Complexity of lichen symbiosis: genomic diversity and coexistence of various green microalgae in the epigeous lichen Buellia zoharyi

Autores UPV
Año
CONGRESO Complexity of lichen symbiosis: genomic diversity and coexistence of various green microalgae in the epigeous lichen Buellia zoharyi

Abstract

Lichens illustrate how individuality in eukaryotes is composite, complex and multidimensional. Lichen thalli are complex holobionts, which have originated from cyclical symbiosis involving a fungus, one or several photoautotrophs-green microalgae, cyanobacteria or both, and abundant non-photosynthetic bacteria. Lichenization allows the partners to thrive in extreme environmental conditions. Buellia zoharyi Galun is a lichen prevailing in Biological Soil Crusts (BSC) in xeric areas. It seems to be specific to gypsum and carbonated soils. Six populations were selected, three on Miocene gypsum soils from the Iberian Peninsula and three more growing in other substrata: two from the Canary Islands and another one from the Balearic Islands. Also, herbarium samples from Morocco and Greece were included. The B. zoharyi mycobiont was identified using ITS rDNA as barcode. Green microalgae phylogenetic analyses were made using both chloroplast (LSU rDNA) and nuclear (nrDNA ITS) molecular markers. In addition, ultrastructural microscopic techniques were used to characterize each phycobiont found. Our results suggest the presence of at least three different Trebouxia lineages. Furthermore, phycobiont coexistence inside a single thallus occurs in all the populations analyzed, defined by the presence of at least two taxa of intrathalline symbiotic microalgae. The intrathalline coexistence of different algal species and/or genera inside a single lichen thallus has recently been reported by our team. This process could be advantageous under extreme environmental conditions, and might be a common phenomenon in ecologically adaptive lichens, as in the case of B. zoharyi