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The presence of small RNAs in sperm is a relatively recent discovery and little is currently known about their importance and functions. Environmental changes including social conditions and dietary manipulations are known to affect the... more
The presence of small RNAs in sperm is a relatively recent discovery and little is currently known about their importance and functions. Environmental changes including social conditions and dietary manipulations are known to affect the composition and expression of some small RNAs in sperm and may elicit a physiological stress response resulting in an associated change in gamete miRNA profiles. Here, we tested how microRNA profiles in sperm are affected by variation in both sexual selection and dietary regimes in Drosophila melanogaster selection lines. The selection lines were exposed to standard versus low yeast diet treatments and three different population sex ratios (male‐biased, female‐biased, or equal sex) in a full‐factorial design. After 38 generations of selection, all males were maintained on their selected diet and in a common garden male‐only environment prior to sperm sampling. We performed transcriptome analyses on miRNAs in purified sperm samples. We found 11 differentially expressed miRNAs with the majority showing differences between male‐ and female‐biased lines. Dietary treatment only had a significant effect on miRNA expression levels in interaction with sex ratio. Our findings suggest that long‐term adaptation may affect miRNA profiles in sperm and that these may show varied interactions with short‐term environmental changes.
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Transposable elements (TEs) are mobile DNA sequences that are able to copy themselves within a host genome. They were initially characterized as selfish genes because of documented or presumed costs to host fitness, but it has become... more
Transposable elements (TEs) are mobile DNA sequences that are able to copy themselves within a host genome. They were initially characterized as selfish genes because of documented or presumed costs to host fitness, but it has become increasingly clear that not all TEs reduce host fitness. A good example of TEs benefiting hosts is seen with insecticide resistance, where in a number of cases, TE insertions near specific genes confer resistance to these man-made products. This is particularly true of Accord and associated TEs in Drosophila melanogaster and Doc insertions in Drosophila simulans. The first of these insertions also has sexually antagonistic fitness effects in the absence of insecticides, and although the magnitude of this effect depends on the genetic background in which Accord finds itself, this represents an excellent example of intralocus sexual conflict where the precise allele involved is well characterized. We discuss this finding and the role of TEs in insecticide resistance. We also highlight areas for further research, including the need for surveys of the prevalence and fitness consequences of the Doc insertion and how Drosophila can be used as models to investigate resistance in pest species.
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Data collected from watching videos of behavioural assays using programs JWatcher + Video and BORIS. We analysed the data in R
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Stronger condition-dependence in sexually selected traits is well-documented, but how this relationship is established remains unknown. Moreover, resource availability can shape responses to sexual selection, but resource effects on the... more
Stronger condition-dependence in sexually selected traits is well-documented, but how this relationship is established remains unknown. Moreover, resource availability can shape responses to sexual selection, but resource effects on the relationship between sexual selection and condition-dependence are also unknown. In this study, we directly test the hypotheses that sexual selection drives the evolution of stronger-condition-dependence and that resource availability affects the outcome, by evolving fruit flies (Drosophila melanogaster) under relatively strong or weak sexual selection (through varied sex ratios) and at resource-poor or resource-rich adult diets. We then experimentally manipulated condition via developmental diet and assessed condition-dependence in adult morphology, behavior, and reproduction. We observed stronger condition-dependence in female size in male-biased populations and in female ovariole production in resource-limited populations. However, we found no evi...
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Supplementary Methods and Figures
Model outputs for all models in main text
Sexual dimorphism for lifespan (SDL) is widespread, but poorly understood. A leading hypothesis, which we test here, is that strong SDL can reduce sexual conflict, by allowing each sex to maximize its sex-specific fitness. We used... more
Sexual dimorphism for lifespan (SDL) is widespread, but poorly understood. A leading hypothesis, which we test here, is that strong SDL can reduce sexual conflict, by allowing each sex to maximize its sex-specific fitness. We used replicated experimental evolution lines of the fruit fly, <i>Drosophila melanogaster</i>, which had been maintained for over 360 generations on either unpredictable 'Random' or predictable 'Regular' feeding regimes. This evolutionary manipulation of feeding regime led to robust, enhanced SDL in Random over control, Regular lines. Enhanced SDL was associated with a significant increase in the fitness of focal males, tested with wild-type (WT) females. This was due to sex-specific changes to male life history, manifested as increased early reproductive output and reduced survival. In contrast, focal female fitness, tested with WT males, did not differ across regimes. Hence increased SDL was associated with a reduction in sexual co...
Sexual dimorphism for lifespan (SDL) is widespread, but poorly understood. A leading hypothesis, which we test here, is that strong SDL can reduce sexual conflict by allowing each sex to maximize its sex-specific fitness. We used... more
Sexual dimorphism for lifespan (SDL) is widespread, but poorly understood. A leading hypothesis, which we test here, is that strong SDL can reduce sexual conflict by allowing each sex to maximize its sex-specific fitness. We used replicated experimental evolution lines of the fruit fly, Drosophila melanogaster, which had been maintained for over 360 generations on either unpredictable ‘Random’ or predictable ‘Regular’ feeding regimes. This evolutionary manipulation of feeding regime led to robust, enhanced SDL in Random over control, Regular lines. Enhanced SDL was associated with a significant increase in the fitness of focal males, tested with wild-type (WT) females. This was due to sex-specific changes to male life history, manifested as increased early reproductive output and reduced survival. In contrast, focal female fitness, tested with WT males, did not differ across regimes. Hence increased SDL was associated with a reduction in sexual conflict, which increased male fitness and maintained fitness in females. Differences in SDL were not associated with developmental time or developmental survival. Overall, the results showed that the expression of enhanced SDL, resulting from experimental evolution of feeding regimes, was associated with male-specific changes in life history, leading to increased fitness and reduced sexual conflict
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Animals can exhibit remarkable reproductive plasticity in response to their social surroundings, with profound fitness consequences. The study of such plasticity in females, particularly in same-sex interactions, has been severely... more
Animals can exhibit remarkable reproductive plasticity in response to their social surroundings, with profound fitness consequences. The study of such plasticity in females, particularly in same-sex interactions, has been severely neglected. Here we measured the impact of variation in the pre-mating social environment on reproductive success in females and tested the underlying mechanisms involved. We used the Drosophila melanogaster model system to test the effect of varying female group size prior to mating and deployed physical and genetic methods to manipulate the perception of different social cues and sensory pathways. We found that socially isolated females were significantly more likely to retain unfertilised eggs before mating, but to show the opposite pattern and lay significantly more fertilised eggs in the 24h after mating, in comparison to grouped females. More than 48h of exposure to other females was necessary for this socially-induced plasticity to be expressed. Neit...
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Understanding the evolution and spread of insecticide resistance requires knowing the relative fitness of resistant organisms. In the absence of insecticides, resistance is predicted to be costly. The Drosophila melanogaster DDT... more
Understanding the evolution and spread of insecticide resistance requires knowing the relative fitness of resistant organisms. In the absence of insecticides, resistance is predicted to be costly. The Drosophila melanogaster DDT resistance allele (DDT-R) is associated with a male mating cost. This could be because resistant males are generally smaller, but DDT-R may also alter courtship behaviours. Here we tested for body size and courtship effects of DDT-R on mating success in competitive and non-competitive mating trials respectively. We also assessed relative aggression in resistant and susceptible males because aggression can also influence mating success. While the effect of DDT-R on male size partly contributed to reduced mating success, resistant males also had lower rates of courtship and were less aggressive than susceptible males. These differences contribute to the observed DDT-R mating costs. Additionally, these pleiotropic effects of DDT-R are consistent with the histor...
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Aggressive behaviours are among the most striking displayed by animals, and aggression strongly impacts fitness in many species. Aggression varies plastically in response to the social environment, but we lack direct tests of how... more
Aggressive behaviours are among the most striking displayed by animals, and aggression strongly impacts fitness in many species. Aggression varies plastically in response to the social environment, but we lack direct tests of how aggression evolves in response to intra-sexual competition. We investigated how aggression in both sexes evolves in response to the competitive environment, using populations of Drosophila melanogaster that we experimentally evolved under female-biased, equal, and male-biased sex ratios. We found that after evolution in a female-biased environment—with less male competition for mates—males fought less often on food patches, although the total frequency and duration of aggressive behaviour did not change. In females, evolution in a female-biased environment—where female competition for resources is higher—resulted in more frequent aggressive interactions among mated females, along with a greater increase in post-mating aggression. These changes in female agg...
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Ecological assessment entails the application of ecological knowledge to environmental problem-solving. Resting on a systems approach, it considers problems from a multi-disciplinary perspective including environmental conditions and... more
Ecological assessment entails the application of ecological knowledge to environmental problem-solving. Resting on a systems approach, it considers problems from a multi-disciplinary perspective including environmental conditions and ecological systems, and by including humans as an integral part of ecosystems, logically includes socioeconomic systems. Water resources and aquatic biodiversity are intimately interrela ted and interdependent. Both provide a wide range of functions and have intrinsic value as well as provide for the sustenance of human populations. Degradation of water quality, depletion of water resources and loss of aquatic biodiversity are prominent features of the environmental landscape requiring urgent attention at global and national scales. Recent research on the rivers of Trinidad and Tobago forms the basis of an ecological assessment of these rivers and their watersheds. Over a seven year period, comprehensive studies were undertaken on the fish, decapod crus...
Research Interests: Geography, Water quality, Invasive Species, Biodiversity Conservation, System Approach, and 12 moreHeavy Metal, Trinidad and Tobago, Knowledge base, Human health, River Basin, Tool Development, Environmental Conditions, Water Resource, Water Quality, Biological Monitoring, Service Provider, and Environmental Problem
In D. melanogaster, resistance to DDT is conferred by the upregulation of a cytochrome P450 enzyme, CYP6G1. Resistant flies have tandemly duplicated Cyp6g1 alleles that possess the LTR (Long Terminal Repeat) of an Accord retrotransposon... more
In D. melanogaster, resistance to DDT is conferred by the upregulation of a cytochrome P450 enzyme, CYP6G1. Resistant flies have tandemly duplicated Cyp6g1 alleles that possess the LTR (Long Terminal Repeat) of an Accord retrotransposon inserted in the cis-regulatory region, 291bp upstream of the transcription start site. This DDT resistance allele (DDT-R) has been shown to have pleiotropic fitness benefits for female flies in at least one genetic background and with evidence of sexually antagonistic selection at this locus. In this thesis, I first review the role of transposable elements in conferring insecticide resistance and the evidence to date regarding the pleiotropic effects of DDT-R in D. melanogaster. By conducting life history and behavioural tests on flies of two genetic backgrounds I examine the sex-specific effects of expressing DDT-R in the absence of DDT. Finally I develop a single locus population genetics model based on these sex-specific effects and test the model...
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Based on the literature reviewed, there are at least two species of freshwater mussels in Trinidad and the range for both Anodontites and Mycetopoda is very limited. Our collections and the appearance of the shells of these two species... more
Based on the literature reviewed, there are at least two species of freshwater mussels in Trinidad and the range for both Anodontites and Mycetopoda is very limited. Our collections and the appearance of the shells of these two species suggest that they are still present in our environment, but the current rate of land use for various forms of development is placing these species at risk of extinction in Trinidad. The Poole/Ortoire region lies within the Central Block oil reserve, the Caparo sites are within impacted range of the proposed Caparo/Mamoral dam and the Plum Mitan/Nariva area is presently under oil exploration and heavy agricultural use. With this in mind, further investigations would be undertaken to look at the present distribution of these species before there is a total loss of habitat.
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INTRODUCTION Heavy metals are simply defined as metals with high atomic number for example, lead, copper or chromium. They are considered important environmental pollutants because they are toxic to plants and animals in low... more
INTRODUCTION Heavy metals are simply defined as metals with high atomic number for example, lead, copper or chromium. They are considered important environmental pollutants because they are toxic to plants and animals in low concentrations and can be accumulated and transferred along a food chain. They occur naturally, however many anthropogenic activities such as quarrying and combustion of fossil fuels, increase the rate of release of these pollutants to the natural environment.
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Estuaries are highly productive aquatic systems. Five rivers in Guayaguayare Bay were sampled for fish by seining. During the survey, 25 species in 21 families representing eight orders were collected or observed. The most abundant... more
Estuaries are highly productive aquatic systems. Five rivers in Guayaguayare Bay were sampled for fish by seining. During the survey, 25 species in 21 families representing eight orders were collected or observed. The most abundant species, Mugil curema , accounted for 56% of total catch. For the majority of species encountered, the size-frequency distributions revealed populations comprised largely of subadults and juveniles. Dissimilarity of inventories between sites may be related to a combination of biotic and abiotic factors. It is proposed that each species is maintained over the entire coastline by a series of incompletely independent populations and that these estuaries collectively represent one large metacommunity.
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Over the last decade, we have sampled various rivers across Trinidad using multiple techniques including seining and cast netting. This allowed us to compile a large database which includes the distribution of Trinidad’s freshwater fish... more
Over the last decade, we have sampled various rivers across Trinidad using multiple techniques including seining and cast netting. This allowed us to compile a large database which includes the distribution of Trinidad’s freshwater fish species. The following report summarizes our findings for the changed distribution for nine species of fish native to Trinidad. Our findings also indicate a new fish species ( Trichogaster trichopterus ) record for Trinidad. Key words: Ancistrus, Awaous, Callichthys callichthys, Dormitator maculatus, Eleotris pisonis, Erythrinus erythrinus, Gasteropelecus sternicla, Gymnotus carapo, Triportheus elongatus, Trichogaster trichopterus, distribution, Trinidad.
The satyr of Greek mythology was half‐man, half‐goat, with an animal persona signifying immoderate sexual appetites. In biology, satyrization is the disruption of reproduction in matings between closely related species. Interestingly, its... more
The satyr of Greek mythology was half‐man, half‐goat, with an animal persona signifying immoderate sexual appetites. In biology, satyrization is the disruption of reproduction in matings between closely related species. Interestingly, its effects are often reciprocally asymmetric, manifesting more strongly in one direction of heterospecific mating than the other. Heterospecific matings are well known to result in female fitness costs due to the production of sterile or inviable hybrid offspring and can also occur due to reduced female sexual receptivity, lowering the likelihood of any subsequent conspecific matings. Here we investigated the costs and mechanisms of satyrization in the Drosophila melanogaster species subgroup of fruitflies. The results showed that D. simulans females experienced higher fitness costs from a loss of remating opportunities due to significantly reduced post‐mating sexual receptivity than did D. melanogaster females, as a result of reciprocal heterospecific matings. Reciprocal tests of the effects of male reproductive accessory gland protein (Acp) injections on female receptivity in pairwise comparisons between D. melanogaster and five other species within the melanogaster species subgroup revealed significant post‐mating receptivity asymmetries. This was due to variation in the effects of heterospecific Acps within species with which D. melanogaster can mate, and significant but nonasymmetric Acp effects in species with which it cannot. We conclude that asymmetric satyrization due to post‐mating effects of Acps may be common among diverging and hybridising species. The findings are of interest in understanding the evolution of reproductive isolation and species divergence.
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Male reproductive phenotypes can evolve in response to the social and sexual environment. The expression of many such phenotypes may also be plastic within an individual's lifetime. For example, male Drosophila melanogaster show... more
Male reproductive phenotypes can evolve in response to the social and sexual environment. The expression of many such phenotypes may also be plastic within an individual's lifetime. For example, male Drosophila melanogaster show significantly extended mating duration following a period of exposure to conspecific male rivals. The costs and benefits of reproductive investment, and plasticity itself, can be shaped by the prevailing sociosexual environment and by resource availability. We investigated these ideas using experimental evolution lines of D. melanogaster evolving under three fixed sex ratios (high, medium, and low male‐male competition) on either rich or poor adult diets. We found that males evolving in high‐competition environments evolved longer mating durations overall. In addition, these males expressed a novel type of plastic behavioral response following exposure to rival males: they both significantly reduced and showed altered courtship delivery, and exhibited si...
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Aggressive behaviours are among the most striking displayed by animals, and aggression strongly impacts fitness in many species. Aggression varies plastically in response to the social environment, but we lack direct tests of how... more
Aggressive behaviours are among the most striking displayed by animals, and aggression strongly impacts fitness in many species. Aggression varies plastically in response to the social environment, but we lack direct tests of how aggression evolves in response to intra-sexual competition. We investigated how aggression in both sexes evolves in response to the competitive environment, using populations of Drosophila melanogaster that we experimentally evolved under female-biased, equal, and male-biased sex ratios. We found that after evolution in a female-biased environment—with less male competition for mates—males fought less often on food patches, although the total frequency and duration of aggressive behaviour did not change. In females, evolution in a female-biased environment—where female competition for resources is higher—resulted in more frequent aggressive interactions among mated females, along with a greater increase in post-mating aggression. These changes in female agg...
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Estuaries are highly productive aquatic systems. Five rivers in Guayaguayare Bay were sampled for fish and decapods by seining. During the survey, 33 species in 27 families representing nine orders were collected or observed. The most... more
Estuaries are highly productive aquatic systems. Five rivers in Guayaguayare Bay were sampled for fish and decapods by seining. During the survey, 33 species in 27 families representing nine orders were collected or observed. The most abundant species Mugil curema accounted for 54% of total catch. For the majority of species encountered, the size-frequency distributions revealed populations comprised largely of subadults and juveniles. Populations found within each small estuarine habitat are maintained over the entire coastline by a series of incompletely independent populations, which together can be termed metapopulations.
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Freshwater mussels belong to the family Unionidae (Order Paleoheterodonta, Suborder Unionidea). This family also includes some brackish water species. Their substrate requirements are quite varied and range from soft clays to pebbles and... more
Freshwater mussels belong to the family Unionidae (Order Paleoheterodonta, Suborder Unionidea). This family also includes some brackish water species. Their substrate requirements are quite varied and range from soft clays to pebbles and cobble. The family has a worldwide distribution. Members of the Unionidae family are filter feeders and this makes them quite susceptible to bio-accumulation of many residual compounds such as heavy metals. Pathogenic bacteria also form pools of infections in these filter feeders. Nonetheless, they are very important to the ecology of a river for several reasons. Firstly, the overall filtering effect of colonies decreases turbidity in the river. Secondly, because of their high sensitivity to pollution, they are used worldwide as bio-indicators. Finally, their life cycles are complex and some species rely on host fish to support the newly hatched larvae (Cummings et al. 1997). The shells of freshwater mussels were found during May, 2007 at three sepa...
Over the last decade, we have sampled various rivers across Trinidad using multiple techniques including seining and cast netting. This allowed us to compile a large database which includes the distribution of Trinidad's freshwater... more
Over the last decade, we have sampled various rivers across Trinidad using multiple techniques including seining and cast netting. This allowed us to compile a large database which includes the distribution of Trinidad's freshwater fish species. The following report summarizes our findings for the changed distribution for nine species of fish native to Trinidad. Our findings also indicate a new fish species (Trichogaster trichopterus) record for Trinidad. INTRODUCTION The three most recent accounts of local freshwater fish distributions include Kenny (1995), Phillip (1998), and Ramnarine and Phillip (2001). Distributions outlined by Kenny (1995) had been based on extensive sampling over almost two decades prior to publication, while the distributions indicated in the latter two works draw from Phillip's national survey which spanned the years 1996-1997 and covered 22 sites across Trinidad. Kenny (1995) divided the drainage systems and the associated ichthyofauna of Trinidad ...