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Guppy - Poecilia reticulata, an exotic species, is recorded from a natural freshwater in Hormuz basin, which shows the range extension of the fish to southern Iran. This fish was probably introduced as an aquarium fish, but seems it is established in Sabz-poushan Spring. This study also describes the length-weight relationship (LWR) for the 13 caught specimens of the fish. The length-weight parameter b for this species was 3.01 with a high regression coefficients (r² > 0.95). [ABSTRACT FROM AUTHOR]

This study evaluated fish beta diversity in six headwater creeks located in the area affected by the largest ornamental aquaculture center implemented in the Minas Gerais State, southeastern Brazil. We sampled fish assemblages in 2017 and 2018 to investigate changes in assemblage structure (species richness and beta diversity), comparing these data with the historic species pool. We recorded 60 fish species, of which 16 were native and 44 non-native with 19 translocated, and 25 exotic. The exotics Poecilia reticulata, Xiphophorus maculatus, X. variatus, Danio rerio, and Misgurnus anguillicaudatus were the most widely distributed in the headwater creeks. The Contamination Index showed that most creeks had high proportional contamination by exotic species (above 60%). Beta diversity increased from historical to contemporary periods in all creeks due to the introduction and differential colonization pressure of several non-native translocated and exotic species, indicating biotic differentiation. Temperature and number of ponds were the main preditors of change in beta diversity in the headwater creeks during the contemporary period. In summary, we observed that invaders have induced substantial changes to fish communities under influence of environmental filters. Our results support the hipothesis that aquaculture is a main driver of fish non-native fish introduction and native biodiversity loss in the Neotropics. [ABSTRACT FROM AUTHOR]

Many aquarium fish species have diverse morphotypes. Since different morphotypes may have different preferences for various prey items, offering a single prey species is inadequate for successful aquaculture. Poecilia reticulata, a popular aquarium species, occurs in different morphotypes. To test whether the four morphotypes (yellow tail YT, red tail RT, metallic blue tail MBT and black tail BT) of this fish prefer different items, we quantified somatic growth, feeding behaviour, zooplankton selectivity and functional responses. Standard length (4.5 vs. 11.7 mm) and gape size (0.37 vs. 0.91 mm) of four morphotypes increased linearly with larval age; YT and RT had 25% longer body length and larger gape than the others. Prey encounters, attacks, captures and ingestions increased with larval age. Lowest ingestion rates were recorded for the RT morphotype on rotifers. At any given larval age, prey consumption increased with increasing prey availability. During the fourth and fifth weeks, larval YT and RT consumed higher number (37 ± 1 ind./predator/30 min) of cladocerans compared with other two morphotypes (24 ± 1 ind./predator/30 min). Prey selectivity data showed that larvae of MBT and BT continued to prefer rotifers up to 4 weeks, while those of YT and RT preferred cladocerans during the 4th week. [ABSTRACT FROM AUTHOR]

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[Display omitted] • First comprehensive phylogenetic hypothesis of Poeciliidae based on genome-scale data. • Gene tree discordance in Poeciliidae is related to rapid diversifications and reticulation events. • A phylogenetic network best explains the diversification of poeciliids. • A taxonomic re-examination of the group is needed. Poeciliids (Cyprinodontiformes: Poeciliidae), commonly known as livebearers, are popular fishes in the aquarium trade (e.g., guppies, mollies, swordtails) that are widely distributed in the Americas, with 274 valid species in 27 genera. This group has undergone various taxonomic changes recently, spurred by investigations using traditional genetic markers. Here we used over 1,000 ultraconserved loci to infer the relationships within Poeciliidae in the first attempt at understanding their diversification based on genome-scale data. We explore gene tree discordance and investigate potential incongruence between concatenation and coalescent inference methods. Our aim is to examine the influence of incomplete lineage sorting and reticulate evolution on the poeciliids' evolutionary history and how these factors contribute to the observed gene tree discordace. Our concatenated and coalescent phylogenomic inferences recovered four major clades within Poeciliidae. Most supra-generic level relationships we inferred were congruent with previous molecular studies, but we found some disagreements; the Middle American taxa Phallichthys and Poecilia (Mollienesia) were recovered as non-monophyletic, and unlike other recent molecular studies, we recovered Brachyrhaphis as monophyletic. Our study is the first to provide signatures of reticulate evolution in Poeciliidae at the family level; however, continued finer-scale investigations are needed to understand the complex evolutionary history of the family along with a much-needed taxonomic re-evaluation. [ABSTRACT FROM AUTHOR]

Well-supported correlations between swim speed and mouth size during prey capture suggest the broad existence of an integrated relationship between locomotion and feeding in suction-feeding fishes. However, the influence of specialization on this relationship is unclear. We used divergent populations of Trinidadian guppies (Poecilia reticulata) to test whether integration during suction is generalizable to a non-suction specialist and whether intraspecific specialization of component systems affects their integration. Guppies from replicate high- and low-predation streams were recorded capturing wild-type zooplankton using suction. Alternative general linear models supported a positive correlation between swim speed and mouth size in derived low-predation populations, suggesting that the relationship can be extended in some cases. High-predation populations lack this integration, which may be the result of direct selection or constraints imposed by selection on locomotion. As guppies invade new habitats they may be evolving a new, integrated performance phenotype from a non-integrated ancestor. [ABSTRACT FROM AUTHOR]

Associating with conspecifics afflicted with infectious diseases increases the risk of becoming infected, but engaging in avoidance behaviour incurs the cost of lost social benefits. Across systems, infected individuals vary in the transmission risk they pose, so natural selection should favour risk‐sensitive avoidance behaviour that optimally balances the costs and benefits of sociality.Here, we use the guppy Poecilia reticulata–Gyrodactylus turnbulli host–parasite system to test the prediction that individuals avoid infected conspecifics in proportion to the transmission risk they pose.In dichotomous choice tests, uninfected fish avoided both the chemical and visual cues, presented separately, of infected conspecifics only in the later stages of infection.A transmission experiment indicated that this avoidance behaviour accurately tracked transmission risk (quantified as both the speed at which transmission occurs and the number of parasites transmitting) through the course of infection.Together, these findings reveal that uninfected hosts can use redundant cues across sensory systems to inform dynamic risk‐sensitive avoidance behaviour. This correlation between the transmission risk posed by infected individuals and the avoidance response they elicit has implications for the evolutionary ecology of infectious disease, and its explicit inclusion may improve the ability of epidemic models to predict disease spread. Animals should avoid conspecifics infected with directly transmitted diseases, but this avoidance incurs the cost of lost social benefits. Individuals may balance this trade‐off by selectively avoiding the most infectious conspecifics. Here, behavioural experiments and models derived from a transmission experiment demonstrate that guppies employ dynamic, risk‐sensitive infection‐avoidance behaviour. [ABSTRACT FROM AUTHOR]

The size and maturity of Trinidadian guppy (Poecilia reticulata) offspring vary among populations adapted to environments of differential predation. Guppy offspring born to low-predation, high-competition environments are larger and more mature than their high-predation ancestors. Here we ask: what specific changes in developmental or birth timing occur to produce the larger, more mature neonates? We collected specimens across the perinatal window of development from five populations and quantified musculoskeletal maturation. We found that all populations undergo similar ontogenetic trajectories in skeletal and muscle acquisition; the only difference among populations is when neonates emerge along the trajectory. The smallest neonates are born with 20% of their skeleton ossified, whereas the largest neonates are born with over 70% of their skeleton ossified. The area of the major jaw-closing muscle is relatively larger in larger offspring, scaling with length as L2.5. The size range over which offspring are birthed among populations sits along the steepest part of the size- maturity relationship, which provides a large marginal increase in fitness for the high-competition female. Because of the functional effects of producing more mature offspring at birth, offspring size may be the first and most critical life-history trait selected upon in highly competitive environments. [ABSTRACT FROM AUTHOR]

Eighty nine fish including guppies (n=55), Siamese fighting fish (n=12), Swordtails (n=10), Platies (n=6) and goldfish (n=6) showing emaciation, scoliosis and loss of pigmentation, and 30 apparently healthy guppies collected from pet shops and fish breeding farms in Sri Lanka were examined and sampled to culture and isolate non-tuberculous mycobacteria (NTM). A total of 35 mycobacteria (diseased=28, healthy=7) isolated from these fish were subjected to biochemical identification and Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCRRFLP). Only 24 NTM isolated from diseased fish were identified at the species level, namely Mycobacterium fortuitum type I (n=7), M. fortuitum type II (n=3), M. kansasii type IV (n=5), M. marinum (n=8) and M. chelonae (n=1). Five of the seven NTM species isolated from apparently healthy fish were identified as M. fortuitum type I (n=2), M. fortuitum type II (n=1), M. kansasii type IV (n=1) and M. marinum (n=1). Irrespective of the NTM species involved, guppies most often showed skeletal deformities while chronic ulcers were common in goldfish and fighting fish. Histopathologically, granulomatous inflammation was minimum in guppies. All four NTM species isolated in this study are potentially zoonotic and it is necessary to implement appropriate biosecurity measures to prevent spread of these organisms. [ABSTRACT FROM AUTHOR]

Ectotherms depend on the environmental temperature for thermoregulation and exploit thermal regimes that optimise physiological functioning. They may also frequent warmer conditions to up-regulate their immune response against parasite infection and/or impede parasite development. This adaptive response, known as 'behavioural fever', has been documented in various taxa including insects, reptiles and fish, but only in response to endoparasite infections. Here, a choice chamber experiment was used to investigate the thermal preferences of a tropical freshwater fish, the Trinidadian guppy ( Poecilia reticulata), when infected with a common helminth ectoparasite Gyrodactylus turnbulli, in female-only and mixed-sex shoals. The temperature tolerance of G. turnbulli was also investigated by monitoring parasite population trajectories on guppies maintained at a continuous 18, 24 or 32 °C. Regardless of shoal composition, infected fish frequented the 32 °C choice chamber more often than when uninfected, significantly increasing their mean temperature preference. Parasites maintained continuously at 32 °C decreased to extinction within 3 days, whereas mean parasite abundance increased on hosts incubated at 18 and 24 °C. We show for the first time that gyrodactylid-infected fish have a preference for warmer waters and speculate that sick fish exploit the upper thermal tolerances of their parasites to self medicate. [ABSTRACT FROM AUTHOR]

Guppies (Poecilia reticulata) were reported as indicators of waters in poor conditions, representing one of the most significant models in evolutionary ecology due to the species' quick response to natural selection. The inability of these species to develop perfect symmetry can be associated to the disturbances in their environment. Determining the fluctuating asymmetry (FA) as a measure of the species developmental instability of P. reticulata found in Lake Sebu, South Cotabato, Philippines is an effective tool in finding out the ecological health and to fully understand the shape variability of guppies found in the area. Landmark-based geometric morphometries was used in the study to analyze the biological shape information of the samples. Procrustes ANOVA was employed for the assessment of FA. Statistical analyses showed that there is a significant FA on both sexes of the fishes (p<0.05) while individual symmetry showed otherwise. Results revealed that female guppy showed higher value in FA (83.69%) compared to male's (81.63%). The results taken reflect a high FA in the body shapes of P. reticulata, thus, imply a high level of stress in the water systems in Lake Sebu. This study proves the effectiveness of FA studies to indicate perturbations in the water environment using guppies as stress indicators. [ABSTRACT FROM AUTHOR]

Guppies ( Poecilia reticulata) are colorful fish that have attracted the attention of pigmentation researchers for almost a century. Here, we report that the blond phenotype of the guppy is caused by a spontaneous mutation in the guppy ortholog of adenylate cyclase 5 ( adcy5). Using double digest restriction site-associated DNA sequencing (dd RADseq) and quantitative trait locus ( QTL) mapping, we linked the blond phenotype to a candidate region of 118 kb, in which we subsequently identified a 2-bp deletion in adcy5 that alters splicing and leads to a premature stop codon. We show that adcy5, which affects life span and melanoma growth in mouse, is required for melanophore development and formation of male orange pigmentation traits in the guppy. We find that some components of the male orange pattern are particularly sensitive to loss of Adcy5 function. Our work thus reveals a function for Adcy5 in patterning of fish color ornaments. [ABSTRACT FROM AUTHOR]

Predation of newborn fish by cannibalistic adults is a major cause of fry loss in guppy breeding tanks. The efficacy of using light to attract newborn guppies into a safe area, thereby reducing the cannibalism rate, was evaluated in aquaria. The aquaria were divided using small-mesh netting into a section with adult fish and a safe section without adults, above which a light source was installed to attract the newborns. Both, the presence of cannibalistic adults and the light, increased the number of newborns in the safe section. The effect of the cannibals was pronounced during the day, and the effect of light seemed to be more pronounced at night. The presence of light significantly decreased cannibalism rate after 30 min, but not 16 h after the introduction of newborns. When tested with cannibalistic adults that have not been fed for 5 days prior to testing, cannibalism rate was higher and the effect of light on reducing cannibalism was evident both 30 min and 16 h after the introduction of newborns. The results demonstrated the potential efficacy of using white light in reducing cannibalism and increasing fry yields in guppy hatcheries. [ABSTRACT FROM AUTHOR]

We address the bioinformatic issue of accurately separating amplified genes of the major histocompatibility complex ( MHC) from artefacts generated during high-throughput sequencing workflows. We fit observed ultra-deep sequencing depths (hundreds to thousands of sequences per amplicon) of allelic variants to expectations from genetic models of copy number variation ( CNV). We provide a simple, accurate and repeatable method for genotyping multigene families, evaluating our method via analyses of 209 b of MHC class IIb exon 2 in guppies ( Poecilia reticulata). Genotype repeatability for resequenced individuals ( N = 49) was high (100%) within the same sequencing run. However, repeatability dropped to 83.7% between independent runs, either because of lower mean amplicon sequencing depth in the initial run or random PCR effects. This highlights the importance of fully independent replicates. Significant improvements in genotyping accuracy were made by greatly reducing type I genotyping error (i.e. accepting an artefact as a true allele), which may occur when using low-depth allele validation thresholds used by previous methods. Only a small amount (4.9%) of type II error (i.e. rejecting a genuine allele as an artefact) was detected through fully independent sequencing runs. We observed 1-6 alleles per individual, and evidence of sharing of alleles across loci. Variation in the total number of MHC class II loci among individuals, both among and within populations was also observed, and some genotypes appeared to be partially hemizygous; total allelic dosage added up to an odd number of allelic copies. Collectively, observations provide evidence of MHC CNV and its complex basis in natural populations. [ABSTRACT FROM AUTHOR]

Abstract: Monogenean infections of commercially farmed fishes are responsible for significant economic losses. Garlic (Allium sativum) is a well-known spice which also possesses anti-microbial and anti-parasitical properties. The current work aimed to test the efficacy of garlic-based treatments against infection with monogenean sp. in the guppy (Poecilia reticulata). Clipped sections of tail fins of guppies heavily infected with Gyrodactylus turnbulli were exposed to aqueous garlic extract (7.5 to 30mLL−1) and visually observed under a dissecting microscope. Results revealed that exposure to garlic caused detachment of parasite and cessation of movement indicating death. A positive correlation was seen between garlic concentration and time to detachment and death of parasites, which, at the highest concentration of 30mLL−1, occurred at 4.1 and 8.6min, respectively. Bathing in aqueous garlic extract (7.5 and 12.5mLL−1) was tested in guppies infected with G. turnbulli. Prior acute toxicity tests revealed the maximum tolerance levels of guppies to garlic extract to be 12.5mLL−1 for 1h. Bathing of infected fish in garlic extract (7.5 and 12.5mLL−1) significantly (p <0.05) reduced infection prevalence and intensity as compared to the control. Oral treatments using dry garlic powder-supplemented diet were tested on guppies infected with G. turnbulli and Dactylogyrus sp. Fish were fed with food containing 10% and 20% dry garlic powder for 14 days. Groups fed with garlic supplemented diets showed significantly reduced (p <0.05) mean prevalence and mean intensity of parasites as compared to the control. Dietary application of garlic did not appear to affect palatability. Fresh crushed garlic was added at a level of 1gL−1 and applied as an indefinite bath for 14 days. This treatment was seen to significantly reduce (p <0.05) parasite prevalence and mean intensity as compared to the control. Histopathology revealed elevated muscular dystrophy in the 20% garlic-fed group, as compared to control. These findings demonstrate the potential of garlic as a natural alternative to currently used chemical treatments for monogenean sp. infection in the guppy. [Copyright &y& Elsevier]

Although traditional sexual selection theories for the evolution of ornamental male traits often assume consistency in female preferences for the traits over time, recent theories predict plasticity in female mate preferences and the contribution of plastic female preferences to the maintenance of polymorphism in male sexual ornaments. However, the plasticity of female preferences and its influences on male ornaments are almost unknown in natural populations. Here we examined both the intensity of female preferences and the exaggeration of a male ornament (relative area of orange spots) in a wild population of the guppy ( Poecilia reticulata) every few months over a period of 3 years. Results indicated that female preference intensity was negatively correlated with the relative area of orange spots of males. In addition, we found a positive correlation between female preference intensity and the relative area of orange spots of males of their offspring generation. Because the relative area of orange spots of male guppies is a heritable trait, female preferences might have a strong influence on male orange spot size in the next generation. This study provides the first evidence of plastic female preferences depending on the scarcity of males with large ornaments in a natural population. Results of this study imply a possible contribution of female preferences for the maintenance of variation in male ornamentation. [ABSTRACT FROM AUTHOR]

Success of reproduction may be affected by personality traits. Previous studies in the guppy concentrated on the effect of male’s boldness on reproductive success. Less attention was however given to female’s boldness on reproductive success. Using mate choice and mating trials, we show that a female's boldness did not affect mate choice or number of babies produced. However, mates with similar boldness level were more likely to have babies than pairs with different boldness level.Consistent individual differences in personality or temperament have been observed in many animal taxa, and one particular trait, boldness, has been studied extensively. Most studies on mate choice and personality have focused on female preference and have showed that females prefer to mate with bolder males. However, the influence of the female’s personality on this mate preference and on her compatibility with a mate with particular traits has been largely neglected. Here, using the guppy Poecilia reticulata, we investigated the effect of female boldness on mate choice and of the combinations of this trait in the male and female of a mating pair on parturition and brood size. Our results showed that female boldness did not affect mate choice, and brood size was independent of the boldness of the male and female in a pair. However, overall, females who mated with males with a dissimilar degree of boldness to themselves had a lower parturition success than females who mated with males with a similar degree of boldness. This work suggests that the combination of boldness characteristics within a pair influences reproductive success and that individuals of similar personality are more compatible in reproduction. The lower success of disassortative matings is consistent with the hypothesis that variation in personalities is maintained by disruptive or frequency-dependent selection, driven by contrasting physical or social environments that favor alternative rather than intermediate behavioral phenotypes. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Light was used to attract newborn guppies into net baskets that prevent cannibalism. [•] Illumination can increase fry yields and save labor in guppy hatcheries. [ABSTRACT FROM AUTHOR]

Background: Humans and non-human animals share an approximate non-verbal system for representing and comparing numerosities that has no upper limit and for which accuracy is dependent on the numerical ratio. Current evidence indicates that the mechanism for keeping track of individual objects can also be used for numerical purposes; if so, its accuracy will be independent of numerical ratio, but its capacity is limited to the number of items that can be tracked, about four. There is, however, growing controversy as to whether two separate number systems are present in other vertebrate species. Methodology/Principal Findings: In this study, we compared the ability of undergraduate students and guppies to discriminate the same numerical ratios, both within and beyond the small number range. In both students and fish the performance was ratio-independent for the numbers 1-4, while it steadily increased with numerical distance when larger numbers were presented. Conclusions/Significance: Our results suggest that two distinct systems underlie quantity discrimination in both humans and fish, implying that the building blocks of uniquely human mathematical abilities may be evolutionarily ancient, dating back to before the divergence of bony fish and tetrapod lineages. [ABSTRACT FROM AUTHOR]

The potential causes of adult sex ratio variation in guppies Poecilia reticulata were tested in laboratory experiments that evaluated the mortality rates of male and female P. reticulata exposed to potential predators (Hart's rivulus Rivulus hartii and freshwater prawns Macrobrachium crenulatum) and to different resource levels. Poecilia reticulata mortality increased in the presence of R. hartii and M. crenulatum, and low resource levels had an effect on mortality only in the presence of M. crenulatum. Rivulus hartii preyed more often on male than on female P. reticulata, and this sex-biased predation was not simply the result of males being smaller than females. In contrast, no sex-biased mortality was attributable to M. crenulatum or low resource levels. [ABSTRACT FROM AUTHOR]

Abstract: Salt is commonly recommended as an inexpensive treatment against many fish parasites in freshwater fish culture; however, few studies have scientifically evaluated its efficacy. Amongst the monogeneans, salt has only been previously tested against Gyrodactylus salaris infecting Atlantic salmon (Salmo salar) and G. derjavini infecting rainbow trout (Oncorhynchus mykiss). Here we tested the efficacy of salt treatments against G. bullatarudis and G. turnbulli on guppies (Poecilia reticulata), both commercially important pathogens in the ornamental fish industry. In vitro survival of both parasites was negatively correlated with increasing salinities of 3, 5, 7 and 33gL−1. Parasite establishment on guppies maintained at 0, 3 and 7gL−1 salinity decreased drastically for G. turnbulli from 94% in the control to 78 and 0% on fish in 3 and 7gL−1 salinity, respectively. G. bullatarudis establishment was still 100% at 3gL−1 salinity but was reduced to 73% in 7gL−1. Throughout an infection, parasite populations of both species increased faster on guppies in 3gL−1 salinity compared to dechlorinated water, whereas population growth was severely affected at 7gL−1 salinity. Overall a short duration, high concentration salt bath was most effective at treating gyrodactylid infections: 15min exposure to 25gL−1 salinity for adults or 5min for juvenile fish removed 100% of G. turnbulli or 72% of G. bullatarudis. The results reflect the generalist characteristics of the more tolerant G. bullatarudis compared to G. turnbulli, but have wider implications for treatment application: clearly one treatment regime does not suit all even within a genus. [ABSTRACT FROM AUTHOR]

Background: Next-generation sequencing is providing researchers with a relatively fast and affordable option for developing genomic resources for organisms that are not among the traditional genetic models. Here we present a de novo assembly of the guppy (Poecilia reticulata) transcriptome using 454 sequence reads, and we evaluate potential uses of this transcriptome, including detection of sex-specific transcripts and deployment as a reference for gene expression analysis in guppies and a related species. Guppies have been model organisms in ecology, evolutionary biology, and animal behaviour for over 100 years. An annotated transcriptome and other genomic tools will facilitate understanding the genetic and molecular bases of adaptation and variation in a vertebrate species with a uniquely well known natural history. Results: We generated approximately 336 Mbp of mRNA sequence data from male brain, male body, female brain, and female body. The resulting 1,162,670 reads assembled into 54,921 contigs, creating a reference transcriptome for the guppy with an average read depth of 28×. We annotated nearly 40% of this reference transcriptome by searching protein and gene ontology databases. Using this annotated transcriptome database, we identified candidate genes of interest to the guppy research community, putative single nucleotide polymorphisms (SNPs), and male-specific expressed genes. We also showed that our reference transcriptome can be used for RNA-sequencing- based analysis of differential gene expression. We identified transcripts that, in juveniles, are regulated differently in the presence and absence of an important predator, Rivulus hartii, including two genes implicated in stress response. For each sample in the RNA-seq study, >50% of high-quality reads mapped to unique sequences in the reference database with high confidence. In addition, we evaluated the use of the guppy reference transcriptome for gene expression analyses in a congeneric species, the sailfin molly (Poecilia latipinna). Over 40% of reads from the sailfin molly sample aligned to the guppy transcriptome. Conclusions: We show that next-generation sequencing provided a reliable and broad reference transcriptome. This resource allowed us to identify candidate gene variants, SNPs in coding regions, and sex-specific gene expression, and permitted quantitative analysis of differential gene expression. [ABSTRACT FROM AUTHOR]

Local adaptation to different environments can promote mating isolation - either as an incidental by-product of trait divergence, or as a result of selection to avoid maladaptive mating. Numerous recent empirical examples point to the common influence of divergent natural selection on speciation based largely on evidence of strong pre-mating isolation between populations from different habitat types. Accumulating evidence for natural selection's influence on speciation is therefore no longer a challenge. The difficulty, rather, is in determining the mechanisms involved in the progress of adaptive divergence to speciation once barriers to gene flow are already present. Here, we present results of both laboratory and field experiments with Trinidadian guppies (Poecilia reticulata) from different environments, who do not show complete reproductive isolation despite adaptive divergence. We investigate patterns of mating isolation between populations that do and do not exchange migrants and show evidence for both by-product and reinforcement mechanisms depending on female ecology. Specifically, low-predation females discriminate against all high-predation males thus implying a byproduct mechanism, whereas high-predation females only discriminate against low-predation males from further upstream in the same river, implying selection to avoid maladaptive mating. Our study thus confirms that mechanisms of adaptive speciation are not necessarily mutually exclusive and uncovers the complex ecology-geography interactions that underlie the evolution of mating isolation in nature. [ABSTRACT FROM AUTHOR]

Sexual displays and mate choice often take place under the same set of environmental conditions and, as a consequence, may be exposed to the same set of environmental constraints. Surprisingly, however, very few studies consider the effects of environmental costs on sexual displays and mate choice simultaneously. We conducted an experiment, manipulating water flow in large flume tanks, to examine how an energetically costly environment might affect the sexual display and mate choice behavior of male and female guppies, Poecilia reticulata. We found that male guppies performed fewer sexual displays and became less choosy, with respect to female size, in the presence of a water current compared to those tested in still water. In contrast to males, female responsive to male displays did not differ between the water current treatments and females exhibited no mate preferences with respect to male size or coloration in either treatment. The results of our study underscore the importance of considering the simultaneous effects of environmental costs on the sexual behaviors of both sexes. [ABSTRACT FROM AUTHOR]

The reproductive effort that a male directs to a familiar female declines over time, suggesting decreasing marginal returns. But is this diminishing returns a function of increasing reproductive costs or decreasing benefits of sustained effort? Here, we use the restoration of male reproductive effort with unfamiliar females to differentiate the role of diminishing returns and lifetime costs of increased reproductive effort of male guppies. We kept males with familiar or unfamiliar females throughout their lives and manipulated their ability to either court or mate with females. We found that increased male reproductive effort with novel mates lead to an immediate trade-off in the form of reduced foraging effort. Further, males able to mate with a series of unfamiliar females had lower lifetime growth, indicating the primary cost of male reproductive effort in guppies arises from copulation rather than courtship. The lifetime growth trade-offs were significant only when males mated with unfamiliar mates, suggesting that male reproductive effort with familiar females declines before it is restricted by physical exhaustion. These findings provide some of the first evidence of longitudinal costs of increased male reproductive effort in a vertebrate. [ABSTRACT FROM AUTHOR]

Background: It has been hypothesised that human adults, infants, and non-human primates share two non-verbal systems for enumerating objects, one for representing precisely small quantities (up to 3-4 items) and one for representing approximately larger quantities. Recent studies exploiting fish's spontaneous tendency to join the larger group showed that their ability in numerical discrimination closely resembles that of primates but little is known as to whether these capacities are innate or acquired. Methodology/Principal Findings: We used the spontaneous tendency to join the larger shoal to study the limits of the quantity discrimination of newborn and juvenile guppies. One-day old fish chose the larger shoal when the choice was between numbers in the small quantity range, 2 vs. 3 fish, but not when they had to choose between large numbers, 4 vs. 8 or 4 vs. 12, although the numerical ratio was larger in the latter case. To investigate the relative role of maturation and experience in large number discrimination, fish were raised in pairs (with no numerical experience) or in large social groups and tested at three ages. Forty-day old guppies from both treatments were able to discriminate 4 vs. 8 fish while at 20 days this was only observed in fish grown in groups. Control experiments showed that these capacities were maintained after guppies were prevented from using non numerical perceptual variables that co-vary with numerosity. Conclusions/Significance: Overall, our results suggest the ability of guppies to discriminate small numbers is innate and is displayed immediately at birth while discrimination of large numbers emerges later as a result of both maturation and social experience. This developmental dissociation suggests that fish like primates might have separate systems for small and large number representation. [ABSTRACT FROM AUTHOR]

Digitally modified videos of male guppies Poecilia reticulata were used to examine the relative importance of the area and intensity of the orange spots as mating traits preferred by females. The females prioritized the area of the orange spots over intensity for their mate preference. [ABSTRACT FROM AUTHOR]

Females that invest adaptively in their offspring are predicted to channel more resources to the sex that will be at an advantage in the prevailing environmental conditions. Here, we report, for the first time, that female Trinidadian guppy, Poecilia reticulata, respond in reproductively distinct ways when faced with differences in operational sex ratio. We show that females assigned to a female-biased sex ratio produce larger male offspring than females in an environment in which males predominate. Given the link between size at birth and fitness, and the marked reproductive skew in this species, larger male offspring are expected to have reproductive advantages in guppy populations with an excess of females. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 414–419. [ABSTRACT FROM AUTHOR]

The sex allocation hypothesis predicts that females manipulate the offspring sex ratios according to mate attractiveness. Although there is increasing evidence to support this prediction, it is possible that paternal effects may often obscure the relationship between female control of offspring sex ratios and male attractiveness. In the present study, we examined whether females played a primary role in the manipulation their offspring sex ratios based on male attractiveness, in the guppy Poecilia reticulata, a live-bearing fish. We excluded the paternal effects by controlling the relative sexual attractiveness of the male by presenting them to the females along with a more attractive or less attractive stimulus male. The test male was perceived to be relatively more attractive by females when it was presented along with a less attractive stimulus male, or vice versa. Subsequently, test male was mated in two different roles (relatively more and less attractive) with two females. If females were responsible for offspring sex ratio manipulation, the sex ratio of the brood would be altered on the basis of the relative attractiveness of the test male. On the other hand, if males play a primary role in offspring sex ratio manipulation, the sex ratios would not differ with the relative attractiveness of the test male. We found that females gave birth to more male-biased broods when they mated with test males in the attractive role than when they mated with males in the less attractive role. This finding suggests that females are responsible for the manipulation of offspring sex ratios based on the attractiveness of their mates. [ABSTRACT FROM AUTHOR]

1. Factors contributing to the maintenance of phenotypic variation in nature are often difficult to determine. Secondary sexual traits might be particularly interesting in this regard due to the interaction they experience between multiple selective agents. One way to examine such effects is to monitor populations following environmental change. Human-caused changes can be particularly useful here because they often involve an abrupt and extreme alteration of specific habitat features. This alteration can then precipitate phenotypic plasticity, changes in adaptive landscapes, and modified evolutionary trajectories. The consequences of habitat manipulations on local populations can therefore improve our understanding of phenotypic variation in complex ecological systems. 2. We took advantage of a human-caused environmental disturbance to examine factors influencing phenotypic variation in Trinidadian guppies ( Poecilia reticulata). Differences in canopy cover along the stream have been hypothesized to explain some of this variation, but this has been hard to test directly. We here attempt a direct test of this hypothesis by monitoring changes in guppy size and colour following a dramatic decrease in canopy cover due to tree removal for agricultural activity. 3. Although male and female body size increased following canopy clearing, little change was observed in the overall amount of melanin-based colours, carotenoid-based colours, and structural colours on males. We further compared phenotypes before and after canopy clearing at the disturbed site to those from two nearby reference sites that are at extreme ends of canopy cover. Overall, variation in colour was attributed to differences among sites, irrespective of canopy differences. We also found considerable temporal variation in some colour elements at a given site. 4. Our results suggest that differences in light availability do not cause rapid and dramatic changes in guppy colour. The substantial unexplained variation must therefore be due to factors other than canopy (measured here) and predation regime (all sites were ‘low-predation’). Because of the multiple and complex interactions involved in the expression and maintenance of sexually selected traits, our study emphasizes the need for a better understanding of both the genetic and environmental sources of co-variation between sexual ornaments and preferences. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Many fish species exhibit size-assortative shoaling, which is often thought to be driven by predation risk. Recent fieldwork has revealed that guppies ( Poecilia reticulata) are more size assorted in high-predation populations than in low-predation ones. However, size assortment does nonetheless occur in some low-predation populations, suggesting that predation is unlikely the sole driving force behind size-assortment. Here, we investigated in the laboratory the potential role of active choice in size-assortative shoaling in wild-caught female guppies originating from two populations of the same river system in Trinidad. Small or large focal females from each population were offered a binary choice of shoaling with either four small female conspecifics or four large ones. Observed shoaling preferences depended on the body size of the focal fish, suggesting phenotype-mediated conflict over group composition. Large focal fish preferred to shoal with the size-matched stimulus shoal of large fish. In contrast, small focal fish did not shoal assortatively but also preferred to shoal with larger females. Our results suggest that size-assortative shoaling in female guppies is likely to be due to factors other than active choice, such as habitat segregation and sexual harassment. [ABSTRACT FROM AUTHOR]

Deleterious mutations can accumulate in the germline with age, decreasing the genetic quality of sperm and imposing a cost on female fitness. If these mutations also affect sperm competition ability or sperm production, then females will benefit from polyandry as it incites sperm competition and, consequently, minimizes the mutational load in the offspring. We tested this hypothesis in the guppy ( Poecilia reticulata), a species characterized by polyandry and intense sperm competition, by investigating whether age affects post-copulatory male traits and sperm competition success. Females did not discriminate between old and young males in a mate choice experiment. While old males produced longer and slower sperm with larger reserves of strippable sperm, compared to young males, artificial insemination did not reveal any effect of age on sperm competition success. Altogether, these results do not support the hypothesis that polyandry evolved in response to costs associated with mating with old males in the guppy. [ABSTRACT FROM AUTHOR]

The role of learning ability as a potentially desirable male trait in sexual selection was investigated in the guppy Poecilia reticulata. Mate preference tests and the rate at which a male learnt two mazes were used to determine whether female preference was related to male learning ability. In addition, male body size and saturation of the orange patches were measured. Female preference was found to be related to rate of learning, such that males that learnt the mazes faster were found to be more attractive to females, but was not found to be related to body size or saturation. [ABSTRACT FROM AUTHOR]

Tetrahymena sp. infection was diagnosed in guppies imported from Singapore. The parasite was isolated (Tet-NI) and optimally cultured in vitro in RM-9 medium. Cytological analyses [silver-staining and scanning electron microscopy (SEM)] revealed a pyriform-shaped, 64 × 41-μm holotrich ciliate without caudal cilium, containing a macro-nucleus (18.25 × 16.83 μm) and micro-nucleus (5.73 × 5.40 μm). Wet-mount examination and histological analyses of fish exposed to the parasite by co-habitation, immersion and infection by i.p. (intra-peritoneal) and i.m. (intra-muscular) injection revealed numerous ciliates on the skin, and in the gill and caudal fin blood vessels. Ciliates surrounded internal organs, the peri-orbital region of the eye, and were observed inside developing guppy embryos. Some muscle necrosis was associated with infection, but little or no inflammatory response. Immersion, co-habitation and i.m. injection caused relatively high infection rates and levels in the skin and tail, and lower infection in the gill blood vessels and internal organs; i.p. injection caused higher infection in the gill blood vessels and internal organs. Co-habited fish had relatively high infection levels in the hind-gut sub-mucosa. This is the first report of controlled systemic infection by Tetrahymena sp. [ABSTRACT FROM AUTHOR]

The attractiveness hypothesis predicts that females produce offspring with male-biased sex ratios when they mate with attractive males because their male offspring will inherit the paternal sexual attractiveness and may have high reproductive success. In this study, we examined the effect of the attractiveness of the male guppy Poecilia reticulata in terms of the conspicuousness of its orange spot patterns, important criteria affecting female choice in this species, on the offspring sex ratios. We found that food-manipulation treatment altered the conspicuousness of the orange spot patterns in a full-sibling male pair. When females were presented to these males, they showed a greater mate preference for males having brighter orange spots than for those having duller orange spots. Subsequently, half of the females were mated with the preferred males and the remaining females were mated with the less preferred males. When the females exhibited a greater preference for their mates, their offspring sex ratios were more male biased. These results appear to be consistent with the prediction of the attractiveness hypothesis. In the guppy, as male sexual attractiveness is heritable, the male-biased sex ratios of the broods of attractive males may be adaptive. [ABSTRACT FROM AUTHOR]

The effects of the social environment during development on life-history decisions and adult behaviour were assessed using male guppies Poecilia reticulata. Males raised with adults developed secondary sexual characteristics later than males raised either singly or with four of their siblings indicating social inhibition of maturation was evident in P. reticulata. There was no effect, however, of rearing environment on male behaviour. The results reveal that social environment during development can influence life-history decisions but is less important than immediate social context in determining male behavioural phenotype in P. reticulata. [ABSTRACT FROM AUTHOR]

High water temperature influences the survival, growth, and maturation of fish. Genetically characterizing thermal tolerance is one of the most important subjects in fish culture. To identify the genetic characterization of thermal tolerance, this characteristic was compared among strains, and among parents and their offspring, in the guppy Poecilia reticulata. In the strain comparison, significant differences in survival rate were observed among the five strains examined, and between females and males. Females exhibited greater tolerance than males in four of five strains examined. In the comparison between parents and their offspring, stronger influence of female parent than of male parent was observed. Offspring obtained from surviving females exhibited greater tolerance than those from dead females. This tendency was typically observed in male offspring. The survival rate in male offspring obtained from dead female parents was lower than that of those from surviving females. The high-temperature tolerance of male parents did not influence this characteristic in offspring as strongly as that of female parents. These results suggest that the major gene or genes, which has a dominant resistant allele and a recessive sensitive allele, are probably passed on by sex-linked inheritance, located on the X chromosome. [ABSTRACT FROM AUTHOR]

Frequency-dependent mating behaviour has the potential to maintain genetic variation in characteristics of organisms. The colour patterns of guppies ( Poecilia reticulata) provide an example of one of the most extreme genetically based polymorphisms known in nature, for which frequency-dependent mate choice could be a mechanism. Numerous studies have shown that female guppies base mating preferences on male colour patterns and there is evidence that females prefer to mate with males displaying novel or unfamiliar colour patterns. This preference could lead to frequency-dependent mating success in males. Nevertheless, the possibility that female sexual responsiveness itself may depend on the frequency of male types has not been tested systematically in guppies or any other species. This study examined the sexual responses of female guppies in experimental groups consisting of two males with similar (redundant) and two males with different (unique) colour patterns. We found that female guppies were much more likely to respond sexually to the displays of unique males than to those of redundant males. Further, there was no effect of orange colouration on female responsiveness as has been documented for this population in several previous studies, thus, discrimination against redundant male types appears to have overridden directional selection based on colour pattern characteristics. This discrimination against redundant male types could in turn lead to frequency-dependent mating success in males and maintenance of colour pattern polymorphism. [ABSTRACT FROM AUTHOR]

Among different teleost fish species, diverse sex-determining mechanisms exist, including environ- mental and genetic sex determination, yet chromosomal sex determination with male heterogamety (XY) prevails. Different pairs of autosomes have evolved as sex chromosomes among species in the same genus without evidence for a master sex-determining locus being identical. Models for evolution of V chromosomes predict that male-advantageous genes become linked to a sex-determining locus and suppressed recombination ensures their co-inheritance. In the guppy, Poecilia reticulala, a set of genes responsible for adult male ornaments are linked to the sex-determining locus on the incipient Y chromosome. We have identified >60 sex-linked molecular markers to generate a detailed map for the sex linkage group of the guppy and compared it with the syntenic autosome 12 of medaka. We mapped the sex-determining locus to the distal end of the sex chromosome. We report a sex-biased distribution of recombination events in female and male meiosis on sex chromosomes. In one mapping cross, we observed sex ratio and male phenotype deviations and propose an atypical mode of genetic sex inheritance as its basis. [ABSTRACT FROM AUTHOR]

Sex ratios can influence mating behaviour, population dynamics and evolutionary trajectories; yet the causes of natural sex ratio variation are often uncertain. Although secondary (birth) sex ratios in guppies ( Poecilia reticulata) are typically 1:1, we recorded female-biased tertiary (adult) sex ratios in about half of our 48 samples and male-biased sex ratios in none of them. This pattern implies that some populations experience male-biased mortality, perhaps owing to variation in predation or resource limitation. We assessed the effects of predation and/or inter-specific resource competition (intraguild predation) by measuring the local catch-per-unit-effort (CPUE) of species ( Rivulus killifish and Macrobrachium prawns) that may differentially prey on male guppies. We assessed the effects of resource levels by measuring canopy openness and algal biomass (chlorophyll a concentration). We found that guppy sex ratios were increasingly female-biased with increasing CPUE of Macrobrachium, and perhaps also Rivulus, and with decreasing canopy openness. We also found an interaction between predators and resource levels in that the effect of canopy openness was greatest when Macrobrachium CPUE was highest. Our study thus also reveals the value of simultaneously testing multiple environmental factors that may drive tertiary sex ratio variation. [ABSTRACT FROM AUTHOR]

The antipredator behaviour of prey organisms is shaped by a series of threat-sensitive trade-offs between the benefits associated with successful predator avoidance and a suite of other fitness-related behaviours such as foraging, mating and territorial defence. Recent research has shown that the overall intensity of antipredator response and the pattern of threat-sensitive trade-offs are influenced by current conditions, including variability in predation risk over a period of days to weeks. In this study, we tested the hypothesis that long-term predation pressure will likewise have shaped the nature of the threat-sensitive antipredator behaviour of wild-caught Trinidadian guppies ( Poecilia reticulata). Female guppies were collected from two populations that have evolved under high- and low-predation pressure, respectively, in the Aripo River, Northern Mountain Range, Trinidad. Under laboratory conditions, we exposed shoals of three guppies to varying concentrations of conspecific damage-released chemical alarm cues. Lower Aripo (high-predation) guppies exhibited the strongest antipredator response when exposed to the highest alarm cue concentration and a graded decline in response intensity with decreasing concentrations of alarm cue. Upper Aripo (low-predation) guppies, however, exhibited a nongraded (hypersensitive) response pattern. Our results suggest that long-term predation pressure shapes not only the overall intensity of antipredator responses of Trinidadian guppies but also their threat-sensitive behavioural response patterns. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Visually mediated mating behaviour has been extensively studied in guppies, Poecilia reticulata. In contrast, the effects of signals from other sensory modalities on receiver behaviour have received very little attention. Here we describe three field and laboratory experiments to investigate the attraction of females to conspecific chemosensory cues using guppies from the Caroni drainage of Trinidad. In an experiment with stationary water and concentrated stimulus solutions, guppies were equally attracted to chemosensory cues from males and females, and did not respond to control stimuli without conspecific cues. In the wild, guppies showed no attraction to conspecific chemosensory cues. In a laboratory flow chamber, set up to mimic the natural situation but without distractions from visual and other chemosensory stimuli, guppies were also not attracted to chemosensory cues from male or female guppies. In addition, the attraction of individual females to conspecific chemosensory cues was not repeatable. These experiments suggest that the use of conspecific chemosensory cues can attract female guppies only when in high concentrations. We discuss the effects of differences in experimental design on our findings, and the possibility of multimodal interactions between visual and chemosensory cues. [ABSTRACT FROM AUTHOR]

Female mate choice by multiple male traits is an important current topic in animal behavior. However, the relative importance among the multiple cues in female choice is not explored in most cases. Female guppies Poecilia reticulata use both the color saturation of orange spots and the total length of males as mate choice criteria. In the present study, we used digitally modified video playbacks to examine the relative importance of these two male traits to female mate preferences. We initially examined the effective difference in the color saturation of orange spots as well as that in total length between two stimulus male images. Females only showed a strong preference for a bright male image (compared to the dull image) when the difference in color saturation was large (91% versus 25%). Conversely, females only exhibited a preference for larger size when they were presented a choice between two relatively small male images (total length 26.0 mm versus 23.0 mm). When two male images in which both the two traits were modified were presented to females, they prioritized male images possessing higher color saturation of orange spots, indicating the color saturation of male orange spots to be a more important factor than the total length in their mate choice. The color saturation of orange spots may convey more reliable information about the males to the females than their total lengths. These findings imply that females may rank multiple male criteria depending on relative benefits or costs derived from their mate choice based on each criterion. [ABSTRACT FROM AUTHOR]

We use microsatellite loci to detail the multiple paternity patterns in broods from 10 wild populations of the guppy ( Poecilia reticulata) found in Northern Trinidad. The populations span two major drainages comprising the Caroni and the Oropouche, and include sites that are characterized by either high or low predation. Across the populations the frequency of multiple paternity is high with 95% (range: 70%–100%) of broods having multiple sires. Broods have an average of 3.5 sires (range: 1–9) and a mixed-model analysis suggests that broods from high predation sites have marginally more sires than do those from low predation sites, but this is true only in the Oropouche drainage. There is no difference in sire number between predation sites in the Caroni drainage. Brood size, but not female body length, is correlated with the number of sires and the correlation cannot be attributed solely to the stochastic process associated with sperm competition and a ‘fair raffle’. Within broods there is significant skew in reproductive success among males, which may reflect variation in sperm competitiveness or female choice. There is, however, no difference in the skew among populations from different predation regimes or drainages. Finally, high predation populations were characterized by increased genetic variability at the microsatellite loci, suggesting a larger effective population size. We discuss explanations for the high degree of multiple paternity but the general lack of any major differences among broods from ecologically different populations. [ABSTRACT FROM AUTHOR]

We used guppies to study repeatability in sperm competitiveness and postcopulatory sexual selection on male ornamentation. In a block design involving 25 pairs of males, artificial insemination was used to mate each pair (A and B) to four unrelated females—two that were mated with the combined ejaculates of both males (sperm-competition treatment) and two receiving sperm from each of the two males individually (single-male treatment). Our analysis revealed significantly repeatable patterns of paternity across females in the sperm-competition treatment, suggesting that certain males are intrinsically better sperm competitors than others, irrespective of female identity. Next, we compared mean brood success (number of offspring per brood) between sperm competition and single-male treatments. We found no significant effect of treatment on female fecundity, suggesting that the previously reported direct benefits of polyandry in this species may be due to factors such as differential maternal effects or differences in the number of inseminated sperm between treatments. Our artificial insemination assay was designed to control both factors. Finally, we determined whether variation in relative paternity was random with respect to male phenotype. Unlike previous work on Trinidadian populations, we found no significant relationship between male sexual ornamentation and sperm competitiveness in the focal population. [ABSTRACT FROM AUTHOR]

1. Carotenoids transferred from mother to offspring may enhance the quality of the offspring. Whether such maternal effects occur in guppies ( Poecilia reticulata) has an important bearing on mate preference evolution. 2. By raising female guppies from birth on different dietary carotenoid levels, we examined the pattern of carotenoid allocation to maternal tissue (skin) vs. eggs. Skin carotenoid content was only weakly affected by carotenoid intake while egg carotenoid content was strongly affected. 3. We then tested for effects of maternal carotenoid intake on several measures of offspring quality, including size and condition at birth, juvenile growth rate, and the size, condition, skin carotenoid content and colouration of mature sons. To test for interactions between maternal and offspring carotenoid intake, broods were split and offspring were reared on one of two carotenoid levels. 4. Offspring carotenoid intake had the expected effects on male colouration, but otherwise we found no evidence that maternal or offspring carotenoid intake influences offspring quality. It remains possible that maternal carotenoids affect offspring fitness parameters that we did not measure or that such effects depend on environmental factors that were absent in our laboratory aquaria. 5. Our review of the literature on maternal carotenoid effects in birds and fishes suggests that such effects may be taxon-specific. Thus, it seems unwarranted to assume that an adaptive trade-off necessarily exists between allocation of carotenoids to eggs vs. maternal tissues. Alternative hypotheses, such as the possibility that eggs provide a means of excreting excess carotenoids, also merit consideration. 6. Our results indirectly support the indicator model of mate preference evolution by casting doubt on an alternative hypothesis that requires females to benefit more from consuming carotenoids than males do. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Hamilton–Zuk hypothesis proposes that females prefer male secondary sexual traits because they are honest indicators of parasite resistance. Despite the attention that this hypothesis has received, its role in sexual selection remains equivocal. This study presents the first field test in guppies of two key predictions of the Hamilton–Zuk hypothesis: (1) that within populations, the most highly ornamented males have the fewest parasites and (2) that among populations, males in high parasite populations have the most conspicuous ornaments. Five hundred male guppies from 19 distinct populations in the Northern Range of Trinidad were inspected for Gyrodactylus parasites and photographed. Eight measures of orange spot ornamentation were used to test the predictions: hue, saturation, lightness, relative area, number, and area-weighted hue, saturation, and lightness. Parasite load had no significant effect on any of these measures. There was also no relationship between orange spot ornamentation and parasite abundance among populations. Guppies from high-predation environments had significantly more parasites, and their orange coloration was lighter and less saturated than that in guppies from low-predation environments. Despite previous lab results, this study found no relationship between parasite load and male orange spot ornamentation. [ABSTRACT FROM AUTHOR]