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Diversity in the reproductive modes of European Daphnia pulicaria deviates from the geographical parthenogenesis.

Dufresne F, Marková S, Vergilino R, Ventura M, Kotlík P - PLoS ONE (2011)

Bottom Line: These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes.Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result of hybridizations.In contrast to North American populations, these transitions do not appear to involve meiosis suppressor genes and have not been accompanied by polyploidy.

View Article: PubMed Central - PubMed

Affiliation: Département de Biologie, Centre d'Études Nordiques, Université du Québec à Rimouski, Rimouski, Québec, Canada. france_dufresne@uqar.qc.ca

ABSTRACT

Background: Multiple transitions to obligate parthenogenesis have occurred in the Daphnia pulex complex in North America. These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes. This conforms to the rule of geographical parthenogenesis postulating prevalence of asexuals at high latitudes and altitudes. While the reproductive mode of high-latitude populations is relatively well studied, little is known about the reproduction mode in high altitudes. This study aimed to assess the reproductive mode of Daphnia pulicaria, a species of the D. pulex complex, from high altitude lakes in Europe.

Methodology/principal findings: Variation at eight microsatellite loci revealed that D. pulicaria from the High Tatra Mountains (HTM) had low genotype richness and showed excess of heterozygotes and significant deviations from Hardy-Weinberg expectations, and was thus congruent with reproduction by obligate parthenogenesis. By contrast, populations from the Pyrenees (Pyr) were generally in Hardy-Weinberg equilibrium and had higher genotypic richness, suggesting that they are cyclic parthenogens. Four lakes from lowland areas (LLaP) had populations with an uncertain or mixed breeding mode. All D. pulicaria had mtDNA ND5 haplotypes of the European D. pulicaria lineage. Pyr were distinct from LLaP and HTM at the ND5 gene. By contrast, HTM shared two haplotypes with LLaP and one with Pyr. Principal Coordinate Analysis of the microsatellite data revealed clear genetic differentiation into three groups. HTM isolates were intermediate to Pyr and LLaP, congruent with a hybrid origin.

Conclusion/significance: Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result of hybridizations. In contrast to North American populations, these transitions do not appear to involve meiosis suppressor genes and have not been accompanied by polyploidy. The absence of obligate parthenogenesis in Pyr, an environment highly similar to the HTM, may be due to the lack of opportunities for hybridization.

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Restriction map of the mtDNA ND5 amplicon.The ApoI site at position 344 distinguishes species [11] of the tenebrosa group (European Daphnia pulicaria, EuroPC; and D. tenebrosa, TENE) from those of the pulicaria group (polar, PPC; western, WPC; and eastern D. pulicaria, EPC; D. middendorffiana, MIDD; and panarctic D. pulex, PanPX). Some lineages yield short fragments under 100 bp in size difficult to visualize using agarose gels but this does not affect scoring the individuals as either tenebrosa or pulicaria group.
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pone-0020049-g005: Restriction map of the mtDNA ND5 amplicon.The ApoI site at position 344 distinguishes species [11] of the tenebrosa group (European Daphnia pulicaria, EuroPC; and D. tenebrosa, TENE) from those of the pulicaria group (polar, PPC; western, WPC; and eastern D. pulicaria, EPC; D. middendorffiana, MIDD; and panarctic D. pulex, PanPX). Some lineages yield short fragments under 100 bp in size difficult to visualize using agarose gels but this does not affect scoring the individuals as either tenebrosa or pulicaria group.

Mentions: PCR products of all the remaining isolates were subjected to RFLP analysis in order to verify that they belonged to European D. pulicaria and not to other species that exist within the D. pulex complex [11]. Species delimitation and taxonomy is problematic in the D. pulex complex. North American and European populations of D. pulicaria have the same species name despite the fact that these two groups should not belong to the same species since they are genetically distinct [11]. This study focuses on European D. pulicaria. ND5 haplotypes from other lineages are included for genetic comparisons. A restriction map was generated using the CLC Free Workbench 4.6.2 (CLC Bio A/S) based on available ND5 sequences of all mtDNA clades of the D. pulex complex [11], [20]. The six-base cutting endonuclease ApoI was predicted to yield group-specific RFLP profiles following digestion of the ND5 amplicon due to a diagnostic cleavage site present only in the pulicaria group of species of the complex that is absent in the tenebrosa group (Figure 5), which unambiguously identified each isolate to either the tenebrosa or the pulicaria group [11]. The PCR products were digested with ApoI following the manufacturer's (New England Biolabs, Ipswich, MA) specification. Daphnia tenebrosa (clade TENE) does not occur in Europe except in the Arctic [23], and the European D. pulicaria (EuroPC) is therefore the only representative of the tenebrosa group in the area covered by this study. It was therefore safe to assign all isolates showing the RFLP profile specific for the tenebrosa group (Figure 5) as belonging to EuroPC.


Diversity in the reproductive modes of European Daphnia pulicaria deviates from the geographical parthenogenesis.

Dufresne F, Marková S, Vergilino R, Ventura M, Kotlík P - PLoS ONE (2011)

Restriction map of the mtDNA ND5 amplicon.The ApoI site at position 344 distinguishes species [11] of the tenebrosa group (European Daphnia pulicaria, EuroPC; and D. tenebrosa, TENE) from those of the pulicaria group (polar, PPC; western, WPC; and eastern D. pulicaria, EPC; D. middendorffiana, MIDD; and panarctic D. pulex, PanPX). Some lineages yield short fragments under 100 bp in size difficult to visualize using agarose gels but this does not affect scoring the individuals as either tenebrosa or pulicaria group.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3104988&req=5

pone-0020049-g005: Restriction map of the mtDNA ND5 amplicon.The ApoI site at position 344 distinguishes species [11] of the tenebrosa group (European Daphnia pulicaria, EuroPC; and D. tenebrosa, TENE) from those of the pulicaria group (polar, PPC; western, WPC; and eastern D. pulicaria, EPC; D. middendorffiana, MIDD; and panarctic D. pulex, PanPX). Some lineages yield short fragments under 100 bp in size difficult to visualize using agarose gels but this does not affect scoring the individuals as either tenebrosa or pulicaria group.
Mentions: PCR products of all the remaining isolates were subjected to RFLP analysis in order to verify that they belonged to European D. pulicaria and not to other species that exist within the D. pulex complex [11]. Species delimitation and taxonomy is problematic in the D. pulex complex. North American and European populations of D. pulicaria have the same species name despite the fact that these two groups should not belong to the same species since they are genetically distinct [11]. This study focuses on European D. pulicaria. ND5 haplotypes from other lineages are included for genetic comparisons. A restriction map was generated using the CLC Free Workbench 4.6.2 (CLC Bio A/S) based on available ND5 sequences of all mtDNA clades of the D. pulex complex [11], [20]. The six-base cutting endonuclease ApoI was predicted to yield group-specific RFLP profiles following digestion of the ND5 amplicon due to a diagnostic cleavage site present only in the pulicaria group of species of the complex that is absent in the tenebrosa group (Figure 5), which unambiguously identified each isolate to either the tenebrosa or the pulicaria group [11]. The PCR products were digested with ApoI following the manufacturer's (New England Biolabs, Ipswich, MA) specification. Daphnia tenebrosa (clade TENE) does not occur in Europe except in the Arctic [23], and the European D. pulicaria (EuroPC) is therefore the only representative of the tenebrosa group in the area covered by this study. It was therefore safe to assign all isolates showing the RFLP profile specific for the tenebrosa group (Figure 5) as belonging to EuroPC.

Bottom Line: These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes.Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result of hybridizations.In contrast to North American populations, these transitions do not appear to involve meiosis suppressor genes and have not been accompanied by polyploidy.

View Article: PubMed Central - PubMed

Affiliation: Département de Biologie, Centre d'Études Nordiques, Université du Québec à Rimouski, Rimouski, Québec, Canada. france_dufresne@uqar.qc.ca

ABSTRACT

Background: Multiple transitions to obligate parthenogenesis have occurred in the Daphnia pulex complex in North America. These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes. This conforms to the rule of geographical parthenogenesis postulating prevalence of asexuals at high latitudes and altitudes. While the reproductive mode of high-latitude populations is relatively well studied, little is known about the reproduction mode in high altitudes. This study aimed to assess the reproductive mode of Daphnia pulicaria, a species of the D. pulex complex, from high altitude lakes in Europe.

Methodology/principal findings: Variation at eight microsatellite loci revealed that D. pulicaria from the High Tatra Mountains (HTM) had low genotype richness and showed excess of heterozygotes and significant deviations from Hardy-Weinberg expectations, and was thus congruent with reproduction by obligate parthenogenesis. By contrast, populations from the Pyrenees (Pyr) were generally in Hardy-Weinberg equilibrium and had higher genotypic richness, suggesting that they are cyclic parthenogens. Four lakes from lowland areas (LLaP) had populations with an uncertain or mixed breeding mode. All D. pulicaria had mtDNA ND5 haplotypes of the European D. pulicaria lineage. Pyr were distinct from LLaP and HTM at the ND5 gene. By contrast, HTM shared two haplotypes with LLaP and one with Pyr. Principal Coordinate Analysis of the microsatellite data revealed clear genetic differentiation into three groups. HTM isolates were intermediate to Pyr and LLaP, congruent with a hybrid origin.

Conclusion/significance: Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result of hybridizations. In contrast to North American populations, these transitions do not appear to involve meiosis suppressor genes and have not been accompanied by polyploidy. The absence of obligate parthenogenesis in Pyr, an environment highly similar to the HTM, may be due to the lack of opportunities for hybridization.

Show MeSH
Related in: MedlinePlus