Publications

infections of gyrodactylus bullatarudis and gyrodactylus turnbulli on guppies (poecilia reticulata) in trinidad.	gyrodactylus bullatarudis turnbull, 1956, and gyrodactylus turnbulli harris, 1986, are recorded from guppies (poecilia reticulata) from the northern mountains of trinidad. mixed infections of the 2 species were found at 9 localities. gyrodactylus turnbulli had a predominantly posterior distribution on the fishes, whereas g. bullatarudis was more anteriorly distributed. this is the first record of these species from guppies collected from within their original range.	1992	1403438
slipped-strand mispairing at noncontiguous repeats in poecilia reticulata: a model for minisatellite birth.	the standard slipped-strand mispairing (ssm) model for the formation of variable number tandem repeats (vntrs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for vntr expansion. however, this model is unlikely to explain the formation of vntrs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. phylogenetic reconstruction of the birth of a ...	2000	10880490
rapid evolution of escape ability in trinidadian guppies (poecilia reticulata).	predators are widely assumed to create selection that shapes the evolution of prey escape abilities. however, this assumption is difficult to test directly due to the challenge of recording both predation and its evolutionary consequences in the wild. we examined these events by studying natural and experimental populations of trinidadian guppies, poecilia reticulata, which occur in distinct high-predation and low-predation environments within streams. importantly, in the last two decades severa ...	2002	12038535
sex-biased movement in the guppy (poecilia reticulata).	the movement strategies of birds and mammals are often closely linked to their mating system, but few studies have examined the relationship between mating systems and movement in fishes. we examined the movement patterns of the guppy ( poecilia reticulata) in the arima river of trinidad and predicted that sexual asymmetry in reproductive investment would result in male-biased movement. since male guppies maximize their reproductive success by mating with as many different females as possible, t ...	2003	12856201
multiple mating and sequential mate choice in guppies: females trade up.	the trade-up hypothesis outlines a behavioural strategy that females could use to maximize the genetic benefits to their offspring. the hypothesis proposes that females should be more willing to accept a mate when the new male encountered is a superior genetic source to previous mates. we provide a direct test of the trade-up hypothesis using guppies (poecilia reticulata), and evaluate both behavioural and paternity data. virgin female guppies were presented sequentially with two males of varyin ...	2003	12908984
morphological and enzymatic correlates of aerobic and burst performance in different populations of trinidadian guppies poecilia reticulata.	we examined the mechanistic basis for two whole-animal performance traits, aerobic capacity and burst speed, in six laboratory-reared trinidadian guppy populations from different native drainages with contrasting levels of predation. using within- and between-population variation, we tested whether variation in organs and organ systems (heart, gill and swimming motor mass) and the activities of several enzymes that support locomotion (citrate synthetase, lactate dehydrogenase and myofibrillar at ...	2003	12966062
inbreeding depression and genetic load of sexually selected traits: how the guppy lost its spots.	to date, few studies have investigated the effects of inbreeding on sexually selected traits, although inbreeding depression on such traits can play an important role in the evolution and ecology of wild populations. sexually selected traits such as ornamentation and courtship behaviour may not be primary fitness characters, but selection and dominance coefficients of their mutations will resemble those of traits under natural selection. strong directional selection, for instance, through female ...	2003	14635866
marginal differentiation between the sexual and general carotenoid pigmentation of guppies (poecilia reticulata) and a possible visual explanation.	we present the first detailed analysis of carotenoid pigmentation of the integument of guppies (poecilia reticulata peters), quantifying variation in carotenoid content and composition of wild guppies from three drainages on trinidad (1) between the sexual and general pigmentation of males, (2) between the sexes, and (3) geographically in relation to carotenoid availability. we report that the carotenoid pigments in the integument of guppies are predominantly esters of tunaxanthin. the peak wave ...	2003	14988793
sex-specific effects of carotenoid intake on the immunological response to allografts in guppies (poecilia reticulata).	rarely are the evolutionary origins of mate preferences known, but, recently, the preference of female guppies (poecilia reticulata) for males with carotenoid-based sexual coloration has been linked to a sensory bias that may have originally evolved for detecting carotenoid-rich fruits. if carotenoids enhance the immune systems of these fishes, as has been suggested for other species, this could explain the origin of the attraction to orange fruits as well as the maintenance of the female prefer ...	2004	15002770
predation intensity does not cause microevolutionary change in maximum speed or aerobic capacity in trinidadian guppies (poecilia reticulata peters).	we measured maximal oxygen consumption (vo(2max)) and burst speed in populations of trinidadian guppies (poecilia reticulata) from contrasting high- and low-predation habitats but reared in "common garden" conditions. we tested two hypothesis: first, that predation, which causes rapid life-history evolution in guppies, also impacts locomotor physiology, and second, that trade-offs would occur between burst and aerobic performance. vo(2max) was higher than predicted from allometry, and resting vo ...	2004	15057715
cryptic female preference for colorful males in guppies.	cryptic female choice (cfc) refers to female-mediated processes occurring during or after copulation that result in biased sperm use in favor of preferred or compatible males. despite recent empirical support for this hypothesis, evidence that cfc contributes towards the evolution of male body ornaments, in the same way that precopulatory female choice does, is currently lacking. here, we tested the possibility that cfc selects for increased male attractiveness in the guppy poecilia reticulata, ...	2004	15119451
multiple mating and reproductive skew in trinidadian guppies.	male offspring production in promiscuously mating species is typically more skewed than female offspring production. it is therefore advantageous for males to seek as many mating partners as possible. however, given the documented benefits of polyandry we expect females, as well as males, to mate multiply. we tested these ideas using trinidadian guppies, poecilia reticulata. fishes were collected from the wild, housed in groups of 10 males and 10 females and allowed to reproduce freely over a pe ...	2004	15293853
sexual isolation and extreme morphological divergence in the cumana guppy: a possible case of incipient speciation.	theory predicts that sexual selection can promote the evolution of reproductive isolation and speciation. those cases in which sexual selection has led to speciation should be characterized by significant differentiation in male display traits and correlated female preferences in the absence of post-zygotic isolation, accompanied by little genetic or other morphological differentiation. previous evidence indicates that a cluster of populations of the guppy (poecilia reticulata peters) from cuman ...	2004	15525409
countergradient variation in the sexual coloration of guppies (poecilia reticulata): drosopterin synthesis balances carotenoid availability.	trinidad guppies (poecilia reticulata) are distributed along an environmental gradient in carotenoid availability that limits the carotenoid content of the orange spots of males. the amount of synthetic red pteridines (drosopterins) in the orange spots covaries with the carotenoid content, such that the ratio of the two types of pigments is roughly conserved across streams. carotenoids and drosopterins have different spectral properties and thus the ratio of the two types of pigments affects the ...	2005	15792237
uncoupling the links between male mating tactics and female attractiveness.	because not all females are equally attractive, and because mating reduces the chances of getting further copulations, males should prefer better-quality mates. in this paper, we use the trinidadian guppy (poecilia reticulata) to explore the effects of two non-correlated measures of female quality--size and reproductive status--on male mating decisions. all male guppies employ two alternative mating tactics. we found that large females, particularly those from a high predation site, were the tar ...	2004	15801594
social networks in the guppy (poecilia reticulata).	social network theory is used to elicit details of the social structure of a population of free-ranging guppies, poecilia reticulata. they were found to have a complex and highly structured social network, which exhibited characteristics consistent with the 'small world' phenomenon. stable partner associations between individuals were observed, a finding that fulfils the basic prerequisite for the evolution of reciprocal altruism. the findings are discussed in relation to the ecology and evoluti ...	2004	15801620
carotenoid availability affects the development of a colour-based mate preference and the sensory bias to which it is genetically linked.	regardless of their origins, mate preferences should, in theory, be shaped by their benefits in a mating context. here we show that the female preference for carotenoid colouration in guppies (poecilia reticulata) exhibits a phenotypically plastic response to carotenoid availability, confirming a key prediction of sexual selection theory. earlier work indicated that this mate preference is genetically linked to, and may be derived from, a sensory bias that occurs in both sexes: attraction to ora ...	2005	16191629
the relative influence of natural selection and geography on gene flow in guppies.	two general processes may influence gene flow among populations. one involves divergent selection, wherein the maladaptation of immigrants and hybrids impedes gene flow between ecological environments (i.e. ecological speciation). the other involves geographic features that limit dispersal. we determined the relative influence of these two processes in natural populations of trinidadian guppies (poecilia reticulata). if selection is important, gene flow should be reduced between different select ...	2006	16367829
parallel evolution of the sexes? effects of predation and habitat features on the size and shape of wild guppies.	environmental gradients often lead to the parallel evolution of populations and species. to what extent do such gradients also lead to parallel evolution of the sexes? we used guppies (poecilia reticulata) to examine the parallel and independent (sex-specific) aspects of population divergence in response to predation and habitat features. geometric morphometrics was used to analyse size and shape variation for 1335 guppies from 27 to 31 sites sampled in each of 2 years. body size showed strong p ...	2006	16674571
frequency-dependent survival in natural guppy populations.	the maintenance of genetic variation in traits under natural selection is a long-standing paradox in evolutionary biology. of the processes capable of maintaining variation, negative frequency-dependent selection (where rare types are favoured by selection) is the most powerful, at least in theory; however, few experimental studies have confirmed that this process operates in nature. one of the most extreme, unexplained genetic polymorphisms is seen in the colour patterns of male guppies (poecil ...	2006	16738659
the effects of different predator species on antipredator behavior in the trinidadian guppy, poecilia reticulata.	different types of predators often elicit different antipredator responses in a common type of prey. alternatively, some prey species may adopt a general response, which provides limited protection from many different types of predator. the trinidadian guppy, poecilia reticulata, is faced with a wide range of different predators throughout its range and is known to display varying levels of antipredator behavior depending on the predator assemblage. pike cichlids, crenicichla frenata, are regard ...	2006	16896976
selection by parasites in spate conditions in wild trinidadian guppies (poecilia reticulata).	gyrodactylids are ubiquitous fish parasites and yet, with the notable exception of gyrodactylus salaris, few studies have reported the effect of these parasites on host survival in natural populations. here, we assess the impact of the parasite load of gyrodactylids (g. turnbulli and g. bullatarudis) on the survival and migration of guppies (poecilia reticulata) in their natural habitat of the aripo river in trinidad. the recapture rate of males declined by 19% with every additional parasite, a ...	2007	17307185
the impact of parasites on the life history evolution of guppies (poecilia reticulata): the effects of host size on parasite virulence.	there is large spatial and temporal variation in the gyrodactylus parasite fauna across natural guppy (poecilia reticulata) populations in trinidad. the life history evolution of these fish could be affected differently in the various habitats depending on the local parasite selection pressure. here, we experimentally infected three guppy populations with three gyrodactylid strains in the laboratory and monitored the infection by recording the number of parasites and host mortality in a full fac ...	2007	17561023
experimental studies of evolution in guppies: a model for understanding the evolutionary consequences of predator removal in natural communities.	guppies (poecilia reticulata) in trinidadian streams are found with a diversity of predators in the lower reaches of streams, but few predators in the headwaters. these differences have caused the adaptive evolution of guppy behaviour, morphology, male colouration and life history. waterfalls often serve as barriers to the upstream distribution of predators and/or guppies. such discontinuities make it possible to treat streams like giant test tubes by introducing guppies or predators to small se ...	2008	17725576
multiple paternity and kin recognition mechanisms in a guppy population.	help directed toward kin (nepotism) is an important example of social behaviour. such helping behaviour requires a mechanism to distinguish kin from nonkin. the prevailing kin recognition hypothesis is that when familiarity is a reliable cue of relatedness, other mechanisms of recognition will not evolve. however, when familiarity is an unreliable cue of relatedness, kin recognition by phenotype matching is instead predicted to evolve. here we use genetic markers to show that guppies (poecilia r ...	2007	17850555
inter-population variation in multiple paternity and reproductive skew in the guppy.	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) a ...	2008	18494765
male harassment drives females to alter habitat use and leads to segregation of the sexes.	sexual conflict is ubiquitous across taxa. it often results in male harassment of females for mating opportunities that are costly for females, in some cases reducing reproductive success and increasing mortality. one strategy that females may employ to avoid sexual harassment is to segregate spatially from males. in fact, we do find sexual segregation in habitat use in species that have high levels of sexual conflict; however, the role of sexual harassment in driving such segregation remains po ...	2008	18682356
environmental factors influencing adult sex ratio in trinidadian guppies.	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 ...	2009	19132402
population genetic analysis of microsatellite variation of guppies (poecilia reticulata) in trinidad and tobago: evidence for a dynamic source-sink metapopulation structure, founder events and population bottlenecks.	riverine fish populations are traditionally considered to be highly structured and subject to strong genetic drift. here, we use microsatellites to analyse the population structure of the guppy (poecilia reticulata), focussing on the headwater floodplain area of the caroni drainage in trinidad. we also analyse the population genetics of guppies in the northern drainage in trinidad, a habitat characterized by rivers flowing directly into the sea, and a small isolated population in tobago. upland ...	2009	19210594
experimental evaluation of evolution and coevolution as agents of ecosystem change in trinidadian streams.	evolution has been shown to be a critical determinant of ecological processes in some systems, but its importance relative to traditional ecological effects is not well known. in addition, almost nothing is known about the role of coevolution in shaping ecosystem function. here, we experimentally evaluated the relative effects of species invasion (a traditional ecological effect), evolution and coevolution on ecosystem processes in trinidadian streams. we manipulated the presence and population- ...	2009	19414475
selection at the mhc class iib locus across guppy (poecilia reticulata) populations.	the highly diverse genes of the major histocompatibility complex (mhc) are important in the adaptive immune system and are expected to be under selection from pathogens. thus, the mhc genes provide an exceptional opportunity to investigate patterns of selection within and across populations. in this study, we analyzed genetic variation at the mhc class iib gene and six microsatellite loci across 10 populations of guppies (poecilia reticulata) in the northern range of trinidad. we found a high le ...	2010	19639010
predicting the direction of ornament evolution in trinidadian guppies (poecilia reticulata).	sexual selection is thought to be opposed by natural selection such that ornamental traits express a balance between these two antagonistic influences. phenotypic variation among populations may indicate local shifts in this balance, or that different stable 'solutions' are possible, but testing these alternatives presents a major challenge. in the guppy (poecilia reticulata), a small freshwater fish with male-limited ornamental coloration, these issues can be addressed by transplanting fish amo ...	2009	19776075
spatiotemporal variation in linear natural selection on body color in wild guppies (poecilia reticulata).	we conducted 10 mark-recapture experiments in natural populations of trinidadian guppies to test hypotheses concerning the role of viability selection in geographic patterns of male color variation. previous work has reported that male guppies are more colorful in low-predation sites than in high-predation sites. this pattern of phenotypic variation has been theorized to reflect differences in the balance between natural (viability) selection that disfavors bright male color (owing to predation) ...	2010	20067520
genome-wide single nucleotide polymorphisms reveal population history and adaptive divergence in wild guppies.	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 availabl ...	2010	20149094