Allozyme-based genetic variability of the Daphnia atkinsoni–bolivari species complex (Cladocera: Daphniidae) in the Hungarian Great Plain

Nédli, J., Forró, L. (2013): Allozyme-Based Genetic Variability Of The Daphnia Atkinsoni-Bolivari Species Complex (Cladocera: Daphniidae) In The Hungarian Great Plain. Acta Zoologica Academiae Scientiarum Hungaricae 59 (1): 67-79, DOI: http://doi.org/10.5281/zenodo.573611

An experimental test on the probability of extinction of new genetic variants

In 1927, J.B.S. Haldane reasoned that the probability of fixation of new beneficial alleles is twice their fitness effect. This result, later generalized by M. Kimura, has since become the cornerstone of modern population genetics. There is no experimental test of Haldane's insight that new beneficial alleles are lost with high probability. Here we demonstrate that extinction rates decrease with increasing initial numbers of beneficial alleles, as expected, by performing invasion experiments with inbred lines of the nematode Caenorhabditis elegans. We further show that the extinction rates of deleterious alleles are higher than those of beneficial alleles, also as expected. Interestingly, we also find that for these inbred lines, when at intermediate frequencies, the fate of invaders might not result in their ultimate fixation or loss but on their maintenance. Our study confirms the key results from classical population genetics and highlights that the nature of adaptation can be complex.Human Frontiers Science Program grant: (RGP0045/2010)

Population dynamics and genetic changes of Picea abies in the South Carpathians revealed by pollen and ancient DNA analyses

Background: Studies on allele length polymorphism designate several glacial refugia for Norway spruce (Picea abies) in the South Carpathian Mountains, but infer only limited expansion from these refugia after the last glaciation. To better understand the genetic dynamics of a South Carpathian spruce lineage, we compared ancient DNA from 10,700 and 11,000-year-old spruce pollen and macrofossils retrieved from Holocene lake sediment in the Retezat Mountains with DNA extracted from extant material from the same site. We used eight primer pairs that amplified short and variable regions of the spruce cpDNA. In addition, from the same lake sediment we obtained a 15,000-years-long pollen accumulation rate (PAR) record for spruce that helped us to infer changes in population size at this site. Results: We obtained successful amplifications for Norway spruce from 17 out of 462 pollen grains tested, while the macrofossil material provided 22 DNA sequences. Two fossil sequences were found to be unique to the ancient material. Population genetic statistics showed higher genetic diversity in the ancient individuals compared to the extant ones. Similarly, statistically significant Ks and Kst values showed a considerable level of differentiation between extant and ancient populations at the same loci. Lateglacial and Holocene PAR values suggested that population size of the ancient population was small, in the range of 1/10 or 1/5 of the extant population. PAR analysis also detected two periods of rapid population growths (from ca. 11,100 and 3900 calibrated years before present (cal yr BP)) and three bottlenecks (around 9180, 7200 and 2200 cal yr BP), likely triggered by climatic change and human impact. Conclusion: Our results suggest that the paternal lineages observed today in the Retezat Mountains persisted at this site at least since the early Holocene. Combination of the results from the genetic and the PAR analyses furthermore suggests that the higher level of genetic variation found in the ancient populations and the loss of ancient allele types detected in the extant individuals were likely due to the repeated bottlenecks during the Holocene. This study demonstrates how past population size changes inferred from PAR records can be efficiently used in combination with ancient DNA studies. The joint application of palaeoecological and population genetic analyses proved to be a powerful tool to understand the influence of past population demographic changes on the haplotype diversity and genetic composition of forest tree species

Morphometric characteristics and COI haplotype diversity of Arctodiaptomus spinosus (Copedoda) populations in soda pans in Hungary

Arctodiaptomus spinosus (Daday, 1891) is a characteristic species of the soda pan zooplankton in the Great Hungarian Plain. The biogeographical distribution of the species is interesting, since its range expands from the Pannonian Biogeographic region to the other side of the Carpathians, occurring in saline lakes in Eastern Anatolia, Armenia, Iran and in temporary waters in Ukraine. Our investigations focused on the morphometric characteristics and the COI haplotype diversity of four Hungarian populations in the Kiskunság area. We detected substantial morphological differences between the Böddi-szék population and the rest of the sampling sites, however considerable differences were not observable in the COI haplotypes in the populations. The 20 animals investigated for COI haplotypes belonged to the same haplotype network. Tajima?s D indicated departures from the neutral Wright ? Fisher population model and suggested population expansion. The genetic composition of Arctodiaptomus spinosus populations in the Kiskunság area is rather uniform

Salinity and depth as structuring factors of cryptic divergence in Moina brachiata (Crustacea: Cladocera)

Microcrustacean taxa in temporary waters are important contributors to aquatic biodiversity on the landscape scale even though much of the diversity at the molecular level is still undiscovered. Cladoceran species other than Daphnia are not frequently targeted in molecular investigations. We used nuclear allozyme polymorphisms as well as DNA sequence variation in mitochondrial 16 S and COI gene regions to reveal patterns of genetic differentiation among populations of a cladoceran species ? Moina brachiata ? that typically inhabits temporary aquatic habitats. Samples originated from 20 temporary to semi-permanent waterbodies in the Hungarian Great Plain of the Pannonian biogeographic region. We observed strong genetic differentiation in the phylogenetic analyses of the concatenated 16 S and COI genes, based on which M. brachiata was found to represent a complex of four cryptic lineages (A, B, C and D) with, however, one of these (lineage D) detected based on only one individual. Regarding the nuclear markers, diagnostic alleles of the PGM and MDH enzyme loci in complete linkage disequilibrium were observed separating the 'B' lineage from the rest. In addition, indirect evidence was provided by the AAT locus, where the AAT1 allele was found to be potentially diagnostic for lineage 'C'. The three phylogenetically defined lineages ('A', 'B', 'C') could be separated from each other along the first canonical axis of a multivariate analysis of occurrence, and this first axis was strongly correlated with depth and salinity of the ponds. There is a strong association between habitat depth and the occurrence of the 'B' lineage. Our results indicate that habitat depth and associated ecological characteristics driven by differences in hydroperiod likely are responsible for the present distribution of the lineages