Allozyme variation in Pinus cembra and P. sibirica: differentiation between populations and species

<p>Two closely related Eurasian species of 5-needle pines, Swiss stone pine<br />(Pinus cembra L.) and Siberian stone pine (P. sibirica Du Tour) occupy two disjunctive parts of the formerly common range in Europe and<br />Siberia, respectively. These forms show so close morphological and genetic similarity that in some classifications they are treated as subspecies. Using a set of 29 allozyme loci (Adh-1,-2, Fdh, Fest-2, Gdh, Got-1,-2,-3, Idh, Lap- 2,-3, Mdh-1,-2,-3,-4, Mnr-1, Pepca, 6-Pgd-1,-<br />2,-3, Pgi-1,-2, Pgm-1,-2, Skdh-1,-2, Sod-2,-3,- 4) we analyzed genetic differentiation within the Alpine-Carpathian part of the range (P.<br />cembra) and found relatively low genetic diversity for conifers (HE=0,08) and moderate level of differentiation (FST=7,4%). For the<br />same loci set within Siberian populations (P. sibirica) genic diversity was higher (0,14), while differentiation was lower (3%). The fact<br />that differentiation within the highly fragmented range of Swiss stone pine is just 2.5 times higher than in widespread closely related P.<br />sibirica makes us consider factors other than unlimited gene flow responsible for uniformity of allelic frequencies. Among these factors the leading role belongs to balancing selection.<br />Heterozygote superiority leads to both (i) increasing of heterozygosity in course of stand development and (ii) through balancing selection<br />to stable equilibrium state. Under this equilibrium, virtually the same genetic structure is maintained, even when remote and isolated<br />parts of the species' ranges are compared. For many studied loci, Swiss and Siberian stone pines have the same allelic profiles despite the fact that gene flow among them ceased a long time ago. According to one point of view fragmentation of the formerly united range might take place in the Atlantic time of the Holocene (about 5000 years BC), however, an alternative hypothesis refers to a much earlier<br />Pleistocene glacial time. Analysis of a combined data set (P. cembra + P. sibirica) including samples of both species showed that a subdivision of genetic variation is about 10 times higher than within each species. A problem of distinction between selective and nonselective<br />differentiation for allozymes and other genetic markers is discussed.<br /><br /></p

Population genetic structure and mating system in the hybrid zone between Pinus sibirica Du Tour and P. pumila (Pall.) Regel at the Eastern Baikal Lake shore

<span style="font-family: Arial,Helvetica,sans-serif; font-size: small;">Genetic structure of sympatric Pinus sibirica Du Tour and P. pumila (Pall.) Regel populations and putative interspecific hybrids between them was analyzed in the Baikal Lake region (Barguzin Biosphere Natural Reserve, Davsha River basin) by means of 31 allozyme loci controlling 18 enzyme systems. Several alleles at loci Adh-1, Fest-2, Lap-3, Pgi-1, Sod-3 and Skdh-1 were diagnostic for P. sibirica, while alleles typical for P. pumila were detected at loci Gdh, Got-3, Lap-3, Mdh-2, Mdh-4, Pepca, Pgi-1, Pgd-2, Pgd-3, Pgm-1 and Pgm-2. All hybrids were heterozygous for the diagnostic Skdh-2 locus. Classification into hybrids and parental species using PCA analysis of multilocus allozyme genotypes had good correspondence with diagnoses made by morphological and anatomical analyses. Approximately 27% of embryos in P. pumila seeds had P. sibirica paternal contribution, and 8% of haplotypes in effective pollen pool combined alleles typical for P. pumila and P. sibirica, and therefore were classified as pollinated by the hybrids. About 83% of embryos in seeds from the hybrids most likely originated from fertilization by P. sibirica pollen, 14% from P. pumila and 3% from hybrid trees. This result favours the view that hybrids make both male and female contributions to the reproductive output of the population and confirm the presence of backcrosses and F2 hybrids.</span

Start of reproduction and allozyme heterozygosity in Pinus sibirica under different techniques of artificial forest stand establishment

<p>Siberian stone pine (Pinus sibirica Du Tour) is one of the main forest-forming tree species in boreal forests of Eurasia. Large edible<br />seeds of this species have an important resource value because of their high nutritious properties. Development of approaches to<br />establishment of early cone producing Siberian stone pine stands including utilization of corresponding genetic background is one of the priorities of forest resource management. The goal of our study was to evaluate the effect of stand density on the differentiation of trees by<br />the age of first reproduction and the relationship of allozyme heterozygosity and morphological traits variability in Siberian stone pine.<br />Morphological and allozyme variability in artificial Pinus sibirica stands with high and low density was investigated. In the high-density<br />stand the distance between trees was 0.7 and 3 meters (4080 trees per ha) while in the lowdensity stand it was 8 and 8 meters (144 trees<br />per ha). Age of formation of first male and female cones was evaluated by retrospective method based on analysis of tracks of cones on<br />a shoot bark. Tree height, diameter and number of male, female and vegetative shoots in a crown of model trees were measured.<br />Genotypes of the trees were determined by 29 isozyme loci coding for 16 enzymes (ADH, FDH, FEST, GDH, GOT, IDH, LAP, MDH, MNR, PEPCA, 6-PGD, PGI, PGM, SDH, SKDH, SOD). In the low-density stand, the portion of generative trees was higher and differentiation of trees by age of reproduction starting was lower in spite of the smaller age of trees as compared to the high-density stand. In<br />both samples, the age of formation of first generative organs was related negatively with stem height, stem diameter and number of<br />female shoots. In the high-density stand, positive relation of age of first reproduction with total number of shoots and number of<br />male shoots was found. In both samples nonreproductive trees were less heterozygous at isozyme loci as compared to trees starting cone<br />production. Allozyme heterozygosity correlated positively with the age of first cone production in the high-density stand only. We<br />conclude that the degree of competition between trees due to different stand density determined age and timing of first reproduction<br />and development of tree crowns. The relationship of allozyme heterozygosity and the age of first reproduction was expressed more in the high-density stand of Siberian stone pine.</p

Testing of microsatellite primers with different populations of Eurasian spruces Picea abies (L.) Karst. and Picea obovata Ledeb.

From a clone library containing microsatellite DNA fragments of Norway spruce, seven pairs of primers were selected. These primers were tested as markers in the genetic structure analysis of nine populations of Eurasian spruce species Picea abies (L.) Karst. and Picea obovata Ledeb. Five pairs of these primers identified polymorphic loci with allele numbers ranging from 6 to 15. In the populations examined, the observed and expected heterozygosity values assessed at five loci varied from 0.1778 to 0.6556 and from 0.7800 to 0.900, respectively. In the populations examined, the values of Fst index varied from 0.0691 to 0.2551 with the mean value of 0.1318. On the dendrogram based on Nei genetic distances, the populations formed three groups: Pskov–Ciscarpathya, Komi–Tatarstan–Arkhangelsk, Kazakhstan–Karelia(natural)–Karelia(plantation)–Krasnoyarsk. Five of the primer pairs tested proved to be useful for analysis of the population genetic structure in Eurasian spruce species