South European populations of Ramalina farinacea (L.) Ach. share different Trebouxia algae

Abstract

[EN] Little is currently known about the population structure of lichen photobionts. Accordingly, in this study we analyzed the nature and distribution of phycobionts in different Spanish populations of Ramalina farinacea. Two different Trebouxia algae were isolated and identified on the basis of anatomical and chloroplast LSU rDNA sequence studies. Interestingly, most of the thalli contained the same two algae. To search for possible genetic variability among these algae, the internal transcribed sequences (ITS) of nuclear rDNA were compared. Surprisingly, only one ITS sequence was found in each thallus, even in those exhibiting multiple morphologically differentiated algae observed in thallus TEM sections. Therefore, ITS sequence analyses are probably only indicative of the predominant photobiont while the other photobiont remains undetected. One photobiont seemed to predominate in the Canary Islands populations and the other in peninsular ones. Additionally, here we describe a new potential DNA marker, based on plastid LSU rDNA, which may allow rapid identification of coexisting algae within the same thallus.