Searching for the origin of the so-called Bödmerenwald-spruce

Norway spruce of the Bödmerenwald. Photo: T. Liechti

The present distribution of European forest trees is largely the result of colonization from refugia where the species survived the last glaciation. In this project, we combine genetic and paleoecological data for studying the history of the so-called Bödmerenwald-spruce, a geographically limited Picea population with outstanding high genetic diversity in the north-central Swiss Alps.

Background

The so-called Bödmerenwald-spruce is a geographically limited population of Picea abies forming one of the few near-natural spruce forests in the Alps (46° 59’ N, 8° 51’ E), part of which is now under protection. Earlier we showed that this forest is part of a geographically larger but clearly defined population with a unique genetic signature and high genetic diversity of mitochondrial DNA bounded within Switzerland on the east, south, and west by spruce of extremely low diversity, whereas the northern limits are still unclear due to introduction of spruce of foreign origin but might lie in southern Germany (Sperisen et al. 2005). Geographically, the high genetic diversity of these forests interrupts the general genetic pattern in the Alps, grading from high genetic diversity in the eastern Alps to low in the western Alps (including most of Switzerland), a pattern that is understood to result from successive founder events during the general east-to-west expansion of spruce in the Holocene (Gugerli et al. 2001). Van der Knaap et al. (2005) and Latalowa & van der Knaap (2006) traced this spruce expansion by means of pollen data. The timing of the Bödmerenwald-spruce expansion around 7000 years ago is in line with the general east-to-west spruce migration through the Alps, but speed of expansion falls out of the pattern. Westward expansion was rapid from the far eastern Alps to the Jura Mountains in the west, except for a narrow north-south oriented strip just over the Bödmerenwald area where it was extremely slow: less than 50 km expansion in two millennia (8000-6000 yr BP). So both the genetic structure and the early expansion history stand out from the general patterns, and it is tempting to think that the two are related.

Objectives

• Through the analysis of modern DNA, determine the geographical limits of the genetically outstanding spruce population in the north-central Swiss Alps;
• For the study of ancient DNA (aDNA), extract and analyse early fossil material of spruce from peat in the geographic centre of the genetically outstanding spruce population;
• Integrate the results of analysis of modern DNA, aDNA, and published pollen analysis, in an attempt to identify the historical causes of the unique genetic signature of the spruce populations in the north-central Swiss Alps.

Methods

Work with aDNA will be carried out in two independent laboratories (Birmensdorf and Copenhagen) to validate results. Extraction of aDNA and PCR setup will be performed in clean laboratory facilities, physically separated from other laboratories and equipped with air over-pressure and laminar flows with UV-radiation. Extraction of aDNA will follow the protocols established in Birmensdorf (Liepelt et al. 2006) and Copenhagen. Variation will be assessed in the second intron of the mitochondrial nad1 gene (Sperisen et al. 2001).

Partners

• Eske Willerslev (University of Copenhagen), Pim van der Knaap (University of Bern)

References

• Gugerli, F., Sperisen, C., Büchler, U., Magni, F., Geburek, T., Jeandroz, S., Senn, J. (2001). Haplotype variation in a mitochondrial tandem repeat of Norway spruce (Picea abies) populations suggests a serious founder effect during postglacial re-colonization of the Western Alps. Molecular Ecology 10: 1255-1263.
• Latalowa, M., van der Knaap, W.O. (2006). Late Quaternary expansion of Norway spruce Picea abies (L.) Karst. in Europe according to pollen data. Quaternary Science Reviews 25: 2780–2805.
• Liepelt, S., Sperisen, C., Deguilloux, M.-F., Petit R.J., Kissling, R., Spencer, M., Beaulieu J.-L., Taberlet, P., Gielly, L., Ziegenhagen, B. (2006). Authenticated DNA from ancient wood remains. Annals of Botany 98: 1107-1111.
• Sperisen, C., Büchler, U., Gugerli, F., Mátyás, G., Geburek, T., Vendramin, G.G. (2001). Tandem repeats in plant mitochondrial genomes: application to the analysis of population differentiation in the conifer Norway spruce. Molecular Ecology 10: 257-263.
• Sperisen, C., van der Knaap, W.O., Scrob, E., Lampart, T., van Leeuwen, J.F.N. (2005). Einwanderungsgeschichte der Bödmerenfichten. In: Liechti, T. (Ed.), Urwaldcharakteristiken des Bödmerenwaldes. Burger&Stocker, Lenzburg, pp 81-93.
• van der Knaap, W.O., van Leeuwen, J.F.N., Sperisen, C. (2005). Vegetationsgeschichte des Bödmerenwaldes. In: Liechti, T. (Ed.), Urwaldcharakteristiken des Bödmerenwaldes. Burger&Stocker, Lenzburg pp 69–80.