Acknowledgements
The research was financed by the Federal State Mecklenburg-Vorpommern, Germany (project EMAU 13(95, 96)1997), and was supervised by Konrad Billwitz (Geographical Institute, Greifswald University, Greifswald, Germany). Samples were collected by Knut Kaiser (ibid.). Hannelore Rabe (ibid.) is thanked for preparing the pollen samples. The author wants to thank Steffen Wolters and an anonymous reviewer for valuable comments on the text.
Disclosure statement
No potential conflict of interest was reported by the author.