Abstract
Currently, the information on the gene pool of silver fir (Abies alba Mill.) at the northeastern edge of its distribution in Poland is scarce and insufficient. Using the advantage provided by markers with different modes of inheritance, a hypothesis that gene flow via both seeds and pollen contributed to the genetic structure across the entire analyzed region was investigated. The geographic distribution of maternally inherited mitochondrial DNA (mtDNA, nad5-4) and paternally inherited chloroplast DNA (cpDNA, psbC) variation was studied in 81 Polish populations and three reference populations from Ukraine and Romania. The spatial pattern of mtDNA haplotypes (dispersed via seeds) indicated that the Apennine Peninsula was the only maternal glacial refugium for the entire territory of Poland and also the Ukraine no 1 population, whereas the other two populations—Ukraine no 2 and Romania—had the haplotype representing the Balkan origin. By contrast, the cpDNA haplotypes (dispersed via pollen) from all studied Polish and reference populations showed that A. alba colonized the current natural range from two genetically distinct glacial refugia located on the Apennine and Balkan peninsulas. The occurrence of cpDNA haplotypes varied among the studied populations. Additionally, statistical analyses were used to infer the genetic structure of examined populations. Two distinct groups of A. alba populations were identified showing the postglacial geographic distribution of haplotypes of both mtDNA and cpDNA. A. alba is an important ecological and economic component of forest ecosystems in Europe. An understanding of the Holocene history of this species is relevant for planning sustainable forest management, and acquired data can contribute to strategies of conservation and restoration.
Highlights
The modern geographical distribution and pattern of genetic diversity of forest tree populations within their natural range are, to a large extent, a consequence of the strong climatic fluctuations of the Quaternary, with a dominant series of cold and dry glacial periods that alternated with shorter intervals of warmer and moister interglacial periods [1,2,3]
In individuals of the A. alba populations from the western natural range, representing the Apennine refuge, the allele was 80 bp longer than that detected in the individuals of fir populations from the eastern part of the range, representing the Balkan refugium
Based on the distribution of both mitochondrial DNA (mtDNA) haplotypes, the origin of fir populations was determined within Polish territory and the Ukrainian and Romanian territory
Summary
The modern geographical distribution and pattern of genetic diversity of forest tree populations within their natural range are, to a large extent, a consequence of the strong climatic fluctuations of the Quaternary, with a dominant series of cold and dry glacial periods that alternated with shorter intervals of warmer and moister interglacial periods [1,2,3]. On the scale of Europe, many temperate trees survived these glacial periods as small, low-density populations that retreated into favorable microenvironments and distinct refugia located in deep valleys among the mountains of southern Europe [4,5,6] With their isolation in these refugia for many tens of thousands of years, populations had opportunities to differentiate through selection and genetic drift. Forests 2016, 7, 284; doi:10.3390/f7110284 www.mdpi.com/journal/forests postglacial migrations northwards and the associated demographic processes, created durable genetic thousands of genetic years, populations had variation opportunities to differentiate selection and genetic imprints on the structure (e.g., in allelic frequency through and genetic diversity) of extant drift. Spatiotemporal gene flow is pollen characterized via seeds and pollen a different via seeds only (mtDNA)
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