PHYSIOLOGICAL ECOLOGY - ORIGINAL RESEARCH Ecophysiology and genetic structure of polar versus temperate populations of the lichen Cetraria aculeata S. Domaschke • M. Vivas • L. G. Sancho • C. Printzen Received: 18 July 2012 / Accepted: 17 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract We studied polar and temperate samples of the lichen Cetraria aculeata to investigate whether genetical differences between photobionts are correlated with phys- iological properties of the lichen holobiont. Net photo- synthesis and dark respiration (DR) at different temperatures (from 0 to 30 °C) and photon flux densities (from 0 to 1,200 lmol m -2 s -1 ) were studied for four populations of Cetraria aculeata. Samples were collected from maritime Antarctica, Svalbard, Germany and Spain, representing different climatic situations. Sequencing of the photobiont showed that the investigated samples fall in the polar and temperate clade described in Ferna´ndez- Mendoza et al. (Mol Ecol 20:1208–1232, 2011). Lichens with photobionts from these clades differ in their temper- ature optimum for photosynthesis, maximal net photosyn- thesis, maximal DR and chlorophyll content. Maximal net photosynthesis was much lower in Antarctica and Svalbard than in Germany and Spain. The difference was smaller when rates were expressed by chlorophyll content. The same is true for the temperature optima of polar (11 °C) and temperate (15 and 17 °C) lichens. Our results indicate that lichen mycobionts may adapt or acclimate to local environmental conditions either by selecting algae from regional pools or by regulating algal cell numbers (chlo- rophyll content) within the thallus. Keywords Photosynthesis  Lichens  Cetraria aculeata  Trebouxia jamesii  Acclimation  Genetic adaptation Introduction Lichens are highly specialised symbiotic associations of a mycobiont (the fungal partner) and an autotrophic photo- biont (green algae and/or cyanobacteria) that supplies the fungus with carbohydrates. Their ability to withstand unfavourable environmental conditions in a desiccated, physiologically inactive state makes them pioneers in many ecosystems, especially in polar and alpine regions, where competition from vascular plants is low. The distributional ranges of many lichen species are generally larger than those of vascular plants and often extend over several biomes. The wide ecological amplitude of many lichens is probably facilitated by their ability to display physiological adaptations to different climatic parameters such as tem- perature, moisture availability and light intensity. For example, the temperature optima for photosynthesis may Communicated by Allan Green. Electronic supplementary material The online version of this article (doi:10.1007/s00442-013-2670-3) contains supplementary material, which is available to authorized users. S. Domaschke (&)  C. Printzen Department of Botany and Molecular Evolution, Senckenberg Research Institute, Senckenberganlage 25, 60325 Frankfurt am Main, Germany e-mail: stephanie.domaschke@senckenberg.de C. Printzen e-mail: cprintzen@senckenberg.de S. Domaschke  C. Printzen Biodiversity and Climate Research Center, Senckenberganlage 25, 60325, Frankfurt am Main, Germany M. Vivas  L. G. Sancho Biologı ´a Vegetal II, Fac. de Farmacia, Universidad Complutense, 28040 Madrid, Spain e-mail: mpvivas@farm.ucm.es L. G. Sancho e-mail: sancholg@farm.ucm.es 123 Oecologia DOI 10.1007/s00442-013-2670-3