Clonal diversity, clonal persistence and rapid taxon replacement in natural populations of species and hybrids of the Daphnia longispina complex

Abstract

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.

Cytonuclear diversity and shared mitochondrial haplotypes among Daphnia galeata populations separated by seven thousand kilometres

“…A genetic separation of VIR, ZEL and GOSL from other D. galeata populations in Europe might have resulted from introgression of D. cucullata to D. galeata . In all three localities, we detected D. cucullata (although its hybrids with D. galeata apparently were not very common in ZEL and VIR [28]), whereas communities of other analysed European lakes often consist of D. galeata hybridizing with D. longispina [24, 48, 49]. Furthermore, we observed a discordant pattern between mitochondrial and nuclear markers, as some individuals from the above localities were classified to D. galeata based on microsatellites, but carried D. cucullata mitochondrial haplotypes (data not shown).…”

“…The individual DNA extractions followed the protocol reported in [24]. Fifteen microsatellite loci [25] were amplified in two multiplex polymerase chain reactions [24]. The PCR products were then analysed on an ABI PRISM 3730 capillary sequencer, using a LIZ 500 labelled size standard.…”

“…In Europe, D. galeata often coexists with other species from the D. longispina complex (e.g. [14, 24]). Recurrent hybridization has been reported [26–28] which requires careful multi-locus species identification [24, 29, 30].…”

“…Recurrent hybridization has been reported [26–28] which requires careful multi-locus species identification [24, 29, 30]. Thus, only true D. galeata specimens (based on Bayesian analyses of microsatellite data and comparison of obtained results with reference species [19, 24]) were included in the analyses of European populations (about 40 individuals per population, except for AMME: 12 individuals, Table 1; 483 individuals in total). In addition to 14 newly sampled and genotyped populations, microsatellite analyses included data that have already been published from eight Chinese and three European lakes [19, 24] (see Table 1).…”

“…Forty-nine well-defined genotypes, representing three species of the D. longispina complex ( D. galeata , D. longispina and D. cucullata ) and their interspecific hybrids, were included as reference taxa in FCA (the same reference genotypes were used in [24]). Then, NewHybrids [31] was applied to double-check if all FCA-identified individuals were pure D. galeata .…”