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Data from: Plasticity in gene transcription explains the differential performance of two invasive fish species
Wellband, Kyle W.; Heath, Daniel D. — 2017-01-31 Phenotypic plasticity buffers organisms from environmental change and is hypothesized to aid the initial establishment of non-indigenous species in novel environments and post-establishment range expansion. The genetic mechanisms that underpin phenotypically plastic traits are generally poorly characterized; however, there is strong evidence that modulation of gene transcription is an important component of these responses. Here we use RNA sequencing to examine the transcriptional basis of temperature tolerance for round and tubenose goby, two non-indigenous fish species that differ dramatically in the extent of their Great Lakes invasions despite similar invasion dates. We used generalized linear models of read count data to compare gene transcription responses of organisms exposed to increased and decreased water temperature from those at ambient conditions. We identify greater response in the magnitude of transcriptional changes for the more successful round goby compared with the less successful tubenose goby. Round goby transcriptional responses reflect alteration of biological function consistent with adaptive responses to maintain or regain homeostatic function in other species. In contrast, tubenose goby transcription patterns indicate a response to stressful conditions, but the pattern of change in biological functions do not match those expected for a return to homeostatic status. Transcriptional plasticity plays an important role in the acute thermal tolerance for these species; however, the impaired response to stress we demonstrate in the tubenose goby may contribute to their limited invasion success relative to the round goby. Transcriptional profiling allows the simultaneous assessment of the magnitude of transcriptional response as well as the biological functions involved in the response to environmental stress and is thus a valuable approach for evaluating invasion potential.
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Data from: Benefits of turbid river plume habitat for Lake Erie yellow perch (Perca flavescens) recruitment determined by juvenile to larval genotype assignment
Carreon-Martinez, Lucia B.; Walter, Ryan P.; Johnson, Timothy B.; Ludsin, Stuart A.; Heath, Daniel D. — 2016-04-09 Nutrient-rich, turbid river plumes that are common to large lakes and coastal marine ecosystems have been hypothesized to benefit survival of fish during early life stages by increasing food availability and (or) reducing vulnerability to visual predators. However, evidence that river plumes truly benefit the recruitment process remains meager for both freshwater and marine fishes. Here, we use genotype assignment between juvenile and larval yellow perch (Perca flavescens) from western Lake Erie to estimate and compare recruitment to the age-0 juvenile stage for larvae residing inside the highly turbid, south-shore Maumee River plume versus those occupying the less turbid, more northerly Detroit River plume. Bayesian genotype assignment of a mixed assemblage of juvenile (age-0) yellow perch to putative larval source populations established that recruitment of larvae was higher from the turbid Maumee River plume than for the less turbid Detroit River plume during 2006 and 2007, but not in 2008. Our findings add to the growing evidence that turbid river plumes can indeed enhance survival of fish larvae to recruited life stages, and also demonstrate how novel population genetic analyses of early life stages can contribute to determining critical early life stage processes in the fish recruitment process.
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Data from: Environmental and genetic determinants of transcriptional plasticity in Chinook salmon
Wellband, Kyle W.; Heath, John W.; Heath, Daniel D. — 2017-09-14 Variation in gene transcription is widely believed to be the mechanistic basis of phenotypically plastic traits; however, comparatively little is known about the inheritance patterns of transcriptional variation that would allow us to predict its response to selection. In addition, acclimation to different environmental conditions influences acute transcriptional responses to stress and it is unclear if these effects are heritable. To address these gaps in knowledge, we assayed levels of messenger RNA for 14 candidate genes at rest and in response to a 24-hour confinement stress for 72 half-sib families of Chinook salmon reared in two different environments (hatchery and semi-natural stream channel). We observed extensive plasticity for mRNA levels of metabolic and stress response genes and demonstrated that mRNA-level plasticity due to rearing environment affects mRNA-level plasticity in response to stress. These effects have important implications for natural populations experiencing multiple stressors. We identified genotype-by-environment interactions for mRNA levels that were dominated by maternal-effects; however, mRNA level response to challenge also exhibited a non-additive genetic basis. Our results indicate that while plasticity for mRNA-levels can evolve, predicting the outcome of selection will be difficult. The inconsistency in genetic architecture among treatment groups suggests there is considerable cryptic genetic variation for gene expression.
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Data from: Inbreeding effects on gene-specific DNA methylation among tissues of Chinook salmon
Venney, Clare J.; Johansson, Mattias L.; Heath, Daniel D. — 2016-07-29 Inbreeding depression is the loss of fitness resulting from the mating of genetically related individuals. Traditionally, the study of inbreeding depression focused on genetic effects, although recent research has identified DNA methylation as also having a role in inbreeding effects. Since inbreeding depression and DNA methylation change with age and environmental stress, DNA methylation is a likely candidate for the regulation of genes associated with inbreeding depression. Here, we use a targeted, multigene approach to assess methylation at 22 growth-, metabolic-, immune- and stress-related genes. We developed PCR-based DNA methylation assays to test the effects of intense inbreeding on intragenic gene-specific methylation in inbred and outbred Chinook salmon. Inbred fish had altered methylation at three genes, CK-1, GTIIBS and hsp70, suggesting that methylation changes associated with inbreeding depression are targeted to specific genes and are not whole-genome effects. While we did not find a significant inbreeding by age interaction, we found that DNA methylation generally increases with age, although methylation decreased with age in five genes, CK-1, IFN-ɣ, HNRNPL, hsc71 and FSHb, potentially due to environmental context and sexual maturation. As expected, we found methylation patterns differed among tissue types, highlighting the need for careful selection of target tissue for methylation studies. This study provides insight into the role of epigenetic effects on ageing, environmental response and tissue function in Chinook salmon and shows that methylation is a targeted and regulated cellular process. We provide the first evidence of epigenetically based inbreeding depression in vertebrates.
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Data from: Dispersal influences genetic and acoustic spatial structure for both males and females in a tropical songbird
Graham, Brendan A.; Heath, Daniel D.; Mennill, Dan J.; Mennill, Daniel J. — 2018-09-22 1. Animals exhibit diverse dispersal strategies, including sex-biased dispersal, a phenomenon common in vertebrates. Dispersal influences the genetic structure of populations as well as geographic variation in phenotypic traits. Patterns of spatial genetic structure and geographic variation may vary between the sexes whenever males and females exhibit different dispersal behaviours. 2. Here, we examine dispersal, spatial genetic structure, and spatial acoustic structure in Rufous-and-white Wrens, a year-round resident tropical bird. Both sexes sing in this species, allowing us to compare acoustic variation between males and females, and examine the relationship between dispersal and song sharing for both sexes. 3. Using a long-term dataset collected over an 11-year period, we used banding data and molecular genetic analyses to quantify natal and breeding dispersal distance in Rufous-and-white Wrens. We quantified song-sharing and examined whether sharing varied with dispersal distance, for both males and females. 4. Observational data and molecular genetic analyses indicate that dispersal is female-biased. Females dispersed farther from natal territories than males, and more often between breeding territories than males. Furthermore, females showed no significant spatial genetic structure, consistent with expectations, whereas males showed significant spatial genetic structure. Overall, natal dispersal appears to have more influence than breeding dispersal on spatial genetic structure and spatial acoustic structure, given that the majority of breeding dispersal events resulted in individuals moving only short distances. 5. Song sharing between pairs of same-sex animals decreases with the distance between their territories for both males and females, although males exhibited significantly greater song-sharing than females. 6. Lastly, we measured the relationship between natal dispersal distance and song sharing. We found that sons shared fewer songs with their fathers the farther they dispersed from their natal territories, but that song sharing between daughters and mothers was not significantly correlated with natal dispersal distance. 7. Our results reveal cultural differences between the sexes, suggesting a relationship between culture and sex-biased dispersal
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Data from: Environmental DNA detection of rare and invasive fish species in two Great Lakes tributaries
Balasingham, Katherine D.; Walter, Ryan P.; Mandrak, Nicholas E.; Heath, Daniel D. — 2017-10-26 The extraction and characterization of DNA from aquatic environmental samples offers an alternative, non-invasive approach for the detection of rare species. Environmental DNA, coupled with PCR and next-generation sequencing (“metabarcoding”), has proven to be very sensitive for the detection of rare aquatic species. Our study used a custom designed group-specific primer set and next-generation sequencing for the detection of three species at risk; (Eastern Sand Darter, Ammocrypta pellucida; Northern Madtom, Noturus stigmosus; and Silver Shiner, Notropis photogenis), one invasive species (Round Goby, Neogobius melanostomus) and an additional 78 native species from two large Great Lakes tributary rivers in southern Ontario, Canada; the Grand River and the Sydenham River. Out of 82 fish species detected in both rivers using capture-based and eDNA methods, our eDNA method detected 86.2% and 72.0% of the fish species in the Grand River and the Sydenham River, respectively, which included our four target species. Our analyses also identified significant positive and negative species co-occurrence patterns between our target species and other identified species. Our results demonstrate that eDNA metabarcoding that targets the fish community as well as individual species of interest provides a better understanding of factors affecting the target species spatial distribution in an ecosystem than possible with only target species data. Additionally, eDNA is easily implemented as an initial survey tool, or alongside capture-based methods, for improved mapping of species distribution patterns.
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Data from: Red and white Chinook salmon: genetic divergence and mate choice
Dryad
Lehnert, Sarah J.; Pitcher, Trevor E.; Devlin, Robert H.; Heath, Daniel D. — 2016-01-25 Chinook salmon (Oncorhynchus tshawytscha) exhibit extreme differences in coloration of skin, eggs and flesh due to genetic polymorphisms affecting carotenoid deposition, where colour can range from white to bright red. A sympatric population of red and white Chinook salmon occurs in the Quesnel River, British Columbia, where frequencies of each phenotype are relatively equal. In our study, we examined evolutionary mechanisms responsible for the maintenance of the morphs, where we first tested whether morphs were reproductively isolated using microsatellite genotyping, and second, using breeding trials in seminatural spawning channels, we tested whether colour assortative mate choice could be operating to maintain the polymorphism in nature. Next, given extreme difference in carotenoid assimilation and the importance of carotenoids to immune function, we examined mate choice and selection between colour morphs at immune genes (major histocompatibility complex genes: MHC I-A1 and MHC II-B1). In our study, red and white individuals were found to interbreed, and under seminatural conditions, some degree of colour assortative mate choice (71% of matings) was observed. We found significant genetic differences at both MHC genes between morphs, but no evidence of MHC II-B1-based mate choice. White individuals were more heterozygous at MHC II-B1 compared with red individuals, and morphs showed significant allele frequency differences at MHC I-A1. Although colour assortative mate choice is likely not a primary mechanism maintaining the polymorphisms in the population, our results suggest that selection is operating differentially at immune genes in red and white Chinook salmon, possibly due to differences in carotenoid utilization.
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Data from: Redder isn’t always better: cost of carotenoids in Chinook salmon eggs
Dryad
Lehnert, Sarah J.; Devlin, Robert H.; Pitcher, Trevor E.; Semeniuk, Christina A.D.; Heath, Daniel D. — 2016-11-30 Carotenoids provide animals with many fitness benefits through increased mating success, immune function, gamete quality, and antioxidant capacity. Despite these benefits, carotenoids are not utilized equally by all animals, implying trade-offs associated with the pigments; although, few studies have quantified fitness costs of carotenoid pigmentation. Salmon are known for their conspicuous red coloration; however, amongst Chinook salmon (Oncorhynchus tshawytscha), a natural genetic color polymorphism exists (red and white morphs) which results in carotenoid-based color differences in eggs and other tissues. Although the fitness benefit of egg carotenoid content on egg incubation survival has been demonstrated, carotenoid pigmentation also results in highly visible eggs vulnerable to predation. Therefore, although white Chinook salmon eggs experience costs in terms of viability, a potential benefit in terms of reduced predation could help explain the maintenance of the polymorphism. Here, using red and white eggs from wild Chinook salmon, we show that increased carotenoid content of salmon eggs leads to greater predation risk. We found that 2 populations of wild-type rainbow trout (O. mykiss; an ecologically relevant predator) showed a significant bias for red eggs over white eggs under choice experiments, where red eggs were consumed first twice as often and significantly faster than white eggs. Our study suggests that trade-offs between red and white Chinook salmon during the egg stage provide an evolutionary mechanism promoting the maintenance of the unique Chinook salmon color polymorphism in nature, while also, for the first time, demonstrating a direct fitness cost of carotenoids in salmon.
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Data from: Sex-biased genetic component distribution among populations: additive genetic and maternal contributions to phenotypic differences among populations of Chinook salmon
Dryad
Aykanat, Tutku; Bryden, Colleen A.; Heath, Daniel D. — 2012-01-18 An approach frequently used to demonstrate a genetic basis to population-level phenotypic differences is to employ common garden rearing designs, where observed differences are assumed to be attributable to primarily additive genetic effects. Here, in two common garden experiments, we employed factorial breeding designs between wild and domestic, and among wild populations of Chinook salmon (Oncorhynchus tshawytscha). We measured the contribution of additive (VA) and maternal (VM) effects to the observed population differences for 17 life history and fitness-related traits. Our results show that, in general, maternal effects contribute more to phenotypic differences among populations than additive genetic effects. These results suggest that maternal effects are important in population phenotypic differentiation, and also signify that the inclusion of the maternal source of variation is critical when employing models to test population differences in salmon, such as in local adaptation studies.
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Data from: Significant differences in maternal carotenoid provisioning and effects on offspring fitness in Chinook salmon colour morphs
Dryad
Lehnert, Sarah J.; Garver, Kyle A.; Richard, Jon; Devlin, Robert H.; Lajoie, Celine; Pitcher, Trevor E.; Heath, Daniel D. — 2018-10-02 In oviparous species, maternal carotenoid provisioning can deliver diverse fitness benefits to offspring via increased survival, growth, and immune function. Despite demonstrated advantages of carotenoids, large intra‐ and interspecific variation in carotenoid utilization exists, suggesting trade‐offs associated with carotenoids. In Chinook salmon (Oncorhynchus tshawytscha), extreme variation in carotenoid utilization delineates two colour morphs (red and white) that differ genetically in their ability to deposit carotenoids into tissues. Here, we take advantage of this natural variation to examine how large differences in maternal carotenoid provisioning influence offspring fitness. Using a full‐factorial breeding design crossing morphs and common‐garden rearing, we measured differences in a suite of fitness‐related traits, including survival, growth, viral susceptibility, and host response, in offspring of red (carotenoid‐rich eggs) and white (carotenoid‐poor eggs) females. Eggs of red females had significantly higher carotenoid content than those of white females (6X more); however, this did not translate into measurable differences in offspring fitness. Given that white Chinook salmon may have evolved to counteract their maternal carotenoid deficiency, we also examined the relationship between egg carotenoid content and offspring fitness within each morph separately. Egg carotenoids only had a positive effect within the red morph on survival to eyed‐egg (earliest measured trait), but not within the white morph. While previous work shows that white females benefit from reduced egg predation, our study also supports a hypothesis that white Chinook salmon have evolved additional mechanisms to improve egg survival despite low carotenoids, providing novel insight into evolutionary mechanisms that maintain this stable polymorphism.
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Data from: Environmental associations with gene transcription in Babine Lake rainbow trout: evidence for local adaptation
Dryad
Wellband, Kyle W.; Heath, Daniel D. — 2013-05-21 The molecular genetic mechanisms facilitating local adaptation in salmonids continue to be poorly characterized. Gene transcription is a highly regulated step in the expression of a phenotype and it has been shown to respond to selection and thus may be one mechanism that facilitates the development of local adaptation. Advances in molecular genetic tools and an increased understanding of the functional roles of specific genes allow us to test hypotheses concerning the role of variable environments in shaping transcription at known-function candidate loci. To address these hypotheses, wild rainbow trout were collected in their first summer and subjected to metabolic and immune challenges. We assayed gene transcription at candidate loci that play a role in the molecular genetic response to these stresses, and correlated transcription with temperature data from the streams and the abundance and diversity of bacteria as characterized by massively parallel pyrosequencing. Patterns of transcriptional regulation from resting to induced levels varied among populations for both treatments. Co-inertia analysis demonstrated significant associations between resting levels of metabolic gene transcription and thermal regime (R2 = 0.19, P = 0.013) as well as in response to challenge (R2 = 0.39, P = 0.001) and resting state and challenged levels of cytokine gene transcription with relative abundances of bacteria (resting: R2 = 0.25, P = 0.009, challenged: R2 = 0.65, P = 0.001). These results show that variable environments, even within a small geographic range (<250 km), can drive divergent selection among populations for transcription of genes related to surviving stress.
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Data from: Effects of ovarian fluid and genetic differences on sperm performance and fertilization success of alternative reproductive tactics in Chinook salmon
Lehnert, Sarah J.; Butts, Ian A.E.; Flannery, Erin W.; Peters, Kia M.; Heath, Daniel D.; Pitcher, Trevor E.; Butts, I. A. E. — 2017-04-04 In many species, sperm velocity affects variation in the outcome of male competitive fertilization success. In fishes, ovarian fluid (OF) released with the eggs can increase male sperm velocity and potentially facilitate cryptic female choice for males of specific phenotypes and/or genotypes. Therefore, to investigate the role of OF on fertilization success, we measured sperm velocity and conducted in vitro competitive fertilizations with paired Chinook salmon (Oncorhynchus tshawytscha) males representing two alternative reproductive tactics, jacks (small sneaker males) and hooknoses (large guarding males), in the presence of river water alone and OF mixed with river water. To determine the role of genetic differences on fertilization success, we genotyped fish at neutral (microsatellites) and functional [major histocompatibility complex (MHC) II ß1] markers. We found that when sperm were competed in river water, jacks sired significantly more offspring than hooknoses, however, in OF there was no difference in paternity between the tactics. Sperm velocity was significantly correlated with paternity success in river water but not in ovarian fluid. Paternity success in OF, but not in river water alone, was correlated with genetic relatedness between male and female, where males that were less related to the female attained greater paternity. We found no relationship between MHC II ß1 divergence between mates and paternity success in water or OF. Our results indicate that OF can influence the outcome of sperm competition in Chinook salmon, where OF provides both male tactics with fertilization opportunities, which may in part explain what maintains both tactics in nature.
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Data from: Neutral genetic variation in adult Chinook salmon (Oncorhynchus tshawytscha) affects brain-to-body trade-off and brain laterality
Wiper, Mallory L.; Lehnert, Sarah J.; Heath, Daniel D.; Higgs, Dennis M. — 2017-11-06 Low levels of heterozygosity can have detrimental effects on life history and growth characteristics of organisms but more subtle effects such as those on trade-offs of expensive tissues and morphological laterality, especially of the brain, have not been explicitly tested. The objective of the current study was to investigate how estimated differences in heterozygosity may potentially affect brain-to-body trade-offs and to explore how these heterozygosity differences may affect differential brain growth, focusing on directional asymmetry in adult Chinook salmon (Oncorhynchus tshawytscha) using the laterality and absolute laterality indices. Level of inbreeding was estimated as mean microsatellite heterozygosity resulting in four ‘inbreeding level groups’ (Very High, High, Medium, Low). A higher inbreeding level corresponded with a decreased brain-to-body ratio, thus a decrease in investment in brain tissue, and also showed a decrease in the laterality index for the cerebellum, where the left hemisphere was larger than the right across all groups. These results begin to show the role that differences in heterozygosity may play in differential tissue investment and in morphological laterality, and may be useful in two ways. Firstly, the results may be valuable for restocking programmes that wish to emphasize brain or body growth when crossing adults to generate individuals for release, as we show that genetic variation does affect these trade-offs. Secondly, this study is one of the first examinations to test the hypothesized relationship between genetic variation and laterality, finding that in Chinook salmon there is potential for an effect of inbreeding on lateralized morphology, but not in the expected direction.
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Data from: Parallel evolutionary forces influence the evolution of male and female songs in a tropical songbird
Dryad
Graham, Brendan A.; Heath, Daniel D.; Walter, Ryan P.; Mark, Melissa M.; Mennill, Daniel J. — 2018-04-04 Given the important role that animal vocalizations play in mate attraction and resource defence, acoustic signals are expected to play a significant role in speciation. Most studies, however, have focused on the acoustic traits of male animals living in the temperate zone. In contrast to temperate environments, in the tropics it is commonplace for both sexes to produce complex acoustic signals. Therefore tropical birds offer the opportunity to compare the sexes and provide a more comprehensive understanding of the evolution of animal signals. In this study we quantified patterns of acoustic variation in Rufous-and-white Wrens (Thryophilus rufalbus) from five populations in Central America. We quantified similarities and differences between male and female song by comparing the role that acoustic adaptation, cultural isolation, and neutral genetic divergence have played in shaping acoustic divergence. We found that males and females showed considerable acoustic variation across populations, although females exhibited greater population divergence than males. Redundancy analysis and partial-redundancy analysis revealed significant relationships between acoustic variation and ecological variables, genetic distance, and geographic distance. Both ambient background noise and geographic distance explained a high proportion of variance for both males and females, suggesting that both acoustic adaptation and cultural isolation influence song. Overall, our results indicate that parallel evolutionary forces act on male and female acoustic signals and highlight the important role that cultural drift and selection play in the evolution of both male and female songs.
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Data from: Hierarchical analysis of genetic structure in the habitat-specialist Eastern Sand Darter (Ammocrypta pellucida)
Dryad
Ginson, Robert; Walter, Ryan P.; Mandrak, Nicholas E.; Beneteau, Courtney L.; Heath, Daniel D. — 2016-01-08 Quantifying spatial genetic structure can reveal the relative influences of contemporary and historic factors underlying localized and regional patterns of genetic diversity and gene flow – important considerations for the development of effective conservation efforts. Using 10 polymorphic microsatellite loci, we characterize genetic variation among populations across the range of the Eastern Sand Darter (Ammocrypta pellucida), a small riverine percid that is highly dependent on sandy substrate microhabitats. We tested for fine scale, regional, and historic patterns of genetic structure. As expected, significant differentiation was detected among rivers within drainages and among drainages. At finer scales, an unexpected lack of within-river genetic structure among fragmented sandy microhabitats suggests that stratified dispersal resulting from unstable sand bar habitat degradation (natural and anthropogenic) may preclude substantial genetic differentiation within rivers. Among-drainage genetic structure indicates that postglacial (14 kya) drainage connectivity continues to influence contemporary genetic structure among Eastern Sand Darter populations in southern Ontario. These results provide an unexpected contrast to other benthic riverine fish in the Great Lakes drainage and suggest that habitat-specific fishes, such as the Eastern Sand Darter, can evolve dispersal strategies that overcome fragmented and temporally unstable habitats.
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Data from: Historical and anthropogenic factors affecting the population genetic structure of Ontario’s inland lake populations of walleye (Sander vitreus)
Walter, Ryan P.; Cena, Christopher J.; Morgan, George C.; Heath, Daniel D. — 2015-08-20 Populations existing in formerly glaciated areas often display composite historical and contemporary patterns of genetic structure. For Canadian freshwater fishes, population genetic structure is largely reflective of dispersal from glacial refugia and isolation within drainage basins across a range of scales. Enhancement of sport fisheries via hatchery stocking programs and other means has the potential to alter signatures of natural evolutionary processes. Using 11 microsatellite loci genotyped from 2182 individuals, we analyzed the genetic structure of 46 inland lake walleye (Sander vitreus) populations spanning five major drainage basins within the province of Ontario, Canada. Population genetic analyses coupled with genotype assignment allowed us to; 1) characterize broad and fine scale genetic structure among Ontario walleye populations; and 2) determine if the observed population divergence is primarily due to natural / historical processes or recent anthropogenic events. The partitioning of genetic variation revealed higher genetic divergence among lakes than among drainage basins or proposed ancestries—indicative of relatively high isolation among lakes, study-wide. Walleye genotypes were clustered into three major groups, likely reflective of Missourian, Mississippian, and Atlantic glacial refugial ancestry. Despite detectable genetic signatures indicative of anthropogenic influences, province-wide spatial genetic structure remains consistent with the hypothesis of dispersal from distinct glacial refugia and subsequent isolation of lakes within primary drainage basins. Our results provide a novel example of minimal impacts from fishery enhancement to the broad-scale genetic structure of inland fish populations.
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Data from: Human-mediated and natural dispersal of an invasive fish in the eastern Great Lakes
Dryad
Johansson, Mattias L.; Dufour, Bradley A.; Wellband, Kyle W.; Corkum, Lynda D.; MacIsaac, Hugh J.; Heath, Daniel D. — 2017-11-21 The globally invasive Round Goby (Neogobius melanostomus) was introduced to the Great Lakes around 1990, spreading widely and becoming the dominant benthic fish in many areas. The speed and scope of this invasion is remarkable and calls into question conventional secondary spread models and scenarios. We utilized 9 microsatellites to identify large-scale genetic structure in Round Goby populations in the eastern Great Lakes, and assessed the role of colonization versus secondary transport and dispersal in developing this structure. We identified three clusters, corresponding with Lake Huron, eastern Lake Erie, and western Lake Erie plus eastern Lake Ontario, along with three highly-divergent populations. Bottleneck analysis identified founder effects in two divergent populations. Regression analyses of isolation-by-distance and allelic richness vs. distance from the initial invasion site were consistent with limited migration. However, some populations in eastern Lake Erie and Lake Ontario showed anomalously low genetic distance from the original site of colonization, consistent with secondary transport of large numbers of individuals via ballast water. Genetic structure of Round Goby in the Great Lakes principally resulted from long-distance secondary transport via ballast water with additional movement of individual via bait buckets and natural dispersal. The success of Round Gobies represents an interesting model for colonization characterization; however, those same attributes present significant challenges for conservation and fisheries management. Current management likely prevents many new species from arriving in the Great Lakes, but fails to address the transport of species within the lakes after they arrive; an issue of clear and pressing importance.
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Data from: Residual eDNA detection sensitivity assessed by quantitative real-time PCR in a river ecosystem
Dryad
Balasingham, Katherine D.; Walter, Ryan P.; Heath, Daniel D. — 2016-09-12 Several studies have demonstrated that environmental DNA (eDNA) can be used to detect the presence of aquatic species, days to weeks after the target species has been removed. However, most studies used eDNA analysis in lentic systems (ponds or lakes), or in controlled laboratory experiments. While eDNA degrades rapidly in all aquatic systems, it also undergoes dilution effects and physical destruction in flowing systems, complicating detection in rivers. However, some eDNA (i.e. residual eDNA) can be retained in aquatic systems, even those subject to high flow regimes. Our goal was to determine residual eDNA detection sensitivity using quantitative real-time polymerase chain reaction (qRT-PCR), in a flowing, uncontrolled river after the eDNA source was removed from the system; we repeated the experiment over two years. Residual eDNA had the strongest signal strength at the original source site and was detectable there up to 11.5 hours after eDNA source removal. Residual eDNA signal strength decreased as sampling distance downstream from the eDNA source site increased, and was no longer detectable at the source site 48 hours after the eDNA source water was exhausted in both experiments. This experiment shows that residual eDNA sampled in surface water can be mapped quantitatively using qRT-PCR, which allows a more accurate spatial identification of the target species location in lotic systems, and relative residual eDNA signal strength may allow the determination of the timing of the presence of target species.
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Data from: Sperm competition, but not major histocompatibility divergence, drives differential fertilization success between alternative reproductive tactics in Chinook salmon
Dryad
Lehnert, Sarah J.; Helou, Leila; Pitcher, Trevor E.; Heath, John W.; Heath, Daniel D. — 2017-10-17 Post-copulatory sexual selection processes, including sperm competition and cryptic female choice (CFC), can operate based on major histocompatibility (MH) genes. We investigated sperm competition between male alternative reproductive tactics [jack (sneaker) and hooknose (guard)] of Chinook salmon (Oncorhynchus tshawytscha). Using a full factorial design, we examined in vitro competitive fertilization success of paired jack and hooknose males at three time points after sperm activation (0, 15 and 60 s) to test for male competition, CFC and time effects on male fertilization success. We also examined egg-mediated CFC at two MH genes by examining both the relationship between competitive fertilization success and MH divergence as well as inheritance patterns of MH alleles in resulting offspring. We found that jacks sired more offspring than hooknose males at 0 s post-activation; however, jack fertilization success declined over time post-activation, suggesting a trade-off between sperm speed and longevity. Enhanced fertilization success of jacks (presumably via higher sperm quality) may serve to increase sneaker tactic competitiveness relative to dominant hooknose males. We also found evidence of egg-mediated CFC (i.e. female × male interaction) influencing competitive fertilization success; however, CFC was not acting on the MH genes as we found no relationship between fertilization success and MH II β1 or MH I α1 divergence and we found no deviations from Mendelian inheritance of MH alleles in the offspring. Our study provides insight into evolutionary mechanisms influencing variation in male mating success within alternative reproductive tactics, thus underscoring different strategies that males can adopt to attain success.
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Data from: Standing genetic diversity and selection at functional gene loci are associated with differential invasion success in two non-native fish species
Dryad
Wellband, Kyle W.; Pettitt-Wade, Harri; Fisk, Aaron T.; Heath, Daniel D. — 2018-03-08 Invasive species are expected to experience a unique combination of high genetic drift due to demographic factors while also experiencing strong selective pressures. The paradigm that reduced genetic diversity should limit the evolutionary potential of invasive species and thus their potential for range expansion has received little empirical support, possibly due to the choice of genetic markers. Our goal was to test for effects of genetic drift and selection at functional genetic markers as they relate to the invasion success of two paired invasive goby species, one widespread (successful) and one with limited range expansion (less successful). We genotyped fish using two marker types: single nucleotide polymorphisms (SNPs) in known-function, protein-coding genes and microsatellites to contrast the effects of neutral genetic processes. We identified reduced allelic variation in the invaded range for the less-successful tubenose goby. SNPs putatively under selection were responsible for the observed differences in population structure between marker types for round goby (successful) but not tubenose goby (less successful). A higher proportion of functional loci experienced divergent selection for round goby, suggesting increased evolutionary potential in invaded ranges may be associated with round goby's greater invasion success. Genes involved in thermal tolerance were divergent for round goby populations but not tubenose goby, consistent with the hypothesis that invasion success for fish in temperate regions is influenced by capacity for thermal tolerance. Our results highlight the need to incorporate functional genetic markers in studies to better assess evolutionary potential for the improved conservation and management of species.

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(source : Dryad) AND (auteur : Heath, Daniel D.)

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