Parallel and nonparallel behavioural evolution in response to parasitism and predation in Trinidadian guppies

Adaptive plastic responses to metal contamination in a multistress context: a field experiment in fish

Wild populations often differ in their tolerance to environmental stressors, but intraspecific variability is rarely taken into account in ecotoxicology. In addition, plastic responses to multiple stressors have rarely been investigated in realistic field conditions. In this study, we compared the responses to metal contamination of gudgeon populations (Gobio occitaniae) differing in their past chronic exposure to metal contamination, using a reciprocal transplant experiment and an immune challenge mimicking a parasite attack to test for potential effects of multiple stressors across biological levels. We measured fish survival and traits involved in metal bioaccumulation, oxidative stress, immunity, cell apoptosis, and energy management to decipher underpinning physiological mechanisms across biological levels (i.e., gene expression, cell, organism). Fish from the two replicate High Contamination sites had higher survival when transferred into contaminated sites, suggesting a local adaptation to the contaminated site, possibly explained by higher levels of detoxification and antioxidant capacity but with potential higher apoptosis costs compared to their naïve counterparts. We found no evidence of co- or maladaptation to the immune stressor, suggesting no specific costs to face pathogens. In the emerging field of evolutionary ecotoxicology, this study underlines the need to consider intraspecific variability to better understand the effects of pollution in heterogeneous populations.

UDP-Glycosyltransferases in Edible Fungi: Function, Structure, and Catalytic Mechanism

UDP-glycosyltransferases (UGTs) are the most studied glycosyltransferases, and belong to large GT1 family performing the key roles in antibiotic synthesis, the development of bacterial glycosyltransferase inhibitors, and in animal inflammation. They transfer the glycosyl groups from nucleotide UDP-sugars (UDP-glucose, UDP-galactose, UDP-xylose, and UDP-rhamnose) to the acceptors including saccharides, proteins, lipids, and secondary metabolites. The present review summarized the recent of UDP-glycosyltransferases, including their structures, functions, and catalytic mechanism, especially in edible fungi. The future perspectives and new challenges were also summarized to understand of their structure–function relationships in the future. The outputs in this field could provide a reference to recognize function, structure, and catalytic mechanism of UDP-glycosyltransferases for understanding the biosynthesis pathways of secondary metabolites, such as hydrocarbons, monoterpenes, sesquiterpene, and polysaccharides in edible fungi.

Compiling forty years of guppy research to investigate the factors contributing to (non)parallel evolution

Examples of parallel evolution have been crucial for our understanding of adaptation via natural selection. However, strong parallelism is not always observed even in seemingly similar environments where natural selection is expected to favour similar phenotypes. Leveraging this variation in parallelism within well-researched study systems can provide insight into the factors that contribute to variation in adaptive responses. Here we analyse the results of 36 studies reporting 446 average trait values in Trinidadian guppies, Poecilia reticulata, from different predation regimes. We examine how the extent of predator-driven phenotypic parallelism is influenced by six factors: sex, trait type, rearing environment, ecological complexity, evolutionary history, and time since colonization. Analyses show that parallel evolution in guppies is highly variable and weak on average, with only 24.7% of the variation among populations being explained by predation regime. Levels of parallelism appeared to be especially weak for colour traits, and parallelism decreased with increasing complexity of evolutionary history (i.e., when estimates of parallelism from populations within a single drainage were compared to estimates of parallelism from populations pooled between two major drainages). Suggestive - but not significant - trends that warrant further research include interactions between the sexes and different trait categories. Quantifying and accounting for these and other sources of variation among evolutionary 'replicates' can be leveraged to better understand the extent to which seemingly similar environments drive parallel and nonparallel aspects of phenotypic divergence.

An investigation of population variation in maze exploration and its predictors in wild Trinidadian guppies (Poecilia reticulata)

Individuals often face unpredictable and harsh environments, presenting them with novel ecological problems. Behaviour can provide an adaptive response in such conditions and where these conditions vary between populations, we may predict development and evolution to shape differences in behaviour such as exploration, innovation, and learning, as well as other traits. Here, we compared in the wild the maze swimming performance of groups of female guppies from two Trinidadian populations that differ in numerous ecological characteristics, the Upper and Lower Aripo river. Compared to Upper Aripo fish, Lower Aripo fish were slower to complete the maze, our measure of propensity to innovate, and scored lower on a combined measure of activity and exploration. More active-exploratory groups were faster to complete the maze, but only in the Lower Aripo. We found no evidence for learning the maze. Our results suggest that activity-exploratory and innovative propensities can vary between populations, as can predictors of innovation. These findings are consistent with high predation risk shaping decreased activity-exploratory propensities, but further population comparisons are required to reliably determine the drivers of the observed population difference. Our results emphasize that individual and population differences in activity-exploration and innovation can be shaped by numerous factors.

The complex ecology of genitalia: Gonopodium length and allometry in the Trinidadian guppy

Male genitalia present an extraordinary pattern of rapid divergence in animals with internal fertilization, which is usually attributed to sexual selection. However, the effect of ecological factors on genitalia divergence could also be important, especially so in animals with nonretractable genitalia because of their stronger interaction with the surrounding environment in comparison with animals with retractable genitalia. Here, we examine the potential of a pervasive ecological factor (predation) to influence the length and allometry of the male genitalia in guppies. We sampled guppies from pairs of low-predation (LP) and high-predation (HP) populations in seven rivers in Trinidad, and measured their body and gonopodium length. A key finding was that HP adult males do not have consistently longer gonopodia than do LP adult males, as had been described in previous work. However, we did find such divergence for juvenile males: HP juveniles have longer gonopodia than do LP juveniles. We therefore suggest that an evolutionary trend toward the development of longer gonopodia in HP males (as seen in the juveniles) is erased after maturity owing to the higher mortality of mature males with longer gonopodia. Beyond these generalities, gonopodium length and gonopodium allometry were remarkably variable among populations even within a predation regime, thus indicating strong context dependence to their development/evolution. Our findings highlight the complex dynamics of genitalia evolution in Trinidadian guppies.

Bidirectional interactions between host social behaviour and parasites arise through ecological and evolutionary processes

An animal's social behaviour both influences and changes in response to its parasites. Here we consider these bidirectional links between host social behaviours and parasite infection, both those that occur from ecological vs evolutionary processes. First, we review how social behaviours of individuals and groups influence ecological patterns of parasite transmission. We then discuss how parasite infection, in turn, can alter host social interactions by changing the behaviour of both infected and uninfected individuals. Together, these ecological feedbacks between social behaviour and parasite infection can result in important epidemiological consequences. Next, we consider the ways in which host social behaviours evolve in response to parasites, highlighting constraints that arise from the need for hosts to maintain benefits of sociality while minimizing fitness costs of parasites. Finally, we consider how host social behaviours shape the population genetic structure of parasites and the evolution of key parasite traits, such as virulence. Overall, these bidirectional relationships between host social behaviours and parasites are an important yet often underappreciated component of population-level disease dynamics and host-parasite coevolution.

Expansion of frozen hybrids in the guppy ectoparasite, Gyrodactylus turnbulli

Hybridization is one of the major factors contributing to the emergence of highly successful parasites. Hybrid vigour can play an important role in this process, but subsequent rounds of recombination in the hybrid population may dilute its effects. Increased fitness of hybrids can, however, be frozen by asexual reproduction. Here, we identify invasion of a 'frozen hybrid' genotype in natural populations of Gyrodactylus turnbulli, a facultatively sexual ectoparasitic flatworm that causes significant damage to its fish host. We resequenced genomes of these parasites infecting guppies from six Trinidad and Tobago populations, and found surprisingly high discrepancy in genome-wide nucleotide diversity between islands. The elevated heterozygosity on Tobago is maintained by predominantly clonal reproduction of hybrids formed from two diverged genomes. Hybridization has been followed by spread of the hybrids across the island, implying a selective advantage compared with native genotypes. Our results thus highlight that a single outcrossing event may be independently sufficient to cause pathogen expansion.

Direct and indirect effects of multiple environmental stressors on fish health in human-altered rivers

Freshwater fish face multiple challenges in human-altered rivers such as trace metal contamination, temperature increase and parasitism. These multiple stressors could have unexpected interactive effects on fish health due to shared physiological pathways, but few studies investigated this question in wild fish populations. In this study, we compared 16 populations of gudgeon (Gobio occitaniae) distributed along perturbation gradients in human-altered rivers in the South of France. We tested the effects of single and combined stressors (i.e., metal contamination, temperature, parasitism) on key traits linked to fish health across different biological levels using a Structural Equation Modelling approach. Parasitism and temperature alone had limited deleterious effects on fish health. In contrast, fish living in metal-contaminated sites had higher metal bioaccumulation and higher levels of cellular damage in the liver through the induction of an inflammatory response. In addition, temperature and contamination had interactive negative effects on growth. These results suggest that trace metal contamination has deleterious effects on fish health at environmentally realistic concentrations and that temperature can modulate the effects of trace metals on fish growth. With this study, we hope to encourage integrative approaches in realistic field conditions to better predict the effects of natural and anthropogenic stressors on aquatic organisms.

Negative associations between parasite avoidance, resistance and tolerance predict host health in salmonid fish populations

Genetic variation in defence against parasite infections is fundamental for host-parasite evolution. The overall level of defence of a host individual or population includes mechanisms that reduce parasite exposure (avoidance), establishment (resistance) or pathogenicity (tolerance). However, how these traits operate and evolve in concert is not well understood. Here, we investigated genetic variation in and associations between avoidance, resistance and tolerance in a natural host-parasite system. Replicated populations of Atlantic salmon (Salmo salar) and sea trout (an anadromous form of brown trout, Salmo trutta) were raised under common garden conditions and infected with the eye fluke Diplostomum pseudospathaceum. We demonstrate significant genetic variation in the defence traits across host populations and negative associations between the traits, with the most resistant populations showing the weakest avoidance and the lowest infection tolerance. These results are suggestive of trade-offs between different components of defence and possibly underlie the genetic variation in defence traits observed in the wild. Because the three defence mechanisms affect host-parasite evolution in profoundly different ways, we emphasize the importance of studying these traits in concert.

Gene duplications, divergence and recombination shape adaptive evolution of the fish ectoparasite Gyrodactylus bullatarudis

Determining the molecular basis of parasite adaptation to its host is an important component in understanding host-parasite coevolution and the epidemiology of parasitic infections. Here, we investigate short- and long-term adaptive evolution in the eukaryotic parasite Gyrodactylus bullatarudis infecting Caribbean guppies (Poecilia reticulata), by comparing the reference genome of Tobagonian G. bullatarudis with other Platyhelminthes, and by analysing resequenced samples from local Trinidadian populations. At the macroevolutionary timescale, we observed duplication of G-protein and serine proteases genes, which are probably important in host-parasite arms races. Serine protease also showed strong evidence of ongoing, diversifying selection at the microevolutionary timescale. Furthermore, our analyses revealed that a hybridization event, involving two divergent genomes, followed by recombination has dramatically affected the genetic composition of Trinidadian populations. The recombinant genotypes invaded Trinidad and replaced local parasites in all populations. We localized more than 300 genes in regions fixed in local populations for variants of different origin, possibly due to diversifying selection pressure from local host populations. In addition, around 70 genes were localized in regions identified as heterozygous in some, but not all, individuals. This pattern is consistent with a very recent spread of recombinant parasites. Overall, our results are consistent with the idea that recombination between divergent genomes can result in particularly successful parasites.

Evidence for contemporary and historical gene flow between guppy populations in different watersheds, with a test for associations with adaptive traits

In dendritic river systems, gene flow is expected to occur primarily within watersheds. Yet, rare cross-watershed transfers can also occur, whether mediated by (often historical) geological events or (often contemporary) human activities. We explored these events and their potential evolutionary consequences by analyzing patterns of neutral genetic variation (microsatellites) and adaptive phenotypic variation (male color) in wild guppies (Poecilia reticulata) distributed across two watersheds in northern Trinidad. We found the expected signatures of within-watershed gene flow; yet we also inferred at least two instances of cross-watershed gene flow-one in the upstream reaches and one further downstream. The upstream cross-watershed event appears to be very recent (41 ± 13 years), suggesting dispersal via recent flooding or undocumented human-mediated transport. The downstream cross-watershed event appears to be considerably older (577 ± 265 years), suggesting a role for rare geological or climatological events. Alongside these strong signatures of both contemporary and historical gene flow, we found little evidence of impacts on presumably adaptive phenotypic differentiation, except perhaps in the one instance of very recent cross-watershed gene flow. Selection in this system seems to overpower gene flow-at least on the spatiotemporal scales investigated here.

Do replicates of independent guppy lineages evolve similarly in a predator-free laboratory environment?

The Trinidadian guppy is emblematic of parallel and convergent evolution, with repeated demonstrations that predation regime is a driver of adaptive trait evolution. A classic and foundational experiment in this system was conducted by John Endler 40 years ago, where male guppies placed into low-predation environments in the laboratory evolved increased color in a few generations. However, Endler's experiment did not employ the now typical design for a parallel/convergent evolution study, which would employ replicates of different ancestral lineages. We therefore implemented an experiment that seeded replicate mesocosms with small founding populations of guppies originating from high-predation populations of two very different lineages. The different mesocosms were maintained identically, and male guppy color was quantified every four months. After one year, we tested whether male color had increased, whether replicates within a lineage had parallel phenotypic trajectories, and whether the different lineages converged on a common phenotype. Results showed that male guppy color generally increased through time, primarily due to changes in melanic color, whereas the other colors showed inconsistent and highly variable trajectories. Most of the nonparallelism in phenotypic trajectories was among mesocosms containing different lineages. In addition to this mixture of parallelism and nonparallelism, convergence was not evident in that the variance in color among the mesocosms actually increased through time. We suggest that our results reflect the potential importance of high variation in female preference and stochastic processes such as drift and founder effects, both of which could be important in nature.

Gene flow does not prevent personality and morphological differentiation between two blue tit populations

Understanding the causes and consequences of population phenotypic divergence is a central goal in ecology and evolution. Phenotypic divergence among populations can result from genetic divergence, phenotypic plasticity or a combination of the two. However, few studies have deciphered these mechanisms for populations geographically close and connected by gene flow, especially in the case of personality traits. In this study, we used a common garden experiment to explore the genetic basis of the phenotypic divergence observed between two blue tit (Cyanistes caeruleus) populations inhabiting contrasting habitats separated by 25 km, for two personality traits (exploration speed and handling aggression), one physiological trait (heart rate during restraint) and two morphological traits (tarsus length and body mass). Blue tit nestlings were removed from their population and raised in a common garden for up to 5 years. We then compared adult phenotypes between the two populations, as well as trait-specific Q_st and F_st . Our results revealed differences between populations similar to those found in the wild, suggesting a genetic divergence for all traits. Q_st -F_st comparisons revealed that the trait divergences likely result from dissimilar selection patterns rather than from genetic drift. Our study is one of the first to report a Q_st -F_st comparison for personality traits and adds to the growing body of evidence that population genetic divergence is possible at a small scale for a variety of traits including behavioural traits.

Dissolved organic carbon and unimodal variation in sexual signal coloration in mosquitofish: a role for light limitation?

Natural selection plays an important role in the evolution of sexual communication systems. Here, we assess the effect of two well-known selection agents, transmission environment and predation, on interpopulation variation in sexual signals. Our model system is a series of 21 populations of Bahamian mosquitofish subjected to independent variation in optical conditions and predation risk. We show that optically diverse environments, caused by locally variable dissolved organic carbon concentrations, rather than spatial variation in predation, drove divergence in fin coloration (fin redness). We found a unimodal pattern of phenotypic variation along the optical gradient indicating a threshold-type response of visual signals to broad variation in optical conditions. We discuss evolutionary and ecological mechanisms that may drive such a pattern as well as the implications of non-monotonic clines for evolutionary differentiation.

Genome-wide analysis of UDP-glycosyltransferase super family in Brassica rapa and Brassica oleracea reveals its evolutionary history and functional characterization

Background

Glycosyltransferases comprise a highly divergent and polyphyletic multigene family that is involved in widespread modification of plant secondary metabolites in a process called glycosylation. According to conserved domains identified in their amino acid sequences, these glycosyltransferases can be classified into a single UDP-glycosyltransferase (UGT) 1 superfamily.

Results

We performed genome-wide comparative analysis of UGT genes to trace evolutionary history in algae, bryophytes, pteridophytes, and angiosperms; then, we further investigated the expansion mechanisms and function characterization of UGT gene families in Brassica rapa and Brassica oleracea. Using Hidden Markov Model search, we identified 3, 21, 140, 200, 115, 147, and 147 UGTs in Chlamydomonas reinhardtii, Physcomitrella patens, Selaginella moellendorffii, Oryza sativa, Arabidopsis thaliana, B. rapa, and B. oleracea, respectively. Phylogenetic analysis revealed that UGT80 gene family is an ancient gene family, which is shared by all plants and UGT74 gene family is shared by ferns and angiosperms, but the remaining UGT gene families were shared by angiosperms. In dicot lineage, UGTs among three species were classified into three subgroups containing 3, 6, and 12 UGT gene families. Analysis of chromosomal distribution indicates that 98.6 and 71.4% of UGTs were located on B. rapa and B. oleracea pseudo-molecules, respectively. Expansion mechanism analyses uncovered that whole genome duplication event exerted larger influence than tandem duplication on expansion of UGT gene families in B. rapa, and B. oleracea. Analysis of selection forces of UGT orthologous gene pairs in B. rapa, and B. oleracea compared to A. thaliana suggested that orthologous genes in B. rapa, and B. oleracea have undergone negative selection, but there were no significant differences between A. thaliana –B. rapa and A. thaliana –B. oleracea lineages. Our comparisons of expression profiling illustrated that UGTs in B. rapa performed more discrete expression patterns than these in B. oleracea indicating stronger function divergence. Combing with phylogeny and expression analysis, the UGTs in B. rapa and B. oleracea experienced parallel evolution after they diverged from a common ancestor.

Conclusion

We first traced the evolutionary history of UGT gene families in plants and revealed its evolutionary and functional characterization of UGTs in B. rapa, and B. oleracea. This study provides novel insights into the evolutionary history and functional divergence of important traits or phenotype-related gene families in plants.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3844-x) contains supplementary material, which is available to authorized users.