be explained according to an optimal foraging model. In single-prey experiments we quantified the predators' pre-capture costs (time), capture success, and post-capture costs (time) for four different prey sizes spanning from 10 to 40 mm total length. To see which of the components of the prey cycle the predator takes into account for its choice, we then predicted prey values and optimal prey size with 6 different models that included one or more of the prey cycle components. In two multiple prey experiments, the cichlids were given the choice of the two and four different prey sizes simultaneously. Crenicichlasaxatilis actively selected the largest guppies in both cases. The three prey-value functions that included handling time (post-capture cost) did not accurately predict the prey choice. Instead the prey-value functions that took into account pre-capture cost (approach and attack time) were able to correctly predict the choice of the largest guppy size, suggesting that pre-capture costs may be more important than post-capture costs for prey choice in Crenicichlasaxatilis. The study confirms that Crenicichlasaxatilis is a size-selective predator selecting large guppies, while earlier evidence for selectivity for large prey in Crenicichla cichlids has been weak and equivocal. Our result strengthen the possibility that size-selective predation is a mechanism in life-history evolution in guppies. [source] Parasite resistance and genetic variation in the endangered Gila topminnowANIMAL CONSERVATION, Issue 2 2001Philip W. Hedrick In recent years, it has become apparent that introduced or novel pathogens or parasites may have a significant negative impact on endangered species. Here we examine experimentally the effect of an exotic fluke from guppies on the endangered Gila topminnow. Populations from different sources showed variable responses (although statistically non-significant) to the fluke and, in particular, the most homozygous population had high fluke infections and high subsequent mortality. Homozygotes for a MHC (major histocompatibility complex) gene had lower (although statistically non-significant) survival when infected with flukes than did heterozygotes. An inbred line from one of the populations had statistically significant lower survival and higher fluke infection than did a simultaneous outbred control. Overall, Gila topminnows appear quite susceptible to infection by the non-native fluke compared to other related species. In addition, it was shown that Gila topminnows can be infected by casual contact with infected guppies. This is another example of the potential detrimental effects of a parasite on an endangered species, a threat that may constitute a particular problem for species with low genetic variation, either in general, for important MHC genes, or for populations with a past history of inbreeding. [source] Short-term dietary supplementation with the microalga Parietochloris incisa enhances stress resistance in guppies Poecilia reticulataAQUACULTURE RESEARCH, Issue 2 2010Anurag Dagar Abstract Two trials were conducted to determine the effects of dietary enrichments with the microalga Parietochloris incisa, rich in arachidonic acid (ARA), on stress resistance in guppies Poecilia reticulata. The microalga was added to commercial diets as a neutral lipid (NL) extract and its fractions or as broken cells. Experimental diets were applied for a period of 14 days. In trial 1, commercial diets were supplemented with NL (containing 25 mg ARA and 0.11 mg ,-carotene g,1 feed), its triacylglycerol (TAG) fraction (containing 25 mg ARA g,1 feed and no ,-carotene) and the ,-carotene fraction (containing 0.11 mg carotenoid g,1 feed and minute amounts of ARA). Neutral lipid-fed fish demonstrated the highest resistance (P<0.05) to osmotic stress (32-ppt NaCl), followed by fish fed with diets supplemented with TAG and ,-carotene alone, which were more resistant than control (P<0.05). In trial 2, fish fed diets supplemented with higher levels of broken alga (26.1 mg ARA g,1 feed) were more resistant (P<0.05) to stress as compared with fish fed lower ARA (16.3 mg g g,1) or an unsupplemented control diet. We suggest a dietary supplementation with broken P. incisa cells to enhance stress resistance in guppies before a stressful event. [source] Sperm transfer through forced matings and its evolutionary implications in natural guppy (Poecilia reticulata ) populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2003JONATHAN P. EVANS In species in which individuals alternate between mating strategies, males may respond to elevated predation risk by switching from conspicuous courtship displays to less risky or more profitable sneaky mating attempts. As a consequence, in such species female choice is likely to be undermined more frequently in relatively dangerous localities. We tested this prediction using the guppy, a species of fish in which individual males alternate between courtship (solicited) and forced (unsolicited) copulations according to prevailing levels of predation. We collected females at late stages of gestation from four high- and four low-predation populations in Trinidad and examined them for the presence of sperm in their gonoducts. Due to the patterns of sperm storage in guppies, sperm found in the gonoducts of such late-cycle females can only arise from unsolicited copulations. We anticipated that because female guppies are subject to greater sexual harassment in the form of forced mating attempts in high-risk localities, a higher proportion of females in these populations would contain sperm in their gonoducts arising from recent unsolicited copulations. Contrary to this prediction, only one of the four paired comparisons (from the Quaré River) revealed a significant difference in the proportion of females recently inseminated through forced copulations. The paired comparisons for the remaining three rivers revealed no significant differences in the proportion of females with recoverable sperm in their gonoducts. However, overall, we found that 44.5% (±4.3 SE) of females had sperm in their gonoduct arising from sneaky mating, a figure three times higher than previously reported for this species. We discuss these findings in relation to recent predictions concerning the strength of sexual selection in natural populations. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78, 605,612. [source] Adaptive Offspring Sex Ratio Depends on Male Tail Length in the GuppyETHOLOGY, Issue 11 2006Kenji Karino A biased sex ratio in a brood is considered to be an adaptive strategy under certain circumstances. For example, if the expected reproductive success of one sex is greater than that of the other, parents should produce more offspring of the former sex than the latter. A previous study has documented that in the guppy, Poecilia reticulata, the female offspring of males possessing proportionally longer tails exhibit smaller body sizes and show decreased reproductive outputs than those of males having shorter tails. On the other hand, the total lengths of the male offspring of the long-tailed males are larger because of their longer tails; consequently, they exhibit greater sexual attractiveness to females. Therefore, it has been hypothesized that this asymmetry in the expected reproductive success between the male and female offspring of long-tailed males may result in a biased sex ratio that is dependent on the tail lengths of their fathers. This hypothesis was tested in the present study. The results showed that the females that mated with long-tailed males produced more male offspring than those that mated with short-tailed males. Logistic regression analysis showed that the ratio of tail length to the standard length of the fathers is a determinant factor of the sex of their offspring. These results suggest that the manipulation of the offspring sex ratios by parents enhances the overall fitness of the offspring. [source] Male Mate Choice in the Guppy (Poecilia reticulata): Do Males Prefer Larger Females as Mates?ETHOLOGY, Issue 2 2004Emily J. E. Herdman Although females are the choosier sex in most species, male mate choice is expected to occur under certain conditions. Theoretically, males should prefer larger females as mates in species where female fecundity increases with body size. However, any fecundity-related benefits accruing to a male that has mated with a large female may be offset by an associated fitness cost of shared paternity if large females are more likely to be multiply mated than smaller females in nature. We tested the above hypothesis and assumption using the Trinidadian guppy (Poecilia reticulata) by behaviourally testing for male mate choice in the laboratory and by ascertaining (with the use of microsatellite DNA genotyping) patterns of male paternity in wild-caught females. We observed significant positive relationships between female body length and fecundity (brood size) and between body length and level of multiple paternity in the broods of females collected in the Quaré River, Trinidad. In laboratory tests, a preference for the larger of two simultaneously-presented virgin females was clearly expressed only when males were exposed to the full range of natural stimuli from the females, but not when they were limited to visual stimuli alone. However, as suggested by our multiple paternity data, males that choose to mate with large females may incur a larger potential cost of sperm competition and shared paternity compared with males that mate with smaller females on average. Our results thus suggest that male guppies originating from the Quaré River possess mating preferences for relatively large females, but that such preferences are expressed only when males can accurately assess the mating status of encountered females that differ in body size. [source] BALANCING SELECTION, RANDOM GENETIC DRIFT, AND GENETIC VARIATION AT THE MAJOR HISTOCOMPATIBILITY COMPLEX IN TWO WILD POPULATIONS OF GUPPIES (POECILIA RETICULATA)EVOLUTION, Issue 12 2006Cock van Oosterhout Abstract Our understanding of the evolution of genes of the major histocompatibility complex (MHC) is rapidly increasing, but there are still enigmatic questions remaining, particularly regarding the maintenance of high levels of MHC polymorphisms in small, isolated populations. Here, we analyze the genetic variation at eight microsatellite loci and sequence variation at exon 2 of the MHC class IIB (DAB) genes in two wild populations of the Trinidadian guppy, Poecilia reticulata. We compare the genetic variation of a small (Ne, 100) and relatively isolated upland population to that of its much larger (Ne, 2400) downstream counterpart. As predicted, microsatellite diversity in the upland population is significantly lower and highly differentiated from the population further downstream. Surprisingly, however, these guppy populations are not differentiated by MHC genetic variation and show very similar levels of allelic richness. Computer simulations indicate that the observed level of genetic variation can be maintained with overdominant selection acting at three DAB loci. The selection coefficients differ dramatically between the upland (s 0.2) and lowland (s, 0.01) populations. Parasitological analysis on wild-caught fish shows that parasite load is significantly higher on upland than on lowland fish, which suggests that large differences in selection intensity may indeed exist between populations. Based on the infection intensity, a substantial proportion of the upland fish would have suffered direct or indirect fitness consequences as a result of their high parasite loads. Selection by parasites plays a particularly important role in the evolution of guppies in the upland habitat, which has resulted in high levels of MHC diversity being maintained in this population despite considerable genetic drift. [source] CROSS-GENERATIONAL ENVIRONMENTAL EFFECTS AND THE EVOLUTION OF OFFSPRING SIZE IN THE TRINIDADIAN GUPPY POECILIA RETICULATAEVOLUTION, Issue 2 2006Farrah Bashey Abstract The existence of adaptive phenotypic plasticity demands that we study the evolution of reaction norms, rather than just the evolution of fixed traits. This approach requires the examination of functional relationships among traits not only in a single environment but across environments and between traits and plasticity itself. In this study, I examined the interplay of plasticity and local adaptation of offspring size in the Trinidadian guppy, Poecilia reticulata. Guppies respond to food restriction by growing and reproducing less but also by producing larger offspring. This plastic difference in offspring size is of the same order of magnitude as evolved genetic differences among populations. Larger offspring sizes are thought to have evolved as an adaptation to the competitive environment faced by newborn guppies in some environments. If plastic responses to maternal food limitation can achieve the same fitness benefit, then why has guppy offspring size evolved at all? To explore this question, I examined the plastic response to food level of females from two natural populations that experience different selective environments. My goals were to examine whether the plastic responses to food level varied between populations, test the consequences of maternal manipulation of offspring size for offspring fitness, and assess whether costs of plasticity exist that could account for the evolution of mean offspring size across populations. In each population, full-sib sisters were exposed to either a low- or high-food treatment. Females from both populations produced larger, leaner offspring in response to food limitation. However, the population that was thought to have a history of selection for larger offspring was less plastic in its investment per offspring in response to maternal mass, maternal food level, and fecundity than the population under selection for small offspring size. To test the consequences of maternal manipulation of offspring size for offspring fitness, I raised the offspring of low- and high-food mothers in either low- or high-food environments. No maternal effects were detected at high food levels, supporting the prediction that mothers should increase fecundity rather than offspring size in noncompetitive environments. For offspring raised under low food levels, maternal effects on juvenile size and male size at maturity varied significantly between populations, reflecting their initial differences in maternal manipulation of offspring size; nevertheless, in both populations, increased investment per offspring increased offspring fitness. Several correlates of plasticity in investment per offspring that could affect the evolution of offspring size in guppies were identified. Under low-food conditions, mothers from more plastic families invested more in future reproduction and less in their own soma. Similarly, offspring from more plastic families were smaller as juveniles and female offspring reproduced earlier. These correlations suggest that a fixed, high level of investment per offspring might be favored over a plastic response in a chronically low-resource environment or in an environment that selects for lower reproductive effort [source] | |||||||||||||