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Adam Petrusek - One of the best experts on this subject based on the ideXlab platform.
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establishment of a new microsporidian genus and species pseudoberwaldia Daphniae microsporidia opisthosporidia a common parasite of the Daphnia longispina complex in europe
Journal of Invertebrate Pathology, 2019Co-Authors: Jiři Vavra, Adam Petrusek, Ivan Fiala, Pavla Krylova, Miroslav HylisAbstract:Abstract Microsporidia are among the most common microparasites of cladocerans and have potentially significant impact on host populations. However, many of these pathogens are known only from molecular-based studies. We provide ultrastructural data supported by molecular phylogeny for a common microsporidium infecting the Daphnia longispina complex, important planktonic filter-feeders in reservoirs and ponds in the temperate Holarctic region. This parasite, previously characterized only by molecular means, infects adipose cells around the Daphnia midgut and eventually fills the centre of the host body with ovoid-shaped spores. A new microsporidian genus and species belonging to the Agglomeratidae superclade is described as Pseudoberwaldia Daphniae gen. et sp. nov. Molecular data indicate its widespread presence in Central European reservoirs (reported as isolate “MIC1”) but also in Swedish coastal rockpools (“Angskars-klubben”). The most closely related lineage was reported from a caddisfly larva; we thus speculate that this taxon may have an insect secondary host in its life cycle. Morphological characterization and differential diagnosis of most commonly encountered microsporidian taxa infecting hosts in the D. longispina complex in Europe opens new possibilities for studies of their ecological and evolutionary interactions.
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congruent patterns of lineage diversity in two species complexes of planktonic crustaceans Daphnia longispina cladocera and eucyclops serrulatus copepoda in east european mountain lakes
Zoological Journal of the Linnean Society, 2012Co-Authors: Eva Hamrova, Martin Cerný, Martin Krajicek, Tomislav Karanovic, Adam PetrusekAbstract:Cladocerans and copepods are globally important freshwater zooplankton groups, differing in reproductive modes and dispersal abilities. We compared genetic variation of two common taxa of these crustaceans, the Daphnia longispina species complex (known to harbour multiple cryptic lineages) and Eucyclops serrulatus (morphologically and ecologically variable morphospecies), in lakes of ten Eastern European mountain ranges. We expected to discover cryptic lineages in both groups, and to observe different geographical patterns of diversity because of differences in life cycles. Within E . serrulatus , limited sampling through lowland habitats indeed showed the presence of eight highly divergent clades, probably cryptic species, but most of these were not found in the studied mountain lakes. Such a pattern was congruent with the diversity of the D. longispina complex. Regional coexistence of multiple clades within respective species complexes (two in Eucyclops and three in Daphnia ) was observed only in the Tatra Mountains (on the Polish−Slovak border). In all other studied mountain ranges (in the Balkans), only single lineages of Daphnia and Eucyclops , respectively, were present, showing similar intraspecific patterns and no evidence for stronger dispersal limitation in Eucyclops than in Daphnia . Our results indicate that substantial cryptic variation may be expected in seemingly widespread copepod taxa. However, detection of cryptic lineages is not a general pattern in mountain lakes, although these habitats harbour substantial genetic diversity in crustacean zooplankton.
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mitochondrial sequence variation suggests extensive cryptic diversity within the western palearctic Daphnia longispina complex
Limnology and Oceanography, 2012Co-Authors: Adam Petrusek, Anne Thielsch, Klaus SchwenkAbstract:We ; report on a discovery of six divergent lineages within the European Daphnia longispina complex from various localities in central to northeast Europe. The levels of divergence from well-known species of the complex suggest that they represent as yet unrecognized distinct taxa. These newly recognized lineages always coexisted in syntopy with widespread species of the complex. Particularly rich in cryptic diversity (with four of the six lineages present) was the delta of the River Pechora in northern European Russia, a region not covered by an ice sheet during most of the last glacial period. We suggest that ice-free regions of northeastern Europe may have been important refugia for planktonic species, and still are overlooked hot spots of diversity. Our findings confirm that the real diversity within widespread crustacean planktonic taxa is much higher than presently recognized. The potential presence of cryptic species should be considered in ecological studies. Cryptic species, i.e., phenotypically similar but evolutionarily distinct (and often genetically highly divergent) species, are common throughout the animal kingdom (Pfenninger and Schwenk 2007), and cladocerans are not
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natural distribution and co infection patterns of microsporidia parasites in the Daphnia longispina complex
Parasitology, 2012Co-Authors: S Weigl, Adam Petrusek, H Korner, Jaromir Seda, Justyna WolinskaAbstract:Microsporidia are intracellular parasites, frequently infecting the planktonic crustacean Daphnia. Questioning the ability to detect and identify microsporidia with conventional microscopic techniques, we applied molecular methods in order to investigate the distribution and co-infection patterns of this parasite among 8 communities of the Daphnia longispina hybrid complex. Eight microsporidian taxa were detected, including 3 that previously had not been characterized genetically. Microsporidian communities from nearby lakes were found to be more similar to each other, apparently due to short distance dispersal via secondary hosts. Moreover, we detected seasonal (but not interannual) changes in microsporidian community structure. With some microsporidia being host-specific, these changes might have resulted from seasonal changes in host taxon and clonal composition. The 2 dominant and closely related parasite species were found mainly in single infections, whereas another pair of related microsporidians was found predominantly in co-infections; suggesting species-level differences in the ability to colonize infected hosts. By applying molecular methods, we were not only able to unambiguously identify parasite taxa but also to reveal multiple infections that otherwise would have remained undetected. Given the increased level of accuracy and sensitivity, we highly recommend molecular approaches in future parasite surveys of Daphnia infections.
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fine scale temporal and spatial variation of taxon and clonal structure in the Daphnia longispina hybrid complex in heterogeneous environments
BMC Evolutionary Biology, 2012Co-Authors: Jaromir Seda, Adam Petrusek, Mingbo Yin, Justyna WolinskaAbstract:Cyclical parthenogenetic water fleas of the genus Daphnia have become a prominent model organism in ecology and evolution. In the past, analyses of their population structure have been limited by the prevailing use of allozyme markers, which in general do not allow for the distinction of individual clones. In this study, we used 10 microsatellite markers to track changes in the taxonomic and clonal composition of Daphnia populations, and traced the abundance of the most common clones in two European reservoirs. One of the localities was inhabited by a single species of the Daphnia longispina complex (D. galeata), the other by two parental species (D. galeata and D. longispina) and their interspecific hybrids. The study took place during the transition from summer stratification to autumn mixing, representing a period of major environmental change within lake habitats. In both reservoirs, we observed temporal (generation-to-generation) and spatial (along the heterogeneous reservoir environment) changes in Daphnia community structure. In the single-species reservoir, the clonal diversity of D. galeata increased with time, as a few dominant clones were replaced by a higher number of less common clones. A loss in selective advantage for the dominant clones may have been due to gradual changes in the environment, or due to selection acting in a negative frequency-dependent manner. In the multispecies reservoir, there were no apparent temporal trends in clonal diversity but we observed significantly lower clonal diversity in the interspecific hybrids than in the coexisting parental species, supporting the existence of reproductive barriers between the parental genomes. Our study, tracing clonal lineages of Daphnia in time and space by the fine-resolution markers, contributes to the understanding of how clonal reproduction impacts community structure in cyclically parthenogenetic organisms.
Justyna Wolinska - One of the best experts on this subject based on the ideXlab platform.
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The establishment of hybrids of the Daphnia longispina complex explained by a mathematical model incorporating different overwintering life history strategies
PloS one, 2018Co-Authors: Johanna Griebel, Margarete Utz, Joachim Hermisson, Justyna WolinskaAbstract:Interspecific hybridization (i.e. mating between species) occurs frequently in animals. Among cyclical parthenogens, hybrids can proliferate and establish through parthenogenetic reproduction, even if their sexual reproduction is impaired. In water fleas of the Daphnia longispina species complex, interspecific hybrids hatch from sexually produced dormant eggs. However, fewer hybrid genotypes contribute to the dormant egg bank and their hatching rate from dormant eggs is reduced, compared to eggs resulting from intraspecific crosses. Therefore, Daphnia hybrids would benefit from adaptations that increase their survival over winter as parthenogenetic lineages, avoiding the need to re-establish populations after winter from sexually produced dormant eggs. Here, we constructed a mathematical model to examine the conditions that could explain the frequently observed establishment of hybrids in the D. longispina species complex. Specifically, we compared the outcome of hybrid and parental taxa competition given a reduced contribution of hybrids to hatchlings from the sexually produced dormant egg bank, but their increased ability to survive winter as parthenogenetic lineages. In addition, different growth rates of parental species and differences in average annual temperatures were evaluated for their influence on hybrid production and establishment. Our model shows that increased overwinter performance as parthenogenetic females can compensate for reduced success in sexual reproduction, across all tested scenarios for varying relative growth rates of parental species. This pattern holds true for lower annual temperatures, but at higher temperatures hybrids were less successful. Consequently, hybrids might become less abundant as temperatures rise due to climate change, resulting in reduced diversity and faster differentiation of the parental species.
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natural distribution and co infection patterns of microsporidia parasites in the Daphnia longispina complex
Parasitology, 2012Co-Authors: S Weigl, Adam Petrusek, H Korner, Jaromir Seda, Justyna WolinskaAbstract:Microsporidia are intracellular parasites, frequently infecting the planktonic crustacean Daphnia. Questioning the ability to detect and identify microsporidia with conventional microscopic techniques, we applied molecular methods in order to investigate the distribution and co-infection patterns of this parasite among 8 communities of the Daphnia longispina hybrid complex. Eight microsporidian taxa were detected, including 3 that previously had not been characterized genetically. Microsporidian communities from nearby lakes were found to be more similar to each other, apparently due to short distance dispersal via secondary hosts. Moreover, we detected seasonal (but not interannual) changes in microsporidian community structure. With some microsporidia being host-specific, these changes might have resulted from seasonal changes in host taxon and clonal composition. The 2 dominant and closely related parasite species were found mainly in single infections, whereas another pair of related microsporidians was found predominantly in co-infections; suggesting species-level differences in the ability to colonize infected hosts. By applying molecular methods, we were not only able to unambiguously identify parasite taxa but also to reveal multiple infections that otherwise would have remained undetected. Given the increased level of accuracy and sensitivity, we highly recommend molecular approaches in future parasite surveys of Daphnia infections.
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fine scale temporal and spatial variation of taxon and clonal structure in the Daphnia longispina hybrid complex in heterogeneous environments
BMC Evolutionary Biology, 2012Co-Authors: Jaromir Seda, Adam Petrusek, Mingbo Yin, Justyna WolinskaAbstract:Cyclical parthenogenetic water fleas of the genus Daphnia have become a prominent model organism in ecology and evolution. In the past, analyses of their population structure have been limited by the prevailing use of allozyme markers, which in general do not allow for the distinction of individual clones. In this study, we used 10 microsatellite markers to track changes in the taxonomic and clonal composition of Daphnia populations, and traced the abundance of the most common clones in two European reservoirs. One of the localities was inhabited by a single species of the Daphnia longispina complex (D. galeata), the other by two parental species (D. galeata and D. longispina) and their interspecific hybrids. The study took place during the transition from summer stratification to autumn mixing, representing a period of major environmental change within lake habitats. In both reservoirs, we observed temporal (generation-to-generation) and spatial (along the heterogeneous reservoir environment) changes in Daphnia community structure. In the single-species reservoir, the clonal diversity of D. galeata increased with time, as a few dominant clones were replaced by a higher number of less common clones. A loss in selective advantage for the dominant clones may have been due to gradual changes in the environment, or due to selection acting in a negative frequency-dependent manner. In the multispecies reservoir, there were no apparent temporal trends in clonal diversity but we observed significantly lower clonal diversity in the interspecific hybrids than in the coexisting parental species, supporting the existence of reproductive barriers between the parental genomes. Our study, tracing clonal lineages of Daphnia in time and space by the fine-resolution markers, contributes to the understanding of how clonal reproduction impacts community structure in cyclically parthenogenetic organisms.
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clonal diversity clonal persistence and rapid taxon replacement in natural populations of species and hybrids of the Daphnia longispina complex
Molecular Ecology, 2010Co-Authors: Mingbo Yin, Justyna Wolinska, Sabine GieslerAbstract:Hybridization is common among cyclical parthenogens, especially in zooplankton species assemblages of the genus Daphnia. To explore hybridization dynamics and the extent of clonal diversity in the Daphnia longispina complex, we analysed population structure in eight permanent lakes. Based on 15 microsatellite loci, three major taxonomic units emerged: two species, D. galeata and D. longispina and their F1 hybrids, supported by factorial correspondence analysis and two Bayesian methods. At the same time, the detection of backcross classes differed between methods. Mean clonal diversity was lowest in the F1 hybrids, as expected from the high rate of asexual reproduction. Within taxa, replicated genotypes were of clonal origin, but clonal lineages persisted in subsequent years in only one of three resampled lakes. In another lake, the taxon composition changed from being dominated by hybrids to complete dominance by one parental taxon. Such a year-to-year taxon replacement has not been reported for the D. longispina complex before. Our data on this hybrid complex illustrate that high-resolution genotyping is essential for the understanding of ecological and evolutionary outcomes of hybridization in partially clonal taxa.
Klaus Schwenk - One of the best experts on this subject based on the ideXlab platform.
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hybridization dynamics and extensive introgression in the Daphnia longispina species complex new insights from a high quality Daphnia galeata reference genome
bioRxiv, 2021Co-Authors: Jana Nickel, Tilman Schell, T Holtzem, A Thielsch, Birgit C Schlicksteiner, Florian M Steiner, Markus Most, Markus Pfenninger, Klaus Schwenk, Mathilde CordellierAbstract:Hybridization and introgression are recognized as an important source of variation that influence adaptive processes; both phenomena are frequent in the genus Daphnia, a keystone zooplankton taxon in freshwater ecosystems that comprises several species complexes. To investigate genome-wide consequences of introgression between species, we provide here the first high-quality genome assembly for a member of the Daphnia longispina species complex, Daphnia galeata. We further re-sequenced 49 whole genomes of three species of the complex and their interspecific hybrids both from genotypes sampled in the water column and from single resting eggs extracted from sediment cores. Populations from habitats with diverse ecological conditions offered an opportunity to study the dynamics of hybridization linked to ecological changes and revealed a high prevalence of hybrids. Using phylogenetic and population genomic approaches, we provide first insights into the intra- and interspecific genome-wide variability in this species complex and identify regions of high divergence. Finally, we assess the length of ancestry tracts in hybrids to characterize introgression patterns across the genome. Our analyses uncover a complex history of hybridization and introgression reflecting multiple generations of hybridization and backcrossing in the Daphnia longispina species complex. Overall, this study and the new resources presented here pave the way for a better understanding of ancient and contemporary gene flow in the species complex, and facilitate future studies on resting egg banks accumulating in lake sediment.
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Ecology of predator-induced morphological defense traits in Daphnia longispina (Cladocera, Arthropoda)
Oecologia, 2020Co-Authors: Erik Sperfeld, Klaus Schwenk, Jens Petter Nilssen, Shelby Rinehart, Dag Olav HessenAbstract:Inducible defenses against predators are widespread among plants and animals. For example, some Daphnia species form neckteeth against predatory larvae of the dipteran genus Chaoborus . Though thoroughly studied in D. pulex , knowledge about neckteeth in other Daphnia species is limited. The occurrence of this trait in the D. longispina species complex is only sporadically reported and the specific shape of neckteeth or the occurrence of other morphological defense traits is scarcely known in this widespread group. Here, we explored neckteeth occurrence in a large number of D. longispina populations across Scandinavia and studied neckteeth formation and other morphological defense traits on three D. longispina clones in the laboratory. In the study region, neckteeth on juvenile D. longispina s. str. were observed frequently in permanent ponds, but only when Chaoborus spp. larvae were present. In the laboratory experiments, all three D. longispina clones developed neckteeth (very similar to D. pulex ) in response to Chaoborus kairomone exposure. The D. longispina clones also developed a longer tail spine, wider body, and larger neckteeth pedestal in response to predation threat—likely as a defense against the gape-limited predator. The intensity of neckteeth expression also depended on the clone studied and the concentration of Chaoborus kairomone. Our results demonstrate that neckteeth on D. longispina can be common in nature and that D. longispina can also induce other morphological defenses against predators. The similarity of neckteeth in D. longispina and D. pulex imposes yet unresolved questions on the evolutionary origin in these distantly related Daphnia groups.
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mitochondrial sequence variation suggests extensive cryptic diversity within the western palearctic Daphnia longispina complex
Limnology and Oceanography, 2012Co-Authors: Adam Petrusek, Anne Thielsch, Klaus SchwenkAbstract:We ; report on a discovery of six divergent lineages within the European Daphnia longispina complex from various localities in central to northeast Europe. The levels of divergence from well-known species of the complex suggest that they represent as yet unrecognized distinct taxa. These newly recognized lineages always coexisted in syntopy with widespread species of the complex. Particularly rich in cryptic diversity (with four of the six lineages present) was the delta of the River Pechora in northern European Russia, a region not covered by an ice sheet during most of the last glacial period. We suggest that ice-free regions of northeastern Europe may have been important refugia for planktonic species, and still are overlooked hot spots of diversity. Our findings confirm that the real diversity within widespread crustacean planktonic taxa is much higher than presently recognized. The potential presence of cryptic species should be considered in ecological studies. Cryptic species, i.e., phenotypically similar but evolutionarily distinct (and often genetically highly divergent) species, are common throughout the animal kingdom (Pfenninger and Schwenk 2007), and cladocerans are not
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a taxonomic reappraisal of the european Daphnia longispina complex crustacea cladocera anomopoda
Zoologica Scripta, 2008Co-Authors: Adam Petrusek, Anders Hobæk, Jens Petter Nilssen, Morten Skage, Martin Cerný, Nora Brede, Klaus SchwenkAbstract:The Daphnia longispina complex contains some of the most common water flea species in the northern hemisphere, and has been a model organism for many ecological and evolutionary studies. Nevertheless, the systematics and nomenclature of this group, in particular its Palaearctic members, have been in flux for the past 150 years; this hinders the correct interpretation of scientific results and promotes the erroneous use of species names. We revise the systematics of this species complex based on mitochondrial sequence variation (12S rDNA and COI) of representative populations across Europe, with a special focus on samples from type localities of the respective taxa. Combining genetic evidence and morphological assignments of analysed individuals, we propose a comprehensive revision of the European members of the D. longispina complex. We show that D. hyalina and D. rosea morphotypes have evolved several times independently, and we find no evidence to maintain these morphotypes as distinct biological species. Alpine individuals described as D. zschokkei are conspecific with the above-mentioned lineage. We suggest that this morphologically and ecologically plastic but genetically uniform hyalina–rosea–zschokkei clade should be identified as D. longispina (O. F. Muller, 1776). The valid name of Fennoscandian individuals labelled D. longispina sensu stricto in the recent literature is D. lacustris G. O. Sars, 1862. Additionally, we discovered another divergent lineage of this group, likely an undescribed species, in southern Norway. Our results present a solution for several prevailing taxonomic problems in the genus Daphnia, and have broad implications for interpretation of biogeographical patterns, and ecological and evolutionary studies.
Sabine Giesler - One of the best experts on this subject based on the ideXlab platform.
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clonal diversity clonal persistence and rapid taxon replacement in natural populations of species and hybrids of the Daphnia longispina complex
Molecular Ecology, 2010Co-Authors: Mingbo Yin, Justyna Wolinska, Sabine GieslerAbstract:Hybridization is common among cyclical parthenogens, especially in zooplankton species assemblages of the genus Daphnia. To explore hybridization dynamics and the extent of clonal diversity in the Daphnia longispina complex, we analysed population structure in eight permanent lakes. Based on 15 microsatellite loci, three major taxonomic units emerged: two species, D. galeata and D. longispina and their F1 hybrids, supported by factorial correspondence analysis and two Bayesian methods. At the same time, the detection of backcross classes differed between methods. Mean clonal diversity was lowest in the F1 hybrids, as expected from the high rate of asexual reproduction. Within taxa, replicated genotypes were of clonal origin, but clonal lineages persisted in subsequent years in only one of three resampled lakes. In another lake, the taxon composition changed from being dominated by hybrids to complete dominance by one parental taxon. Such a year-to-year taxon replacement has not been reported for the D. longispina complex before. Our data on this hybrid complex illustrate that high-resolution genotyping is essential for the understanding of ecological and evolutionary outcomes of hybridization in partially clonal taxa.
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morphological differentiation within the Daphnia longispina group
Hydrobiologia, 2001Co-Authors: Sabine GieslerAbstract:Although morphological evolution is assumed to be slow within Daphnia species complexes, discontinuities in morphological space can be detected. Here, morphological data derived from females of genetically-defined clones (cf. Giesler et al., 1999) are presented, in order to estimate the genetic component of phenotypic variance under standardised laboratory conditions. Animals originated from clonal assemblages of pre-alpine lakes and ponds, and a remote lake in western Germany, covering a wide range of morphotypes known from the traditional species D. cucullata, D. galeata, D. hyalina, D. rosea, and a variety of interspecific hybrids. Phenotypic analyses were based on quantitative and qualitative morphological characters of females in the first and fifth instars. Morphological divergence between clones was analysed using discriminant analysis or multidimensional scaling and the significance of the morphological groupings was estimated using neighbour-joining trees and bootstrapping. All analyses confirmed that (a) phenotypic similarities among taxa change with instar, (b) in contrast to low genetic divergence, pronounced morphological divergence exists between animals separated on the lake/pond level favouring speciation by the habitat shift hypothesis.
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analysis of reticulate relationships within the Daphnia longispina species complex allozyme phenotype and morphology
Journal of Evolutionary Biology, 1997Co-Authors: Sabine GieslerAbstract:A two-step method is proposed to get reliable associations between morphology and genotype in clonal assemblages in which more than two predominantly parthenogenetic species are thought to coexist with hybrids. In dataset 1, the genetic relationships among clones of the Daphnia longispina hybrid complex from seven prealpine lakes in southern Germany were studied based on the variation at 21 enzyme loci. The spatial arrangement in the multidimensional scaling plot revealed a reticulate pattern among three presumably parental species, D. cucullata, D. galeata and D. hyalina, and three hybrid groups, D. cucullata/galeata, D. cucullata/hyalina and D. galeata/hyalina. The Got1 locus was believed to be a discriminating factor between species and hybrids (cf. Wolf and Mort, 1986). However, this locus is more variable, and 57% of the clones would have been misidentified using it. Moreover, the morphological variation within genetically defined groups is also higher than previously assumed. In dataset 2, the revision of morphological and genetic markers greatly improved the association between morphology and genotype in newly collected animals. The spatial arrangement of clones in multidimensional scaling plots and morphological asymmetries to parents suggest both, different degrees of introgression and bidirectional hybridization. Most unexpected genotypes were found in the cxh hybrid group, suggesting that F1-hybrids are fertile. The results showed (1) that the clonal diversity was very high (2) that detailed analyses of multiple morphological and allozyme markers are necessary to resolve taxonomic relationships within clonal assemblages consisting of multiple species, hybrids and differently introgressed backcrosses, and (3) that the three original species seem to have sufficient within-species recombination and a low enough rate of backcrossing to allow taxonomic identification. It must remain undecided if the present situation is locally restricted, if it is stable or represents a transient situation which could lead to either a consolidation of the three species by gradual elimination of the hybrids, to a taxonomic breakdown, or to hybrid speciation.
Rui Ribeiro - One of the best experts on this subject based on the ideXlab platform.
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survival recovery rates by six clonal lineages of Daphnia longispina after intermittent exposures to copper
Chemosphere, 2021Co-Authors: Catia Venâncio, Amadeu M V M Soares, Rui Ribeiro, Isabel LopesAbstract:Natural populations are commonly exposed to sequential pulses of contaminants. Accordingly, this study aimed at testing the existence of an association between the tolerance to lethal levels of copper (Cu) and the survival recovery ability from pulsed partially lethal copper exposures in six clonal lineages of Daphnia longispina. It was hypothesized that the most tolerant genotypes would be the ones exhibiting a faster survival recovery from a pulsed contaminant exposure. For each clonal lineage, the intensity of pulses corresponded to the respective concentration of Cu causing 30% of mortality after 24h of exposure (LC30,24h). The initial hypothesis was not corroborated: obtained results showed no association between survival recovery and lethal tolerance to Cu. Nevertheless, some patterns could be detected. Firstly, the most sensitive lineages to lethal levels of copper revealed a faster survival recovery from a first Cu pulse comparatively to the most tolerant ones, though they were the most sensitive to a second pulse exposure. Secondly, the most tolerant lineages, though being more tolerant to a second exposure, exhibited the lowest survival recovery capacity after exposure to a first pulse of Cu. However, differences in the survival recovery capacity of the six clonal lineages after the exposure to the two pulses of Cu were not observed. Increasing the duration of the recovery period from 24h to 72h did not significantly alter mortality rates, except for the most sensitive and most tolerant clonal lineages. The results here obtained suggests that standard lethality assays may sub-estimate the toxicity of chemicals under realistic exposure scenarios, since sequential pulses are not infrequent in natural conditions.
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multigenerational effects of salinity in six clonal lineages of Daphnia longispina
Science of The Total Environment, 2018Co-Authors: Catia Venâncio, Amadeu M V M Soares, Rui Ribeiro, Isabel LopesAbstract:Sea level rise, as a consequence of climate changes, is already causing seawater intrusion in some freshwater coastal ecosystems worldwide. The increase in salinity at these freshwater coastal ecosystems may occur gradually (through groundwater) or abruptly (through extreme weather events). Moreover, many of them are also being altered and threatened by anthropogenic activities. Accordingly, the present study aimed at assessing the multigenerational lethal and sublethal effects caused by increased salinity in six clonal lineages of the freshwater cladoceran Daphnia longispina differing in their sensitivity to lethal levels of copper. Three specific objectives were delineated: i) to compare the lethal and sublethal toxicity of sodium chloride (NaCl) and natural seawater (SW); ii) to evaluate possible multigenerational effects after exposure to low levels of salinity, and iii) to evaluate if an association exists between tolerance to lethal and sublethal levels of salinity and tolerance to metals. Overall, NaCl was found to elicit sublethal effects at lower or similar concentrations than SW, suggesting its use as a protective surrogate of SW in early phases of ecological risk assessment schemes. Multigenerational exposure to conductivities of 0.73±0.015mScm-1 led to dissimilar responses by the six clonal lineages. Significant associations were found neither between lethal and sublethal endpoints nor between salinity and metals, possibly indicating the absence of common mechanisms responsible to confer metal tolerance and salt stress. However, some clonal lineages presented an inverse sensitivity to lethal levels of NaCl and of copper. These results suggest that natural populations of D. longispina, by exhibiting clonal lineages with differential tolerance to increased salinity, may cope with long-term exposure to small increases of this stressor. However, over time those populations may face the occurrence of genetic erosion due to the loss of the most sensitive genotypes before or after a multigenerational exposure.
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tolerance to copper and to salinity in Daphnia longispina implications within a climate change scenario
PLOS ONE, 2013Co-Authors: Joao Leitao, Amadeu M V M Soares, Rui Ribeiro, Isabel LopesAbstract:Considering IPPC climate change scenarios, it is pertinent to predict situations where coastal ecosystems already impacted with chemical contamination became exposed to an additional stressor under a future scenario of seawater intrusion. Accordingly, the present study aimed at evaluating if a negative association between tolerance to a metal and to saltwater exists among genotypes of a freshwater organism. For this, five clonal lineages of the cladoceran Daphnia longispina O.F. Muller, exhibiting a differential tolerance to lethal levels of copper, were selected. Each clonal lineage was exposed to lethal and sublethal concentrations of sodium chloride (assumed as a protective surrogate to evaluate the toxicity of increased salinity to freshwater organisms). Mortality, time to release the first brood and total number of neonates per female were monitored and the somatic growth rate and intrinsic rate of natural increase were computed for each clonal lineage. Data here obtained were compared with their lethal responses to copper and significant negative correlations were found. These results suggest that genetically eroded populations of D. longispina, due to copper or salinity, may be particularly susceptible to a later exposure to the other contaminant supporting the multiple stressors differential tolerance.
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contaminant driven genetic erosion a case study with Daphnia longispina
Environmental Toxicology and Chemistry, 2012Co-Authors: Rui Ribeiro, Donald J Baird, Amadeu M V M Soares, Isabel LopesAbstract:Natural populations exposed to pollutants are predicted to experience a loss of genetic diversity, especially through genetic drift, gene flow (emigration), and/or selection (as sensitive genotypes may be lost). In the present study, the authors discuss the use of selectable markers and neutral markers to evaluate a contaminant-driven loss of genetic diversity and possible implications of genetic erosion on populations' viability. Viability could be reduced by altering life history parameters, especially due to fitness costs associated with the acquisition of resistance and/or by compromising the resilience and adaptation to future environmental changes. This discussion aims at an integrated and critical analysis of this topic; it is illustrated by several independent studies (each with its own specific objectives) that were carried out at the same location with Daphnia longispina populations. To the best of the authors' knowledge, this is the most extensively documented case study on genetic erosion of a natural zooplankton population. Directional selection has been found to be a main factor of microevolution; therefore, genetic erosion was detected by monitoring suitable phenotypic markers. Genetic drift was found to be probably irrelevant or masked by other factors, especially gene flow. Although the acquisition of resistance apparently did not entail genetically determined fitness costs under uncontaminated conditions, the present case study suggests the possibility of a further loss of genotypes due to some negative linkages between the sensitivity to potential ulterior toxicants. Environ. Toxicol. Chem. 2012; 31: 977–982. © 2012 SETAC
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testing hypotheses on the resistance to metals by Daphnia longispina differential acclimation endpoints association and fitness costs
Environmental Toxicology and Chemistry, 2012Co-Authors: Liliana Saro, Isabel Lopes, Nelson Martins, Rui RibeiroAbstract:Pollution by metals may lead to an increased tolerance in the exposed population through adaptive microevolution, with resistant genotypes becoming more abundant than in reference sites. This work investigated the outcomes associated with selection for resistance by testing three hypotheses to assess the following: Do resistant versus sensitive clonal lineages of Daphnia longispina differentially acclimate to metals during a long-term sublethal exposure, is there a significant correlation between lethal and sublethal responses, and does resistance to metals entail costs to fitness under uncontaminated conditions? No evidence of acclimation was observed. The median effective dilutions of acid mine drainage for reproduction were similar for successive broods within clones during long-term exposures. Lethal and sublethal responses were not correlated, indicating that mechanisms regulating the two types of response were more than likely different. Finally, fitness costs associated with the resistance to lethal levels of metals were not detected, but resistance to sublethal levels of Cu was found to be correlated with a lower intrinsic growth rate under control conditions. Environ. Toxicol. Chem. 2012;31:909-915. # 2012 SETAC Keywords—Tolerance Tradeoffs Life-traits Acid mine drainage Cladocera
