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  • 1
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    New possibilities arise for studies of hybridization: SNP-based markers for the multi-species Daphnia longispina complex derived from transcriptome data (2014)
    PANGAEA
    Details
    Publication Date: 2023-01-13
    Description: In order to trace population community dynamics and reticulate evolution in hybrid species complexes, long-term comparative studies of natural populations are necessary and thus, tools for fine-scale genetic analyses are needed. In the present study, we developed species-diagnostic SNP markers for hybridizing freshwater crustaceans: the multispecies Daphnia longispina complex. Specifically, we took advantage of transcriptome data from a key species of this hybrid complex, the annotated genome of a related Daphnia species and well-defined reference genotypes from three parental species. Altogether eleven nuclear loci with several species-specific SNP sites were identified in sequence alignments of 22 individuals of three parental species and their hybrids. A PCR-RFLP assay was developed for cost-efficient large population screening by SNP-genotyping. Taxon assignment by RFLP-patterns was nearly perfectly concordant with microsatellite genotyping across several screened populations from Europe. Finally, we were able to amplify two short regions of these loci in formaldehyde-preserved samples dating back to the year 1960. The species-specific SNP markers developed here provide valuable tools to study hybridization over time, including the long-term impact of various environmental factors on hybridization and biodiversity changes. SNP-based genotyping will finally allow for revealing eco-evolutionary dynamics at different time scales.
    Type: Dataset
    Format: application/zip, 5.7 kBytes
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    Acoustic observations of zooplankton in lakes using a Doppler current profiler (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. In this paper we test the usefulness of acoustic backscatter measurements from a 614 kHz Acoustic Doppler Current Profiler (ADCP) for the qualitative and quantitative characterisation of zooplankton distributions in lakes. ADCP-based backscatter estimates were compared with frequent net hauls obtained during a calibration experiment in which the acoustic backscatter was strongly dominated by vertical migrating Chaoborus flavicans larvae.2. The correlation between backscatter estimates and the C. flavicans concentration was very good. Vertical swimming speed of larvae, measured directly by the ADCP, was up to a maximum of 5 mm s−1 and agreed very well with the observed vertical movement of the backscatter contour lines. Although the strong backscatter from C. flavicans overwhelmed the signal from the remaining zooplankton, a good correlation between backscatter strength and the total remaining zooplankton concentration, dominated by Cyclops spp., was found for the depth and time intervals where no C. flavicans were present.3. In addition to the calibration experiment, longer-term ADCP measurements from different lakes revealed a strong temporal correlation between the onset of the up- and downward migration of zooplankton and the local sunset and sunrise.4. We conclude that ADCPs can be used to monitor plankton distributions both temporally and spatially. It also seems possible to estimate plankton densities after appropriate calibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01267.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Life history patterns of parental and hybrid Daphnia differ between lakes (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes.2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata.3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina.4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade-off for this twofold protection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01272.x
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanisms regulating zooplankton populations in a high-mountain lake (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. We studied the seasonal succession of phyto- and zooplankton and the potential impact of predation by salmonids on zooplankton population dynamics in a high-mountain Swiss lake.2. A comparison of patterns in the abundance, body length, fecundity and age structure in the Daphnia galeata population strongly suggests that trout predation had little impact on the population and was not the cause for a decline in summer.3. The dominance in the lake of adult trout that feed mainly on benthic prey may buffer the effect of predation on the larger zooplankton. Further, the relatively high amount of phytoplankton after spring thaw could be important for sustaining the Daphnia population under moderate fish predation.4. Partial correlation analyses proved circumstantial evidence for both exploitative and interference competition between some zooplankton taxa. D. galeata depressed performance of other plankton species through exploitative competition.5. Our study shows that the impact of fish on zooplankton in high-mountain lakes depends strongly on food web structure and trophic state of the lake. Where fish predation is weak, invertebrate predation combined with competition for food may be responsible for the dominance of large-bodied zooplankton species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01054.x
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  • 5
    Electronic Resource
    Electronic Resource
    Sexual reproduction in Daphnia: interspecific differences in a hybrid species complex (1995)
    Springer
    Oecologia 104 (1995), S. 501-507 
    Details
    ISSN: 1432-1939
    Keywords: Daphnia ; Cladocera ; Interspecific-hybridization ; Sex allocation ; Parthenogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate whether reproductive variation in the Daphnia galeata-cucullata-hyalina hybrid species complex can explain the occurrence of hybrids and backcrosses, a total of 43 clones from three north German lakes were tested for allocation to sexual reproduction under equal stress conditions. Six replicates per clone were followed until the seventh adult instar. I used the following cues to promote sexual reproduction: short photoperiod, water from a crowded Daphnia culture, fish-conditioned water and low food concentration. For each animal, clutch size and clutch sex were recorded. Ephippia, which were empty since the animals were cultured individually, were only produced by D. cucullata and D. cucullata x hyalina (26% and 6% of the broods, respectively), whereas almost all taxa produced males (the range was 2–15%). Intraspecific variation for male and ephippial production was also found. The fact that the taxa tested show different responses to the stimuli of-fered may indicate that there is reproductive isolation between them. This is supported by field data from the Tjeukemeer (The Netherlands) which shows that D. galeata mostly produces ephippia in spring and D. cucullata in autumn. The presence of hybrids with ephippia in both seasons, however, shows that backcrossing is also possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00341348
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  • 6
    Electronic Resource
    Electronic Resource
    Tail spine length in the Daphnia galeata complex: costs and benefits of induction by fish (1997)
    Springer
    Aquatic ecology 31 (1997), S. 89-98 
    Details
    ISSN: 1573-5125
    Keywords: fish predation ; inducible defence ; interspecific hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the combined effect of fish kairomones and food conditions on the relative tail spine length (RTL) of five Daphnia taxa, and the interaction of these factors with the vertical distribution of the daphnids. The experiment was done in two large-scale indoor containers, the so-called plankton towers in Plön, Germany. We conducted a competition experiment in which food level and the presence of fish chemicals and later fish were varied. A strong response of RTL to fish kairomones (e.g., longer tail spines), significant differences in RTL between species, but no differences in RTL with water depth were found. Further, we observed that these Daphnia taxa produced a higher RTL only under high food conditions. This suggests that there is a cost related to the production of longer tail spines. In a preliminary study in lake Plußsee, we found that Daphnia had longer average RTL than in the towers. Further, we noted significant differences in RTL between the two sampling dates, which may be related to a lower food level. We also detected a strong inverse correlation between RTL and depth. We discuss the implications of these findings for the co-existence of co-occurring Daphnia species and their hybrids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009935100804
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic markers, genealogies and biogeographic patterns in the cladocera (1998)
    Springer
    Aquatic ecology 32 (1998), S. 37-51 
    Details
    ISSN: 1573-5125
    Keywords: microcrustaceans ; Daphnia ; evolution ; interspecific hybridization ; molecular systematics ; aquatic ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cladoceran crustaceans are an important component of zooplankton in a wide range of freshwater habitats. Although the ecological characteristics of several cladoceran species have been well studied, biogeographical studies have been hampered by problematic taxonomic affiliations. However, recently developed molecular techniques, provide a powerful tool to subject aquatic taxa to comparative analyses. Here we highlight recent molecular approaches in aquatic ecology by presenting a simple method of DNA preparation and PCR amplification of the mitochondrial DNA (16S rDNA) in species from nine different families within the cladocera. On a broad taxonomic scale, sequence analysis of this mtDNA fragment has been used to produce the first molecular based phylogeny of the cladocera. This analysis clustered the cladoceran families in a fashion similar to that suggested by previous systematic classifications. In a more detailed analysis of the family Daphniidae, nuclear randomly amplified polymorphic DNA (RAPD), mitochondrial restriction fragment length polymorphism (RFLP) and morphological analyses were combined to identify species and interspecific hybrids within the Daphnia galeata species complex across 50 lakes in 13 European countries and one lake in Africa. The study revealed interspecific hybridization and backcrossing between some taxa (D. cucullata and D. galeata) to be widespread, and species and hybrids to frequently occur in sympatry. Genetic, as well as morphological information, suggests the occurrence of D. hyalina outside the Holarctic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009939901198
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  • 8
    Electronic Resource
    Electronic Resource
    Cyclomorphosis as a factor explaining success of a Daphnia hybrid in Tjeukemeer (1995)
    Springer
    Hydrobiologia 307 (1995), S. 283-289 
    Details
    ISSN: 1573-5117
    Keywords: Cyclomorphosis ; daphnia ; interspecific hybridization ; invertebrate predation ; life histories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recent studies have shown that Daphnia hybrids are intermediate to their parental species for several life history traits, and that they combine advantageous traits of the parental species, thereby decreasing their risk of being preyed upon by planktivorous fish. In this study D. galeata, D. cucullata and their interspecific hybrid are compared with respect to cyclomorphosis and juvenile growth as a potential mechanism to avoid invertebrate predation. Helmets and tail spines are known to reduce predation risk, whereas fast juvenile growth reduces the period that Daphnia are vulnerable to predation. In laboratory cultures, I tested the hypothesis that, with regard to cyclomorphosis, juvenile hybrids are more comparable to the juveniles of D. cucullata, and with respect to growth rate, they are more comparable to D. galeata. The hybrid did not differ significantly from D. galeata in the time needed to reach 0.9 mm body length. In contrast, the relative spine and helmet length of juvenile hybrids were more comparable with those of D. cucullata, whereas in adult instars these characters were more similar to D. galeata. Thus during the first juvenile instars, the hybrids combine the relative long helmet and spine of D. cucullata, with the faster growth of D. galeata. This combination of characteristics might reduce hybrid vulnerability to invertebrate predation in field situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032022
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  • 9
    Electronic Resource
    Electronic Resource
    Hybridization in the Daphnia galeata complex: are hybrids locally produced? (1997)
    Springer
    Hydrobiologia 360 (1997), S. 127-133 
    Details
    ISSN: 1573-5117
    Keywords: genetic distances ; cladocera ; allozymes ; genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Within the species complex of Daphnia galeata,D. cucullata and D. hyalina variouscombinations of hybrids and parental taxa occur inlakes throughout Europe. Since daphnids are cyclicparthenogens and mostly reproduce asexually, hybridpopulations can be maintained by asexual reproductionand without recurrent hybridization events. Therefore,it is possible that hybridization events have beenrare, with range expansion occurring by dispersal ofhybrids.Allozyme data from seven European populations wereused to compare genetic variation within and betweenhybrid and parental taxa. An UPGMA cluster analysis ofgenetic distances showed that D. cucullata × galeatahybrids from different lakes grouped indifferent clusters according to the lake from whichthey were isolated, suggesting multiple hybridizationevents. Clonal diversity within hybrid taxa wascomparable to parental taxa. Furthermore, evidence wasfound for introgression of the Pgi-S allele fromD. cucullata to D. galeata in three lakes.These results indicate that multiple hybridizationevents within this species complex are likely, andthat hybrid taxa can reproduce sexually.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003157117667
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  • 10
    Electronic Resource
    Electronic Resource
    Differential behaviour and shifts in genotype composition during the beginning of a seasonal period of diel vertical migration (1997)
    Springer
    Hydrobiologia 360 (1997), S. 177-185 
    Details
    ISSN: 1573-5117
    Keywords: Daphnia ; 0+ perch ; genotypes ; selective predation ; allozyme analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the first few weeks of a recurring seasonalperiod of diel vertical migration in Lake Maarsseveen(The Netherlands), part of the hybrid Daphniagaleata × hyalina population migrated, whileanother part remained in the epilimnion. In theepilimnion, 0+ perch prey upon daphnids duringdaytime. Gradually, the number of adult Daphniain the epilimnion decrease until the epilimnion isnearly devoid of daphnids. The population as a wholemay decrease, as in 1991, or may increase asin 1992. Genotype composition, as determined byallozyme analysis, changed substantially within afortnight in 1992, and one genotype became dominant.Our data are in agreement with the hypothesis thatpredation on different genotypes (clones)occurs during the beginning of a seasonal period ofdiel vertical migration, though our data do not allowto exclude alternativeexplanations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003121520393
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